Svetlana SV572-10 SET Amplifier Before Rebuild 

I think I understand what you are trying to say. I have tried some experiments with my musician friends using harmonic profiles from different violines. I made a video of it but it was not widely received. The nuances of my voice vs your voice is what makes us unique and I surmise these harmonic nuances is what distinguishes the sound of "good" from "not-as-good" in audio reproduction equipment. With that said, the artifacts introduced by the amplifier at the end - our Stereo System - et al - can actually add to the "quality" of the sound of the system. I have made audio amplifiers that do not perform well on the test bench but sound great. The problem is, we can't reproduce equipment on such subjective grounds as personal preference although, in the end, it is all about how-it -sounds. I think I described that in the sound of my Acrosound Williamson design vs the UTC LS Williamson design. There seems to be something in the energy of the "iron" of an amplifier that pleases our ears that comes from a voltage-centric vacuum tube amplifier that is not present in a current-centric transistor amplifier - besides the common concept that it is about the abrupt transitions inherent to the SS amplifiers and the less-abrupt transitions at maximum power (clipping level) of vacuum tube amplifiers. The part that is hardest to explain is the harmonic profile of the SE amplifier being pleasing to the ear with such a high level of harmonic distortion. Some claim this is true because of "even harmonics" vs "odd harmonics" but I simply do not believe that. Just my thoughts.

I have been building amplifiers a long time and a lot of years ago I would alot $40 to an amplifier project. I probably had military surplus transformers and the such but that was all I could afford on my salary working for NASA... 🙂 SET amplifiers have a charm of sounding "alive" but sometimes 5 watts is just not enough. I don't need to go to 120 dB SPL anymore as I have already measured that and felt the thrill - or terror - of that volume level but I can appreciate a 25WPC amplifier. My two main amplifiers are a Acrosound Williamson design that will do 25 WPC and the other a UTC LS Williamson good for 15 WPC that is in the main house on my Klipschorns and is the best sounding amplifier I have ever had including all the Mac amplifiers I have. I am going to admit something here --- I had a MC30 that I could kick myself for selling along with its C8 Preamp. I also had the MC240 that just never thrilled me. When I came to El Paso in 1976, I bought a MC275 that I still have. Guess what --- just doesn't thrill me like it is supposed to. It is those Williamson amplifiers that I mentioned that I love to listen to. I mentioned that the best performing amplifiers on the bench may not be the ones we like to listen to the most. As for performance, the Acrosound amplifiers have better bass - I listen to one every day but the UTC Williamson has better highs. On the bench the Acrosound will easily do 20 Hz but not perfect at 20KHz. The UTC transformers fall apart below 30 Hz but have a better high end. That is my measurement and listening experience. The Mac amps, they perform flawlessly - vacuum tube and solid state - and they are Good and will produce a volume level on those Klipschorns that will drive the nails out of the wall without distortion. I have found that our ears distort at extreme volume levels and ear plugs allows us to hear the music without the pain and see it is virtually distortion free. That is what McIntosh amplifiers are capable of doing but for any sane listening level on high efficiency speakers, 15WPC is plenty. Thanks for keeping in touch with me. I just took a break from disassembling the big SET.

@@ElPasoTubeAmps Thank you for your detailed explanation! What really gets me is when someone says they have a surround sound system that has hundreds of watts per channel and multi driver speakers, yet they don't realize that anything over a few watts is all they are using! Of course that has to do with the efficiency of their speakers, but generally only a few watts of power is all that is needed for thunderous sound. I am not bragging, but I have speakers that I have always wanted ever since I saw a pair in a theater... Altec Lansing Voice of the theaters. VERY efficient and VERY little power needed to get to high sound pressure levels. In my "home theater", I have been hard pressed to find surround speakers that are up to the VOT's efficiency. Even pricey ones aren't really as good. My receiver has WAY more power than I ever use, but it has the features that I wanted and that is why I have it. Of course, my tweeter amps are Dyanco MK3's! Great sounding AND they are tube! Take care and stay well!

@@pomonabill220 Voice Of The Theater speakers - I am impressed with those guys. When I was a much younger man in Huntsville, I lived in an apartment that had a bar in the middle of the complex and everyone was told that rented there - you could not complain about the noise - it was wild. The point is, one of the guys had VOT speakers and I have loved them ever since. Those are real speakers the way I see things. Now I want some... 🙂

@@ElPasoTubeAmps And your Klipsch's in your living room are marvelous too! Aren't those corner horns? Klipschorn? They are a beautiful piece of furniture as well! I know years ago, when I had stars in my eyes for the Altec's, I also feel in love with the big Tannoys. The cabinets, I think, were about 5 feet tall and were mostly reflex and port, but I heard them in a HiFi store and oooooo they were NICE! I do not remember the model, but I do know they were Tannoy. I was going to fabricate my own VOT's and have the plans for them, but I found a guy selling a pair for $400, and I snapped them up. He said that his wife said "either they go or I go". I would have said "see ya later".... That was back in Set 19, 1980. Now you can't touch them for less than $2-3000 EACH! And NO I won't sell them, even though they take a large part of my living room! They are a part of me and my memories... even though alot of people don't like them because they are horns... (or jealous?)

