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Old 17th September 2010, 10:12 AM   #21
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Quote:
Originally Posted by Tekko View Post
Mr. Apex, is it me or do all of your amp schematics look the same ?
You can see in all my threads completly different amp topology, but look similar becouse of drawing. Just compare this schematics: MOSFET Amplifier IRFP240/IRFP9240 , Tube/Mosfet 100W Hybrid Amplifier , 500W PA amplifier with Limiter , LM3886 Schematics + PCB , 100W Ultimate Fidelity Amplifier ...
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Last edited by apexaudio; 17th September 2010 at 10:18 AM.
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Old 17th September 2010, 11:19 AM   #22
macd is offline macd  South Africa
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Default PCB Please........

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Originally Posted by apexaudio View Post
Schematic with corrected caps voltage (100V instead 63V)
Hi Apex.......Do you have PCB for Studio Reference amp.........

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Macd.......
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Old 17th September 2010, 03:32 PM   #23
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Originally Posted by macd View Post
Hi Apex.......Do you have PCB for Studio Reference amp.........

Regards,
Macd.......
This circuit is made for test useing pcb from DC Servo Mosfet Amp (see post #4). Final version will be more powerfull with add another two pairs outputs in triple darlington topology (adding MJE340/MJE350 as predriver). I will share pcb for final version, and diyers with more expirience can use this circuit for design own pcb. Power of this amp is enough for small studio monitor speakers, but for large studio monitors power must be increase up to 200W/8R RMS useing 3 pairs of outputs.
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Old 17th September 2010, 04:18 PM   #24
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Default SR50

SR50 is Studio Ref Amp for small studio monitors without cascode in VAS.
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Old 18th September 2010, 05:14 PM   #25
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Pin layout for MPSA42/92 on Regulated PSU pcb is incorrect, this is correct pcb. Pin layout on first pcb is for BC639/640.
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File Type: jpg APEXaudio Reg Amp PSU PCB.jpg (183.6 KB, 4420 views)
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Old 19th September 2010, 01:09 AM   #26
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Default SR200

SR200 Studio Ref Amp for large studio monitors.
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Old 19th September 2010, 04:20 AM   #27
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Originally Posted by apexaudio View Post
SR200 Studio Ref Amp for large studio monitors.
Every time I see a servo amplifier with an integrator in the feedback loop I cringe. Integrators MUST dither to run which means the output MUST be slowly cycling pos/neg to work. Has anybody tried using an operational transconductance amp for this job? That type of amp will converge and settle with no dithering. It made a massive difference in my DC restored video amps.

G
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Old 19th September 2010, 10:21 AM   #28
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Originally Posted by stratus46 View Post
Every time I see a servo amplifier with an integrator in the feedback loop I cringe. Integrators MUST dither to run which means the output MUST be slowly cycling pos/neg to work. Has anybody tried using an operational transconductance amp for this job? That type of amp will converge and settle with no dithering. It made a massive difference in my DC restored video amps.

G
Amplifier DC offset is about +/-20mV without DC sevo, and no matching transistors are used. Offset is stabil after few hours, so there is no pos/neg cycling, just litle DC current thru RCR filter (220k-220nF-220k) in base of input transistor to compensate unmatching. Amplifier can work without DC servo or can use trimpot to set offset, but I think this cicuit is best way. Feedback for DC servo use 1M resistor and there is no influence to GNF.
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Old 19th September 2010, 05:27 PM   #29
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Quote:
Originally Posted by apexaudio View Post
Amplifier DC offset is about +/-20mV without DC sevo, and no matching transistors are used. Offset is stabil after few hours, so there is no pos/neg cycling, just litle DC current thru RCR filter (220k-220nF-220k) in base of input transistor to compensate unmatching. Amplifier can work without DC servo or can use trimpot to set offset, but I think this cicuit is best way. Feedback for DC servo use 1M resistor and there is no influence to GNF.
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I'm not disputing the servo idea, just if it's been tried without the integrator.

G
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Old 19th September 2010, 05:48 PM   #30
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Quote:
Originally Posted by stratus46 View Post
I'm not disputing the servo idea, just if it's been tried without the integrator.

G
I'm sorry for my bad English, can You post schematic for servo with OTA?
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