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Are output transformers voiced with specific brand/model tubes?

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Posted on July 7, 2015 at 11:28:40
HiFiOd
Audiophile

Posts: 707
Location: Oakland, Califonia
Joined: May 30, 2001
 The reason is I was comparing my 2A3 (magnequest transformers)
amp to the ST70. When I out a pair of RCA blackplates the bass of the 2a3 from the midrange down just became much more fluid and articulated as in more layers of low frequency sounds, some almost puffy, more noticible than with the JJ's which are more extended in the treble.
To my surprise, as good as the ST70 sounded the Fi X was just more fluid and refined sounding in my system, that day....

 

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RE: Are output transformers voiced with specific brand/model tubes?, posted on July 7, 2015 at 13:22:44
hottattoo
Audiophile

Posts: 141
Location: New York
Joined: July 30, 2011
 Transformers don't have a particular sound. Transformers are wound according to the electrical needs of the output tubes. It is a matter of physics and math. Output tubes sound different. Different winding practices and core materials can sound different but can be attributed to measured electrical differences of LCR.

 

Really?, posted on July 7, 2015 at 14:20:35
HiFiOd
Audiophile

Posts: 707
Location: Oakland, Califonia
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 Thanks, but I know the theory, the reality is all parts have an effect on the signal/sound, how noticible that sonic effect is is another issue. Do you really think all transformers with the same voltage specs sound the same? What about the materials? silver, nickel, copper?

 

they generally don't have the same specs, posted on July 7, 2015 at 16:21:55
richardl
Audiophile

Posts: 3555
Joined: September 5, 2002
 For the original Williamson amps, the partridge transformers were well known not to oscillate in a properly built circuit. They were also better built than the average transformer. you get what you pay for in transformers, read what Mike Lefevre said a couple years ago in Vacuum Tube Valley and here on the asylums about the difference between a good output transformer and a bad one. Transformers are not designed for a brand of tubes ever to my knowledge and as Paul Joppa pointed out a while ago, you can make a tube in many ways, it is the way that it meets the tube curve specs that makes it a 6L6 or 6BQ5 etc. not what it looks like.

Richard

 

RE: Really?, posted on July 7, 2015 at 17:12:20
Tre'
Industry Professional

Posts: 17294
Location: So. Cal.
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 There's a lot more to an output transformer than voltage specs.

The inductance of the primary will determine the low frequency -3db point.

The winding capacitance and winding to core capacitance will determine the high frequency -3db point.

There's also the leakage inductance.

The winder has to strike a balance in a full range output transformer.

Different materials and different size air gaps and different size cores with different winding technique will expand the range possible.

I don't think (but it could be true) that a winder of a full range output transformer would give up bass for highs, etc. I think he would just, as best he could given the materials he was using, strike a balance.

Better material, better winding technique, better extension at both ends of the spectrum.

On a different note,

I've come to realize that single ended gapped series output transformers never have enough inductance to play the bass correctly. Neither do output tube plate chokes for parafeed circuits.

I'm thinking of having output transformers wound that give up even more bass extension for better high frequency extension and then just filter out the bass feeding the amp.

Tre'


Have Fun and Enjoy the Music
"Still Working the Problem"

 

"just filter out the bass feeding the amp", posted on July 7, 2015 at 18:13:51
Chip647
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Posts: 2649
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 Oh yeah. Not putting low bass through a SET or through your main mid/woofer is about as big of an improvement to overall sound as one can make for such a small investment. Apparent loudness of using a bass bin/bass amp with a SET is at least double and the bass quality can be optimized.

 

RE: "just filter out the bass feeding the amp", posted on July 7, 2015 at 18:47:39
Tre'
Industry Professional

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Location: So. Cal.
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 I've been bi-amping for years.

What I have learned is that if the low frequencies are allowed to get to the output tube and the output transformer all the frequencies will suffer.

My midrange speakers are just that, midrange speakers and I wasn't blocking the lows to my amp since the midrange doesn't play those frequencies anyway.....big mistake.

Reading voltsecond's paper on the MagneQuest website made me understand that the undesirable load line given by too little inductance is the load line (in the presents of low frequency) that all the frequencies will follow. Block the lows and the load line for everything else gets better, way better.

