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The last 26-26 DC 45 amp schematic ....

99.5.232.186
Posted on January 23, 2015 at 12:04:05
drummerwill
Audiophile

Posts: 965
Location: St Louis Mo.
Joined: January 7, 2003
 Well the smoke has settled enough, that I'll post the last revision for this amp.

It's in you guys hands now !

If you have any questions shoot me an email. I would also really love to hear of any builds.

Have fun !
Willie






 

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Many thanks nt, posted on January 24, 2015 at 00:49:26
Frihed89
Audiophile

Posts: 15703
Location: Copenhagen
Joined: March 21, 2005
 nt

 

RE: The last 26-26 DC 45 amp schematic ...., posted on January 24, 2015 at 00:50:20
smart845
Audiophile

Posts: 668
Location: East london
Joined: May 24, 2000
 Looking good Willie,

But why the grid choke and not a 380k Shinkoh or similar?

And does B+ not come off the CT.

Do you really need the hum pot? Is it a hum pot?
Only needed if you have poorly sonically matched tubes.

I settled on the Tung Sol 5u4GB but have a pair of 5as4a to try.

Still plenty of room to add some more bypasses and keep those RK values low.

the hammond opt letting it down. Try my fave Electraprint PSSS. Though I do run 16ohm on 8 ohm out and like what I hear.

Give it plenty of hours 500 at least before judgement on sound quality.

Pictures please.

Smart

 

RE: The last 26-26 DC 45 amp schematic ...., posted on January 24, 2015 at 08:00:22
kyle
Audiophile

Posts: 1839
Location: London Ontario
Joined: September 29, 1999
 I have a Hammond 274BX that is labeled 175mA as is yours but the Hammond catalog now shows it as 201mA.
Also, without the 6.3V @ 6A winding in use the B+ voltage could be higher than expected.

 

RE: The last 26-26 DC 45 amp schematic ...., posted on January 24, 2015 at 09:27:42
drlowmu
Manufacturer

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

Willie's earlier schematics showed a Hammond 274X with a 134 Ohm DCR high voltage winding. Likely, ..... that is what he used.

The 274BX, with about an 80 ohm DCR winding, will work FINE, especially if yours is a later one and has the 115 and 125 primary taps - use it on 0-125 VAC input !!

An unused 6.3 VAC winding will not be very much of a factor in overall VAC output with the lightly-loaded high voltage secondary winding. PT is working in a loaf mode.

Over Christmas 2014, Willie's unique / original build inspired me to design a 26-26-45 amp, ( without the cap couple ), and I gave it an absolutely over-the-top KICK-ASS, easy-to-implement power supply.

I did not bother to build it, ( 'am more interested in optimized two stage amps ), but ..... I would be happy to post my schematics IF anyone is interested and / or thinking of doing a 26-26-45 amp. I believe it is a solid design.

One day, later in the year, I hope to drive to St. Louis ( 225 miles one way ) and visit Willie, so we can A-B our various DIY amps on his MLTLs, and have some FUN !!

Jeff Medwin

 

RE: The last 26-26 DC 45 amp schematic ...., posted on January 24, 2015 at 09:33:40
Frihed89
Audiophile

Posts: 15703
Location: Copenhagen
Joined: March 21, 2005
 Somewhere in his thread, he mentioned better iron. I'm surprised you haven't suggested Magnequest OPTs.

 

RE: The last 26-26 DC 45 amp schematic ...., posted on January 24, 2015 at 10:13:01
drlowmu
Manufacturer

Posts: 9730
Location: East of Kansas City
Joined: January 10, 2005
 Yeah, I'd use my M.Q. DS-050s, ( and "rob" my 1/2 12AT7 - 6AQ5 triode connected DC two stage amp ), ... which I am unwilling to do !!

Output iron is not that big of a deal-breaker here IMHO, but me getting RID of the amp's one cap couple, is what "I" honed-in-on doing in December.

Jeff Medwin

 

The P.T. I used was from......, posted on January 24, 2015 at 13:50:17
drummerwill
Audiophile

Posts: 965
Location: St Louis Mo.
Joined: January 7, 2003

Antique Electronic Supply . They list it as Hammond P-T274BX..
It sells for about $90.00.

