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In Reply to: RE: +1 posted by smart845 on October 28, 2014 at 14:31:42
Look at the 6SF5 in the Schematic below of a direct coupled 6B4G monoblock. This same circuit type will, and does in practice, work well for the 45 tube, as well.See the discussion on AA at: http://www.audioasylum.com/cgi/t.mpl?f=tubediy&m=230346
This circuit (with different values) is essentially = a Fi Audio 2A3 Monoblock.
They are worth waiting for. In the meantime, so pretty good budget-type 45 amps do pop up for sale on AA and Audiogon.
Observe, before you think. Think before you open your yap. Act on the basis of experience.
Edits: 10/28/14Follow Ups:
That is the 1947 Lipman-Robin amp. A 6SF5 is like a 6F5, with a mu of 100, which is also much like a 12AX7. or, more correctly, half of a 12AX7. The $2.00 ( in 1947 ) Lipman-Robin book entitled " Practical Amplifier Designs" and subtitled "45 Proven Circuits for the Technician and Experimentor", describes this circuit you show us, and has a parts list. If anyone wants this data, contact me.
In Japan in the 1960s, 1970s, people like Isamu Asano had "their" versions of the same Lipman-Robin amp, as did Nobu Shishido who unfortunately, paralleled both sections of the 12AX7, an inherently inferior approach. ( Skews the music on a mu of 100 tube ). Maybe we didn't really get Nobu's "best" DC circuit, just "one published for the public " ??
Readers should realize, a indirectly heated mu of 100-DHT finals amp of this type, ( two stage and DC coupled )done properly, is about as good as it gets on efficient speakers.
Andy Evans in the UK has a small listening area and does NOT use efficient speakers, so, he builds "current" amps for his ten inch 92 dB (?) driver, not voltage-swinging amps.
Also, most experienced people I have met in audio, and on this Forum, do not know how to effectively bypass an Rk!! Dennis Fraker knows how !!
On efficient speakers, Andy's double 4P1L amp will get eaten by any well made 1/2 12AX7-DHT Finals amp. The low overall gain of Andy's amp, will make the efficient speaker play "dead and lifeless" at lower listening levels, no fun, and the amp will only come somewhat alive when pushed hard. Remember, its a current amp, not a voltage-swinging amp. Now on Andy's less efficient speakers, its hard to say if the opposite would occur.
Poor Andy, has never had the pleasure of hearing a recent pair of Serious Stereo amps, with a INdirectly heated mu of 100 input tube, and a 2A3 output tube. The Serious Stereo amp, particularly recent production, that only Dennis Fraker properly pulls off, is still my favorite for efficient speakers ( 98 dB and above ) in THIS world.
Have fun,
Jeff Medwin
Andy Evans in the UK has a small listening area and does NOT use efficient speakers, so, he builds "current" amps for his ten inch 92 dB (?) driver, not voltage-swinging amps. > >Explain how a 300b amp is a voltage amp and a 4P1L PSE is a current amp?
On efficient speakers, Andy's double 4P1L amp will get eaten by any well made 1/2 12AX7-DHT Finals amp.> >
This is pure sales talk with no evidential evidence of any kind. Does your amp also cure warts and improve one's golf swing?
The low overall gain of Andy's amp, will make the efficient speaker play "dead and lifeless" at lower listening levels, no fun, and the amp will only come somewhat alive when pushed hard.> >
Well, you see the problem here is that I'm a professional musician and I don't listen "for fun". I require micro detail in orchestral parts and I also require very accurate timbre when reproducing acoustic instruments. You may not need the elements that musicians require for their critical listening.
Poor Andy, has never had the pleasure of hearing a recent pair of Serious Stereo amps> >
My God! How have I lived until now!! Boo hoo...... I've built about 25 amplifiers, mostly with DHT finals, and not one of them a Serious Stereo amp...... The world must be doomed because I imagine 99.999999999999999999999999999% of the global population are as bereft as I am. Should we talk to the United Nations about this situation.................?
