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In Reply to: RE: Sonically, its called the " choir effect ". posted by kyle on December 09, 2016 at 08:28:08
So you, and - some others may think !!Wrong, wrong, wrong.
Obviously, ANY and ALL doubters have NEVER heard a Serious Stereo amp, in a good setting, play !! It " wiped the floor " in a SET amp shoot out at RMAF ten years or so ago, at Terry Cain's after-hours shoot-out. Dennis' amp got a STANDING ovation.
Kyle, if you properly engineer it, as Dennis Fraker uniquely KNOWS how to do, and if you operate the 2A3 at 43 mA., not 60 mA. at 250 P-K, AND use a direct couple ( the ONLY "way" to go ), and pay CAREFUL attention to ALL aspects of the build, the 12AX7 can easily drive the 2A3.
Or, let me put it this way, Kyle, Using the ABOVE low current driver operating parameters, Dennis' amps THIS year, in 2016, two months ago, were rated by Herb Reichert, Stereophile reviewer, as being one ( of the two ) of his "most favorite" rooms to visit and LISTEN to, at the recent RMAF show, out of HOW MANY ...250 - 300 exhibitors??
Besides the URL on the easy-click at the bottom of my post ( read it first ) look also at THIS following URL, cut and paste it, please scroll down to under the heading " FAVORITE ROOMS "
\\http://www.stereophile.com/content/rmaf-2016-assessment#kyTkLrxdjfMsQ22z.97
So Kyle, What do I need to DO to get credibility with people who have no experience hearing what I am talking about, and who don't fully understand ??? Thats you, AND I am sure - some others.
Regards, best wishes, Merry Christmas
Jeff Medwin
Edits: 12/09/16 12/09/16Follow Ups:
"So Kyle, What do I need to DO to get credibility with people who have no experience hearing what I am talking about ???"
Hi Jeff.
This is a relatively easy question to answer and one you should have asked years ago.
Stop posting your opinions as facts. No matter how many times you repeat an opinion, it doesn't become less subjective.
Stop using the CAPS button to emphasize your opinions. It's annoying and bad forum etiquette.
Two simple steps and voila, instant credibility.
On your behalf; You've been making amps for a long time. I remember seeing you in Sound Practices magazine in the 1990s so you have the history and you've shown everyone pics of your amps for years, so we all know you can design/build. You've shared your ideas to anyone that would listen, so you're helpful.
None of that means that your opinions are suddenly new electrical laws or that they're the only way to do things or that everyone will like the results. That's OK. It's just a hobby and it's supposed to be fun.
I enjoy your posts and enthusiasm as do others so carry on and enjoy yourself as well.
You know this subject of paralleled sections has come up many times over the span of this forum. Others as well regarded as PJ have weighed in on the negative side IIRC (forgive caps). I've tried it several times because of the theoretical benefits. All I can say is I don't like it. Things seem smeared. I also know the theoretical benefits of negative feedback but I've heard both ways and I think with NFB amps sound like crap. All are entitled to their opuntia I've never heard a great sounding slide rule. :-)
OK, so I think by "smeared" or "Choir effect" people here mean to say that a second signal is produced due to the unmatched delay of the two tube sections?
Essentially adding a delayed signal back to the un-delayed signal which would produce an echo effect? Right?
Yet nobody to date has shown us the output of such a circuit on a scope where a delay would be very obvious!
Can't be measured? I disagree. We can easily measure time differences down to the pico-seconds on commodity bench scopes. Yet in order to hear such a delay, we are talking tens of not hundreds of milliseconds. That's based on our hearing deficiencies.
Furthermore when you consider the physics in tube construction, the standard manufacturing tolerances are magnitudes lower than would be required to produce such a long electrical delay.
This is layman's logic! Plain and simple. There is no evidence of this phenomenon that can be measured and quantified - because it doesn't exist at audio frequencies.
I don't doubt people hear things they don't like when paralleling tube sections. But I have to ask if the circuit parameters have been adjusted for the good old LCR changes the additional tube section makes? because that's most likely what you are hearing.