Willie

 

RE: The P.T. I used was from......, posted on January 24, 2015 at 14:13:02
kyle
Audiophile

Posts: 1839
Location: London Ontario
Joined: September 29, 1999
 As I mentioned, I have the same transformer as yours, labeled 175mA. Mine is about 10 years old. For those buying a new one, apparently it is rated at 201mA now as per the link in my previous post.
Just in case someone questioned the numbers posted versus those published.

 

RE: The last 26-26 DC 45 amp schematic ...., posted on January 24, 2015 at 18:14:24
Caucasian Blackplate
Industry Professional

Posts: 8313
Location: Seattle
Joined: June 18, 2004
 9H of inductance won't get you much bass, which is clearly reflected in the specifications for the Hammond 125 series transformers.

 

RE: The last 26-26 DC 45 amp schematic ...., posted on January 24, 2015 at 20:46:17
drlowmu
Manufacturer

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

What the heck are you talking about? The discussion was on Hammond's "Classic 200-Series" power transformers. Was your post meant by you to be part of this thread?

Please explain or delete it, and I will do likewise. Thanks !

Jeff Medwin

 

RE: The last 26-26 DC 45 amp schematic ...., posted on January 24, 2015 at 21:20:20
Caucasian Blackplate
Industry Professional

Posts: 8313
Location: Seattle
Joined: June 18, 2004
 You said output iron wasn't a deal breaker
..

 

RE: The last 26-26 DC 45 amp schematic ...., posted on January 24, 2015 at 23:10:41
drlowmu
Manufacturer

Posts: 9730
Location: East of Kansas City
Joined: January 10, 2005
 Ohh, OK, it isn't !!

I could build an amp and, (as my friend Dennis Fraker likes to say), put a doorbell transformer on it, and it can outperform 95% of the tube amps out there.

Outrageous?? Not really. Do you know how to do that ?? You may !!

Jeff Medwin

 

RE: The last 26-26 DC 45 amp schematic ...., posted on January 25, 2015 at 01:36:23
rage
Audiophile

Posts: 793
Joined: December 17, 2010
 maybe you can jeff... but in that same amp if you replace the doorbell transformers with hammond or mq iron it will be significantly better.

really though.. I think the doorbell transformer thing is a myth.. and I briefly scrounged for doorbell transformers after reading that line in the past too....

what core material do you suppose they use on those doorbell transformers? suppose they interleave the coil for good doorbell frequency response?

would the doorbell transformer need new leadouts?

is it possible that those doorbell transformers, with their super charged leadouts... could they possibly have an effect similiar to that which you've mentioned of octal pins? that is, an added solder joint vs a noval socket? solder joints add up!

 

RE: The last 26-26 DC 45 amp schematic ...., posted on January 25, 2015 at 02:39:56
Al Noakes
 A doorbell transformer , if it's an EI transformer will have a split bobbin and no airgap . Hence distorted bass and no top-end . If it's a toroid , it will have no airgap and play ok in the HF but have distorted bass unless cap-coupled . Add a choke for the anode load , plus a cap and the costs go above what you'd pay for a basic output transformer . You could scrimp and use a cheap PSU choke as anode choke and a line matching transformer but this is purely an acedemic excercise in attempting to save money rather than build something decent-sounding , especially when there are those inexpensive Edcor transformers out there .

Al

 

Here's a 26 ) 4P1L alternative input, posted on January 25, 2015 at 03:09:26
andy evans
Audiophile

Posts: 4382
Joined: October 20, 2000



Just for a comparison, here's an input section I tried previously. Sounded good! I always use interstages and filament bias - no coupling caps or cathode bypass caps. I discarded the 26 front end when I swapped to PSE 4P1L finals since I didn't need the gain any more. 4P1L has a mu of around 10. 4P1L is a more dynamic driver with better treble than 26 - it was a clear improvement to me.

 

RE: The last 26-26 DC 45 amp schematic ...., posted on January 25, 2015 at 05:57:16
GEO
Audiophile

Posts: 4749
Joined: April 7, 2000
Contributor
  Since: September 9, 2000
 Here we go again.

