Jump to content

Toolshed Amps?


Shakeydeal

Recommended Posts

I had some time to read through the build thread and a couple reviews which leaves me with more questions.

 

I appear to be wrong as these are open loop or zero feedback amps? Which makes sense that you are triode wiring the E180F and D3a, there isn't enough gain for any feedback. E180F triode wired is probably around 32x gain and the 300b is roughly 3.8x. This jives exactly with the 14db gain of your amps and the need for 2.23v for full output. Nice trick to keep noise low is to have a low gain amplifier for high efficient speakers, downside you may need a preamp to reach full power.

 

I guess my question is now what is the output power of the 300b amp measured at 1% THD?  After some quick calculations my guess is the amp is 1% THD at 1 watt output. There is absolutely no way an open loop 300b amp will produce 7-8 watts with only 1% THD.

  • Like 1
Link to comment
Share on other sites

4 hours ago, captainbeefheart said:

After some quick calculations my guess is the amp is 1% THD at 1 watt output. There is absolutely no way an open loop 300b amp will produce 7-8 watts with only 1% THD.


For SE amps, I aim for less than 0.5% THD @ 1Watt, 1kHz.
 

It’s easy to do but you have to carefully choose the primary transformer impedance, driver & output tube load lines to compliment each other. Distortion isn’t the only parameter that matters, but it helps to keep it low to begin. 
 

If you have enough gain, of course you can add some feedback to improve damping and reduce distortion a bit. 

Link to comment
Share on other sites

6 minutes ago, Curious_George said:


For SE amps, I aim for less than 0.5% THD @ 1Watt, 1kHz.
 

It’s easy to do but you have to carefully choose the primary transformer impedance, driver & output tube load lines to compliment each other. Distortion isn’t the only parameter that matters, but it helps to keep it low to begin. 
 

If you have enough gain, of course you can add some feedback to improve damping and reduce distortion a bit. 

 

I am hoping for a confirmation but after some reading I am lead to believe these amps do not have any feedback. You just built a no feedback 300b amp for a member correct? Where were you getting your 1% THD at? And from memory you were around 5% THD with 6.5 watts or so correct?

 

In your experience have you been able to get 1% THD at 8 watts from a single 300b and zero feedback? Maybe I am doing something completely wrong but before feedback I was never close to getting that low distortion at that power and obviously I try and linearize an amp as much as possible even knowing I will use feedback.

Link to comment
Share on other sites

2 minutes ago, captainbeefheart said:

 

I am hoping for a confirmation but after some reading I am lead to believe these amps do not have any feedback. You just built a no feedback 300b amp for a member correct? Where were you getting your 1% THD at? And from memory you were around 5% THD with 6.5 watts or so correct?

 

In your experience have you been able to get 1% THD at 8 watts from a single 300b and zero feedback? Maybe I am doing something completely wrong but before feedback I was never close to getting that low distortion at that power and obviously I try and linearize an amp as much as possible even knowing I will use feedback.

I’ll have to go back and see where 1% is power wise. Unless you drive the 300B into Class A2, you are not going to get 8 Watts @ 1%. And this would be biasing the 300B in an unconventional manner closer to 0V. 
 

This is just a guess messing around with SE Tubecad.

Link to comment
Share on other sites

10 hours ago, captainbeefheart said:

I had some time to read through the build thread and a couple reviews which leaves me with more questions.

 

I appear to be wrong as these are open loop or zero feedback amps? Which makes sense that you are triode wiring the E180F and D3a, there isn't enough gain for any feedback. E180F triode wired is probably around 32x gain and the 300b is roughly 3.8x. This jives exactly with the 14db gain of your amps and the need for 2.23v for full output. Nice trick to keep noise low is to have a low gain amplifier for high efficient speakers, downside you may need a preamp to reach full power.

 

I guess my question is now what is the output power of the 300b amp measured at 1% THD?  After some quick calculations my guess is the amp is 1% THD at 1 watt output. There is absolutely no way an open loop 300b amp will produce 7-8 watts with only 1% THD.

Yes, 0.93% @ 1W w/1KHz sine-wave. No "global" NFB. However, still less than 5% THD at full power. And, yes, carefully selected operating points are key. The C3g driver stage is even slightly more linear, w/distortion slightly lower. However, distortion isn't everything, the design goal was musicality, everything else seems to fall into place within that context given sound engineering practices, a little luck, and mentors such as Gordon, Herb, JC, Joe Roberts... and countless unnamed contributors to MJ Audio magazine over the years.

