What’s the world’s best 2 watt amplifier?

Gregadd

WBF Founding Member
Apr 20, 2010
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The Best low powered amp (non-SET) is from, L.T.A. Linear Tube Amplification. Based on a David Berning Design.
 
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godofwealth

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Feb 8, 2022
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Just bought two matched pairs of Brimar CV 1985 octal preamp tubes from a seller on eBay. NOS tubes from a long time ago. My Cary 300B SET uses these tubes. Quite reasonably priced. About 15 pounds per tube.
 

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godofwealth

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Has anyone heard SET amplifiers using the Western Electric 421a tube? It sounds quite intriguing. Only one tube needed for both channels as it is a dual triode type tube. Originally intended for non-audio purposes, but I understand Donald Garber, the SET genius brought this tube to notice with his 421a design.

 

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Sammy2000

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Sep 21, 2020
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What I find remarkable is the passion these designers bring to their work. Also striking how most market audio rags (Stereophile, TAS etc.) ignore these products.
Not quite ;





and more
 

beaur

Fleetwood Sound
Oct 12, 2011
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Not quite ;





and more
All of the examples were in show reports. Little or no attention is paid to low volume products by the mainstream press. Various listed reasons why. I also get that it can be a 2 edge sword in that more exposure can wreck a company with overwhelming demand. There’s enough of a network that niche products that stand out can find a market.
 
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Joe Cohen

Industry Expert
Jun 10, 2012
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MPA III.jpg
SW1X Morpheus Mono Power Amplifiers

MPA III is a Pure Class A, Zero Negative Feedback, Directly Heated Triode, Fully Valve Rectified, Single Ended, 3 Gain Stage, Interstage Transformer coupled, Mono Power Amplifier.

The Directly Heated 45 Triodes at the output are well known for their superbly refined & magical sound signature.

The 45 valves are de-coupled by Interstage transformers and driven by 6V6 power valves to enhance the refined sound of the 45 triodes with powerful character of the 6V6.

Combined with the finest Materials & Components, MPA III is extremely refined & musical sounding, especially when combined with high sensitivity speakers

SW1X Audio Design™ MPA III Mono Power Amplifier Features:

  • Specially Selected and Harmonically Matched Component & Material Quality
  • Single Ended, absolutely Zero NFB, Class A, Directly Heated Triode Valve Power Amplifier
  • 6V6 Valve Driver/6J5 input Stage driving the 2 x 45 DHT Valves
  • Interstage Transformer de-coupled, 3 Gain Stage Design
  • Hybrid Point 2 Point Hardwiring Technique for the most consistent production results
  • Internally wired exclusively with our SW1X Magnum, Genesis and Opus conductors
  • SW1X Audio DesignCustom Designed Copper wound Super HiB DC Core (50 Watt) Signal Output Transformers
  • Quasi Mono, Directly Heated Double Diode Valve Rectified B+ Power Supply
  • Orient grain M6 EI core mains Transformers & Chokes
  • Valve rectified Fixed Bias Power Supply
 

Atmasphere

Industry Expert
May 4, 2010
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The 45 valves are de-coupled by Interstage transformers and driven by 6V6 power valves to enhance the refined sound of the 45 triodes with powerful character of the 6V6.

[snip]
  • Single Ended, absolutely Zero NFB, Class A, Directly Heated Triode Valve Power Amplifier
  • 6V6 Valve Driver/6J5 input Stage driving the 2 x 45 DHT Valves
?? I don't get this. The 6V6 is not a triode and is considerably less linear. Why would you want that driving the output tube? Could you explain?
 

Joe Cohen

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?? I don't get this. The 6V6 is not a triode and is considerably less linear. Why would you want that driving the output tube? Could you explain?
Yes, 6V6 tubes are not particularly linear in pentode mode but connecting them in triode mode is a different story. SW1X would never use them as pentodes.
All of the pentodes EL84 or 6V6 they employ are always triode strapped. 6V6 tubes have amazing sound and driving capabilities and are extremely linear within their optimum operating points.
The AN Ongaku power amp has 6V6 tubes driving 211 tubes for a reason.
 

Atmasphere

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Yes, 6V6 tubes are not particularly linear in pentode mode but connecting them in triode mode is a different story. SW1X would never use them as pentodes.
All of the pentodes EL84 or 6V6 they employ are always triode strapped. 6V6 tubes have amazing sound and driving capabilities and are extremely linear within their optimum operating points.
The AN Ongaku power amp has 6V6 tubes driving 211 tubes for a reason.
Since its transformer coupled anyway, you could use an ultralinear connection. If the tap were placed correctly (and in most, they are not, to avoid infringing a long-expired patent) you could get linearity better than a triode connected pentode, which otherwise is not as linear as an actual triode. The AN reference doesn't say much to me- our S-30 amp is more powerful, more transparent, wider bandwidth and overall more musical without resorting to something like that, for a lot less money.

Please keep in mind that nearly all ultralinear transformers you know of have been designed to get around that patent I mentioned and don't reflect what ultralinear is really all about.

From a marketing perspective, the tube choice seems like its always going to have to require this explanation. You could get just as robust drive from a 6SN7 if it were wired correctly... the type 45 isn't that hard to drive.
 