 

RE: The last 26-26 DC 45 amp schematic ...., posted on January 25, 2015 at 08:01:16
drlowmu
Manufacturer

Posts: 9730
Location: East of Kansas City
Joined: January 10, 2005
 Well said. Awfully "straight" and thoughtful answer Al, loved it !! I just like to rile the conventional-thinking audio guys up some, every now and then, helps me maintain my image and lack of credibility, gotta remain consistent, otherwise its no FUN !! :-)

Jeff Medwin

 

RE: Here's a 26 ) 4P1L alternative input, posted on January 25, 2015 at 08:20:43
drlowmu
Manufacturer

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

I compute 3.39 Watts 4P1L anode dissipation on a 7.5 Watt plate. I like that for long term stability, IF I figured it correctly. Nice.

What would happen if one gave the Type 26 a grid to ground choke, as Willie does, ( rather than 100K to ground ) and direct coupled it into the second ( 4P1L ) stage with three runs of 19 AWG silver wire ?? What about your use of a 390 Ohm grid stopper, necessary ??, many go direct-in !!

Just thinking out loud.

Jeff Medwin

 

RE: Here's a 26 ) 4P1L alternative input, posted on January 25, 2015 at 09:32:41
andy evans
Audiophile

Posts: 4382
Joined: October 20, 2000
 I've got nothing against grid chokes. And the grid stopper could be omitted if you don't have any stabillity issues. I just put it in for security.

If you direct couple to the 4P1L you then need to ditch the filament bias and use a bypassed cathode resistor. Yes, for sure it's one way of doing it, but I just don't like cathode bypass caps. With my 4P1L>PSE 4P1L amp I just have 2 stages, so I don't have a 26 stage to couple, so that eliminated the issue completely. It sounded cleaner with 2 stages for sure, and I really like 4P1Ls as outputs. You're a bit stuck with the 45 since you don't have the 4P1L's mu of 10, hence the need for 3 stages.

 

Rk Bypassing , posted on January 25, 2015 at 10:06:40
drlowmu
Manufacturer

Posts: 9730
Location: East of Kansas City
Joined: January 10, 2005
 I understand your comments on Rk bypasssing. Dennis Fraker is the only person ( I have seen ) who really can do that well, and he KNOWS how to do it. Its been in every one of his Serious Stereo amps, since 1989. It takes thousands of dollars to do properly, so most DIYers never attempt it !!

It requires a main Rk film cap, of a not too large value, and then, a large number of additional smaller value caps, only of the highest quality AND importantly - the correct specific uF values, to optimally execute a bypassed Rk.

Its been very much FUN ( for me ) to hear the result, when its properly
done !!

One other thing I fully concur with you on, a two stage amp, well done, will ALWAYS be better-sounding, more transparent sounding, than ANY three stage amp !! Do that !!

Jeff Medwin

 

Troll, posted on January 25, 2015 at 10:27:35
Caucasian Blackplate
Industry Professional

Posts: 8313
Location: Seattle
Joined: June 18, 2004

nt

 

RE: Rk Bypassing , posted on January 25, 2015 at 13:51:33
Frihed89
Audiophile

Posts: 15703
Location: Copenhagen
Joined: March 21, 2005
 Wait a second, doesn't Andy's amp have less stuff in the way of the audio signal than the SS 2A3? And i thought that was the whole rationale of DC amps.

 

RE: Rk Bypassing , posted on January 25, 2015 at 17:58:51
drlowmu
Manufacturer

Posts: 9730
Location: East of Kansas City
Joined: January 10, 2005
 Heck no, Andy is going through iron ( interstage transformers ) in SERIES with the signal, whereas we direct couple one tube to the other with 3 pieces of 19 AWG finely-made silver.

One could say, in a SE amp, every part is in the audio signal.

Now, for Rk bypasses, THAT does take a LOT of parts to do it best, going from the top of the Rk, to ground !!! Those highest quality, expensive parts are MIA in your DC amps BTW. Foremost, the amps' designers never knew how to work with them!! But done right, I can tell you, they are essential to include, I LOVE them and what they do. Only DF, to my knowledge, knows to do this, and he executes it first-class in every piece he puts out. YOU can't judge that with one RMAF visit, where we are not always set up well. It took multiple venues and set ups for me to listen and figure this all out. But I am very very SURE of what he builds, and how it plays.