For that reason, and the lack of power and damping, I don't think SET amplifiers have any business being asked to play bass.

The exception would be a CCS loaded output tube with a parafeed output transformer but even that doesn't address the lack of power and damping issue.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

RE: Really?, posted on July 8, 2015 at 11:29:38
Triode_Kingdom
Audiophile

Posts: 10044
Location: Central Texas
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 "I've come to realize that single ended gapped series output transformers never have enough inductance to play the bass correctly."

That's not necessarily true. The FS-100 OPTs in my 211 SETs produce plenty of bass. I suspect a bigger problem is that most people don't have enough power and/or speaker sensitivity at low frequencies to produce the bass they want. The transformers are only one part of that picture.

 

RE: Are output transformers voiced with specific brand/model tubes?, posted on July 8, 2015 at 11:37:58
SETguy
Audiophile

Posts: 35
Joined: July 4, 2015
 Remember that the distortion characteristics of a SET are very different from those of other circuit arrangements, so comparing the sound of your Fi to the ST-70 is really an "apples an oranges" situation. Comparisons are useful, however, when trying different transformers of the same type (i.e. air gapped for single ended use) in the same amplifier. George Anderson ran some nice budget transformer comparisons years ago which you may enjoy looking at:

 

RE: Really?, posted on July 8, 2015 at 12:22:37
Tre'
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With 10k ohms reflected you will need 80Hy to have a inductance reactance of 10k ohms at 20Hz giving you a -3db point of 20Hz and a load line for that frequency that's not optimum.

You would need 160Hy to get 20Hz at -1db.

Even then the load line would not be totally optimum.

Your damping factor, about 3k ohms plate resistance into 10k reflected//the reactance of the inductance at the low frequencies, might not be enough for every speaker.

In the presents of frequencies that cause the load line to become an ellipse, do to the low reactance of the "less than really needed" inductance, all the frequencies follow the elliptical load line and that adds distortion to everything.

How much primary inductance does the FS-100 have?

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

Voicing, posted on July 8, 2015 at 13:19:27
unclestu
Dealer

Posts: 5851
Joined: April 13, 2010
 It is my opinion that voicing components was probably more prevalent in the 50's and 60's. each major recording studio was associated with an electronics company there seemed to be a symbiotic relationship.

For example RCA had its own electronics departments and made everything from Microphones to tubes.

In England you had Decca which also had a an electronics side making and designing Microphones and components.

In the European continent, you had Philips with their fingers in every aspect of sound.

In fact when you listen to recordings of the era, there are distinct sonic regional differences, many of which are reflected in the audio components that were manufactured

The advent of readily available oscilloscopes and signal generators sort of evens certain things out: like transformers, particularly in the modern era. Surplus scopes and generators certainly flood the consumer market after the Korean War (well not necessarily flood, but becomes readily available)

 

RE: Really?, posted on July 8, 2015 at 14:34:18
Paul Joppa
Industry Professional

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 I don't know the FS-100 inductance, but the FS-030 lists at 35 henries for a 3K primary. That's -3dB at 14Hz, and the best bass extension I know of in an airgapped SE transformer.

In the deep bass, parallel feed can maintain bass flatness and keep the phase near zero to a significantly lower frequency than the plate choke alone might suggest. Plus, the parafeed capacitor causes the load impedance seen by the tube to increase below cut-off, instead of decreasing as in series feed. Both effects offer deeper bass at lower distortion, for the same transformer or plate choke inductance.

Nevertheless, I agree with Triode Kingdom that the perceived lack of bass in SETS is often lack of power rather than lack of extension per se.

 

How 'bout just the sub bass?, posted on July 8, 2015 at 19:48:24
Mr_Steady
Audiophile

Posts: 2042
Location: North Florida
Joined: August 19, 2014
 I did try to find what I'm about to relate, but couldn't. I know it's somewhere in the Electro Voice white papers or PA Bible.

