After two weeks of daily operation I checked the offset and bias today. Both unchanged. Whoa!
Probably the best fortnight spent with an amplifier. There has only been signal, no noise. So the psychological SNR or satisfaction is infinite mathematically.
I have some questions. I did not feel a hint of distortion from the class-AB SSA. If the SSA with source follower config already sounds(and measures) so well, then why is there the drain follower TSSA with limited power, hot sinks and big Zout? For the fostexes and lowthers? Or is there a noticeable increase in audible and measured performances? Does it sound the same(or better) through the same speaker drivers? Is it an attempt to eliminate as many gain stages as possible? Or is it for demonstrating the scalability of the SSA front end?
Maybe the input capacitor and the X100 22R to 2K2 scale keeps Shaan's particularly steady without hassle as he reports?
P.S. Shaan, I would be reluctant also to go from rich AB to full class A given the the AB quality and easier power output already. If someone had experienced both modes in a comparable build please comment.
On my point of view, and my experiences, i always find Class Ab amps (with correct quiescent current) to sound nicer than Pure Class A equivalent.
There is always an optimum current after witch you can find sound quality slowly decrease.
And we have to take care of the planet...
Please do not flame-me, sun is soooo hot, yet......
Maybe the input capacitor and the X100 22R to 2K2 scale keeps Shaan's particularly steady without hassle as he reports?
How does the input cap and 100X ratio of feedback resistor and emitter resistor contribute to the stability of the SSA? Please teach me.
In the past I built many popular diy class a amps and they all sound just excellent. The price is lots of money at the time of building the amp and lots of money thereafter if you plan to listen to it often. Well, considering the sound quality and simple circuitry the above could be ignored if one can afford the bucks. Still, when there is a measureable and audible increase in performance and quality, one should adopt the amp which is more efficient, leaving prejudices behind. The Class-AB SSA, IMHO, is the best(if not the only) choice here. I say it again,
"SSA IS A MILESTONE FOR ITS SIMPLICITY, A BENCHMARK FOR ITS SPEED, A CROWN JEWELL FOR ITS MUSIC."
OMG I almost forget you Salas, I'm sure you've had positive experience with SSA too.
Shaan, couldn't agree more with you
Regards Andrej
OMG I almost forget you Salas, I'm sure you've had positive experience with SSA too.
Yep I was messing with it early also. I have written positively in the past too.
I remember that it would jump offset if the source resistance would be changed drastically in my tests (dc input), that is why I wonder if the input cap helped yours. Also that 1Meg you got from input to trimmers bridge maybe helps balance. About 40dB gain, it certainly uses much less feedback, its a difference to a 26dB one. But now that I see it again you got 100 Ohm near the 2K2s so yours is normal gain there, so forget that. We used same driver & output semis in same config and bias nontheless.
My SAA has been serving my music to me in my office everyday for almost one year. It has not been opened nor tweaked or adjusted since the day I closed the box.
I do not care if the offset drifts between +30mV and -30mV. Heck I have seen power supply rails do far worse than that.
Off-set does not affect the sound whatsoever whether the output swings 30mV closer to one rail than the other does not bother me much, my tweeters have capacitors in series so they would not know of this off-set and I promised that I will never tell my woofers any of this off-set stuff.
Personally I feel people read too much hype into off-set.
I do not care if the offset drifts between +30mV and -30mV. Heck I have seen power supply rails do far worse than that.
Off-set does not affect the sound whatsoever whether the output swings 30mV closer to one rail than the other does not bother me much, my tweeters have capacitors in series so they would not know of this off-set and I promised that I will never tell my woofers any of this off-set stuff.
Personally I feel people read too much hype into off-set.
I believe that in the future (especially when recording, amp and speaker design is more advanced) all amps will be made this way (hint: the feedback, slew rate). I think amplifier designers are just too slow to understand what and why (may be because most of them do not have good ears and prefer fiddling with very basic Maths) and choose to believe that to be accurate an amp should sound fatiguing and unmusical
P.S. I don't know much about class-D technology so I can't comment on its possibility.
I hope Sir Alex_mm will make PCB design for this SSA version..Hello everybody!
Glad to see this great thread moving forward(which it should).
