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Old 5th June 2012, 08:53 PM   #761
sonnya is online now sonnya  Denmark
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Quote:
Originally Posted by MiiB View Post
Hey that WAS really cool...nice way to raise open-loop gain and not the output current...This way I believe spec.'s could be really good.. Hats off....

I don't know that beer, but let's have a get together at my place in Aarhus and drink a few.....
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.
Attached Files
File Type: pdf tssav16.pdf (14.5 KB, 257 views)
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Old 5th June 2012, 09:14 PM   #762
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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.
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Old 6th June 2012, 09:10 AM   #763
sonnya is online now sonnya  Denmark
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Many Orders? Real job or amp orders???
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Old 6th June 2012, 09:13 AM   #764
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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
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Old 6th June 2012, 09:15 AM   #765
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Quote:
Originally Posted by sonnya View Post
Many Orders? Real job or amp orders???
Real job

Amps will come latter haha
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Old 6th June 2012, 09:41 AM   #766
brianco is offline brianco  Ireland
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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!
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Old 6th June 2012, 05:19 PM   #767
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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.
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Old 6th June 2012, 06:17 PM   #768
brianco is offline brianco  Ireland
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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
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Old 6th June 2012, 06:36 PM   #769
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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.
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Old 6th June 2012, 06:49 PM   #770
sonnya is online now sonnya  Denmark
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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.
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