Well, I'm probably exaggerating if I call a 12ax7 a guitar tube (it does sound very nice in my stage amp) and if I think that perfecting a cathode bypass cap is like gold plating toilet paper. It probably comes from too many years playing jazz and watching arty French films. But this is only a tube forum and we're all having fun.
Edits: 10/30/14
No good explaining the finer points of listening to music to JM, he's strictly a compressor/effects box man. He thinks only what DF has told him to think. Timbre is what he uses to make speaker boxes.
The usual Ray Moth troll. You are retired, old, do not build anything, living in Indonesia, and have nothing else to do. Got it !! Under that even British exterior is a mighty nasty man.
Jeff Medwin
Nasty I may be but I'm no troll and I'm younger than you. In any case, age discrimination is not PC.
Replete with Rod Colman regulators and interstage transformers: $6,000.
Observe, before you think. Think before you open your yap. Act on the basis of experience.
I published my circuit on DIY Audio about 18 months ago - I've been using it that long. This is exactly my amp as far as I can see - Rod Coleman regs, all stages in filament bias, Lundahl interstage, damper diode rectification, CLCLC, etc etc. It's identical as far as I can see.Wow! Look at the price. Yikes.
But it is THAT good. There you go.
I know the guy who built it - we've been corresponding.
Actually I have three of my amps.....
Edits: 11/02/14 11/02/14
he didn't credit you with the design then? That's not cricket.
Wish I could hear one of these things.
Big J
"... only a very few individuals understand as yet that personal salvation is a contradiction in terms."
It sold quickly.
Observe, before you think. Think before you open your yap. Act on the basis of experience.
What in the world is the inference that DC on a DHT is advantageous??
Its a distinctly non-linear situation, one end the filament is at, say, 6.3 VDC and the other end is a zero VDC.
AC is superior, but it has to implemented well. At least there is an equal sine wave going across the entire filament. It bucks and boost equally across the entire filament.
With high sensitivity speakers, and good amps, we can tell what honors the music.
I have gone to making custom "balanced" filament transformers for AC operation of filaments, where DCRs, inductance, and capacitances are equal. My friends seem to like this, in comparion, say, to ordering a Hammond 2.5 VCT at 2.5 Ampere power trannie for a 2A3 filament.
Balanced AC is the wave of the future in high end tube amplifier DHT audio design. My friend Dennis Fraker taught me much of this, he knows !!
Jeff Medwin
You forget that most of us use the 4P1L in filament bias - it's a special application for which the 4P1L is exceptionally well suited. So Rod Coleman regs, chokes in the DC filament supply etc etc.
It's an entirely different application - different rules apply.
> > > Its a distinctly non-linear situation, one end the filament is at, say, 6.3 VDC and the other end is a zero VDC. < < < <
What is the relevance in practical terms?
> > > AC is superior, but it has to implemented well. At least there is an equal sine wave going across the entire filament. It bucks and boost equally across the entire filament. < < <
and
> > > I have gone to making custom "balanced" filament transformers for AC operation of filaments, where DCRs, inductance, and capacitances are equal. < < <
You know my views on this. The method you propose is limited by the tube's internal construction; I doubt it could null effectively enough for me. I like AC on the filaments, but would still want as low noise as possible. I'd also want the windings of the filament transformer out of the signal path... I thought you might also with your talk of short signal paths, direct coupling, wire quality....
Just a couple of thoughts.
Cheers,
Ray
"In the beginner's mind there are many possibilities, in the expert's mind there are few." Shunryo Suzuki
Ray, can you help me understand this please?
For a 2.5 volt tube with AC, one end is at 3.525 volts and the other is at zero WRT the grid. Then, 1/2 cycle later, one end is at zero and the other is at 3.525 volts. Rinse and repeat!