I remember EV writing that one of the benefits of bi-amping is that when you are talking about a full range audio signal the mids somehow ride on top of the bass signal. This results in the midrange signal being modulated by the bass signal. This modulated signal is a distorted signal. Therefore, if you can remove the bass signal before it gets amplified by the power amplifier, then the distortion is not amplified. That's how I remember it anyway.

I think connecting the amplifier directly to the driver solves many damping issues, and damping is only really important with the bass, and it can be tailored by the amp designer. Lack of power can addressed by higher efficiency.

One day I would like to have one SET amp optimized for bass, and one optimized for mids/treble. It's possible that eliminating the sub bass is the key. I get your point about the Voltsecond article.


--------------------------------------------------------

Big speakers and little amps blew my mind!

 

RE: How 'bout just the sub bass?, posted on July 8, 2015 at 20:10:49
Tre'
Industry Professional

Posts: 17294
Location: So. Cal.
Joined: February 9, 2002
 Thanks for you input.

Paul made some good points as well but the point that I'm not sure everyone is getting is this,

All other frequencies are riding along with the lowest frequency at that moment.

If the load line has turned to an ellipse (or worse, a beach ball) because of a lack of inductance then all the frequencies are traversing that bad load line.

Removing just a little of the low bass (and using a more suitable amp and speaker for that low bass) can make a big improvement in the load line for the rest of the music.

My JBL 2118 midrange speakers only play down to 200Hz so that's where I cut the bass to the SET and use a SS amp into a pair of 15" JBL 2231's for the bass.


Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

RE: Really?, posted on July 8, 2015 at 21:32:37
dave slagle
Manufacturer

Posts: 5430
Location: NYC
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 In order to calculate the -3dB point you need to take into account the source impedance in parallel with the reflected load so in the case of a 3K source and a 10K load with 80hy of inductance you get -3dB just under 5hz.

This doesn't take into account the ability of the source to deliver current to inductive leg and that needs to be addressed on a case by case situation.

dave

 

RE: How 'bout just the sub bass?, posted on July 8, 2015 at 21:44:41
dave slagle
Manufacturer

Posts: 5430
Location: NYC
Joined: April 27, 2001
 If the load line has turned to an ellipse (or worse, a beach ball) because of a lack of inductance then all the frequencies are traversing that bad load line.

I'm not convinced this is as bad as everyone says it is. A while back I looked (in spice) at some small signal 1Khz and 10Khz sine waves added to a large signal 20hz sine. I then used a steep filter to cut out everything below the 1Khz (or 10Khz) and looked at the distortion as I varied the amplitude of the 20Hz signal. Sure I saw a difference with the larger amplitude 20Hz causing slightly more distortion at higher frequencies but unless I was current clipping, I didn't find the results ground breaking enough to interest me.

dave

 

Yea right on paper that is all true, posted on July 9, 2015 at 06:11:52
Gordon Rankin
Manufacturer

Posts: 2928
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 hotty,

Look on paper allot of things appear as physical and mathematical facts. But it really ends there.

You could send 8 transformer designers into separate rooms with the exact same specs and come out with 8 differently sounding transformers.

It's just like cables, they are not just wires.

Both PP and SET configurations have their own issues to command. Designers of these transformers all have their own secret sauce that is used to get rid of these demons. So when applied these transformers that have the same mathematical model, don't really sound the same and it's not a matter of LCR.

As an example this happened the other day. A company was talking to me and Mike from MagneQuest about power and output transformers. They wanted to have XYZ make the transformers. The company XYZ calls Mike and says what is this nomenclature on the build of this output transformer. Really??? Then he asks Mike if he can make it this way instead. Because that is what he has been doing for years.

Many of these companies that tear down no longer available transformers and don't have the drawings for them are making them all wrong.

Transformers like Cartridges are more art than math!

Thanks,
Gordon
J. Gordon Rankin

 

You're right, I'm wrong., posted on July 9, 2015 at 08:17:08
Tre'
Industry Professional

Posts: 17294
Location: So. Cal.
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 I see your point. My calculation is wrong.

It would only be right if the source impedance was equal to the reflected impedance.

I should have just stayed with my concern with the distortion and the shape of the load line.

When the inductive reactance is equal to the reflected impedance the load line gets bad and the distortion goes up.

