PPPUL EL84 Amp...Does one exist?

The old Beard P35? 2nd Hand only of course...

Thor

At 20 bits, you are on the verge of dynamic range covering fly-farts-at-20-feet to intolerable pain. Really, what more could we need?

RE: PPPUL EL84 Amp...Does one exist?, posted on August 1, 2013 at 05:31:34
xaudiomanx Audiophile Posts: 3647 Joined: August 16, 2004	What is the Dynaco ST-35 or any amp of that design?

Completely unrelated I think...the Dynaco and the Beard, posted on August 1, 2013 at 05:36:43
Bas Horneman Audiophile Posts: 4083 Joined: March 28, 2001	that is.

RE: PPPUL EL84 Amp...Does one exist?, posted on August 1, 2013 at 06:42:37

Thorsten
Manufacturer

Posts: 4209
Location: Somewhere nice on planet dirt
Joined: September 25, 1999

Hi,

Beard uses 3 pairs of EL84 in parallel per channel, gives 35W per channel, conservative rating.

Dynaco uses one pair of EL84 and gives around 15W per channel (claimed 17.5 - so the "ST-35" - which is does not meet).

Of course, if I was an Apple Lawyer I would argue it is east to confuse the two and one should pay the other a billion or two...

Thor

At 20 bits, you are on the verge of dynamic range covering fly-farts-at-20-feet to intolerable pain. Really, what more could we need?

Manley Sting-Ray, posted on August 1, 2013 at 07:31:39

Chip647
Audiophile

Posts: 2649
Location: The South
Joined: December 24, 2012

It does exist.

However, it you want 25 watts there are better ways to get them compared to PPPUL EL84.

RE: PPPUL EL84 Amp...Does one exist?, posted on August 1, 2013 at 09:47:40

Stuben
Audiophile

Posts: 669
Location: Guber Ohio
Joined: December 30, 2005

Built such an animal, SE IT coupled input, Push Pull Pentode UL connected output. Dual Mono platform. Nice sound.

Pictures taken when amp was connected in Triode. I finally figured out that Pentodes want to be Pentodes...and how to get the sound I wanted. I have also removed the attenuator since...not enough gain going with 2 stages...

I need to revise the schematic prior to sharing...let me know if you would like a .pdf of the latest schematic...

Stuben

Advantages?, posted on August 1, 2013 at 10:40:52
gusser Audiophile Posts: 3649 Location: So. California Joined: September 6, 2006	Are there any advantages to a EL84 or 6V6 PPP design? I would think you would be better off just using a PP design with a more powerful tube like an EL34 or 6550?

RE: Advantages?, posted on August 1, 2013 at 10:56:08
drlowmu Manufacturer Posts: 9730 Location: East of Kansas City Joined: January 10, 2005	Gusser, Would there be a lower Z in the output trannie, which might be an advantage? Some may like the sound of a small tube over a large tube, that may be a factor / advantage perhaps. Against any advantage is the problem of a "choir" effect from multiple paralleled tubes. Just some random thoughts I had, to share. Regards, Jeff Medwin

RE: Advantages?, posted on August 1, 2013 at 11:50:48

gusser
Audiophile

Posts: 3649
Location: So. California
Joined: September 6, 2006

The first two, lower out Z and the sound of the tubes are quite plausible.

The "choir effect" is not. While it's true the more tubes in parallel, the mis-matched parameters play that much more into the total sonics. But this idea of time delay is silly at audio frequencies.

Cowboy logic! It's simply not a relevant factor. Now I have no doubt mismatched tubes in a PPP produce audible distortions. But I don't see how a echo or AUDIBLE delay is possible - not at baseband audio frequencies.

RE: PPPUL EL84 Amp...Does one exist?, posted on August 1, 2013 at 12:25:00
xaudiomanx Audiophile Posts: 3647 Joined: August 16, 2004	My mistake again Thorsten. I now read the three "P's" instead of two. I should really take more time to read than open my mouth. Maybe I need new reading glasses.

Yes,the lower output impedance and the extra power are a big plus., posted on August 1, 2013 at 12:27:43
Michael Samra Dealer Posts: 36118 Location: saginaw michigan Joined: January 30, 2005	I just posted about this last night over in tubes asylum and it's one of the few times I liked an EL34.PPP is the way to go on some of these tubes. The added transient energy is huge when you get to the upper octaves and especially the lower octaves. "For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken

RE: PPPUL EL84 Amp...Does one exist?, posted on August 1, 2013 at 12:32:33
Michael Samra Dealer Posts: 36118 Location: saginaw michigan Joined: January 30, 2005	Stu I like your amp..Is that Lundahl iron you are using? I see the 100uf EC polys I believe and yes,I would love a schematic to this.Tell us about the iron used. "For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken

RE: Manley Sting-Ray, posted on August 1, 2013 at 12:37:30
Michael Samra Dealer Posts: 36118 Location: saginaw michigan Joined: January 30, 2005	They are only getting 25 watts out of four EL84s in PPP UL? "For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken

RE: Yes,the lower output impedance and the extra power are a big plus., posted on August 1, 2013 at 12:49:27

drlowmu
Manufacturer

Posts: 9730
Location: East of Kansas City
Joined: January 10, 2005

An extra pair of tubes ( PPP )is only 3 dB louder, but it has "X" times more the peak current capability, which is what the speaker LIKES to see to control it !!