@@pomonabill220 I recently purchased some new midrange drivers for my Khorns and I like them even more. It is true that not everyone likes horns. I have recently put an equalizer on the output of my DAC straight into the power amplifier and turned down the mid frequencies a bit and I am happy with that. I think the problem with horns is that they reproduce whatever is fed to them - whether it is Khorns or your VOT and if "anything" is wrong in the sound - anywhere along the line - we hear it and the speakers get blamed. I have felt that way for a long time. Many other speakers can just hide things and sound "better". And, there are many good sounding speakers out there so I am not slamming anything. I was told long ago that the only way to be happy with a sound system is to have the attitude, "There is no HiFi, like my HiFi"... In my backhouse where I spend most of my time, I use the Tekton speakers and my homebrew Williamson with the Acrosound OPT. Watching TV with the sound thru this stereo system and coming out of the Tektons can be downright scary - and wonderful. They are a little heavier on the bass than the Khorns - not at 120 db... but at normal listen level they are probably considered a little 'boomy" to some people - but I like them... $400 - damn - I would buy them also - right now and clear out some room for VOT's... buy a few cases of beer and have a block party. Drive them with a Mac 2205 and they would hear me in Las Cruces, NM. My wife allowed me to get my speakers in 1996 because of their furniture look. She has always been fine and appreciated them but she would never let me put my homebrew AM transmitter in the living room - wonder why... it's beautiful all lit up and sizzling with MV rectifiers and 4000 volts... 🙂

Sorry for such a late reply but RU-vid does not notify email of all comments. It was poor specks not poor sound. It sounds amazing and with plenty of reasonable volume including good low frequency response but on the bench, it measures terrible. If you notice, most demonstrations of SET amplifiers is with music like classical violine music and not heavy metal. It gets "loud" but if you need to loosen the nails in the wall, It can't go there. 🙂

I would not want to take apart a vintage UTC or Acrosound transformer in an attempt to add a gap to the core. I am not sure that would be possible with a push-pull transformer. Plate load into an inductor is not terribly uncommon but surely the best way to go would be to purchase a SE transformer. I believe Hammond makes SE transformers but unless the SE amplifier is the size of a fridge, we have to live with about 7 watts output at 2 or 3% distortion and a 50 pound amplifier. I think I have had my "thrill" with SE amplifiers and will stick to push-pull from here on out. Quite honestly, it is easier to build a good push-pull amplifier than an equivalent good SET amplifier. I have found that out the hard way... Thanks for your comments.

You are the first one I have communicated with that gives real data. I ran them at 1000 volts, I don't recall the current but the graphite plates showed a dull red and were seriously hot. I am used to hot tubes in transmitters at 600 to 1500 watts output with orange plates and 3600 volts but tubes this hot for a stereo is scary. I tilted the amplifier chassis on its side and one of the tubes got too close to the rug I have on the bench to keep from scratching things up and it melted the rug... If you need more, I will make you a deal - I think I have six. Lastly, maybe I am missing something but how are we going to get top quality (test bench) HiFi performance driving grids positive? Maybe your MOSFET follower is the answer. I don't know.

@@ElPasoTubeAmps I did reply you about how to drive the SV572-10's grid positive but my reply was gone for some reason. Anyway, you can drive SV572-10 with direct coupled cathode follower. You may change the driver tube (5881?) to cathode follower direct couple to the SV572 grid. Is your first stage 6SN7? If yes, you can rearrange the driving stage like this: 6SN7(1) -> 6SN7(2) -> 5881 cathode follower -> direct coupled to SV572-10

For MOSFET source follower, you can use "tubelabs power drive" to search the info of how to drive tube's grid positive.

The last option is to use an interstage transformer with low DCR secondary to allow SV572's grid to draw the current. It transformer need to be driven by low Rp tube (800 ohm or less) The SV572-10 works well with 5-6K transformer to get good power out with low distortion. Higher load also works with SV572 but doesn't lower distortion as much.

@@cijtele I don't understand RU-vid sometimes as I will see the message in email and it will not be here, in the video, so I can respond to it. And, as you say, some messages disappear, and I don't know why... I have wanted to respond to messages from you guys lately and I can't... anyway, thanks for the thoughts. I have taken that amplifier apart and started on a couple of other projects so the SVT572-10 SET will have to wait to another day. I appreciate your information and thoughts.

Just snap 9V batteries in series. The + side of one will snap into the - side of another. If you need 72 volts, you need to snap eight, 9V batteries in series, five batteries together for 45 volts, etc. The voltage does not have to be perfect just get as close as you can and it will probably work. Be very careful with polarity connecting into your instrument. One time connected with the wrong polarity and you instrument is probably ruined so you can't make a mistake in polarity - not even once. I fried a TenTec radio years ago with one mistake of wrong polarity 12 volts - but was able to fix it after replacing several shorted transistors. Good luck. You might be interested in this: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-fGj99yUmhSw.html

@@ElPasoTubeAmps How do I know what wire is postive and negative on the counter? there is strange colors that arent usual. would dollar store 9 volts work?

@@dogfortgaming3183 First off - we can spend a lot of money on 9V batteries and things not work out. I have had that happen. As for polarity, hopefully you can find some sort of schematic or determine what the polarity was from any remaining connections from the original battery connections and mark the wires clearly and properly. It is a bit tedious and I recently changed the batteries in my scintillator and was very careful but still a bit apprehensive when I first turned it on again.

You know I agree with you possibly because we have been indoctrinated into believing anything that "sounds good" has to meet high standard measurements in the lab. The harmonic profile of these SET amplifiers look like a triangular wave with a large second harmonic but there is something charming about them. I did not rebuild the amplifier in the video. The 300B SET where I used a choke for a plate load and a James OPT to match to speaker Z is the only SET I will ever likely build. The SV-572-10 (10 is the mu of the tube) draws grid current - ugggg.... you and I know it can't sound good if it draws grid current - right? I guess I will never know. I am pretty much sticking to my ham radio and RF nowadays. Hope you are doing well.