How is that better than one end at 2.5vdc and the other at zero?
Thanks.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Don't know Tre. I was not meaning to give the impression AC was better than DC.
The points I was trying to make were that I do like AC but there are better ways of doing it than using a CT transformer, alone, to do it.
Cheers,
Ray
"In the beginner's mind there are many possibilities, in the expert's mind there are few." Shunryo Suzuki
Use a v4 tube from EML that has the centre tap of the filament connected to a fifth pin. This means the transformer windings are out of the music signal by not using the centre tap.
I should be doing this mod to my amp soon, just a change to an octal socket, so I'll report back.
Cheers
... tap pin guaranteed to be precisely at centre? If yes, great. I look forward to seeing the noise measurements.
Cheers,
Ray
"In the beginner's mind there are many possibilities, in the expert's mind there are few." Shunryo Suzuki
The DHT Ef XFR needs to be redesigned.Ray, the Ef XFR on a DHT is IN the circuit!
Barry, your solution overlooks the Ef XRF when using conventional DHTs me thinks, which needs to be optimized.
Up until a few years ago, "everyone" ordered a Hammond Ef XFR, with crummy lead outs and willy-nilly winding techniques applied to it. Not good enough at all.
The DHT Ef XFR, Dennis Fraker told me, needs to be balanced and equal in terms of its capacitance, inductance, and DCR, and the three seconadary leads need to be audio-optimized !! A double C core would do this, I did mine on a conventional E-I core.
Around 2010, I had the first ( I think ) Ef XFR of this type wound on a custom basis for my AVVT AV32B SE DC amp prototype. We have, since then, made up some custom units for DowdyLama's builds. Jim has taken the time to A-B this new design, and now, that is ALL he will use . YMMV.
I intend to do a small production run for 2A3 tubes in the weeks ahead, maybe we need to do two for your amp Smart 845, custom for your TYPE 45 ?
Jeff Medwin
Edits: 11/02/14 11/02/14 11/02/14 11/02/14
Are these transformers going to have a 240V primary ? If not then why are you recommending he uses these ? Better off getting him to source some locally with M6 cores and a single winding for the his centre tapped filament valves
Al
Anyone local that would do a pair for me.
Sowter perhaps?
Yes, no centre tap required.
Cheers
You would be very wise to have a center tap, and not tie your thousands of dollars in parts amp to ONE tube !! Let it run ANY Type 45 possible.
Anyone can wind a center tapped filament trannie Barry, anyone. The point , which you and Al seem to neglect, is , that I have them designed as BALANCED as far as inductance, capacitance, and DCR .
Now that was never done, to my knowledge, till I did it with Dennis several years ago, and it is THE correct approach to implement AC heating of a DHT Barry. Kills the Hammond Center tap EF filament trannies, according to users who have A-Bed this.
Cheers.
Jeff Medwin
"The point , which you and Al seem to neglect, is , that I have them designed as BALANCED as far as inductance, capacitance, and DCR ."
Really?
Yes, as written, really. Open your mind.Would a double C core do that Gusser, Mr. E.E. ? Could a EI core in two sections do that ?
Think about it, a center tapped Ef XFR possessing equally balanced C, DCR, and L.
BTW, I overstated, I was told yesterday it is only "subtle" improvement sonically, but the poster was certainly thankful for the improvement, it is the ONLY way he will energize a DHT filament - going forward, in "his" amps.
Dennis Fraker is currently working on a new "super" approach, with Mike LeFevre
Jeff Medwin
Edits: 11/07/14 11/07/14 11/07/14
You have not demonstrated the electrical engineering, mathematics, and physics background required to accomplish such a task.Perhaps you specified your requirements to a competent transformer winder but I hardly think you could even design a door bell transformer from the ground up.
Edits: 11/07/14
I am listed on AA as (M) a Manufacturer.
Actually, for the last six years, I have been designing and making available purposefully-designed audio-centric "iron" under the name AMA or Audio Magnetics America.
