OT: Show us your DIY tube amps

[tomt]

How do ageing audiophiles maintain their powers of aural discrimination as their hearing degrades with age?

honestly,

i use caffeine.

There are hi-end audio reviewers who are no Spring-chickens.

aren't most over 50 now?

[Old Guy]

honestly,

i use caffeine.

By the gallon.

[analog addict]

The front end B+ has under 2 mVAC of ripple, and it operates with a KISS one-part shunt regulator with no feedback. There is a final L/C filter to the front end, sub 1 Ohm DCR for the L, with high quality DynamiCaps feeding the driver tube's anode resistor, with less than 1/4 of an inch of lead length between them.

Well, I was under the impression that less than 1 mV of ripple was the goal of a clean PS, especially with DHTs and low powered SE amps. The amp I posted about has about 100uV ripple on the 2A3 B+ and less than 4uV B+ ripple on the driver tubes.

[LowOhms]

well, i was under the impression that less than 1 mv of ripple was the goal of a clean ps, especially with dhts and low powered se amps. The amp i posted about has about 100uv ripple on the 2a3 b+ and less than 4uv b+ ripple on the driver tubes.

Message for Analog Addict

The power supply you designed for your 2A3 amp was a PERFECT example we can use.

I have attached (below) your PSUD ... and my original PSUDed supply filters.

You are "under the impression" that low ripple is the goal of a 2A3 amp B+ supply filter. Nothing could be further from the truth, I am sorry to say.

We have tested B+ ripple amounts on Altec speakers, and we have determined that 500 mVAC is absolutely NO problem with SE amplifiers, and even higher, up to 800 mVAC is tolerable ( tested on ALE drivers, very high efficiency ). Push Pull, over a volt of AC B+ ripple is OK.

The SE output transformer steps down the B+ ripple seen by the speaker by the square root of the primary, often 2,500 Ohms, to the square root of the secondary ( often 8 or 16 Ohms ). That is 50 to 4, or a 12.5 ratio reduction of ripple at the speaker terminals.

In the two attachments, I subjected both of our PSUDED supplies ( up to the Finals ) to a 15% current step test. In each case - increasing the load from an idle of 56 mA. to 65 mA.

Look at your filter.

It dropped 11.71 VDC in B+ with a 9 mA. current change. It took about 1,550 ( estimated by eyeball ) mS. to settle. The computed Z of your B+ filter is 11.71 VDC divided by .009 A. or 1,301 Ohms.

Look at my filter.

For the same increase, a 56 mA. to 65 mA. current step, my B+ dropped only 2.60 VDC and it took only 22 mS. to fully settle. The computed Z of my supply filter is 2.60 VDC divided by .009 A., or 288 Ohms.

TWO POINTS HERE:

(1) John Swenson, E.E. and DIYer, has shown us the importance of obtaining 50 mS. or less as a settle time. Your supply took 1,550 mS. or 70.45 times longer to settle, than mine, and missed 50 mS. by "a country mile."

(2) We are taught that it is good to have a source that is 1/10th the load to ideally drive the load.

The plate resistance of a 2A3 is about 750 Ohms as I recall.

So let me ask you a question, what power supply filter will better drive an 750 Ohm 2A3 plate ?? 1,301 Ohms or 288 Ohms ??

Neither are ideal, ( one to ten ) ... we need solid state rectifiers to get that.

Better that I ask, which TUBE RECTIFIED B+ filter will best supply a 2A3's plate, 1,301 Ohms or 288 Ohms???

As you see, my suggested B+ filter to the Finals implementation simulates and is 4.51 times "stiffer" than yours.

If you Analog Addict are at all serious about audio and audio design, simply write to me for the power supply compilation design notes. You (and most others) have never heard a 2A3 do what it can optimally do...I promise you that !!!

The 2A3 DHT tube is a "direct access to the music" (1) device. As such, it demands a great power supply for high performance.

Thank you, Analog Addict, for sharing and posting precisely as you did !! Your example was "perfect" in a positive way to contrast for you - and all others.