Please let Gusser know, from listening experiences, ( not theory ), a choir effect can always be heard in PPP versus PP, despite what he "thinks".

When listening, PP plays "purer" than PPP, and of course, SE plays purest of them all.

Jeff Medwin

What exactly is "choir effect"?, posted on August 1, 2013 at 12:56:00
gusser Audiophile Posts: 3649 Location: So. California Joined: September 6, 2006	What exactly do you hear?

RE: Manley Sting-Ray, posted on August 1, 2013 at 13:27:04
Tom Bavis Audiophile Posts: 961 Location: Upstate NY Joined: May 25, 2007	They claim 40W in UL, 20 in triode. Both a bit optimistic in my humble opinion...

RE: Advantages?, posted on August 1, 2013 at 13:38:56
Tom Bavis Audiophile Posts: 961 Location: Upstate NY Joined: May 25, 2007	The engineers at Maganvox must have thought there was an advantage to using only one output tube number. They used two, four, six, or eight per amp. Sixteen 6V6s in the Concert Grand console. (six PPP in each bass amp, two P-P in the treble amps).

Sound Quality?, posted on August 1, 2013 at 13:47:26

Thorsten
Manufacturer

Posts: 4209
Location: Somewhere nice on planet dirt
Joined: September 25, 1999

Hi,

Measurements aside, for some reason the EL84 (and related tubes) sound different from bigger pentode tubes. It is a bit like 45/2A3/300B progression with attendant changes in sound quality...

In many ways the EL84 is the 45 of the Push-Pull Tetrode/Pentode world.

It is very difficult to make a bad sounding EL84 Amp, underpowered for american Watthog, near shortcircuit impedance dip "high end" Speakers, sure. Give them the right speakers and they shine.

Thor

At 20 bits, you are on the verge of dynamic range covering fly-farts-at-20-feet to intolerable pain. Really, what more could we need?

"It is very difficult to make a bad sounding EL84 Amp" That is because you can't screw-up the driver., posted on August 1, 2013 at 14:17:03
Chip647 Audiophile Posts: 2649 Location: The South Joined: December 24, 2012	EL84 and 6V6 are really easy to drive. Very hard to mess them up. It does take some engineering to drive most other tubes to satisfying results. Also, people seem to love output tubes that are a bit over-driven with nice even order harmonics. EL84/6V6 can easily be over-driven without upsetting the driver. If that is good or not is up to you.

Maybe he's referring to "chorus effect"?, posted on August 1, 2013 at 15:25:44
Ray Moth Audiophile Posts: 2784 Location: Jakarta, Indonesia Joined: November 10, 2003	I so, he's off the mark. The chorus effect can indeed be simulated electronically, but not in the simple way he suggests.

My experience entirely supports Thorsten's comments. (nt), posted on August 1, 2013 at 20:22:44
Paul Joppa Industry Professional Posts: 7295 Location: Seattle, WA Joined: April 23, 2001	My experience entirely supports Thorsten's comments.

Choir effect?, posted on August 1, 2013 at 21:54:15

Naz
Audiophile

Posts: 2184
Location: Sydney
Joined: September 2, 2005

Jeff,

I agree with your first two thoughts but I respectfully suggest that the "choir" you hear is that generated by your brain cells, conducted by your brain's prejudice against parallel tubes as there is no basis of fact to support its existence. I’m also willing to bet that you could not detect the said effect in a blind test, with a caveat here that I’m not talking about other sonic differences that will aways exist when comparing on an apples and oranges basis.

Indeed, as discussed before on this forum, is the fact that a number of well-respected tubes are actually a pair of smaller parallel tubes. In the past I have also proposed that any tube, (though some more than others) could be seen by its construction to be a multitude of much smaller tubes in parallel (picture multi-slicing a long plate tube across its length). Perhaps not quite the same thing but food for thought.

Naz

RE: Yes,the lower output impedance and the extra power are a big plus., posted on August 1, 2013 at 21:58:58
Michael Samra Dealer Posts: 36118 Location: saginaw michigan Joined: January 30, 2005	OTL is the purest.You don't have the transfer loss characteristics that get with all transformers..I don't buy that all PP plays purer than PPP.I'm talking about the final product,once it reaches the speaker load. "For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken

RE: Manley Sting-Ray, posted on August 1, 2013 at 22:01:15
Michael Samra Dealer Posts: 36118 Location: saginaw michigan Joined: January 30, 2005	Oh they can do 40 if you push it because the Sherwood S5000 with 7189s in PP can do 24 watts UL..Of course they are running 420v on the plates in fixed bias. "For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken

RE: Choir effect?, posted on August 1, 2013 at 22:42:23
drlowmu Manufacturer Posts: 9730 Location: East of Kansas City Joined: January 10, 2005	Hi Naz, You are only speaking honestly from your experience. With the speakers you run, highly inefficient ESLs, you possibly may never hear it. On 100 dB and higher speakers, with a great sources and amplification, it can be rather evident. Since you built and use Parallel SE, to power your ESL load, your post is understood by me completely. Regards. Jeff Medwin

RE: Yes,the lower output impedance and the extra power are a big plus., posted on August 1, 2013 at 22:57:22

drlowmu
Manufacturer

Posts: 9730
Location: East of Kansas City
Joined: January 10, 2005

On my eight chassis 1986-1988 DIY Laboratory amps, everything double regulated, P-P sure played purer than P-P-P. This was in a full-blown Bob Fulton Premiere audio system, low in efficiency.

