Long time lurker, very first post. I have a CCS loaded parafeed push pull 6N6P output stage using an Antek 230:5 volt toriodal transformer and a 1uf russian hybrid PIO capacitor. The driver stage is a 6SN7 LTP with an LM317 in the tail and gyrator plate load capacitively coupled with .22uf FT-3 Russian teflons. I would also like to add that I am using SSG silver mica Russian capacitors in the gyrators, and absolutely love the resolution and air they provide. I cannot think of a better capacitor in this position. They really synergize well with the FT-3's. The amplifier as a whole is very articulated with microdetail compairable to SET amps I have built in the past (Clarinets give me goosebumbs). Very spacious soundstage with heaps of seperation between instruments even when things get crowded. The speakers are Minimus 7's with the Zilch mod. What this setup does lack is presence. It sounds a bit flat, which could be attributed to being push pull. I should also mention I am using the mu output of the CCS's to couple to the output transformer. Taking the input off the plate seemed to make things nervous, and over excited... perhaps a smaller valued cap would help on that front, but I am very happy with the current wiring. So now for the $300 question: is there a capacitor that some of you can recommend that would perhaps add some depth to this amplifier without losing the air and microdetail?
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I look for cheap options first. Then cheaper options second. Recently I found some super-ugly dirt-cheap polystyrene film caps that are delightful.
Honestly it sounds like you are already a happy customer, so why not leave it alone? Btw - Is it your own design? Own build? Feel free to post schematic, pictures, etc. We all love tube/valve porn...
Honestly it sounds like you are already a happy customer, so why not leave it alone? Btw - Is it your own design? Own build? Feel free to post schematic, pictures, etc. We all love tube/valve porn...
It is my own design... with heavy "inspiration" of course. I don't have a schematic handy at the moment, but I will be more than happy to post one when I get home. I have been wanting to try polystyrenes for output coupling, but finding a 1uf with a suitable voltage rating (B+ is 350 volts), has proven difficult.
I didn't notice any appreciable increase in bandwidth over 1uf. I don't have a good way of actually measuring the frequency reposnse, but my ears (just had them calibrated) suggest 1uf is perfect. I'm not looking for boutique parts necessarily... I am looking for synergy. It could be a $2 chinese electrolytic if it mananges to give that "pop" I am looking for.
If you are looking for more 'pop', i am thinking that means more dynamics, or more punch in the bass, etc., maybe you should think of working on your power supply. You did not outline what the PS consists of.
The power supply certainly could use some improvement, as of right now it is a Hammond 300v transformer rectified with 6D22S damper diodes (overkill, but that is what I had handy for the current draw at the time). A 1uf input capacitor then further filtered with a 20uf and a 40uf. There is a small amount of hum, but at this stage of the build, it is quiet enough. The amplifier is still in the prototype phase.
There really isn't a shortage of dynamics. The amplifier is quite snappy and articulate. I am hoping for more of a "3 dimentional" kind of sound.
There really isn't a shortage of dynamics. The amplifier is quite snappy and articulate. I am hoping for more of a "3 dimentional" kind of sound.
OK. Just a thought about your description of the sound quality. It has a similarity to what a set of speakers sounds like when one is connected out of phase with the other. The soundstage gets flattened and confused with the out of phase channeling. So since you are using toroid power transformers that probably have no phase coding on the leads, it's possble you have the leads on one swapped compared to the other and even though you may have your output grounded and speaker phase correct on you speaker wires, you could have reversed phase output trannies. You would never know if there is no FB to create the well known screetching, to provide a clue, or if you don't run a phase check with a scope. ....?
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That is an option certainly worth exploring. I figured no screetching, no problem. I was unaware that it was caused by feedback, and having never used negative feedback, that would explain why I "got it right" the first time. I will definitely delve into this further when I get home... Thank you
There's a way you can check polarity without a scope using you DMM if you can run a 100Hz signal into the amp. Turn the volume up until you get 1-2v AC scale measuring the voltage at the speaker (+) terminal to ground terminal. Then move the grounded probe to the other channel (+) terminal. If the two channels are out of phase you will get 2X the voltage as from just one. If they are in phase the voltage should read close to 0v.
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google dielectrics dissipation related distortion in capacitors.
something like that
you will see that higher permitivity materials make smaller capacitors, but they give more distortion. polyester is such example. fine for guitars but not for hifi.
teflon is best, slivermica, then polypropylene , pio, ....
something like that
you will see that higher permitivity materials make smaller capacitors, but they give more distortion. polyester is such example. fine for guitars but not for hifi.
teflon is best, slivermica, then polypropylene , pio, ....
I've only heard stock Minimus 7s and, while I don't doubt that the modded version is a big improvement, I suspect better speakers would accomplish more than a cap change if the goal is to add more presence.
Have you tried other speakers? Do you really need something that small due to space limitations?
Just curious, how much power does a PP 6N6P amp produce?
Have you tried other speakers? Do you really need something that small due to space limitations?
Just curious, how much power does a PP 6N6P amp produce?
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Is that total or per channel? I recently modded a little SE 6BQ5 Magnavox console amp to use 12BH7s as outputs and I'm guessing it's about 1.5 wpc or so.
Flea Power SET - Magnavox 12BH7 Mod
Flea power will surprise you.
Flea Power SET - Magnavox 12BH7 Mod
Flea power will surprise you.
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