Are You The Self Appointed Minster For SET Topology Corrections ?
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SET amp owners thread
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Are You The Self Appointed Minster For SET Topology Corrections ?
Didn't a tube amp topology thread get opened for this SET amp not done right discussion? Did that thread get closed down or something? It's very confusing that someone will spend so much time in a SET amp owners thread, which, I assume, implies appreciation for said topology. What is the purpose of his postings here rather than there?
Apparently morricab can't see what is on the page at the link. The plots do not show the bandwidth of the amp at full power (which seems to be about 15-16 Watts). How it works is that as you increase the output power at low frequencies, the lack of inductance in the output transformer starts to look like a short to the power tube so output drops off. If you measure the primary winding resistance, you can see how this is so. Its usually just a few hundred Ohms, while the load impedance needed for the tube to make power is usually several thousand Ohms.
FWIW Speltz's ZERO autoformer has helped out a lot of SET owners too. The problem is that many speakers these days are 4 Ohms in the bass and 8 Ohms in the mids and highs. SETs struggle with a load like that as any zero feedback tube amp does. The ZERO is a problem solver; Steve McCormick, who makes very competent solid state amps which can drive 4 Ohms with ease, sent Paul a letter stating that while his amps do so, that isn't the same as saying they sound their best. Steve found that his amps sound better driving 4 Ohms thru the ZEROs; the lesson being that 4 Ohms isn't good for most amps if high quality reproduction is your goal.
The comments Brad makes on his own and about Otala are rubbish: the problem is that any feedback network must be carefully designed to allow the feedback to do its job with the amp properly without the load being able to mess with it (cause oscillation or the like). Clearly Mr. Otala didn't have such an amp at his disposal (and this was a problem in the 1970s and 80s- some amps would oscillate and blow up as described). Poorly designed feedback loops are a problem in audio- most of them really don't do the job. I have laid out what the problems are that have given feedback a bad name. None of them have to do with feedback itself; they have to do with execution.
Brad's comments about 'that back signal' is problematic. He is referring to 'back EMF' if I read that correctly. It most definately messes with the amp (whether OTL or SET)! The 'heat' is created in the power tubes themselves, raising their temperature. IOW they run hotter with a more diffcult load. Many people think that an output transformer isolates the tube from the load; this is only true of DC. Transformers transform impedance which is how they got their name. It goes in both directions, not one (otherwise Kirchoff's Law, a basic law of electronics like Ohm's Law, is violated, which would create a new branch of physics). So an adverse load that might generate back EMF is messing with the power tube(s) directly. It heats them up, causes distortion and shorter life. If you don't beleive me get a thermal camera (cheap on ebay), put the amp on different loads, play it and you'll see.
If anyone reading this wants a more technical explanation of what goes on with feedback, why high feedback amps of the 70s and 80s sucked and so on, read this article. FWIW, since the 1970s and 80s, technology has marched on; we use things like the web that we take for granted. Why could amps not also evolve in that time?? The idea that the problems of the 70s and 80s designs haven't seen some progress is frankly ridiculous.
There's no reason a high feedback amp has to oscillate if the feedback network (usually multiple ordered) is properly designed. A class D design can take a simpler approach though by using the feedback to actually cause the amp to oscillate- and the oscillation is then used as the switching frequency. Of course the feedback network has to be properly designed so the amp can only find one oscillation solution. The formula for that is called the 'oscillation criteria'.
Finally, the 'psychoacoustic findings' I've mentioned in the past are well known and consistent (for example that the 2nd harmonic is interpreted by the ear as 'warmth' or 'bloom'). These are the same findings that are why people like SETs. Brad seems to be shooting himself in the foot here.
Your prior statement you 'don't care' is contradicted by your continued attacks; its obvious to anyone you do care else you would not continue posting. I've found that when someone contradicts themselves in this manner, the comments are never relevent to the thread itself.
As for whether it works for me or not, I've been doing the same stuff for 47th years now, not just 30...
WRT the Internet these are the rules I use:
stick to the truth
don't take anything personally (you have no idea what sort of problems the person on the other end of an argument has)
don't make personal attacks; 'attack the post, not the person' is a principle rule on any website.
Over time people learn who you are. I started on the Internet in 1990 before the web. So yes, it works for me.
Look again Ralph. The left plot shows distortion vs. frequency at powers from 0.1 to 18 watts... please note that at 18 watts the distortion at 20Hz is between 2 and 4% over a 20Hz-20Khz bandwidth. The right plot shows the distortion with power for different frequencies, including 20Hz, which shows that the amp behaves essentially the same at all frequencies up to full power. Based on where the knee is in the distortion vs. power plot (right) full power is around 15-18 watts and a couple % THD+N. The bass keeps up just fine at 20Hz and gives the same knee within a watt or so. Looks like you are wrong about a SET being able to deliver full power at 20Hz.
Again, don't match a SET (or an OTL for that matter) with an incompatible speaker! There are plenty of speakers today that fit that bill.
So, back EMF is not a problem? And I never said the heat was dissipated in the transformer. A little bit of heat in a tube that is already a few hundred degrees is not likely to cause an issue. Into a transistor however, this can mess up it's behavior quite badly as they need stable operating temperatures...just another issue. Do you deny that back EMF won't be injected back into the amplification circuit with a global feedback loop?
"Finally, the 'psychoacoustic findings' I've mentioned in the past are well known and consistent (for example that the 2nd harmonic is interpreted by the ear as 'warmth' or 'bloom'). These are the same findings that are why people like SETs. Brad seems to be shooting himself in the foot here."