I provide custom magnetic designs for myself and my friends, and don't do much at all to market my services to the general public.
Jeff Medwin
So what ? What you suggest sounds like bifilar wound . Not necessary with a centre-tapped filament .
Al
Yes , I have a winder who does my volume runs of iron . I can get you a pair wound if you like
Al
Hello Al,
That is very kind of you to recommend your winder and I surely would like to take up your offer of a pair.
Please mail me offline and I'll arrange payment and specs.
Look forward to chatting
Smart
To be honest with you , a ColemanReg will probably be a more worthwhile solution for your filaments . I think you should try this before investing in those centre-tapped EML 45 .
Al
He does not need a redesign . All he needs to do is move the cathode connection to the centre-tap of the valve .
Al
Right Al, but only if you think of the amp being WEDDED to one tube.
Also, I think it certainly would not hurt the amp if the DHT was driven from a totally balanced Ef XFR with high quality wire leads.
Little things, attention to details, add up. You and Andy ought to visit him in London.
Jeff Medwin
If you have a centre-tapped filament , why go to the trouble of a filament transformer with a balanced centre-tap ? No need for it , the centre tap won't be used .
Al
.
"In the beginner's mind there are many possibilities, in the expert's mind there are few." Shunryo Suzuki
"My God! How have I lived until now!! Boo hoo...... I've built about 25 amplifiers, mostly with DHT finals, and not one of them a Serious Stereo amp...... The world must be doomed because I imagine 99.999999999999999999999999999% of the global population are as bereft as I am. Should we talk to the United Nations about this situation.................?"
Only DF has built or can build a proper Serious Stereo SE 7B4 DC 2A3 ultra-fi mono amp.
And not everyone can count DF as a close personal friend like drlowmu, who has seen/heard the entire Serious Stereo audio system many times.
The rest of us have a few options: go to RMAF or call DF and drive/fly out to his Montana audio lab for an audition.
Or try to cobble together some approximation of the bespoke amplifiers with guidance from the doctor or DF, but it would probably not be the same experience.
In your case, perhaps trying out a more high efficiency speaker and upgraded wirings would be a better fit for the low power SE tube amp you are building.
Chill out, I was not attacking you. I will answer this point by point when I have more time !!!
Cheers,
Jeff Medwin
> Chill out, I was not attacking you. I will answer this point by point when I have more time !!! >Hi Jeff,
I am chilled. And don't make fun of my paranoia - I have to live with it.
We're just doing entirely different things with the topology. It's perfectly good to direct couple - you're ahead of me there because I don't. But if the result is using a cathode bypass cap then I don't, so I'm ahead of you there. Swings and roundabouts. You could see it either way.
I've tried 12ax7 into 300b and I didn't like the input section much, so I'm happier with 4P1L into 4P1L. It's kind of swings and roundabouts again. The 300b or 2a3 is on paper and in theory a better output tube, so are 10Y and 46 for that matter. So theoretically a better solution, but add a cathode bypass cap and they are no better than a couple of 4P1Ls in filament bias - I know this because I've made plenty of 2a3 and 300b amps and compared them with 4P1L in filament bias. What you get, though, with 4P1L outputs (higher gain) is a 2 stage amp which allows you to use a 4P1L as the input tube, so that's where the advantage in sound quality is.
It would be interesting to make a direct coupled 4P1L> 4P1L PSE amp. I'm not building much these days, happy with what I have. I'm sure your amp sounds fine, but I doubt it sounds any better than mine - just different. And bear in mind we hear amps differently - you're a flamboyant kind of guy who likes dynamics, I'm a careful kind of guy who's obsessive about the timbre of acoustic instruments.
Edits: 10/30/14
Andy,Here is what I would like to say herein, much learned from Fraker, but I pretty much agree.
(1) The best tube amp will be about two Watts .
