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Old 29th March 2014, 01:24 PM   #3231
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You desperately need an oscilloscope to see what's going on here. Borrow one.
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Old 29th March 2014, 02:01 PM   #3232
BYRTT is offline BYRTT  Denmark
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Quote:
Originally Posted by Elektrohoolik View Post
Hi again. After some testing i discovered that when I put 47nF (type is K73-9) cap in intput, amp get silent. But, when i let it there, it gonna "eat" hight frequencies? But, we dont need higer frequencies than 20kHz . Or i wrong?
Hehe good humor. Yes in principle 20KHz is maybe enough for simple sinus (use 2n3055 output devices) . LC constructed GB VSSA for 100KHz square wave reprodution if i remember and in lab he had it higher, to benefit this keep input as delivered.

Recommend oscilloscope and LC guide, but if not available now and you have time and patience here suggestions to try:
Concentrate on only one module getting up running perfect, and thereafter the other based on knowledge from first if succeeded.
Dismantle the module, inspect visual for errors and especial see if INPUT pair and VAS pair should by accident be turned around.
Pre calibrate TR1/TR2/TR3 by this guide VSSA Lateral MosFet Amplifier.
Short input by soldering little wire, and don't take this off before amp first is calibrated and later running with speaker connected and no noice at all in speaker.
Many had little smoke from R21/R22 belonging to Zobel filter and then resistence go off spec so with DMM in ohm mode measure them they should be 20ohm.
Mount PCB again and if possible isolate screws for two VAS devices with isolated washers of some kind. But do only this if shure heatsink always have ground potential through box or wire.
Now calibrate as in manual + the amend for calibration that can be found here VSSA Lateral MosFet Amplifier.
If now still sea sound noice try desolder C4/C5, those oversize green 10uF MKT's you used, amp can run without. If no good try another simple PSU for trials.
Good weekend.

Last edited by BYRTT; 29th March 2014 at 02:11 PM.
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Old 29th March 2014, 02:12 PM   #3233
Mihkus is offline Mihkus  Estonia
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Haa... Those 3055/2955 are probably the worst output devices i know, not sure if the slowest.
Try 100k resistor... feedback resistor value?
Power supply GND connection to frame? The input cables should be islolated, So far I havent found anything better than well shielded 50R cable.
Biased to class A?
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Old 29th March 2014, 02:45 PM   #3234
BYRTT is offline BYRTT  Denmark
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Quote:
Originally Posted by Mihkus View Post
Haa... Those 3055/2955 are probably the worst output devices i know, not sure if the slowest..........
No the slowest is Elektrohoolik's VSSA when using 47nF at input filter .......

Quote:
Originally Posted by Mihkus View Post
..........Try 100k resistor... feedback resistor value?..........
You free. Not a LC module anymore, there some error elsewhere at Elektrohoolik's VSSA think better to find that.

Quote:
Originally Posted by Mihkus View Post
..........Power supply GND connection to frame? The input cables should be islolated, So far I havent found anything better than well shielded 50R cable...........
See point 6 here (LC recommended grounding connections for VSSA) VSSA Lateral MosFet Amplifier.

Quote:
Originally Posted by Mihkus View Post
..........Biased to class A?
When calibrated right it do automated class A at low power and AB at higher power as i understand.

Last edited by BYRTT; 29th March 2014 at 03:02 PM.
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Old 8th April 2014, 05:11 AM   #3235
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Hi, I'm newbie.
Can I use VSSA Lateral Mosfet with +/- 45V rails for 125Wrms ?
Are there no other parts modification ?
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Old 8th April 2014, 05:26 AM   #3236
dady is offline dady  Argentina
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I think there could be no problem. I use this voltage.
Watch out with more heat.
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Old 26th April 2014, 02:49 PM   #3237
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Hi again. I finally bought C1-54 scope. Now i can see the noise, It start from input. Noise look like loooooooooong diode symbol. When someone want see this, i try make picture of this miracle. Also i can see little sik-sak at caps, but i think it is 50Hz noise.
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Old 26th April 2014, 03:00 PM   #3238
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Hi, VSSA or First One ,what`s best with Speakers around 92db ?I don`t listen that loud
so don`t need that much Power ,but wan`t the best Soundwise .Soo,what`s the way to go ?
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Old 26th April 2014, 03:17 PM   #3239
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Quote:
Originally Posted by Elektrohoolik View Post
Hi again. I finally bought C1-54 scope. Now i can see the noise, It start from input. Noise look like loooooooooong diode symbol. When someone want see this, i try make picture of this miracle. Also i can see little sik-sak at caps, but i think it is 50Hz noise.
Try to sync the waveform to be still on the scope's screen. Don't forget to record the X,Y values.
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Old 26th April 2014, 03:19 PM   #3240
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Quote:
Originally Posted by taccodude View Post
Hi, VSSA or First One ,what`s best with Speakers around 92db ?I don`t listen that loud
so don`t need that much Power ,but wan`t the best Soundwise .Soo,what`s the way to go ?
For a little higher price and size you'll get much greater performance from a ready made and well tested First One amplifier.
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