 

IMHO, it really is about that 1st watt (or 700mW if you've got K-horns or LaScala's)....... or really anything above 93db efficient. Although headroom is nice. 99% of my customers, family, friends, etc. critically listen with peaks at maybe 88db. Maybe we are all just getting old, who knows.

 

FWIW, the final amplifier design didn't happen in a vacuum, Gordon and I designed the Iron-Coupled DHT Line-Preamplifier to compliment the amplifier w/approximately 5db of total gain, the 01a and 71a's operate right in their own "sweet-spot" allowing the entire volume control to be used, and just enough gain to drive the amplifier to full output with the "industry-standard" 2v input.

 

A phono gain amplifier is in the works for this calendar year. This piece will complete the "Trifecta" for customers (and myself) that just want to stop buying gear and just "enjoy the music". Again, the design goal is ultimate musicality, not just vanishingly-low distortion figures. Gordon has, separately, finished his penultimate DAC, the Pelham, which also uses the 71a DHT in it's gain stage for customers digitally inclined.

 

Lastly, final voicing is being done to the "50" version of the Transcendence amplifier. It uses a choke-loaded driver stage with the EXCELLENT Silk Audio grid choke on the 50. Jury is still out on the input transformer......... it may or may not use it.

 

Cheers all.

 

Matt. 

  • Like 1
Link to comment
Share on other sites

12 hours ago, captainbeefheart said:

 

I am hoping for a confirmation but after some reading I am lead to believe these amps do not have any feedback. You just built a no feedback 300b amp for a member correct? Where were you getting your 1% THD at? And from memory you were around 5% THD with 6.5 watts or so correct?

 

In your experience have you been able to get 1% THD at 8 watts from a single 300b and zero feedback? Maybe I am doing something completely wrong but before feedback I was never close to getting that low distortion at that power and obviously I try and linearize an amp as much as possible even knowing I will use feedback.

300B @ 1% THD+N

 

This measurement was made of 2 different sets of 300B's with about 200 hours on each set. A newer set of 300B's (with only about 75 hours on them) had much higher distorion and lower power output based on 4 Watts as a refererence.

 

300B 1% THD.jpg

Link to comment
Share on other sites

59 minutes ago, Curious_George said:

300B @ 1% THD+N

 

This measurement was made of 2 different sets of 300B's with about 200 hours on each set. A newer set of 300B's (with only about 75 hours on them) had much higher distorion and lower power output based on 4 Watts as a refererence.

 

300B 1% THD.jpg

 

Have you measured the new W.E.300b at 1W ? It's an eye opener for sure, possibly due to the new proprietary filament coating.  None of the other 300b's are even close, although among the "other" high-end brands (EML, KR, Takatsuki), the Elrog ER300b (possibly due to the Thoriated-Tungsten filament) is closest, full disclosure, we have no EAT 300b to evaluate. Also, the Transcendence Amplifier uses a higher-than-typical primary on the output transformers, this helps to keep distortion lower at higher power as well. The amplifier was designed for musicality, not power. If a 3K primary OT was used at this operating point, the power would be in excess of 11W. This said, it really is a "dance" that numbers alone cannot quantify. 

 

Matt.

  • Like 1
Link to comment
Share on other sites

1 hour ago, ToolShedAmps said:

 

Have you measured the new W.E.300b at 1W ? It's an eye opener for sure, possibly due to the new proprietary filament coating.  None of the other 300b's are even close, although among the "other" high-end brands (EML, KR, Takatsuki), the Elrog ER300b (possibly due to the Thoriated-Tungsten filament) is closest, full disclosure, we have no EAT 300b to evaluate. Also, the Transcendence Amplifier uses a higher-than-typical primary on the output transformers, this helps to keep distortion lower at higher power as well. The amplifier was designed for musicality, not power. If a 3K primary OT was used at this operating point, the power would be in excess of 11W. This said, it really is a "dance" that numbers alone cannot quantify. 

 

Matt.

I have not measured new (or even old) WE 300B’s. If someone was to lend me a set, I’d be glad to. 
 

For SE 2A3 and 300B amps, I prefer 5~6k OPT’s… for as you say “musicality” not maximum output power. 