I'm here to share the story of my re-incarnated SSA which I built a week ago.
As the pictures show I built the front end and the VAS+cascode on different boards and interconnected them with 7 wires. BC550C/560C as input, same as cascodes, BD139/140 regulars as VAS, 1N4148s for bias setting and 1058/162 Laterals as outputs. The diodes set the bias to a nice 150mA through the FETs with +-25VDC supply. Total Iq is 180mA. 5pF silver mica caps as bandlimiters in the VAS and 5.6pF(Old Philips ceramic) as input RF filter. Offset control with two 10K small pots from +-15V zeners, filtered with 1uF siemens MKT. Power to the VAS and the front end is supplied through two 1N4007s with 1uF before them and 1uF+1000uF after. 100ohm gate stoppers and no Zobel at the output.
The amplifier worked like a charm the very first time it was turned on and after setting the offset I was listening to music within 5 minutes of the first run.
No hum, No noise, No offset problem, No overheating, No bias drifting, No nothing!!!!! What is this amplifier!?
Music didn't stop for two hours. And people, what dynamics, what purity, what bass, what mid and overall, what sparkling treble! The speakers were singing!
Honestly, I think my fullrange drivers are not truly full-range at all. But I didn't realize what they were capable of until they met SSA! I have found the holy grail of amplifiers!
Great vocals, both male and female, sitar, sarod, tanpura, mridangam, sarangi, guitar, piano, drums, flutes, violins, cellos, saxes, kicks, claps, cymbals, crashes, snares, bells, synthetics... EVERYTHING sounds JUST RIGHT... what a pleasure!
Tonal character unchanged from very low volume right upto very high! How does SSA do this? No other amp I have built or listened can successfully show this charecteristic and SSA does it with ease, even with my 4" $2 drivers! How, where's the magic?
The sound is absolutely non-disturbing for long listening trials. I live with my mom and sis. And they are excellent and sensitive natural scopes
All these with a 5 meter coax from an AC'97 sound card and an input cap which is, ahem, a cheap bipolar 10uF electrolytic.
SSA is a milestone for its simplicity, a benchmark for its speed, a crown jewell for its music.
My drums mentor, the man I respect the most told me that very good things will happen to me this year. One happened a just week ago.
LC, Thank You. We are lucky to have you around.
Hehehe don't take it literally...
One simple basic assumption for an accurate amplifier is that the output sinewave must follow the input sinewave (tho it is not a secret that the feedback actually "adjust" the input).
There are at least 2 drawbacks to this:
1) Audio system performance is not amplifier performance. Good audio system should consider full chain of the system. Otherwise, to justify the amplifier accuracy you need to blame the CD or the speaker for the terrible sound.
2) Before putting the blame on CD and speaker, pick your proper speaker design (You can also stick with turntable but I think CD is the standard). After decided with the speaker, now build the accurate amplifier. Will it sound musical now? Not that easy... Especially with solid state. So, what now to blame? Music is music. You can remove the low order harmonics from the amp and the "musicality" gone. But NO! It is not the second order harmonic that creates musicality. I believe it is what you do to remove the harmonics that remove the "musicality".
Why did i put the musicality in quotes? Because I consider the absence of fatigue as part of musicality. When I listen to live performance, I always sit there until everybody else leave. I cannot stop listening for hours. If I cannot stand listening to a high end setup for hours (or I don't enjoy it as much) then something is absolutely wrong.
And I believe that the root cause is the feedback.
Jay if you lived closer Id demonstrate how wrong you are to blame feedback. Its a amp capable to even push over valve amps costing 5 times more. Ive caught so many so called audiophiles and know-hows out its laughable and profitable. (every loser has to cede bottle of wine, not your supermarket variety). The losers are always the feedback bad mentality, this amp uses it in heaps, more than most others and it sounds better than most non feedback amps. I usually invite to bring any non feedback amp be it valve or solidstate to compare with this amp. They always get it wrong, claiming that the said amp must be non feedback to sound that good.
In most cases you ll find that 99.99 % of what you call creative ideas have already been explored and many of them used in the past, so what may seem creative to you and others might be old news to others.
I didn't say the ideas were new - in fact I think the fact that some ideas are old is why some ignore them.