If there was an infinite amount of inductance (and no shunt/winding capacitance) the load line would remain that of the reflected impedance and the distortion would stay low and be predictable.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

RE: You're right, I'm wrong., posted on July 9, 2015 at 09:15:18
dave slagle
Manufacturer

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 When the inductive reactance is equal to the reflected impedance the load line gets bad and the distortion goes up.

This premise falls apart when you realize that a plate choke can be considered as a 1:1 transformer with a very high reflected load. Since a plate choke has finite inductance, by your premise we should be introducing a finite load to match the inductance to reduce distortion.

dave

 

RE: You're right, I'm wrong., posted on July 9, 2015 at 10:08:12
Tre'
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 You're misunderstanding me.

We want the reactance of the inductance to stay out of the way. We want that reactance to be high when compared to the reflected impedance. Otherwise it messes up the load line.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

RE: Are output transformers "voiced" ?, posted on July 9, 2015 at 12:38:19
Frihed89
Audiophile

Posts: 15703
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 90% of audio transformer makers don't make the equipment that uses their transformers. 98% of audio equipment mfrs don't make their own transformers (of any kind).

What does that tell you?

 

RE: You're right, I'm wrong., posted on July 9, 2015 at 16:08:40
dave slagle
Manufacturer

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Location: NYC
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 I understand what you are saying. So how does a plate choke work with an extremely large reflected impedance? I'll stick with my belief that the inductance needed should be based on the source impedance (tube Rp) and not the reflected load. Sure in a perfect world we would want infinite inductance but in the real world, a 10K transformer designed for a 2A3 needs less inductance than a 10K designed for a 211 and designing a 10K transformer without concern of what will be driving it is just the beginning of that slippery slope of compromise.

dave

 

RE: You're right, I'm wrong., posted on July 9, 2015 at 17:03:38
Tre'
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 "So how does a plate choke work with an extremely large reflected impedance?"

The intended load for the output tube is the reflected impedance of the parafeed output transformer not the reflected impedance of the plate choke, so (since the two are in parallel) the higher the reflected impedance of the plate choke, the better as that will lead to more of the total power getting to the speaker instead of being lost in the plate choke.

We would be better off with a CCS in the plate circuit instead of a choke but as long as the inductance of the plate choke is large enough so that it's reactance at low frequencies stays out of the way of the parafeed output transformer's reflected impedance it will work and not mess up the load line for the output tube too much.

In other words, a plate choke with too little inductance (in a parafeed circuit) leads to the same problem as a series feed output transformer (in a series feed circuit) with too little inductance.

Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

RE: How 'bout just the sub bass?, posted on July 9, 2015 at 18:07:43
Mr_Steady
Audiophile

Posts: 2042
Location: North Florida
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 >"but unless I was current clipping, I didn't find the results ground breaking enough to interest me."

Was there anything remarkable when it did clip? It's hard not to clip with a 2A3 amp.




--------------------------------------------------------
Big speakers and little amps blew my mind!

 

RE: Are output transformers "voiced" ?, posted on July 9, 2015 at 19:35:27
Paul Joppa
Industry Professional

Posts: 7295
Location: Seattle, WA
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 re: "... 98% of audio equipment mfrs don't make their own transformers..."

A lot of manufacturers have custom transformers made for them; sometimes they even design them. There's a big grey area there.

 

RE: You're right, I'm wrong., posted on July 10, 2015 at 06:58:44
dave slagle
Manufacturer

Posts: 5430
Location: NYC
Joined: April 27, 2001
 forget about the parafeed circuit and lets keep it to the simple model.

Assume you need to use a plate choke to drive a 10K load and a 100K load from a 1K source. Does the 100K load require more inductance?

dave

 

RE: You're right, I'm wrong., posted on July 10, 2015 at 07:50:07
Tre'
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 Yes if you want the 1K ohm source to see the same percentage of the midband load at the lower frequencies.

With a 10k load in parallel with the reactance of a plate choke with 80Hy (10k ohms at 20Hz) the tube sees a load of 5k ohms at 20Hz.