A highly inefficient speaker load, like an ESL, will obscure many of these subtle but real differences Mike. The ESL "NEEDS" P-P-P, but what it REALLY needs is a great solid state amp on it. Different horses for different courses.

To do tubes and tube amps optimally, you need high efficiency as as not to have to compromise as much, and so you can HEAR what is happening. Suggest 97 dB or higher, 101 is much better if you have it.

YMMV, no doubt, and we know why !!

Jeff Medwin

RE: Choir effect?, posted on August 1, 2013 at 23:43:41

Naz
Audiophile

Posts: 2184
Location: Sydney
Joined: September 2, 2005

Jeff, you assume that I've never built, listened to or owned any other equipment. In fact, the first tube amp I ever built was an EL84 based SE design driving relatively efficient speakers, followed by a PP version more than 40 years ago. In those days SS wasn't even an option. We wound our own OP trannies by hand and turned and welded our own chassis.

Since then I have built and auditioned so many systems that I've forgotten most. Prior to my first PSE amp I spent many months experimenting with, measuring and listening for differences in parallel and single designs, both SE and PP, mainly because of the doubts I had, having read opinions like yours. I have NEVER heard the "choir" effect you refer to!

I know that our opinions differ on this subject and that I will not change yours, nor am I seeking to. But know that mine is based on real world experience which included much testing, measuring and listening and I’m just offering an alternative view to counterbalance the argument for the benefit of whoever may be interested.

Naz

RE: Yes,the lower output impedance and the extra power are a big plus., posted on August 2, 2013 at 03:26:31

Michael Samra
Dealer

Posts: 36118
Location: saginaw michigan
Joined: January 30, 2005

I know what your saying about PP as it relates to circuit as being purer but when its relative to the load,things change.It isn't true in all cases but with the EL34,it definitely holds true because they don't suffer the lower or high end deficiency that I get with my PP EL34 tube amps.In most cases tho,you would be correct.The dynamic energy is what comes of short with EL34s and the ribbons I run them on are 91db with a flat impedance.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken

http://www.newformresearch.com/r645v3.htm

RE: "claimed 17.5 - so the "ST-35" - which is does not meet", posted on August 2, 2013 at 05:25:37

1973shovel
Audiophile

Posts: 10117
Location: Greenville SC
Joined: February 25, 2007

You're right, not with the stock cathode bias, it doesn't. But add Dave Gillespie's simple EFB bias (redundancy, I know) and it will meet the power spec, lower the distortion specs, and most importantly, be a better sounding amp.

Before and after EFB results are from an SCA-35, but are the same for the ST-35.

That Beard sure is pretty though. No $3 mod is ever going to fix the ST-35 in that regard.

RE: "claimed 17.5 - so the "ST-35" - which is does not meet", posted on August 2, 2013 at 08:15:57

Thorsten
Manufacturer

Posts: 4209
Location: Somewhere nice on planet dirt
Joined: September 25, 1999

Hi,

I am aware of these mods.

The difference in power output is around 1dB. In practical terms this is meaningless.

Better sound or not, I have not tried this.

My biggest argument against this circuit and in favour of the kind of biasing Bill Beard (yes, that his name) uses is that BB's circuit can manage without matched quads (or even sextetts for the P-35) and if measuring with (say) a shaped sine burst or other signals that approximate Music, as opposed to sinewave testing, you are unlikely to find much practical differences.

And actually, even if the tubes are matched quads at purchase, they are VERY unlikely to still be matched after a few 100 hours, spare a few 1,000.

A later version Amp from Bill is reviewed here:

http://www.beardaudio.com/bb3060-hfn.pdf

I suspect either one of Old Bill's EL84 UL-PPP Amplifiers may occasionally crop up 2nd hand, especially in England and Asia, less in the USoA, so the OP may wish to keep a beady eye out..

Thor

At 20 bits, you are on the verge of dynamic range covering fly-farts-at-20-feet to intolerable pain. Really, what more could we need?

RE: Yes,the lower output impedance and the extra power are a big plus., posted on August 2, 2013 at 10:24:18

Lew
Audiophile

Posts: 10911
Location: Bethesda, Maryland
Joined: December 11, 2000

As someone who has used ESLs of one kind or another for about 40 years, I must take issue with your blanket statement that large ESLs "need" a SS amplifier. What HAS happened over the years is that manufacturers have lowered the naturally high input Z of an ESL panel via various "tricks", in order to make them more suitable for driving by SS amplifiers. In pure form, and using reasonable step-up transformers, ESLs like voltage not current and will exhibit high impedances at low to mid-frequencies, where the power is needed most. SS amps can't do that so well. It is true that, being a capacitative load, ESLs have low Z at very high frequencies, but little power is required at such frequencies. Moreover, many well regarded SS amplifiers become very unstable driving an ESL that hasn't been doctored to make it tolerable for an SS amplifier, just due to reactance. And in fact, ESLs that are so doctored usually sound mediocre to me, at best and with any amplifier. They have thrown the baby out with the bathwater.