This is a simpleton's view of psychoacoustics and there are simply much more sophisticated analyses out there. Below a certain level, 2nd harmonic is INAUDIBLE, only when grossly excessive, which according to Cheever is a level greater than the ear's own 2nd harmonic generation, will it do something like you describe. The higher the order of the harmonic, the lower in level it has to be and has to be preceded by the lower harmonic of higher amplitude to benefit from masking. It's all out there, time to read up and catch up Ralph. There is so much more to it than 2nd harmonic makes things sound warm...
Education- if I can be helpful then I try to do that regardless of the topic. Audio is a hobby of mine still after all these years so I participate.
I have owned and built a number of SETs since the early 1990s when Joe Roberts first published Sound Practices magazine. Its not as if I have an EE and designed amps without exploring SETs too...
If you look at my posts, you'll see I made some suggestions about how to get the most out of any SET. That seems to be ignored with all the personal attacks.
2cents incoming ,
Never heard an OTL sound better than a SET , thought i would prefer the OTL from a design point of view but in reality not .
SET’s are like a Giant enigma, when impedance and drive match the sound is really top tier , music dependent also for sure , favoring and best on classical music and natural acoustic instruments vs multi track studio Recordings ..
Never heard an OTL sound better than a SET , thought i would prefer the OTL from a design point of view but in reality not .
SET’s are like a Giant enigma, when impedance and drive match the sound is really top tier , music dependent also for sure , favoring and best on classical music and natural acoustic instruments vs multi track studio Recordings ..
View attachment 138649
Look again Ralph. The left plot shows distortion vs. frequency at powers from 0.1 to 18 watts... please note that at 18 watts the distortion at 20Hz is between 2 and 4% over a 20Hz-20Khz bandwidth. The right plot shows the distortion with power for different frequencies, including 20Hz, which shows that the amp behaves essentially the same at all frequencies up to full power. Based on where the knee is in the distortion vs. power plot (right) full power is around 15-18 watts and a couple % THD+N. The bass keeps up just fine at 20Hz and gives the same knee within a watt or so. Looks like you are wrong about a SET being able to deliver full power at 20Hz.
Again, don't match a SET (or an OTL for that matter) with an incompatible speaker! There are plenty of speakers today that fit that bill.
So, back EMF is not a problem? And I never said the heat was dissipated in the transformer. A little bit of heat in a tube that is already a few hundred degrees is not likely to cause an issue. Into a transistor however, this can mess up it's behavior quite badly as they need stable operating temperatures...just another issue. Do you deny that back EMF won't be injected back into the amplification circuit with a global feedback loop?
"Finally, the 'psychoacoustic findings' I've mentioned in the past are well known and consistent (for example that the 2nd harmonic is interpreted by the ear as 'warmth' or 'bloom'). These are the same findings that are why people like SETs. Brad seems to be shooting himself in the foot here."
This is a simpleton's view of psychoacoustics and there are simply much more sophisticated analyses out there. Below a certain level, 2nd harmonic is INAUDIBLE, only when grossly excessive, which according to Cheever is a level greater than the ear's own 2nd harmonic generation, will it do something like you describe. The higher the order of the harmonic, the lower in level it has to be and has to be preceded by the lower harmonic of higher amplitude to benefit from masking. It's all out there, time to read up and catch up Ralph. There is so much more to it than 2nd harmonic makes things sound warm...
Only power before the knee counts ..!
Education as to why SET can't do bass was being sought after? Got it. I'll come back after the next 3 pages for when the trolling and triggered dust has settled.
For those who say horns cannot rock…we salute you – Zero Distortion
zero-distortion.org
For those who say horns cannot rock…we salute you – Zero Distortion
Love the sound of Leif's system...
This version...lovely amps with el 34 driver
I have rolled Mullards, telefunken dual getter and his Chinese ones on the driver
my favorite is the Svetlana "C" absolutely robust tube can handle much more voltage than the nos tubes. very good resolution and dynamic not a romantic sound. older model light gray lettering.
Leif has used SS amps on lower bass for a long time now, recently only his treble and midrange get the tube treatment.
Leif has used SS amps on lower bass for a long time now, recently only his treble and midrange get the tube treatment.
In the video the SS is 75 and below. And all those videos in that post are sounding great.
Yes, and he has improved his system since that !
He is not dogmatic, he goes by trial and error and only keeps what sounds best, great way of building a system.How do you know that? He changes something everyday, could just be he has more time after retirement when not sailingYes, and he has improved his system since that !
Yes those same ones, well in green at any rate. The hammerton finish is something I will claim credit for. I asked if mine could be finished in hammertone green, which wasn't something Christoph had done before. I got the idea from the Leica MP Hammertone (I don't own one) and wanted them to match my room:
Home by Greg Turner, on Flickr
Home by Greg Turner, on Flickr
hORNS FP15s, Silvercore 833MKII by Greg Turner, on Flickrnice setup. I see the amps are in camouflage colors to blend in with the plantsYes those same ones, well in green at any rate. The hammerton finish is something I will claim credit for. I asked if mine could be finished in hammertone green, which wasn't something Christoph had done before. I got the idea from the Leica MP Hammertone (I don't own one) and wanted them to match my room:
!
Here is my "old timer" Silvercore amp. They also made a 300B version of this (essentially the same but with 300Bs instead of 2A3s). Lots of iron and weighs over 30Kg...for a 3.5watt amp!
I´ve swallowed and left a trail of camel carcasses in my path in the persuit of better soundYes, and he has improved his system since that !
the biggest of them all was using Powersoft modules on both FLH from 550 and down
2kw on the subhorns and 1kw on each JBL 2220B, all with individual dsp......
the transition between 300Bs and the Powersoft is perfect and I had to tell people who visited what I had done, and they refused to believe it.....
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