The classic example is PSU choke regulation - absolutely ideal for low voltage solid state class A or heavy AB amps, can filter HF noise better than any solid state regulator - but generally ignored - I find this almost unbelievable but have to believe it coz it's true.
I very rarely have an original creative thought but I try be open minded & creative enough to try / combine all kinds of old / new ideas to get a good result
The classic example is PSU choke regulation - absolutely ideal for low voltage solid state class A or heavy AB amps, can filter HF noise better than any solid state regulator - but generally ignored - I find this almost unbelievable but have to believe it coz it's true.
I very rarely have an original creative thought but I try be open minded & creative enough to try / combine all kinds of old / new ideas to get a good result
In many ways truth in that but technology progresses whether one thinks its better or worse. It wont be long Class A amps will be banned from use and well all have to choke on those Class D amps.
By choke regulation you mean the filtering ?? If it is I thought most in Class A use it and know the benefits.
By choke regulation you mean the filtering ?? If it is I thought most in Class A use it and know the benefits.
Common prejudice. Don't put bad assumptions if you want to seek the truth. Don't assume that I blame feedback the way you assumed I did (Actually I'm not one of them who hate or love feedback).
You can pick bad "examples" from both the "subjectivists" and the "objectivists", but that wouldn't lead nowhere.
First, everyone must agree and understand very clearly, that the sound of a system is not determined by amplifier alone. There are too many issues with speaker choices (high sensitivity speakers allow for perfect first watts, multi ways speakers allow for complete music bandwidth, etc etc).
You can invite as many visitors as you want, but the result won't mean anything to me. Tho it might be a little better if you bring your amp to the home of those valve amps owners and compare there in their system.
About feedback, the common agreement is that you should avoid it, or use a lot of it. But that is not my concern because I know feedback is just like capacitor. You can avoid capacitors but it doesn't guarantee anything.
Here is how I came to believe that feedback is the root cause...
I'm not rich to buy Feastrex etc. Lowther DX2 was the most expensive I have owned. And I don't believe in high efficiency drivers, because of the harshness only identifiable by sensitive ears.
So multi-way inefficient speaker is assumed in my system. How about the impedance? Yes, it can be difficult for some amplifiers, especially valve amps. So how about feedback? I think it is a must. Call it a necessary evil...
From years of building and thus listening passive crossovers, I found how dangerous phase can be. Not everyone can detect it. I don't trust my ears, but I trust my brain/mind/feeling (but I have learned to correlate my feeling with what I hear and then at last with electronics).
For a good amp, we can agree that the distortion must be low. Can you make a low distortion amp with minimum "poles" and feedback? Difficult, yes.
Any poles will change phase. It is good if we can get away with as minimal poles as possible. Make a perfect power supply, current sources, etc, instead of adding poles. Choose the best transistors. Now we are left with how to apply the feedback...
Only 2 stages, with probably the best current feedback and high slew rate, capable of at worst 0.004% THD at above 100W, why should I want something else?
Just before I found something like the Fetzilla (I started with cloning the ESP P101) I decided that 3-stage is the key to good amp, no more complex and no simpler. But hey, it is also possible with less than three stage, so I stick with the T/SSA (When TSSA was not yet exist, I didn't use the cascades, so my versions are more TSSA than SSA).
Now, how does your amp (that can beat 5x more expensive valve amps) look like. I assume that the valve fans prefer your high feedback solid state amp (Otherwise there will be a major taste issue). Four stage amp? 40X voltage feedback? Caps in signal path? Conventional power supply?
I have no idea what is inside, my neighbour which is the owner wont let me near it with a screwdriver. 
Maybe after I have prized enough wine to feed him Ill have a chance with the screwdriver
Make no mistake its not a cheapy, price is around 8000 Euros last time I checked and holds patents. It sounds in many ways better than my electrocompaniet Nemo monoblocs which are 600 w monsters and the low feedback type.
Maybe after I have prized enough wine to feed him Ill have a chance with the screwdriver
Make no mistake its not a cheapy, price is around 8000 Euros last time I checked and holds patents. It sounds in many ways better than my electrocompaniet Nemo monoblocs which are 600 w monsters and the low feedback type.
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