Shann i known all of that since i follow Peeceebee form begining and respect your point of view. My question above was just curiosity that maybe correlate to your observations. It's avery time a pleasure to follow this thread as it is pure diy work spirit : simple, low budget, doable at house without specific equipment
Marc
I totally agree with you. The difference is so subtle in most case (if there is any), that no need to add any CCS to this amp. Although it strongly depends on personal taste.
BTW mods, You wrote earlier:
"As I mentioned in an earlier post, I decreased input collector load resistors from 470R to 220R and current injectors from 12K to 5K6 [+-28V PS] resulting into about 4.8mA input current, like the SSA of last year. VAS current is about 20mA.
Well, I've been listening to the modified version everyday since then, everyday for at least 2 hours and more than 10 hours for 2 or three days. The sonics are apparently much more close to what I call 'natural'. The overall midrange and drum-strokes are now like the real things, real, 'close your eyes and see'.
Lows and highs seem unaffected, same extra-ordinary I mean."
How about this mod? Stability, heat, offset, etc.?
In most cases, of course strongly dependent to certain level of system's quality, your ears-brain tool will tell you nothing. Is this sufficient to claim that there are no differences? Cable change is noticeable, component-part presence or its value even more.
All nearly the same just except the offset. A re-calibration was necessary.
The change of values aren't much worthwhile. I reverted back, sorry, forgot to post.
Andrej, let us consider these findings 'isolated' and stop questioning system's 'quality', we know it's pathetic here. Thank you.
Let me correct myself. In the given system (good old B&W matrix 805 and Marantz CD5004) I cannot hear significant differences (maybe need more experience and skills to find the right CCS solution). PeeCeeBee is a very elegant solution in this chain. It is as good as it is.
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Thanks for the review egra. New feather added to PeeCeeBee's crown, driving cool systems and delivering quality sound from generic parts.
Another interesting observation: There are two amps (what I heard) wich have very very similar sonical character (or lack thereof) to PeeCeeBee. One of them is Accuphase E207, another is Marantz PM8003. These 3 amps can deliver the musical pleasure what I'm looking for in audiophilia. Thank You shaan and LC for this great DIY gem.
OK, lets just go to isolated view and do some measurements, you'll quickly noticed at least 10 dB difference in worse PSRR coming from low Z resistor injecting input bias current. CSS has thousants times higher Z also its constant current doesn't follow rails ripple and that is the major benefit. It's not just input bias current provided here, there's a direct sum of three currents in feedback node causing extra error to an amp.
Hi L.C please say something about diode+R combination(1n4007+10R).
Any advantage if we power vas and inp with separate stabilized power supply?
Thimios.
Any advantage if we power vas and inp with separate stabilized power supply?
Thimios.
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I think D+R combination is much easier to bypass than to discuss it on pages, then everyone can have a personal opinion. I bypassed it on all my VSSAs as I liked the bass more without them 😉
If I would try a stabilized supply for the Input + VAS then I would definitely go with resistors instead of CCS. One day I will try powering input section with a shunt power supply 🙂 I am afraid though it won't be "Very Simple" anymore...
Cheers!
If I would try a stabilized supply for the Input + VAS then I would definitely go with resistors instead of CCS. One day I will try powering input section with a shunt power supply 🙂 I am afraid though it won't be "Very Simple" anymore...
Cheers!
Hello Andrej.
Everyone knows what you said. I know as a matter of fact that a 100dB difference doesn't matter if the amp as is gives you the sonics you look for, which is, fortunately or unfortunately, purely subjective. See, nobody is saying that CCS can't bring advantages, neither am I, but please, for the sake of peace, keep those debates and suggestions out of this thread. I hope you understand that there are many people with great personality and taste who prefer a simple imperfect amplifier for their entertainment over one with lots of zeroes. Lets consider them blind and deaf, I'm sure they won't mind. Don't you see your creation is bringing smiles here? Please don't spoil it.
Everyone knows what you said. I know as a matter of fact that a 100dB difference doesn't matter if the amp as is gives you the sonics you look for, which is, fortunately or unfortunately, purely subjective. See, nobody is saying that CCS can't bring advantages, neither am I, but please, for the sake of peace, keep those debates and suggestions out of this thread. I hope you understand that there are many people with great personality and taste who prefer a simple imperfect amplifier for their entertainment over one with lots of zeroes. Lets consider them blind and deaf, I'm sure they won't mind. Don't you see your creation is bringing smiles here? Please don't spoil it.
I have now built 5 VSSA "style" amps. One on a veroboard using Shaan's Peeceebee layout, one using TO-3 outputs on Jason's layout but still peeceebee. One one PMI's boards using CCS. One on Jason's latest layout using CCS and a final one using Jason's layout but driving a 5-pair EF3 output stage with +-75V rails. The first 3 use a 25-0-25vac transformer with Mr Evil cap multiplier. The 4th uses a +-36V SMPS and the the last uses a 55-0-55vac transformer through 6X10,000uf filter caps. They all sound identical except at very loud volume where the big one, for obvious reasons, out shines the others. At normal listening levels I would dare any of you to pick out which one you are listening to. Even on the scope they look the same.
Blessings, Terry
Blessings, Terry