It would be very easy to see if measured, as we can measure far lower time based discrepancies on modern test equipment. Two triode sections paralleled act as a uniform composite device even when not perfectly balanced with respect to current and gain. Look at the very well regarded RCA 2A3 as an example, the dual plates. Those are internally connected paralleled sections and they have no issues produced from that construction technique.
Zarni, by now you have been around here long enough that no physical proof will sway a religious fanatic. Take the stuff you may have read about Dennis Fraker's amps...specifically how some magical new term 'transfer efficiency' or some such dreck allows a 2.3641 Watt amp to run circles around more powerful amps in terms of delivered SPL. Makes no sense...and yet you hear it constantly, with no definition given to this new term...only, 'come hear it'.
Hopefully, belief in such things will result in the expected consequences...LOL
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
On a good state of the art, or close to it high fi sytem, there is an audible difference between a single triode, and two paralleled.
In your example, a common NOS bi plate 2A3 will never match the sonics of a single plate 2A3, such as the original HARP 2A3, and the modern EML versions.
Of course, the original Harp 2A3, and the EMLs have symmetrical filament structures, and large emitting filaments, as does the modern JJ 2A3-40, so that is a very large advantage, over a " W" or "V" shaped filament in the standard NOS bi plate.
But people do hear differences, on better audio implementations, parallel versus a single triode. The only instrument that can detect it, is our ears.
No need to discuss Chinese manufacture 2A3s, they are not good enough. Maybe this " single triode in a bottle " is why people with high efficiency speakers like a 45 over a biplate 2A3. Again, "the" measuring device of-choice is a good hi fi, and the parts on either side of our cranium.
Have fun,
Jeff
I'm not going to debate a possible difference in sound between single triode tubes and paralleled section or paralleled separate tubes. People claim they hear all kinds of subtle differences between this that and the other thing.
I just object to calling the inferior sonic quality "smear". That implies some kind of time based latency across paralleled sections giving rise to the music signal that is different from a pure signal. This makes little sense if you know that the electrons involved in carrying the audio signals are moving close to the speed of light, and hence any time discrepancy from taking one different, but very very short path, is of no consequence to the, relatively, very slow audio signal that eventually is produced in your speakers or headphones. Some people tried to use the same logic with feedback loops and time smear was largely debunked as a source of the lesser quality.
I guess same thing with the filament structure. One might be better than an other, but its not due to a lack of time delay effect because of its symmetry.
Hey, you over simplified it, and your conclusions, theoretical, are bogus in practice. I do not mean to offend you in any way. Really !!
The ear can detect many things, and others will support my observations, it is smearing and it is a choir effect. Your "theory " and reasoning would be correct perhaps, if both tube sections were identical in spacing. They never are !!
1 plus 1 equals 2, not 1.
Jeff
"But I have to ask if the circuit parameters have been adjusted for the good old LCR changes the additional tube section makes? because that's most likely what you are hearing."
When paralleling the two triodes of a 6sn7 does the Miller capacitance go up vs. one triode?
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
x
.
Have Fun and Enjoy the Music
"Still Working the Problem"
It goes up but how significant it is depends on the rest of the system.
The preceding stage in my case has output impedance of about 47 ohms and I use a 470 ohm grid stopper. A paralleled 6SN7 has about 8pF of plate to grid capacitance and in the case of using a CCS, a mu of about 20, so about 168pF miller.
I say "about" because the two sections of a 6SN7 don't have the same input capacitance and even with a CCS the mu can vary tube to tube.
So yes it affects the FR but whether it makes a difference is up to the builder and the application.
" So yes it affects the FR but whether it makes a difference is up to the builder and the application."Yes, that's why I brought it up.
If the drive impedance was high and someone switched to parallel from single and noticed a difference in sound, the sound difference could be do to that.
"The preceding stage in my case has output impedance of about 47 ohms"
but not in your case.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 12/13/16 12/13/16
If I were starting an amp from scratch, I might not opt for a paralleled driver. If I were modding an existing amp, I would look at how much effort is is to change the the driver to something completely different. Also, I have a lot of tubes sitting around here that need a home and that could influence the choice. Starting with a blank page, I am liking the 6EJ7 recently. Nice little pentode that sounds good run as is or triode connected.