(2) It will be two stages ONLY !! ( Always more "transparent" than ANY three stage amp ) .
(3) It will be direct coupled. ( just three runs of 19 AWG silver, under 3.5 inches ).
(4) It will be used ( and developed ) on speakers which are 98 dB sensitive, or higher. ONLY such a sensitive speaker will allow the designer to hear all he or she needs to hear - to properly design .
A less sensitive speaker will be TOTALLY ABSENT what needs to be heard to obtain perfection : things such as hearing and eliminating skews in the music, or ghosts as to where you return a ground wire on a buss.
You can NOT design SOTA tube amps ( which IS a two Watt DC amp ) unless you use a sensitive speaker. This kinda leaves you out Andy Evans, with your 92 dB ten inch Alpair speaker. Many other people too. Thats OK !!
(5) Loudspeakers under 98 dB, and requiring more than two Watts, will sound best with highest-quality Solid State amplifiers, and NOT inexpensive ones.
ANY tube amp used with lower efficiency speakers ( under 98 dB ) will get totally TRASHED, performance-wise, by the latest and best solid state amps from MBL in Germany, or Boulder, and Spectral in the USA, easily. Get out yer wallet. Wake up !!
(6) The best two stage tube amps will have a UNregulated output stage, and a simple but well-regulated front end stage. Additionally, it will operate best off of a single power transformer, which one easily hears on a two stage DC amp, and 98 dB plus speakers, as being superior to separate supplies.
I have not heard Barry Black's Avantgard Horn system, but he is only 30 minutes from you in London. I helped him a bit in 2013 - to do his first ever tube amp build, which fits the above criteria. Why not take him up on his invite. Let ME know how it goes !!! Maybe you can shlep your amp over !! Make a new friend, hes a great guy.
Your guessing on "dynamics versus timbre" is that, a guess and somewhat of a reach .
I just want it to be totally honest, and it to ALL be there !! So do you.
I am not attacking you, just setting the record straight on tubes, speakers, and tube amps !! Believe me, I spent decades doing none of the above ( 1 through 6 ) with tube amps !! Now, I know !! Live and learn.
Jeff Medwin
Edits: 10/31/14
(1) The best tube amp will be about two Watts .The best tube amp is what's required for the purpose. If it's driving Apogee full-range ribbons - the best speakers I've ever heard by a long way - it will be at least 25 watts. You're restricting your choice of speakers to suit your amp. I'm not - I'm matching the amp to the speakers because loudspeakers make the biggest difference to the overall sound. I use one full-range unit, Alpair 10 88db, because I have a small room and a small footprint is required, but in a bigger room I'd have Apogees (I used to have Caliper Sigs).
(2) It will be two stages ONLY !! ( Always more "transparent" than ANY three stage amp ) .
That's a good design goal - agree where this is possible for the loudspeaker.
(3) It will be direct coupled.
Yes where possible, but if this means cathode bypass caps that will degrade the sound. I haven't heard Dennis's cocktail but I tried several combinations of polypropylene/teflon/paper and nothing satisfied me. I'm very dubious that this can be done and only have your word for it which means for me it's unproved.
(4) It will be used ( and developed ) on speakers which are 98 dB sensitive, or higher. ONLY such a sensitive speaker will allow the designer to hear all he or she needs to hear - to properly design .
Well you said it - your amp only works into sensitive speakers. I wouldn't design amps with such a restriction.
4a) A less sensitive speaker will be TOTALLY ABSENT what needs to be heard to obtain perfection.
Rubbish, I'm afraid. As said, we listen for different things. You require dynamics, I require micro detail and the closest approach to the timbre of acoustic instruments. Full range ribbon speakers are the most "perfect" approach to this because the thin and large membrane is the most responsive transducer for timbre and micro details. Full range piston speakers are a stand-in and some are very good, but full range ribbon they ain't nor ever gonna be.