OTLs and rarely direct-drive via power tubes linked direct to the stators are the best classic ways to drive a proper ESL. If you heard it, you would like it a lot.

RE: Yes,the lower output impedance and the extra power are a big plus., posted on August 2, 2013 at 10:54:03
drlowmu Manufacturer Posts: 9730 Location: East of Kansas City Joined: January 10, 2005	Lew, Nice comments on amplifiers. Regardless of how you drive an ESL, now-a-days, I do not "like it a lot". I had my first ESLs in about 1974, Infinity Servo Stats and KLH 9s, Quad 57s, single and double panels....about the time when you did. Jeff Medwin

RE: Yes,the lower output impedance and the extra power are a big plus., posted on August 2, 2013 at 12:14:32
Lew Audiophile Posts: 10911 Location: Bethesda, Maryland Joined: December 11, 2000	Jeff, You cannot properly audition a pair of KLH 9s whilst standing up in a Speedster. They are not well suited for car stereo, especially driven by one of those Blaupunkt radios that Porsche used. Get them inside, hook up a Futterman. Then you've got something. (Or at least something great in the 70s.)

Croft Series 5, posted on August 2, 2013 at 12:35:34

Alex M
Audiophile

Posts: 924
Location: Hampshire
Joined: February 9, 2001

If I understand "PPPUL" correctly, I would suggest the Croft Series 5 stereo amplifier, which I have written a short article on below.

Alex

Croft Series 5

RE: Yes,the lower output impedance and the extra power are a big plus., posted on August 2, 2013 at 21:57:20

drlowmu
Manufacturer

Posts: 9730
Location: East of Kansas City
Joined: January 10, 2005

The Futterman I had lasted less than two weeks !! Honest injin. But then, I never had a Porsche 550 Spyder like you - my elite audio friend Lew had. Only saw three in my life.

PS: Venice Blvd. Venice, CA about 1978, 1961 Roadster, Bursch exhaust, my second pair of KLH9s, just bought from Bobby Casner. Audio happiness. Had Marantz 9s back then, rackmount.

RE: The most linear beam/pentode wired in triode am aware of... I would take 6V6 over el84 Any Day-nT, posted on August 3, 2013 at 02:13:47
Cleantimestream Audiophile Posts: 7550 Location: Kentucky Joined: June 30, 2005	! The Mind has No Firewall~ U.S. Army War College.

RE: "In practical terms this is meaningless", posted on August 3, 2013 at 05:56:16

1973shovel
Audiophile

Posts: 10117
Location: Greenville SC
Joined: February 25, 2007

Hi,

You're correct. I posted regarding the EFB mod, mostly as a way to comment regarding the ST-35 not meeting Dynaco's spec. , as a way to correct that.

As for the sonic improvements, I'd suggest if you ever get the opportunity, to give the EFB a try. As I've said before, my SCA-35 sat collecting dust on a shelf for many years. It always sounded like a wet blanket had been thrown over the speakers when in use. After the EFB, the amp now finds its way into my amp rotation, as it is much more musically enjoyable.

Regarding the matched quads of output tubes, that is an issue. My plan is to eventually build a 6BQ5 amp with a better power supply and input stage, using the Dynaco Z-565 output transformers on a new chassis. There I'll have room to install individual EFB for each tube, eliminating the matched quad concerns.

Given the sonic improvement for a few dollars in parts, and biasing the output tubes at 27 mA vs the stock 35 mA, I consider the EFB the only way to go when using the Z-565 output transformers.

RE: "In practical terms this is meaningless", posted on August 3, 2013 at 06:32:23

Thorsten
Manufacturer

Posts: 4209
Location: Somewhere nice on planet dirt
Joined: September 25, 1999

Hi,

A better (IMNSHO) option for something like EFB is to give each tube proper fixed bias.

Even RC cathode circuits using modern capacitors can sound excellent using Z-565 copies.

Alternatively Bill Beards bias system can work very well and as said, with unmatched Tubes.

http://www.keith-snook.info/Schematics/Beard%20Audio%20Service%20data%20P35%20M70.pdf

Thor

At 20 bits, you are on the verge of dynamic range covering fly-farts-at-20-feet to intolerable pain. Really, what more could we need?

RE: "proper fixed bias", posted on August 3, 2013 at 07:15:47

1973shovel
Audiophile

Posts: 10117
Location: Greenville SC
Joined: February 25, 2007

With many output transformers, I'd agree with you that proper fixed bias is the way to proceed. But not with the well regarded Dynaco Z-565's. I could post the "why" here, but I'd simply be parroting Dave Gillespie's research. If you haven't read his full article on the Enhanced Fixed Bias, and the effect of standard fixed bias with Dynaco Z-565 transformers, I think you'll find it interesting. (link below). #10 on page 16 of the EFB article doesn't tell the whole story though. The full article needs to be read.

