Good idea. 😎
I have attached an schematic. The current sources needs to be drawn.
Mirrors uses BC546 and BC556 but they should be KSC3503 and KSA1381 as they can handle the power better.
This is innovative. I have not seen a parallel degenerated current source in this surrounding before.
I have seen degenerated mirrors though in Bob Cordells book. He calls it differential feedback but it is not the same.
I have seen degenerated mirrors though in Bob Cordells book. He calls it differential feedback but it is not the same.
Hi 
Sonny as I said so many times "you're a great man"! Me also bite the problem and not let go until is resolved. 🙂
... so it is the injected current level into the bridge after all. I assumed that something like 0,65 mA through 2 k is just not enought to hold the bridge DC potential stable. Your solution highers mA through the input pair making them much more insensitive to load leakage current conditions, also mid bridge load (any real kind) would do similar, making bridge DC level insensitive to leakage. When you'll do the tests please check the simple (one 100 ohm mid-bridge resistor) solution too. 😎
I apologize not to be present here as I should be but I have so many orders that the job occupies me extensively.
Best regards to all Andrej 😉
P.S. Mid-bridge load influences only to DC conditions, no influence to AC feedback part. Value can be from 0 to infinite so from zero DC to mA*resistance level in mid-bride. Optimum value is somewhere in between 😀
Sonny as I said so many times "you're a great man"! Me also bite the problem and not let go until is resolved. 🙂
... so it is the injected current level into the bridge after all. I assumed that something like 0,65 mA through 2 k is just not enought to hold the bridge DC potential stable. Your solution highers mA through the input pair making them much more insensitive to load leakage current conditions, also mid bridge load (any real kind) would do similar, making bridge DC level insensitive to leakage. When you'll do the tests please check the simple (one 100 ohm mid-bridge resistor) solution too. 😎
I apologize not to be present here as I should be but I have so many orders that the job occupies me extensively.
Best regards to all Andrej 😉
P.S. Mid-bridge load influences only to DC conditions, no influence to AC feedback part. Value can be from 0 to infinite so from zero DC to mA*resistance level in mid-bride. Optimum value is somewhere in between 😀
Just a word of encouragement to you Sonny and Andrej; it is wonderful to see this co-operation and open discussion of your work. Joachim and his team in their work on phono stages etc show the same dedication to the design process and you all offer the DIY person of low experience an 'in situ' training along with the prospect of building very high quality equipment at a comparatively economic cost.
Thank you all!🙂
Thank you all!🙂
Thanks Brian.
I hate only talking and not showing schematics so for me it feels natural.
Ones a project is started it should also be finished if there is enough interest.
And one thing : our team does not only give away know how but we learn too so this is not a one way street.
I hate only talking and not showing schematics so for me it feels natural.
Ones a project is started it should also be finished if there is enough interest.
And one thing : our team does not only give away know how but we learn too so this is not a one way street.
Thanks Joachim....I note the comment about finishing.😱 I am still waiting for a few parts and have yet again spent time in hospital.....this time potassium poisoning!! (I had not been warned about salt+some other foods when taking beta-blockers! Was extremely ill! But this thread I find interesting and will build the simplest version for fun and experience once I have finished your design and listened a bit. (Tapes soon to be posted)
Best,
Brian🙂
Best,
Brian🙂
Brian, the simple version works without problem. I made an improvement by using depletion Mosfet constant current sources instead of the 1kOhm pot meters and i am using a cap multiplier in the PSU. I build double mono. I use 50mA in the current sources so the amp runs rather hot, i would assume on at least 2A idle.
That amp sounds really good. Yesterday i visited the people from Klangmeister in Lemgo and we compared the simple symmetric to a commercial amp from Sauermann.
That amp gets a lot of attention at the moment for sound quality. The simple symmetric had deeper and more musical bass and resolved details better. The Sauermann had a somewhat deeper sound stage though. We used updated Ecouton Audiolabor LQL200 speakers. They have a rather low 83dB sensitivity but they go down really deep under 30Hz. The bass from that speakers is massaging the whole body. Quite an extraordinary effect. The Sauermann has 2 x 30W Class A so it is not a power house ether. With both amps we got decent volume in a rather big room, good enough for natural music but maybe not enough for hard rock. The next candidate will be an Apogee
Duetta. If that works too it will be a surprise.
That amp sounds really good. Yesterday i visited the people from Klangmeister in Lemgo and we compared the simple symmetric to a commercial amp from Sauermann.
That amp gets a lot of attention at the moment for sound quality. The simple symmetric had deeper and more musical bass and resolved details better. The Sauermann had a somewhat deeper sound stage though. We used updated Ecouton Audiolabor LQL200 speakers. They have a rather low 83dB sensitivity but they go down really deep under 30Hz. The bass from that speakers is massaging the whole body. Quite an extraordinary effect. The Sauermann has 2 x 30W Class A so it is not a power house ether. With both amps we got decent volume in a rather big room, good enough for natural music but maybe not enough for hard rock. The next candidate will be an Apogee
Duetta. If that works too it will be a surprise.
Yes there is a lot of fuss around the Sauermann. With its p2p wiring. How can he build to identical amps? 
Just my opinion on it. But i must admit that it casing looks good with the metal front.
Just my opinion on it. But i must admit that it casing looks good with the metal front.
Here is some information about the Sauermann :Gerd Sauermann audio - High End Amplifier
It seems to be two modulated current sources, balanced. He even got a patent on it.
What disturbed me a bit is that he claims that the 3rd harmonic that is dominant here improves the subjective impulse response because the third harmonic is also contained in a square wave.
The circuit itself is also ultra simple and it is claimed that the amp is "mechanically optimized", what ever that is.
I expected that the Sauermann sounds somewhat "harder" or "brighter" then the simple symmetric but that was obviously not the case.
It is priced very fair i think on the other hand.
It seems to be two modulated current sources, balanced. He even got a patent on it.
What disturbed me a bit is that he claims that the 3rd harmonic that is dominant here improves the subjective impulse response because the third harmonic is also contained in a square wave.
The circuit itself is also ultra simple and it is claimed that the amp is "mechanically optimized", what ever that is.
I expected that the Sauermann sounds somewhat "harder" or "brighter" then the simple symmetric but that was obviously not the case.
It is priced very fair i think on the other hand.
By the way, the source was a Hörwege modified M-Dac. I think he changed the elcaps to Panasonic FM mostly.
I Can only agree with you Gerhard. It is true that there is infinite number of harmonics in a perfect square wave, but then to draw a line to third harmonics in a sine signal is completely wrong. An amp that reproduce an perfect squarewave does not necessarely only produce third harmonics when reproducing a sine.
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On the other hand, a little third or ( and ) second does not seem to sound like distortion, rather more like "Character".
This square wave thing is nonsense though.
This square wave thing is nonsense though.
By the Way: the output of the 2 stage is more or less also a modulated current source. I would like to see this patent.
Why not ?
This will not change how much he sells or not.
I think his amp is just fine for the price he charges. I just can not see the revolution in sound.
This will not change how much he sells or not.
I think his amp is just fine for the price he charges. I just can not see the revolution in sound.