(5) Loudspeakers under 98 dB, and requiring more than two Watts, will sound best with highest-quality Solid State amplifiers, and NOT inexpensive ones.
Again rubbish, I'm afraid. My brother's Apogees sound hugely more musical with a Nagra 845 tube amp than with his big and expensive Krell. Same with many friends with Apogee Duettas, Maggies, electrostatics and so on. You just have to make a bigger tube amp - 845 outputs or the like. Perfectly easy. You just aren't set up for this so you've deliberately left it out of the picture.
(6) The best two stage tube amps will have a UNregulated output stage, and a simple but well-regulated front end stage. Additionally, it will operate best off of a single power transformer.
This happens to be true in my case.
Bear in mind your whole theory above only applies to a small tube amp driving high sensitivity speakers. You've maxed out that particular combination as you see it and using your circuit. I'm unwilling to restrict myself to such a narrow design area. I like to see the big picture in life.
Basically you're saying "do what I do - it's the only way because it works for me".
But this is dangerously close to "be me - it works for me so it'll work for you".
This rather neglects the actual situation that there are 7.125 billion people in the world, all with different realities.
Edits: 11/01/14
Speakers are not the problem, turkey amps are !! Amps are the weakest link, always have been. Almost all amps are dishonest.I never mentioned to use KRELL, did I? Nope.
MBL, Boulder, or Spectral, will easily TRASH any 845 amp on that Apogee speaker load. Of course, the MBL may cost $400-500K plus for a pair of Mono Blocks, so you may not be familiar with them. Boulder and Spectral are more reasonable.
I have had my fair share of ESL, panel, flat transducer speakers over the years, "danced the dance" and have no more interest in them now, what so ever. You may be on the same path as I took, and don't know it, and you won't know it - 'till twenty years from now Andy, and maybe never !!
I hear no mention of you listening to Barry's ("Smart 845" on AA) Type 45 DC amps on his Avantgards. It would likely be a good transformative experience for you in London, only thirty minutes away.
Cheers,
Jeff Medwin
Edits: 11/01/14 11/01/14
Those Alpair 10's look like a decent multimedia speaker, something to hook up to a computer and listen to background music while online.
Or a set of speakers for the bedroom or office.
I used to do the same thing with Optimus Pro LX5's and a variety of little SE console amps.
Of course, that would never be a hi to ultra-fi application or something you would see auditioned at RMAF or similar event.
Your and DF's endorsement of Altec horns or duplex speakers seems much more reasonable for the low power SE tube amp builders.
Those Alpair 10's look like a decent multimedia speaker. Of course, that would never be a hi to ultra-fi application> >
You audition loudspeakers by looking at photographs of them?
Be honest - you have no idea what they sound like.
DT should have never written that IMHO. I am sure you got a good ear Andy. Its just your mind we need to work on, a wee bit.
Jeff
I used to have single driver speakers for many years.
Fostex 208 Sigma's, the originals.
A much higher efficiency driver than the Alpair 10.
You could put the Fostex in OB's or backloaded horns and they still needed to be actively biamped with some bass reinforcement for full range applications.
A 6" full ranger of low efficiency will just be too limited in many areas with the kind of low power tube amps drlowmu and others are building.
There are enough videos online showing how guys are using the single alpair 10's.
I usually see SS power amps and subwoofers to augment the bass.
That is good for them, but not the direction I want to go in.
No offense to you intended.
Keep posting, I won't have to answer anything !!! :-)
NO ONE in this world, except what I have seen of Dennis Fraker's work, knows how to properly bypass an Rk, or a C for that matter.
If you knew how to do the Rk bypassing properly, then it opens up some mighty fine possibilities.
Maybe, when you get to be my age, you will learn enough. I went through a LOT of dead ends in my audio life, we all do.
In 2014, I feel AMPS are (still) the worse component in the chain, but I have a good idea as to what amplifier topology gets me closest to the music by now.
Best wishes,
Jeff
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