TSSA - The Simplest Symmetrical Amplifier - Page 81 - diyAudio
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Old 7th June 2012, 05:42 PM   #801
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The heavier the better i would suppose.
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Old 7th June 2012, 07:50 PM   #802
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Quote:
Originally Posted by Nico Ras View Post
Hi Sonnya,

I played with your schematic and found while running Monte Carlo that a practical imbalance in the mirror currents can cause quite severe cross-over distortion. When I say practical, I mean real life components.
Hi Nico

I think the effect of increasing current through TSSA mid-bridge load would result in the same bypassing way like all CCS-s Sonny choose. Collector load resistor (Rgs) can also be 10 k or any other prefered value (defined by mid-bridge load value) in this much more simple solution, which only aim is to prevent mid-bridge DC potential (bias current) from being unstable. Also because the mid-bridge resistance is positioned symmetrical to GND, no imbalance (DC offset) can be expected out of this variant, hopefully.
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Old 7th June 2012, 07:59 PM   #803
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Quote:
Originally Posted by Joachim Gerhard View Post
To answer some more questions :
Do i think that the Sauermann is a good amplifier ?
Yes, i do and i also think it is a good value. He uses good parts and it is well build.
Do i think that my version of the Simple Symmetric is better ?
No, it is different but the differences are small, in the direction of taste. You could also say that the bass from the Sauermann is better controlled and tighter. I just was so mesmerized about the "massaging" effect that the Simple Symmetric had.
Never heard that before in such clarity.
You also have to consider that this assessment is only valid under the special circumstances. A speaker-room combination that is a bit overblown in the bass would certainly benefit from the Sauermann.
We where 3 experienced and professional listeners though and we heard very closely the same. That is quite rare so there is a good chance that it was real what we heard.
Quote:
Originally Posted by Joachim Gerhard View Post
And the more detail and speed we heard from the Simple Symmetric ?
It may simply be that the Simple Symmetric has less damping factor so a peak in the impedance curve between tweeter and woofer may cause that effect by bringing out the presence range just a little. That also would explain the deeper soundstage of the Sauermann.
I do not have an impedance curve of the updated LQL200 so this is an estimation.
Maybe i can get the actual curve from the designer.
I think the amp-cable-speaker-room interface has to be considered as system or we are in muddy waters.
What is fascinating here is how the simplicity of TSSA amplifier topology can even be compared to such high sound quality players on the market as Sauerman is.
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Old 7th June 2012, 08:39 PM   #804
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The Sauermann has a very simple signal path too. That is what i like. The problem is with ultra simple design what MiiB calls the "Household".
LC, do not under estimate the level you work on here. Simplicity is very challenging.
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Old 7th June 2012, 11:13 PM   #805
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This reminds me of the famous quote: 'I apologise for the length of this letter, I did not have time to write a short one'.

Elegant simplicity consumes huge energy and time. I've found this again and again. And it's always misjudged. Imagine how much time JLH spent honing his 10 watt 1969 amp!


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Old 8th June 2012, 12:20 AM   #806
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Taking away hurts, adding is easy.
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Old 8th June 2012, 12:30 AM   #807
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Quote:
Originally Posted by sonnya View Post
Hi Jay. This amp did already sound very good without a bufferstage before the mosfet. With the buffer the distortion is very very low even with a low idle current.
Hi, thanks Sonnya. I have simmed your circuit with 2N5401 and BD139 for the drivers. 1.5% THD at 20kHz. I think it's good for a hexfet (should be lower with laterals). And it is fast too. But too many stages, even tho the topology is a plus. And I can see what was mentioned by Nico. I don't know if it has audible effects but believe it or not top amps just don't have "issues". Later I will build this and compare it with my version of Mooly's M1 Hexfet.

Quote:
Originally Posted by Joachim Gerhard View Post
I just was so mesmerized about the "massaging" effect that the Simple Symmetric had.
Never heard that before in such clarity.
Yes the SS frontend (and FB) I think gives the unique character. I don't know which part of the simulation data is responsible for that. The phase data is I think unique. Almost no issues with 4th order and higher. The spectrum is consistent with power. I like this amp except the 20kHz distortion, and the relatively high noise floor that has effect with bass quality (but can be minimized by careful choice of bypass capacitors and power supply). I have seen tho in my simulation, that this can be cured with integrated J/FET front end.

I haven't seen people simulating amp with a preamp. In real life there is this "matching" issues. A good amp might sound bad when paired with non-matching preamp. That's why I tried to simulate amps with at least simple volume control and buffer.
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Old 8th June 2012, 12:46 AM   #808
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During the next days we should agree on a schematic based on the latest knowledge.
Again i am prepared to build it P-P.
The next week though i am occupied with the Frickelfest.
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Old 8th June 2012, 12:48 AM   #809
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Jay, with my cap multiplier PSU the noise is more or less non existent.
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Old 8th June 2012, 01:03 AM   #810
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Quote:
Originally Posted by Joachim Gerhard View Post
Jay, with my cap multiplier PSU the noise is more or less non existent.
May be I'm using a wrong terminology when I say "noise floor". May be I'm doing it the wrong way, but I cannot see the effect of power supply on what I think is the noise floor in the chart I posted. My Mimesis clone for example, has the "base" for the FFT chart at -240dB. I have seen correlation between this and bass quality.

So from the chart I posted, whatever power supply that I used, the bottom of the 1kHz signal for example won't go down to -180dB.

Yes, I have used cap multiplier also.
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