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Old 10th March 2005, 08:48 AM   #1
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Default advances in tube amp design?

Having just acquired some 100 dB drivers, I am now getting interested in building a tube amp. 20 watts is the probable minimum.
Having no experience and little time, it’ll probably be a kit. There are many, even clones of a 40 yo design the Dynaco.

I believe Dynaco’s are well regarded, but wonder – how much development has there been in the 40 years since then? Maybe only 5% of amps built over that period were tube, but many of the builders are very keen DIYers.

In that time in the rest of the audio world we’ve had eg
- much better understanding of horn design (Edgar, Danley)
- metal cone drivers tamed,
- chip amps for bang for buck,
- woofers and mids with 2-3 times the Xmax of a generation ago,
- powerful FR dipoles that only just break the bank (Linkwitz), etc.
(I know not all would call all of these advances).

So what are the advances in tube amp design?
Yes we need to implement them properly, but what are the great designs?
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Old 10th March 2005, 09:36 AM   #2
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None. All tube topologies were covered 40 years ago (even things as complicated as color television). All topologies that work better than newer, supercomplicated circuits (which again, were developed 40+ years ago) were covered over 70 years ago.

Go with something known and good, two billion of something just means it sold well, not that it was well made. At the very worst we can draw up something for you.

I doubt you'll need much more than 10W at that efficiency level, so something SE might work for 'ya. If you do, well, loud death metal and horns are kind of mutually exclusive, so you don't...

Tim
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Old 10th March 2005, 09:41 AM   #3
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There isn't really all that much new under the sun, especially when it comes to valve circuits. Actually, there is probably a smaller body of knowledge now than, say, 30 years ago when it comes to these things...
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Old 10th March 2005, 12:10 PM   #4
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Interesting answers.

So you two are saying that while the general body of audio knowledge grew, pretty much all of science & technology grew; tube amp knowledge *shrank?

And there are **zero new good ideas in **40 years**??

That sounds like something out of a science fiction horror movie- "the Land where Time stood Still"

What about Direct Reactance Drive (www.welbornelabs.com/)?
- Single-ended OTL pure Class A (www.transcendentsound.com/single%20ended.htm )?

Ie “New Tube power amp topologies 1966 – 2005” = Nil return ??

Is this the most stagnant area of applied science of the late 20th century??

How does a newbie sort the wheat from the chaff?
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Old 10th March 2005, 12:35 PM   #5
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Quote:
Originally posted by rick57
So you two are saying that while the general body of audio knowledge grew, pretty much all of science & technology grew; tube amp knowledge *shrank?
You forget that there was a large chunk of time where virtually everyone ran away from valves as fast as they could. Lots of stuff was forgotten and is being rediscovered.

The examples of "new" you give aren't remotely new!
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Old 10th March 2005, 12:36 PM   #6
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Quote:
Originally posted by rick57
How does a newbie sort the wheat from the chaff?
The only way...
The obvious way...
Listen!
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Old 10th March 2005, 12:40 PM   #7
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There are maybe not so many new ideas but there are, as in all things, stuff that comes into fashion. In fashion right now are probably some of the following:
Interstage and input transformers
Transformer volume controls
Constant current sinks for diff pairs (CCS)
Active CCS loads for tubes
Choke loaded stages
Parafeed
SET amps
Directly Heated Triodes (DHTs)
Zero global feedback in triode output stages

While most of this is old technology there are new implementations, especially with CCS. It is worth pointing out that the Dynaco circuit contains none of the above.
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Old 10th March 2005, 01:00 PM   #8
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The Dyna circuitry wasn't even sota at the time. It was designed to be good enough and low parts count. The iron and chassis are just fine, but any modern design will include regulated power supplies and a high-quality driver.

There are lots of things touted as new, most of which came out of cheap kids' toys, had a fancy name slapped on them, and are now fashionable. Tubes are by their nature quite limiting (there is no "p-channel" tube, for example) so most anything worth doing has been done. The one guy who has done truly new things is Dave Berning- screen drive, switching supplies, tube-FET hybrids, digital autobias, impedance mapping- but this is not the stuff of fashion or audiophile candy.
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Old 10th March 2005, 01:40 PM   #9
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I suspected as much about the Dyna circuitry.
Dave Berning - is it better?? /where do I learn more/ public domain DIY?


Andy
Is there nought but fashion in the tube amp world?
Are new implementations with CCS worthwhile?

JM, you've raised some intriguing issues:
>> You forget that there was a large chunk of time where virtually everyone ran away from valves as fast as they could.

note: I have a few, but I assure it hasn'tv affected my logib
I didn’t know there had been a Diaspora. Not Politically Correct.
If this continues, I’ll write to my local Member about this.

>> Lots of stuff was forgotten and is being rediscovered.

Forgotten? and rediscovered??
Were these the Dark Ages, and now the Renaissance?
I read of events like this, in the LotR. Or was it Harry Potter?
Either way, it looked very good on the Big Screen.

>> The examples of "new" you give aren't remotely new!
I did not know if they were new, but they sounded different, and strangely alluring to my wallet, promising the elusive “Audio Nirvana”.
I hear you can get it in a bottle in outer Tibet? Is this true??

How does a newbie sort the wheat from the chaff?
>> The obvious way... Listen!

What, use my ears?? Let’s not get physical just yet matey.

Some say, the best way, where feasible. If not, (I) seek the (more elusive than a Haitian shakri) “ ‘opinions’ “.
My girlfriend reckons I should just improve my technique, and all will become “cool”? but I could not find that in my Audio Glossary.

That’s why I’m here, blown off a local redneck audio forum where no moderator controlled events when emotions on this issue bubbled brewed and seethed like a witch’s spell.

I just found an amp design approved by Lord Kitchener, as used in the Boer War. Apparently it is pretty well “State of the Art”.
Based on your opinoions, I’m placing my purchase order now, thank you for you assistances.

Yours,

The Colonel
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Old 10th March 2005, 02:02 PM   #10
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Berning's web site is a treasure trove of truly original designs; he's posted schematics for all of his designs going back to the '70s (see the "Support" section). His US patents are well worth some study. www.davidberning.com

Is his stuff "good"? Depends on your definition of "good." It's efficient, lightweight, and stable. For many, that's no fun.
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