Joe Cohen

Industry Expert
Jun 10, 2012
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There are many ways to skin a cat, but in the end it is down the sum total of the final build, each part chosen, their location, associated materials and how they interact and balance each other. That’s the artfulness of it.
 

saturdayboy

Well-Known Member
Aug 3, 2019
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Has anyone heard SET amplifiers using the Western Electric 421a tube? It sounds quite intriguing. Only one tube needed for both channels as it is a dual triode type tube. Originally intended for non-audio purposes, but I understand Donald Garber, the SET genius brought this tube to notice with his 421a design.

I had the fi 421a amp a few years back. I would describe the 421a tube as one of the more linear tubes (meaning no emphasis in any part of the frequency range). I definitely prefer the VT52 or 50 in the 4 watt range.

Don was a really nice guy, and his amps were visually beautiful, but I didn’t find them all that special sound wise.
 

godofwealth

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Feb 8, 2022
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The SET amp I’m hoping to receive by this weekend uses the Western Electric 421a. One dual triode tube for both channels. The WE 421a tube came today and tests perfectly on my Amplitrex. It’s a custom build by Oliver Sayes. Uses a 6SL7 driver and a 6BY5G rectifier. Will update once I get some time to form an initial impression.

1673325343738.jpeg
 

godofwealth

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Feb 8, 2022
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Just got my 421a SET. First impressions are very good. The Western Electric 421a is a marvel. One power tube for both channels. 3 watts is plenty for my La Scalas. Has a beautiful refined tone that is more smooth than a 45, but definitely more transparent than the WE 300B sound, which I would characterize as rich but a bit opaque.

C0F857DB-F61B-450A-987B-28BD9646B900.jpeg
 

adamaley

Well-Known Member
Apr 15, 2016
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Just got my 421a SET. First impressions are very good. The Western Electric 421a is a marvel. One power tube for both channels. 3 watts is plenty for my La Scalas. Has a beautiful refined tone that is more smooth than a 45, but definitely more transparent than the WE 300B sound, which I would characterize as rich but a bit opaque.

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Any sound impressions you can share with us?
 

godofwealth

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Feb 8, 2022
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Thus far, I have listened to it with a WE 421a tube and a Tung Sol NOS 5998. Both sound really nice. The tone is between the lushness of a 300B and the slightly dry sound of a 45 tube. Think of it as a 45 with a bit more richness to the sound. Imaging width and depth are superlative. For the price I paid, it’s a real bargain. Fortunately even NOS Western Electric 421a tubes are not too expensive (yet). I bought a second WE 421a for around $350 on eBay. 5998s are even cheaper.
 
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Cellcbern

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Jul 31, 2015
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This is shocking for me. In ALL amplifiers, I experienced improved performance changing rectifiers. During my life, I spend time and money to find WE-274B, Mullard GZ-34 metal base, GEC 5U4, good 5R4, etc...
Every rectifier I've tried in my Modwright PS 9.0 power supply sounded very different. Designer Dan Wright told me to expect this and encouraged "rectifier rolling". In this device the Sophia blue 274B and GEC/Marconi U52 5U4G are on a level above everything else including the Phillips metal base 5AR4.
 

Atmasphere

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May 4, 2010
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Every rectifier I've tried in my Modwright PS 9.0 power supply sounded very different. Designer Dan Wright told me to expect this and encouraged "rectifier rolling". In this device the Sophia blue 274B and GEC/Marconi U52 5U4G are on a level above everything else including the Phillips metal base 5AR4.
The load that an SET amplifier circuit presents to the rectifier is constant. This means that the difference you are hearing between various rectifier tubes is the voltage drop across them and nothing more- presumably, the less voltage drop, the better the sound.

Guitar players have often been faced with this issue, since a sagging power supply often sounds better for blues guitar in a guitar amplifier. To this end, there is a simple circuit that uses a solid state rectifier system along with a bit of regulation that allows you to dial in the voltage drop for the desired sound.

One advantage of tube rectifiers is they are low noise. You can get similar low noise from solid state rectifiers, but often you have to treat them (snub them) to do it, which can be a bit tricky. I suspect that this would put the rectifier tube thing to bed though, once and for all.
 

Salectric

Well-Known Member
Jan 15, 2012
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The load that an SET amplifier circuit presents to the rectifier is constant. This means that the difference you are hearing between various rectifier tubes is the voltage drop across them and nothing more- presumably, the less voltage drop, the better the sound.

Guitar players have often been faced with this issue, since a sagging power supply often sounds better for blues guitar in a guitar amplifier. To this end, there is a simple circuit that uses a solid state rectifier system along with a bit of regulation that allows you to dial in the voltage drop for the desired sound.

One advantage of tube rectifiers is they are low noise. You can get similar low noise from solid state rectifiers, but often you have to treat them (snub them) to do it, which can be a bit tricky. I suspect that this would put the rectifier tube thing to bed though, once and for all.
There has to be more to the “sound” of rectifier tubes than just the different output voltages. Let me give two illustrations. First, different brands of the same tube can sound very different, and consistently so—-a GE 5u4GB sounds different from a Sylvania 5u4GB and from an RCA 5u4GB despite all of them having the same output voltage. Second, I have a linestage with a regulated B+ voltage—-whether the rectifier outputs 350 or 390 volts the B+ is held tightly at 275 volts, yet different rectifiers sound different.
 

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