The reactance of 80Hy at 1kHz is 500,000ohms. 10k //500k = 9800 ohms

5k ohms is 51% of 9800 ohms.

If we use that same choke for a 100k ohm load the 1kHz load for the tube is 83.333k ohms but the 20Hz load for the tube is 9090 ohms, only 10.9% of 83.333K ohms.

When we have a 100k ohm load, for the 20Hz load impedance presented to the tube to be the same percentage of the midband load impedance, 51%, then we would need there to be 800Hy of inductance in the plate choke.


Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"

 

RE: You're right, I'm wrong. , posted on July 10, 2015 at 13:09:49
dave slagle
Manufacturer

Posts: 5430
Location: NYC
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 I think that is a backwards way to approach a design. I prefer to consider the worst case first and then move onward. in this case the load at 20 hz is 5k. if we deem that as acceptable, and we are driving a tube grid, do we then add additional loading in an attempt to keep the load unchanged?

i much prefer the results of the lighter loadat higher frequencies

dave

 

RE: You're right, I'm wrong. , posted on July 10, 2015 at 15:39:36
Tre'
Industry Professional

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 "i much prefer the results of the lighter load at higher frequencies"

Me too but you've missed my point.

If 20Hz is present in the signal the load for the "higher frequencies" will, in effect, be 5k not 10k (9800).

With the low frequencies filtered out the load for the higher frequencies will be much closer to the value (and shape) of the reflected impedance.


Tre'


Have Fun and Enjoy the Music
"Still Working the Problem"

 

Operating Impedance, posted on July 10, 2015 at 19:34:33
Triode_Kingdom
Audiophile

Posts: 10044
Location: Central Texas
Joined: September 24, 2006
 Tre', you are correct regarding the shunt inductance of the transformer. The required inductance is a function of the *operating impedance* of the circuit, and that in turn is determined by the impedance reflected back onto the primary from the load. This operating impedance can be represented by △E/△I, and that term is controlled by load Z and turns ratio. It is relatively unaffected by the source Z, which generally has more effect on output power and efficiency than anything else.

 

Agreed, Gordon... Well said~nT, posted on July 10, 2015 at 21:18:16
Cleantimestream
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 ~!
The Mind has No Firewall~ U.S. Army War College.

 

RE: Are output transformers "voiced" ?, posted on July 12, 2015 at 01:07:10
Frihed89
Audiophile

Posts: 15703
Location: Copenhagen
Joined: March 21, 2005
 I also know of very active partnerships between transformer builders and audio companies, at least in the SET world. Bottlehead's collaboration with Magnequest is well-known. Wavelength and Magnequest is another, I gather. I also know of a small, high-quality audio company that is working with Andy Gove to design some dual-C-core OPTs for their SET headphone product, and I am sure there are other examples of these more active collaborations.

The only audio company i know that designs and sells their OPTs, chokes, ITs, etc. is Audio Note (although they don't build them, as far as I know).

But in the PP world?

 

RE: You're right, I'm wrong. , posted on July 13, 2015 at 07:27:20
dave slagle
Manufacturer

Posts: 5430
Location: NYC
Joined: April 27, 2001



If 20Hz is present in the signal the load for the "higher frequencies" will, in effect, be 5k not 10k (9800).

I don't see it that way. The higher frequencies will still see the value of the inductance as a load. here are two loadlines of a small signal 1000Hz signal plus a large signal 20Hz signal for a fixed amount of inductance. I do not see the width of the loadline as anywhere near the problem as the overall range of current.

 

Nice work Dave ..., posted on July 18, 2015 at 07:09:53
Naz
Audiophile

Posts: 2184
Location: Sydney
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 Can you share the asc file pease?

Naz

 

RE: Nice work Dave ..., posted on July 20, 2015 at 09:00:40
dave slagle
Manufacturer

Posts: 5430
Location: NYC
Joined: April 27, 2001
 It is just a twist on a file Stephie Bench did and is attached below.

I am still trying to get my head around what is happening particularly in a dynamic sense.

dave

 

Ahh, I remember it now, thanks (nt), posted on July 21, 2015 at 04:21:35
Naz
Audiophile

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

 

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