Gary Kaufman was a knowledgeable poster to this board some years ago, and many still use his Gary's Tube Page as a reference. Here is a link to an Asylum post where he comments that he tried fixed bias with an ST-35. He says the amp sounded "unfocused" but he didn't understand why. Gillespie reveals the "why" in his SCA-35 article. Kaufman's ST-35 fixed bias results

See #10 on page 16

RE: "proper fixed bias", posted on August 3, 2013 at 08:24:09

Thorsten
Manufacturer

Posts: 4209
Location: Somewhere nice on planet dirt
Joined: September 25, 1999

Hi,

I HAVE read the full article (more than once).

First, any of the effects discussed in his article only appear once the Amplifier leaves Class A and only with music where the average level of the music considerably exceeds the Class Operation area OR with steady state sine wave testing. The power differences, while looking impressive when expressed as numbers, pale into not much to worry,once expessed in decibel and related to how we hear.

The first case is only relevant if the Amplifier is used with grossly mismatched speakers (Efficiency/Impedance), the second only in the laboratory.

Contrary to the assertions in the article, the transformers matching does not play the role claimed. I happen to know because in the process of prototyping an EL84 Amplifier I had a range of output Transformers made up, including a "current wisdom bog-standard", a Dynaco copy and a Chicago copy.

Regardless of biasing of the Amplifier AND the transformer used, using shaped sine burst clipping happens at appx. the same power with less than 1dB difference, sonic differences are also quite small with music that does not stress the amplifier unduly, except for the Bass where Dynaco was preferred, because it creates a higher output impedance.

Commenting next on "EFB" and it's sonic improvements to the standard circuit vs. FIXED BIAS (where each tube grid is individually supplied with an adjustable negative voltage), I would suggest that the MAIN reason for the EFB improvement is that cathode circuit impedance of the EFB Amplifier becomes very low, compared to an amplifier with classic RC biasing having a time constant similar to Dynaco. Correct fixed bias delivers the same benefit.

What Gary Kaufman tested was not in fact fixed bias, but cathode bias.

Why he reports "unfocused sound" must remains in the realm of speculation.

Personally I would think that he introduced poor quality electrolytic capacitors into the Cathode circuits.

Where in the case of a single resistor per channel this capacitor only sees the difference between the two (or 4 in the original Dynaco) tubes, which while in class A will be next to nothing and thus the influence of the cathode capacitor on sound quality is much reduced.

In the case of individual RC biasing per tube, this cap carries full signal current and any voltage developed across it (and distorted), will appear in series with the signal to the tube grid, so it has an extraordinary impact on sound quality.

With this known, we can of course take the necessary steps (e.g. use high quality caps, Film etc.) to address this.

But as said, it is speculation.

Thor

At 20 bits, you are on the verge of dynamic range covering fly-farts-at-20-feet to intolerable pain. Really, what more could we need?

RE: Yes,the lower output impedance and the extra power are a big plus., posted on August 3, 2013 at 11:36:55

Lew
Audiophile

Posts: 10911
Location: Bethesda, Maryland
Joined: December 11, 2000

Cripes! Those were the days. I also owned, at various times, three Carrera GT Speedsters. I bought one in Northern Vermont (almost Canada) in 1979 in the dead of winter and then drove it all the way to DC with no top. That was so fun.

KLH9s are bad for the aerodynamics of a Speedster, don't you think?

Me and Spyder

RE: Choir effect?, posted on August 4, 2013 at 00:01:37

drlowmu
Manufacturer

Posts: 9730
Location: East of Kansas City
Joined: January 10, 2005

Naz,

You can offer your view, but it is in the minority...that is why you did all your "testing". I feel you flunked out. No doubt that you write to us honestly, but you are honestly wrong, which is unacceptable, at least to me.

When you parallel tubes, there are skewes to the sonics, as neither tube is exactly like another. It is VERY audible on any reasonable system, by any good listener. I did this experiment tonight. A single rectifier tube played far purer on 97 dB point-source speakers than the two "matched" Sylvania paralleled ones I had been using, listening to, over the last seven months.

I "wanted" my two paralleled 5V3A rectifiers to win out, after all, I designed and BUILT my prototype SE DC amp that way, it PSUDED better, and it IS more dynamic. But tonight, I found out I was wrong with what I was thinking and wanting, after listening. The single tube plays purer, no skewes are heard.

You owe it to yourself to re-evaluate your prejudices by listening on a high efficiency system at a friend's house. There may be a 100 dB horn system yet - in your hi fi future !! :-)

Cheers,

Jeff Medwin

Interesting, posted on August 4, 2013 at 04:51:30

1973shovel
Audiophile

Posts: 10117
Location: Greenville SC
Joined: February 25, 2007

I will leave Gillesipie to debate this matter with you, if that were in fact necessary. I have neither the test equipment nor the level of experience necessary to defend his findings.

I will stand by my contention that subjectively, the SCA-35 became a more musically enjoyable amp after adding a few dollars worth of self-sourced parts to implement the EFB. Much kinder on the output tubes, as well.

I do now see what you mean about Gary Kaufman creating individual cathode bias in his ST-35, rather than fixed bias. Thank you for the education on that. I'm (hopefully) always learning.