Link to comment
Share on other sites

8 hours ago, ToolShedAmps said:

The design goal was musicality, everything else seems to fall into place within that context given sound engineering practices, a little luck, and mentors such as Gordon, Herb, JC, Joe Roberts... and countless unnamed contributors to MJ Audio magazine over the years.

Unfortunately, I have never had the pleasure to (physically) work with mentors in the tube audio field. I guess in a manner of speaking, reading countless hours of forums (with a grain of salt), books, periodicals and RDH4 (from front to back), I had mentors from afar. 
 

I am self-taught, which makes you even more focused sometimes when designing circuitry and amps. 

  • Like 2
Link to comment
Share on other sites

9 hours ago, ToolShedAmps said:

Yes, 0.93% @ 1W w/1KHz sine-wave. No "global" NFB. However, still less than 5% THD at full power. And, yes, carefully selected operating points are key. The C3g driver stage is even slightly more linear, w/distortion slightly lower. However, distortion isn't everything, the design goal was musicality, everything else seems to fall into place within that context given sound engineering practices, a little luck, and mentors such as Gordon, Herb, JC, Joe Roberts... and countless unnamed contributors to MJ Audio magazine over the years.

 

IMHO, it really is about that 1st watt (or 700mW if you've got K-horns or LaScala's)....... or really anything above 93db efficient. Although headroom is nice. 99% of my customers, family, friends, etc. critically listen with peaks at maybe 88db. Maybe we are all just getting old, who knows.

 

FWIW, the final amplifier design didn't happen in a vacuum, Gordon and I designed the Iron-Coupled DHT Line-Preamplifier to compliment the amplifier w/approximately 5db of total gain, the 01a and 71a's operate right in their own "sweet-spot" allowing the entire volume control to be used, and just enough gain to drive the amplifier to full output with the "industry-standard" 2v input.

 

A phono gain amplifier is in the works for this calendar year. This piece will complete the "Trifecta" for customers (and myself) that just want to stop buying gear and just "enjoy the music". Again, the design goal is ultimate musicality, not just vanishingly-low distortion figures. Gordon has, separately, finished his penultimate DAC, the Pelham, which also uses the 71a DHT in it's gain stage for customers digitally inclined.

 

Lastly, final voicing is being done to the "50" version of the Transcendence amplifier. It uses a choke-loaded driver stage with the EXCELLENT Silk Audio grid choke on the 50. Jury is still out on the input transformer......... it may or may not use it.

 

That's great thank you.

 

I would change the specs on your website to what you just wrote here. Your website is misleading, it says no more than 1% THD and people are going to think that is at full output if not otherwise stated. This is the same thing that was just happening to the Crimson 275, they mislead on the specifications which got a lot of people fairly upset the product was sold under false pretenses.

 

Someone has to keep the manufacturers honest, hopefully you understand and not take this personal.

  • Like 1
Link to comment
Share on other sites

3 hours ago, Curious_George said:

This measurement was made of 2 different sets of 300B's with about 200 hours on each set. A newer set of 300B's (with only about 75 hours on them) had much higher distorion and lower power output based on 4 Watts as a refererence.

 

That's the one issue with zero feedback type amplifiers, the performance of the amplifier is much more dependent upon the linearity of the tubes. It's a lot tougher to get consistent numbers.

 

 

Link to comment
Share on other sites

6 minutes ago, captainbeefheart said:

 

That's the one issue with zero feedback type amplifiers, the performance of the amplifier is much more dependent upon the linearity of the tubes. It's a lot tougher to get consistent numbers.

 

 

Yep. When I build an amp without feedback I swap input & output tubes (after a good break in) until I get the best distortion and match output levels to within 0.5dB. Then those tubes are mated for life. 

Link to comment
Share on other sites

11 minutes ago, Curious_George said:

Yep. When I build an amp without feedback I swap input & output tubes (after a good break in) until I get the best distortion and match output levels to within 0.5dB. Then those tubes are mated for life. 

 

Exactly, it's not just distortion it's also matched gain for both channels.