The most recent news is that Dennis' latest amps, he has four built, building four more, are totally unequaled with anything he, or anyone else for that matter, has done to-date in tube audio design. They are simply ...wonderful . Drummerwill, Corona Dope, and I got a "taste" a "preview" of this with RMAF 2013 on Sunday morning, before tear down. Blew us good listeners away, and ... it is certainly well beyond that, right now.

Some of this, I am hoping, will fall into my hands, with my home amps. Hell, I have ALL THREE of my DC two stage amps torn down presently, waiting for my rebuilds with latest ideas and parts !! Progress is being made. If I can come within 50-60% of what DF builds today, I will be a very happy camper.

There is the very latest in audio news, sir !! Capish??

Jeff Medwin

 

RE: The last 26-26 DC 45 amp schematic ....Curious !, posted on January 25, 2015 at 20:25:16
drummerwill
Audiophile

Posts: 965
Location: St Louis Mo.
Joined: January 7, 2003

Just curious C.B. Have you ever used a Hammond 125ESE ?


Willie

 

RE: Rk Bypassing , posted on January 25, 2015 at 21:46:45
cpotl
Audiophile

Posts: 1002
Location: Texas
Joined: December 6, 2009
 "If I can come within 50-60% of what DF builds today, I will be a very happy camper."

Please, so many of us are sick to death of hearing about what your idol DF has been doing, and how wonderful his amplifiers are. Can't you just give it a break? He's just an average chap, making average quality home brewed amplifiers.



 

RE: Rk Bypassing , posted on January 25, 2015 at 22:48:27
tube wrangler
Manufacturer

Posts: 2484
Location: USA
Joined: January 29, 2007
 A word or a few of explanation seems necessary here, Jeff.

RMAF 2013 was after the Pine Creek forest fire out here, which wiped-out my shops, all amps, and parts.

Since I had no amps of any kind-- even to listen to-- a friend loaned me a pair of amps that I had delivered in 2006. Berkeley Audio Designs fixed me up with a new Alpha-DAC2 with their USB link. (NO!-- I wasn't interested in anything else!). My music server P.C., which had been built for me in Virginia (Command Performance) was saved because the guy had had it there for a week! I got lucky there....

I quickly borrowed from him the Triple 12V. power supply that I build for P.C.s to make them come alive. I got it, photographed it's insides, and sent it right back. This saved a lot of time, as all my papers were gone.

I had that, and a Panasonic Plasma T.V. I got at Costco with an equipment rack. I quickly ordered (from a guy on E-Bay) a Pioneer BDP09-FD Blu-Ray player, knowing that the SPDIF on this 30 pound (strong, stable transport) baby could deliver good sound thru the Alpha-DAC2, and it did!

Sooo--- RMAF 2013 was the year I decided to do Blu-Ray-- since I had this rig! I Played The Eagle's farewell Tour-- Melbourne, Australia. This is GREAT audio!

Did audiophiles and reviewers applaud this departure into Blu-Ray? I think not.....!

Was this setup ideal? Hmmmmm!! BUT-- I, and I think quite a few others had a great time! I remember watching Joe Walsh and wishing we were serving Beer.... WHAT a GREAT voice! Hey! Blu-Ray is good! Don't knock a medium-resolution source with a great band that has good equipment....

Since I had no amps or shops, everything is all-new, and so are the latest amps. I got the opportunity to change anything I wanted to, and to buy any parts I thought were superior... They ARE!

The 2006 amps went back to their owner. I spent a couple thousand bucks on them, and charged nothing. I was already doing new engineering, so I just did it--- and really appreciated that he got me thru RMAF 2013...

The man called up and was deliriously happy, but so was I! I had gotten to use his amps while I engineered new stuff!

Well, you haven't heard the new stuff. Few people have yet. I hope to do RMAF 2015. Maybe.... we'll see.

---Dennis---

 

How Rude of you, posted on January 26, 2015 at 00:28:40
smart845
Audiophile

Posts: 668
Location: East london
Joined: May 24, 2000
 There are a few of us who appreciate every comment and every scrap of wisdom that Jeff brings to the forum and those of Dennis too.

Jeff has mentored me in building my own amp and now have what I consider a stunning amp with breathtaking sound. I admit it may only reach 50% of what a SS amp achieves but I'm having great fun building and listening to this amp.