RE: Interesting, posted on August 4, 2013 at 06:03:22
Thorsten Manufacturer Posts: 4209 Location: Somewhere nice on planet dirt Joined: September 25, 1999	Hi, Actually, the more conventional way of applying fixed bias is covered in the article, the reason not to use it was given as "too much work/modification needed"... I can relate to that and it's a good enough call for an easy mod of existing gear. Thor At 20 bits, you are on the verge of dynamic range covering fly-farts-at-20-feet to intolerable pain. Really, what more could we need?

RE: Choir effect?, posted on August 4, 2013 at 06:41:12

Naz
Audiophile

Posts: 2184
Location: Sydney
Joined: September 2, 2005

>>I feel you flunked out<<

Sorry Sir … must not have been listening in class. Perhaps I didn’t like the prejudiced teacher and biased curriculum.

>>When you parallel tubes, there are skewes to the sonics, as neither tube is exactly like another<<

Why is this any different to serial tubes (as in the successive stages of every amp), where ENTIRELY different tubes are used? Does this not "skew the sonics"?

>>It is VERY audible on any reasonable system, by any good listener<<

You have no idea what my system comprises. Nor do you know what I've owned, built or auditioned in my own home, at friend’s places, in high end HiFi shops or in audio shows both local and abroad.

FYI, I NEVER rely solely on my own judgement. I host regular music nights where a number of experienced listeners, each with their own systems and biases appraise every change I make, brutally and honestly! The music nights rotate so I also get to listen to other systems because unlike you, I keep an open mind. I look for particular strengths in each system that may help me further improve my own. This way I have micro sonic goals to strive for on the one hand, while addressing any weaknesses on the other.

>>But tonight, I found out I was wrong with what I was thinking and wanting, after listening<<

NO WAY! Jeff you are never wrong.
Tomorrow, you'll tell us that you thought you were wrong but were mistaken

>>You owe it to yourself to re-evaluate your prejudices by listening on a high efficiency system at a friend's house<<

Pot calling the kettle black or broken record, you choose. See above

>>There may be a 100 dB horn system yet - in your hi fi future !! :-)<<

Whilst unlikely, I DO keep an open mind and I never discount any audio possibility. FWIW, I chose my far more difficult route after auditioning many well respected horns!

Also for the record my ESLs are augmented by dipole arrays for mid bass and series subs for bass below 50Hz.

If you had any real concept of efficiency and the power required to drive speakers handling the various parts of the audio spectrum you would understand that most is needed to gain bass extension. In my system approx 10 fold is a good match.

Cheers to you too Dr Lo Mu

RE: Choir effect?, posted on August 4, 2013 at 11:14:03
drlowmu Manufacturer Posts: 9730 Location: East of Kansas City Joined: January 10, 2005	Naz, Nicely written. I appreciated your response, even if we disagree on points. Good man - you are ! Jeff Medwin

RE: PPPUL EL84 Amp...Does one exist?, posted on August 4, 2013 at 16:38:00

Gingertube
Audiophile

Posts: 545
Location: South Oz
Joined: October 8, 2004

Blowing my own trumpet.

The Baby Huey can easily become a parallel push pull UL. Simply drop the Output tranny Raa to a common 4K3 type and add the extra output tubes and source follower for each of them.
Schematic here:
http://www.diyaudio.com/forums/tubes-valves/72536-el84-amp-baby-huey-61.html
Post #602 amp was final design, the variation in post #604 (shunt feedback from teh UL taps in lieu of anode taps) was evetually abandonned.

I have built about 10 of these now and there have been around 50+ built by other guys arouind the globe. 12AX7 + EL84 were used in the original design but I've also built using 6SL7 and 6V6 which also sound stunning.
My current HiFi Amp is a 6SL7 + 6V6G version.

Cheers,
Ian

RE: PPPUL EL84 Amp...Does one exist?, posted on August 5, 2013 at 09:55:55

Stuben
Audiophile

Posts: 669
Location: Guber Ohio
Joined: December 30, 2005

Mike,

LL1660S are used for the IT. I configured the primaries SE (all in series)to get the most H possible. Those are 47uF Solen power smoothers, 3 per channel.

The OPTs are Lundahl LL1682s, this iron is similar to the LL1663 only 5.5 K primaries and 5 ohm secondaries.

I applied feedback from the secondaries of the LL1682s to the cathodes of the output valves. I'm using a single 6h30p with it's own filament supply as a driver for the LL1660s primaries.

I tried to run this amp Pentode without UL feedback. It had a very engaging sound but the distortion levels were prohibitive. I tried UL and it cleaned it up to good levels without messing the sound up.

I will clean up the schematic and post it.

Thanks Stuben

RE: PPPUL EL84 Amp...Does one exist?, posted on August 5, 2013 at 18:26:28
Stuben Audiophile Posts: 669 Location: Guber Ohio Joined: December 30, 2005	Here's the latest schematic. I think the ability to adjust the cathode feedback would be a good addition.

Hey Everybody, you forgot me!!!, posted on August 5, 2013 at 22:16:07

Audiodyssey
Dealer

Posts: 645
Joined: November 7, 2004

Actually, you ever post a question here and forget that you did? Well, I did!

Anyway, I appreciate all the thoughtful responses.