Cheers.

LowOhms

(1) Robert W. Fulton, phone conversation, 1982.

Tom T, ..... can I use your High Efficiency system to test-out one of my new amps?? You can be brutal, critical, but mostly honest about what you hear !!! ????????????? Fun to do.

[RonSSS]

I'm thinking AA meant 2mv or less ripple at the amps output terminals, not on the B+ supply itself.

Ron

[LowOhms]

I'm thinking AA meant 2mv or less ripple at the amps output terminals, not on the B+ supply itself.

Ron

Hi Ron,

Not at all, as far as I deduce, from AA's writing.

Notice below, AA uses BOTH the terms mV ( as in mVAC ) and also the term uV ( as in uVAC) in his post. Look :

"Well, I was under the impression that less than 1 mV of ripple was the goal of a clean PS, especially with DHTs and low powered SE amps. The amp I posted about has about 100uV ripple on the 2A3 B+ and less than 4uV B+ ripple on the driver tubes."

So Ron, AA has the supply to the Finals filtered as 100 uVAC, which is 0.1mVAC. He has 4/1000ths of 1 mVAC to the driver stage.

A uV is 1/1,000 of a single mVAC , is it not ?!!

In essence, AA has designed exclusively for abnormally low ripple, equating that in his mind with "audio goodness".

Today, some of us know low ripple comes at the horrific expense of other important music parameters that go missing, such as great bass, great dynamics, and PRAT.

AA's amp was not designed to retain the dynamics in music. It will have poor and out-of-time bass and sound like a woolen blanket has been thrown over the Altecs.

Most of you tell me that a SE low powered amp won't play loud and play with good bass and dynamics on Altecs. I say "baloney". Some of us KNOW how to do it today, and the amp (such as AA's) you directly experienced is just mis-designed and mis-made. Music is not steady state test tones, but rather an asymmetrical series of perturbations upon the power supply.

I'm not picking on AA or Zelgall, almost ALL the SE tube amps I hear, DIY and commercial, are mis-designed and I would grow bored listening to them within ten minutes or less.

I always keep in mind, when made properly, the low powered triode amp with no negative feedback loop becomes the holy grail for Altec type speakers !!!

Cheers.

LowOhms

[RonSSS]

Crap darn, I f'n forgot to post my resume.......
I do appreciate the education on basic electronics though.
Thanks!

Ron

[LowOhms]

Here is a very recent ( finished last week ) DIY triode amp, made by a long-time Altec 604 user from Saint Louis, Drummerwill :



The LP 845 amp: It took 4 months of planning..... - drummerwill - Tube DIY Asylum



It employs a 9 Ohm DCR power transformer !! and many sub-10 Ohm DCR power supply chokes. I pretty much was involved in all aspects of this design, but it was made with Willie's hands, and he is using it now.

Very "pretty looking" amp, ( somewhat crowded ), but ultimately, for Altecs, I prefer simpler two stage direct coupled designs.

LowOhms

[LowOhms]

Since this is the "show me" thread....would you be willing to post a picture and schematic of your amp?

Alien_Shore,

Attached is the basic direct-coupled two stage amp schematic.... power supply and audio combined.

I absolutely LOVE this circuit topology when well executed. It is as simple as one can make a practical amp !!!

This is the basic Loftin-White circuit from 1929,as used in well regarded amps today such as made by Fi, Moth, and Serious Stereo.

If any Altec speaker enthusiast wants to DIY build an amp, contact me for additional information, I've written it all up. If you don't like to DIY build, spend $15K and order two of the Serious Stereo monoblocks, a bargain. They are easily THE best sounding amps available for Altec speakers ever made, hands down, no contest. A DIY effort need not use a 2A3 as the Finals tube on A-7s, etc.

LowOhms

[timoteus]

To my ears, assuming a good schematic and build, a 45 will always sound better than a 2A3 on Altecs. And most importantly, more musical. Of the amps I own, my Loftin-White 2A3 is about 4th on the list.