It does cost money and that is perhaps why many DIY builders do not attempt it. With hindsight it may have been easier and cheaper just to purchase a SS amp but I wouldn't have gotten the pleasure of building and learning.

I'm trying to get others here in London to listen to my amp so they have an accurate opinion of its attributes but so far no takers.
All I ask of a forum and its members is courtesy and manners.
Is that too much to ask.

Smart

 

Don't say that, posted on January 26, 2015 at 01:36:10
Frihed89
Audiophile

Posts: 15703
Location: Copenhagen
Joined: March 21, 2005
 "I admit it may only reach 50% of what a SS amp achieves but I'm having great fun building and listening to this amp."

We need to stick together!

Actually, though, I fear you are right, although I would say "some SS amps". However, I am taking cold showers and using other monastic remedies to rid myself of any such thoughts. But my experiences with a small number of SS systems are hard to drive out of my mind.



 

RE: Don't say that, posted on January 26, 2015 at 07:37:28
drlowmu
Manufacturer

Posts: 9730
Location: East of Kansas City
Joined: January 10, 2005
 I have known Dennis for three decades plus. I know the man.

The way he is talking to me about his newest builds, I am pretty darn sure they will be a total sonic treat for people to hear !!!

This is a wonderful development, IMHO.

( As a personal note : It also calms me, when I think ALL THREE of my two stage DC SE amps are ripped apart, waiting for my copy-cat parts and wiring upgrades. )

Have a great day !!

Jeff Medwin

 

RE: How Rude of you, posted on January 26, 2015 at 11:41:42
LinuxGuru
Audiophile

Posts: 582
Location: European Union
Joined: November 11, 2008
 > Jeff has mentored me in building my own amp and now have what I
> consider a stunning amp with breathtaking sound.

We are glad you are happy with your build.

> All I ask of a forum and its members is courtesy and manners.
> Is that too much to ask.

Not much. But how about other forum members who don't appreciate let's say politely - engineering not based upon laws of physics, which have been propagated through 8500+ posts, with the addition of 1500 long and meaningless messages from his "teacher"???
Do these man have anything else to do apart from flooding forums???

 

RE: The last 26-26 DC 45 amp schematic ...., posted on January 26, 2015 at 16:51:54
deafbykhorns
Audiophile

Posts: 1067
Location: Florida
Joined: October 17, 2003
 I was beginning to think this was going to be a constructive discussion until I scrolled down some.....

 

RE: How Rude of you, posted on January 26, 2015 at 18:30:34
GEO
Audiophile

Posts: 4749
Joined: April 7, 2000
Contributor
  Since: September 9, 2000
 Their wives and kids must be proud of them

 

RE: Don't say that, posted on January 26, 2015 at 18:32:57
GEO
Audiophile

Posts: 4749
Joined: April 7, 2000
Contributor
  Since: September 9, 2000
 What hobbies do your wife and kids have?

 

RE: The last 26-26 DC 45 amp schematic ....Curious !, posted on January 26, 2015 at 19:40:52
Caucasian Blackplate
Industry Professional

Posts: 8313
Location: Seattle
Joined: June 18, 2004
 Yes, I used them in some bread board circuits some years ago, but ended up getting rid of them on eBay in the end.

Don't get me wrong, if you don't care about bass and just want to experiment, they work well!

 

RE: The last 26-26 DC 45 amp schematic ....Curious !, posted on January 26, 2015 at 21:14:20
drummerwill
Audiophile

Posts: 965
Location: St Louis Mo.
Joined: January 7, 2003

My experience with the new version of the 125ESE has been totally different.

First off the new 125ESE are almost twice the size of the originals they can actually handle 15 watts..

On my GPA 604's there's plenty of bass. ( Due to reworked Xover and Wiring).

All that, and just as you said " to experiment, they work well".
I just don't want anyone to write them off as not "hifi" enough to listen to.

Willie


 

RE: The last 26-26 DC 45 amp schematic ....Curious !, posted on January 27, 2015 at 18:45:50
Caucasian Blackplate
Industry Professional

Posts: 8313
Location: Seattle
Joined: June 18, 2004
 If you rework your speakers to complement an output transformer with sub-par inductance, that will help mask the issue, but it will make other amplifiers with better iron sound bass heavy.

 

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