I have some personal experience with the 6BQ5 in a stereo clone of the Eico HF-14. I have to say, after many years of fiddling around with different amps, this amp has been a sort of end of the road for me. I can't get over how good it sounds. A little more power would be nice, and I have the perfect UL iron, so I thought I'd go for it.

"I KNOW you can hear it, but are you REALLY listening?"

RE: PPPUL EL84 Amp...Does one exist?, posted on August 5, 2013 at 22:17:21
Audiodyssey Dealer Posts: 645 Joined: November 7, 2004	This schematic is something I came across, and I have considered it. "I KNOW you can hear it, but are you REALLY listening?"

RE: Sound Quality?, posted on August 5, 2013 at 22:23:53

Audiodyssey
Dealer

Posts: 645
Joined: November 7, 2004

Thorsten, I agree. I remember one of my first tube amplifiers was a Magnavox console amp. I didn't realize how much I loved the sound of it until after I changed it for the next thing in line.

I have a stereo clone of the Eico HF-14 and it sounds very good. I have stopped buying & trying amplifiers since I built it. I am looking for a just a bit of nudge in power, and I thought a PPP amp with the UL iron I already have would be perfect.

Thanks!
"I KNOW you can hear it, but are you REALLY listening?"

Proud Papa syndrome contributes largely..., posted on August 5, 2013 at 22:33:33
Audiodyssey Dealer Posts: 645 Joined: November 7, 2004	to the sound of the final product...really =) I want to build it, but should I happen along a BB production, well, I'll fix my beady eyes upon it and grab it. Thanks. "I KNOW you can hear it, but are you REALLY listening?"

RE: PPPUL EL84 Amp...Does one exist?, posted on August 6, 2013 at 10:46:13
Stuben Audiophile Posts: 669 Location: Guber Ohio Joined: December 30, 2005	Duh, I guess I should learn to read... Parallel Push Pull...I'm so accustomed to seeing triode strapped amps, I thought we were talking about Pentode PP. I have never listened to Paralleled output stage...need to try sometime for a listen... Sorry Stuben

Skew?, posted on August 6, 2013 at 12:04:37

gusser
Audiophile

Posts: 3649
Location: So. California
Joined: September 6, 2006

What do you mean by "skewing the sonics"?

Are you implying a time delay? Because again several of us have explained that is simply not possible at audio frequencies. Yes there may well be a sub nanosecond delay difference between two tubes but it's not relevant at audio frequencies. You can't seem to grasp the concept of relevance in physics.

As I said before, I have no doubt multiple parallel output tubes causes increased distortion or other response anomalies. And I also have no doubt these can be heard. But pointing to timing differences is a dead end. As for paralleled rectifiers causing a timing skew in the audio output signal, I find that preposterous.

When you start to design high speed digital or RF/video circuits we can discuss electrical transmission timing issues which are then quite relevant.

Yes, NO Question about it !!, posted on August 7, 2013 at 20:45:02

drlowmu
Manufacturer

Posts: 9730
Location: East of Kansas City
Joined: January 10, 2005

Gusser,

What you have written above, and "believe to be preposterous", is indeed

.................. A FACT.

I have been listening to my SE prototype amp for four days now, with ONE 5V3A instead of two, and it is

(1) Easy to hear

(2) Easy to KNOW non-paralleled 5V3A tube rectifiers sounds purer and better

Considering that I was listening to this amp exclusively at home for six months, ( from first fire-up in February 2013 'till last week, with TWO rectifier tubes ), I would say I KNOW what I am hearing when I have switched to a single tube rectifier !!!

What boggles my mind is how rigid and smug you are in your posting, when indeed ..... you are 100% wrong !!!

I purposefully built my SE DC amp with two rectifier sockets, and I wired it such that either one or two rectifier tubes would run the amp, so I could "one day" make this evaluation. "One day" was last week.

The single rectifier easily won out. Hear that Gusser ?? I was wrong, as I "thought" that two rectifiers ( which theoretically PSUDS better ) would be the best compromise. Nope, the ears tell it differently, easily.

I even have a 4% tap on my Power Transformer primary to adjust B+ higher for one rectifier.

Next, I need to rip out all the excess wiring around the unused rectifier socket, and simplify the execution and fields flying around under the deck.

That wire elimination will help also, and as a high frequency guy, you should know why !!

Should I believe what you think and write as being "preposterous" OR believe what I hear - after living with this amp in my system for six months or more.

How would YOU reconcile these differences my dear Gusser ??

Jeff Medwin

P.S. Three good audio friends "always" told me this would be the result ( DF, TT, JD). Glad I finally listened for myself to hear it.

RE: Yes, NO Question about it !!, posted on August 8, 2013 at 09:42:40

gusser
Audiophile

Posts: 3649
Location: So. California
Joined: September 6, 2006

I didn't say a single rectifier doesn't sound different. Nor did I say it sounded qood or bad. It is easy to identify many technical issues between the two scenarios that would produce different sonics.

What I did say was that a second rectifier does not cause delay changes in the amplification process. Specifically that two rectifier tubes do not produce a timing skew or "choir effect" in the audio presentation.

Now perhaps we are getting hung up on semantics here. What you call a choir effect may be totally different than what I think you mean. Like I said above, multiple output tubes do sound different than basic PP or SE. I have practiced that myself and quite frankly I do not like how my 6L6PPPP sounds. It was a good exercise on building a 200w tube amp though.