In the case of the offending 300B amp mentioned in this thread, it started with a 6SJ7 driver, which sucked, so I tried a variety of other octal tubes so I could use the same size socket.
I will say this, a paralleled driver sounds better to me than a cascade whether DC or cap coupled. The extra stage takes more away than the paralleled version adds.
IME, the EL84 is a *VERY* fine signal tube. Very fine indeed...:) High ratio plate/g2 current. Good gm at low g2 voltages( around 100V ), and with a variable g2 voltage responds very well to tuning the tube characteristics to match a chosen plate load.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
I agree. I first was made aware of the EL84 as a driver by an article by Thorsten Loesch. I just copied his version with a 300B and it absolutely is a great driver. It helps that I've got lots of them as well.
I would be very interested in how your latest amps are designed Douglas. You've had some great ideas in the past and I feel that they align with my view more often than not. I haven't done a PP amp for years but I'm thinking that I would like to apply some of the things I've learned to one now. The SE thing is a bit of a dead end for anyone that likes to listen to music at more than background volumes or that enjoys realistic bass. That should stir up the natives:)
hey-Hey!!!,
Another liddle power tube I plan to examine is the 2E24. It is a DH number about the size of a 6V6 and given the performances of other DH tubes ought to work quite well.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
I would not question your electronics acumen and as some suggested there may be places where this works just fine, like bi-plate 2A3s, though I note that single plate versions seem in higher demand. When I've paralleled sections it has only been in driver circuits of SE amps, so my experience is limited to that and yes, the circuits in my case were optimized for things like the reduced Rp, why else do any of this? Maybe "smeared" (my term) is a poor application of language to what my ears perceive. What I've experienced are things like less clarity in placement of instruments and less ability to hear individual instruments- as in the case of massed strings, etc. Makes no diff to me if it is measurable because I do this for the enjoyment of music, not because I'm making precision test equipment or such. So if one circuit sounds better to my ears, that's what I will build and yes I'm quite familiar with the engineering theory behind it all.
Solid state does the same thing, they basically parallel transistors in most amp circuits. Some manufacturers match transistors which brings us back to the subject of smearing. I think if you match them well enough, most wont notice the difference.As Lawrence said below, there's always a workaround
Edits: 12/10/16
"All are entitled to their opuntia" Cactus?
Anyway, I've also read lots of posts on paralleled tubes and it seems like one of those areas where everybody has an opinion, including some very well respected designers. There are also quite a few that double up on output tubes - an area where I can hear a negative difference. I do not however hear a difference in paralleled driver tubes. Not that others can't, I've said before that I'm a tin ear when it comes to many audiophile things.
As an example, I don't attach huge importance to ultra-precise soundstage because I don't hear it in live performances to the extent that some reproductions systems portray it. I have never heard instruments coming from off stage in a live situation but some audio types think it's a sign of added realism when the sound stage comes from outside the speakers in a home set up.
Perhaps using single driver tubes will allow me to appreciate things like this.
Kyle, i believe you mentioned using paralleled sections of the 6sn7 with a CCS and a LED on the cathode. Would you mind going into more detail about your set up as i would like to try something like that in my amp. Thank you.
.
One of the best sounding, if not THE best sounding system I have yet to hear, used custom SET Monoblocks using the 304TL as its output tube.
OK, the speakers were 5-way Ale horns, so there is that. ;-)
I think what your getting at here is there are 4 separate sections parelled in this tl304 tube?
and .... and sounded very very good.
I agree on all accounts(opinions)but its all in the details on how its done that's what makes or breaks ideas or in this case paralleling tubes, IMO there is almost always a "work around"
Lawrence
That's a good point.
By the same token, I listened to bi-plate 2A3s for years before they started making 300Bs with 2.5V filaments and calling them single plate 2A3s. I never felt that they were smearing the music, in fact I still occasionally pop a pair into my amps and actually enjoy the music they reproduce.
going instead with a pentode of some kind.Also have heard parallel 300B amps that sounded good. As my speakers are 107dB or so horns, I really don't need that much power so one 300B is fine.
Edits: 12/10/16
,!
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