 

Triodes are linear due to internal negative feedback. I don't understand why audiophiles are so opposed to feedback. It's possible that because of so many amplifiers having poor application of it which made people make an unfair correlation. At one point I enjoyed zero feedback amps just because it was fun to weed through tubes and find the best performance possible but this is not something anyone can do. Your average person is just going to pop some tubes in and listen to see if it sounds better or worse. That's too much gray area for my liking, you take a risk purchasing tubes every time not knowing if they will sound good or not. If I make a friend an amplifier, I don't want them to need to bring the amp to me if they want to replace tubes then I have to screen a bunch to get optimal performance. I'm lazy in my old age, I want to have a circuit that you can pop any tube in so long as it's functional and get the best performance. That's one hallmark of a good amplifier, performance isn't reliant on tube parameters.

  • Like 1
Link to comment
Share on other sites

1 hour ago, Curious_George said:

Unfortunately, I have never had the pleasure to (physically) work with mentors in the tube audio field. I guess in a manner of speaking, reading countless hours of forums (with a grain of salt), books, periodicals and RDH4 (from front to back), I had mentors from afar. 
 

I am self-taught, which makes you even more focused sometimes when designing circuitry and amps. 

 

There is really no need to have a 'mentor' for amplifier design. All that is needed is good foundation of electrical engineering and time. Study and analyze circuits, build them and test them, listen, over time you make your own conclusions and not someone else's. You do not need a college degree although having a solid understanding of mathematics is extremely useful and will make life a lot easier.

 

It really boils down to effort and time, you get out what you put in. I never had a mentor of any sort, just lots of books and many files of circuits to study. Then the time to build circuits and test them, listen and evaluate, this is how I made correlations between what I am hearing and what I am measuring. If you learn from a mentor only you not only pick up their good habits, you may also pick up their bad habits as well.

  • Like 1
Link to comment
Share on other sites

2 hours ago, captainbeefheart said:

 

That's great thank you.

 

I would change the specs on your website to what you just wrote here. Your website is misleading, it says no more than 1% THD and people are going to think that is at full output if not otherwise stated. This is the same thing that was just happening to the Crimson 275, they mislead on the specifications which got a lot of people fairly upset the product was sold under false pretenses.

 

Someone has to keep the manufacturers honest, hopefully you understand and not take this personal.

 

Noted, and adjusted....... FWIW, you'll notice that Silbatone doesn't list ANY specifications for the amplifiers on their website....., and believe me when I tell you that JC and Joe know what they are doing. ;)

 

Suffice to say that the amplifier sounds glorious, even at full power, banging out Highway Star at an absolutely absurd volume level, only fit for a teenager! ;)

 

Cheers!

 

Matt.

  • Like 1
Link to comment
Share on other sites

1 hour ago, captainbeefheart said:

 

There is really no need to have a 'mentor' for amplifier design. All that is needed is good foundation of electrical engineering and time. Study and analyze circuits, build them and test them, listen, over time you make your own conclusions and not someone else's. You do not need a college degree although having a solid understanding of mathematics is extremely useful and will make life a lot easier.

 

It really boils down to effort and time, you get out what you put in. I never had a mentor of any sort, just lots of books and many files of circuits to study. Then the time to build circuits and test them, listen and evaluate, this is how I made correlations between what I am hearing and what I am measuring. If you learn from a mentor only you not only pick up their good habits, you may also pick up their bad habits as well.

 

 

As for this.......... I somewhat agree, you can find and read, and disseminate as much information as you can get your hands on, develop a more-than-passable working knowledge of advanced mathematics, crawl down the rabbit-hole of endless forum "suggestions" until you become part of your computer chair, then order up $20K worth of resistors, caps, power transformers, chokes, output transformers, signal tubes, power tubes, rectifier tubes, vr tubes, solder, switches, tube sockets, wire, etc........... and solder together all of the circuits you've read about and see how they sound................. so about 5,000hrs and two marriages later you can be somewhat satisfied? Maybe if it were a hobby. Certainly not the suggested methodology if you've got four kids to feed.

 

I feel eternally blessed to have the help I've been given...... and express it every chance I get. The "help" is usually in the form of not wasting precious time chasing a topology that's been tried by others and is ultimately not good enough. This kind of direction is most welcome. 

 

Bad habits..................... Hmm.... well, everyone knows that audio designers have the capacity to grow like any other human being. Changing one's perspective is part of the human condition. I welcome change................ as long as it sounds better. ;)

 

My recommendation for those wanting to DIY, is to find a topology that several people have used, build from a valid schematic, then rub on it till it shines. You'll learn much in the endeavor. I absolutely believe in empirical evidence to support what I'm hearing. Word of advice: buy the best iron you can afford. There is a difference.