RE: Yes, NO Question about it !!, posted on August 15, 2013 at 23:12:10

drlowmu
Manufacturer

Posts: 9730
Location: East of Kansas City
Joined: January 10, 2005

Gusser,

You seem to say this, quoted directly :

"What I did say was that a second rectifier does not cause delay changes in the amplification process. Specifically that two rectifier tubes do not produce a timing skew or "choir effect" in the audio presentation."

And I can tell you from my listening tests that ........... you are mistaken !!!

It "skews" like CRAZY, or more conservatively said, easily audible. As does uneven wiring paths to a dual or "universal" ( 0-115 VAC, 0-115 VAC ) primary pair of windings that are to be put in parallel for 115-120 VAC line operation !! Skews the sound ALSO, easily heard,..... when uneven wires go to each coil.

How about them beans Gusser !!! Found that out on a SIGNAL TRANSFORMER MPI-250-24 power transformer last week, powering the DAC and preamplifier diodes of my CD Player.

My system is modest, a used $5.00 Maggie CDB480, ( with $220 worth of 10.6 Ampere SIGNAL power trannies hanging on them ), my SE DC 6AQ5 prototype amp, and a pair of about 60 dollar each EV 12TRXBs that Drummerwill gave me to get by with - till I do an Altec speaker system.

Fun stuff to hear !!

Jeff Medwin

RE: Yes, NO Question about it !!, posted on August 16, 2013 at 00:57:06

cpotl
Audiophile

Posts: 1002
Location: Texas
Joined: December 6, 2009

""What I did say was that a second rectifier does not cause delay changes in the amplification process. Specifically that two rectifier tubes do not produce a timing skew or "choir effect" in the audio presentation."

And I can tell you from my listening tests that ........... you are mistaken !!!

It "skews" like CRAZY, or more conservatively said, easily audible. As does uneven wiring paths to a dual or "universal" ( 0-115 VAC, 0-115 VAC ) primary pair of windings that are to be put in parallel for 115-120 VAC line operation !! Skews the sound ALSO, easily heard,..... when uneven wires go to each coil."

Whatever effects you may, or may not, be hearing, it is surely nothing to do with "a timing skew or "choir effect" in the audio presentation."

You appear to be muddling in your mind the fact that you believe you are hearing an audible effect with your (almost certainly incorrect) attempt at an "explanation."

Chris

Why, HEY....Its the OTL guy again !!, posted on August 16, 2013 at 02:28:39

drlowmu
Manufacturer

Posts: 9730
Location: East of Kansas City
Joined: January 10, 2005

Dear Chris,

From your Moniker and audio system's description, we see you are Chris P. "who only listens to OTLs" and just loves them ( cpotl ).

It would be rather "normal" for you to post against my contentions of paralleled rectifiers or paralleled output tubes ( as in your OTL amp) NOT sounding as pure as a single active device ( as in a good SE amp ).

Above, you posted the following :

"Whatever effects you may, or may not, be hearing, it is surely nothing to
do with "a timings skew or "choir effect" in the audio presentation."

Of course, it is 100% a guess on your part, and in particular, the dead give away words you chose " It is surely nothing to do with ".

I will leave it up to YOU, a theoretical research physicist, to prove, dis-prove, or "give a reason" as to what I hear. But rest assured Chris, I hear it plainly and a "skew to the sound" is as BEST a set of words as I know, to describe it.

Maybe a bona fide Electronics Engineer can help you here with paralleling being benign sonically. .

God forbid we have any amp designer who designs by ear discuss paralleling, ghosts, choirs, and skews, or even recognize up here that it exists !!!

Why, lets just bury our heads in the sand, at least so our ears are suitably covered. We can still see ( with our eyes ) an o'silly-scope and "pretend" it is scientifically guiding us all in audio. Ha !!

Cheers,

Jeff Medwin

RE: Why, HEY....Its the OTL guy again !!, posted on August 16, 2013 at 02:50:43

cpotl
Audiophile

Posts: 1002
Location: Texas
Joined: December 6, 2009

""Whatever effects you may, or may not, be hearing, it is surely nothing to
do with "a timings skew or "choir effect" in the audio presentation."

Of course, it is 100% a guess on your part, and in particular, the dead give away words you chose " It is surely nothing to do with "."

No, it is not a 100% guess. It is based on a consideration of the order of magnitude of the possible timing delays, versus the time-scale associated with the audio frequencies that are being processed by the amplifier. Time delays in the signal path are clearly completely insignificant in this context.

I am not saying that you are not hearing differences (although I would actually only believe that you are if they were confirmed by double-blind tests--but that is a different debate). What I am saying is that your proposed "explanation" for what you believe you are hearing is clearly incorrect.

By the way, I was using the word "surely" in the sense of "without doubt; certainly" (OED).

And, further by the way, my OTL that I use most frequently does not have paralleled output tubes.

And, a yet further by the way, I believe you are misquoting from my audio system's description, when you attributed the statement "who only listens to OTLs" to me.

Chris

Tube DIY Asylum

PPPUL EL84 Amp...Does one exist?

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