 

Good Luck!

 

Matt.

  • Like 3
Link to comment
Share on other sites

Hi,  Matt is building my 300b right now....    It will be loaded with Hitachi Fine Met OT and vintage main PS and chokes.  Lots of other good stuff in there , NOS Rectifier and input tubes and new production Western Electric 300b’s

 

Can’t wait,  will post pics and impressions soon

  • Like 1
Link to comment
Share on other sites

2 hours ago, ToolShedAmps said:

Noted, and adjusted....... FWIW, you'll notice that Silbatone doesn't list ANY specifications for the amplifiers on their website....., and believe me when I tell you that JC and Joe know what they are doing. ;)

 

Suffice to say that the amplifier sounds glorious, even at full power, banging out Highway Star at an absolutely absurd volume level, only fit for a teenager!

 

Very good.

 

The sound of your amplifier was never in question, I am sure it sounds great.

 

1 hour ago, ToolShedAmps said:

As for this.......... I somewhat agree, you can find and read, and disseminate as much information as you can get your hands on, develop a more-than-passable working knowledge of advanced mathematics, crawl down the rabbit-hole of endless forum "suggestions" until you become part of your computer chair, then order up $20K worth of resistors, caps, power transformers, chokes, output transformers, signal tubes, power tubes, rectifier tubes, vr tubes, solder, switches, tube sockets, wire, etc........... and solder together all of the circuits you've read about and see how they sound................. so about 5,000hrs and two marriages later you can be somewhat satisfied? Maybe if it were a hobby. Certainly not the suggested methodology if you've got four kids to feed.

 

I feel eternally blessed to have the help I've been given...... and express it every chance I get. The "help" is usually in the form of not wasting precious time chasing a topology that's been tried by others and is ultimately not good enough. This kind of direction is most welcome. 

 

Bad habits..................... Hmm.... well, everyone knows that audio designers have the capacity to grow like any other human being. Changing one's perspective is part of the human condition. I welcome change................ as long as it sounds better. ;)

 

My recommendation for those wanting to DIY, is to find a topology that several people have used, build from a valid schematic, then rub on it till it shines. You'll learn much in the endeavor. I absolutely believe in empirical evidence to support what I'm hearing. Word of advice: buy the best iron you can afford. There is a difference.

 

I am an engineer by trade but have always tinkered with all sorts of electronics for fun and to learn. I always found ways to stock up on parts without purchasing off the shelf, typically salvaged from things going to the junk yard. Free organs people are getting rid of, TV sets, old radios, it doesn't matter whatever has quality parts inside I'll take it and recycle. This has always allowed me to breadboard amps for next to no cost, only time. Being resourceful has major advantages when on a tight budget which I totally understand as I have been there.

 

I suppose I view things much different than your typical tube amplifier 'guru'. I have always just viewed an amplifier as a black box with in and out characteristics, that's it simple as that. Actually that's much the case for everything in electronics, always breaking down something complex into a Thevinen equivalent model. I set myself some goals of what I want to achieve for in and out characteristics and then sort of look at what parts I have laying around or that are common and inexpensive to come by and work from there. If you were to hand me your amplifier and not allow me to look inside it or anything, just allow me to measure some in and out characteristics I will build you an amplifier that sounds identical and nobody would be able to tell the difference in a blind test. Your amp could be tubes and my amp could be solid state but still have the same sonic attributes, by nature of course I will try and accomplish this as inexpensive as possible too.

 

What it boils down to I suppose is everyone is different, we all learn and do things differently. Whatever works for you best is what is best.

  • Like 1
Link to comment
Share on other sites

36 minutes ago, Steve. said:

“If you were to hand me your amplifier and not allow me to look inside it or anything, just allow me to measure some in and out characteristics I will build you an amplifier that sounds identical and nobody would be able to tell the difference in a blind test. Your amp could be tubes and my amp could be solid state but still have the same sonic attributes, by nature of course I will try and accomplish this as inexpensive as possible too.”

 

I call “ BULLSHIT” here.  One of the funniest things I think I’ve ever read

Bob Carver did that very thing 40 years ago and it pissed a whole lot of people off! 

 

https://www.bobcarvercorp.com/carver-challenge

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...