Waiting
Nice single side layout. I can see that you used serial ps regulator instead shunt type.
I soldered all components and tested shunt regulators and it worked as designed (shunt regulator). The preamp part I will test next days and start delivers next week. Here is the photo.
I used Nichicon electrolytic capacitors instead Panasonic FC type I normally prefer, but I don't expect it will degrade the sound. TME where I buy do not have Panasonic FC any more.
By the way I used polystyrene small caps instead silver mica. You have to be more careful wile solder polystyrene caps.
Damir
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Supertex was acquired by Microchip Technology, Inc. DN2540 can be bought directly on their site for 1.30$ and also shipping is not to steep, $12 for Serbia, maybe even less for other destinations. Try ebay also for low or no shipping cost.
I was busy with other things and I couldn't finish mk2 yet so I picked info about mk3 to late for pcb group buy. I hope next GB will not be on so short window of few days, but maybe it's better to have the time to iron things out and test the preamp properly.
Regards, Milan
I was busy with other things and I couldn't finish mk2 yet so I picked info about mk3 to late for pcb group buy. I hope next GB will not be on so short window of few days, but maybe it's better to have the time to iron things out and test the preamp properly.
Regards, Milan
I tested yesterday both channels with signal generator and oscilloscope and it works as it was designed. I've found one silkscreen error (one reversed diode) and changed some resistors value (don't panic, just three).
Today I am going to connect it into my listening chain and then I will report and describe all changes. No changes in the layout.
Damir
Today I am going to connect it into my listening chain and then I will report and describe all changes. No changes in the layout.
Damir
It's not so long thread to find where I wrote the price, but here it is: http://www.diyaudio.com/forums/soli...ne-amp-very-low-distortion-2.html#post4828956
Today I was listening to some music from CDs and SACDs and I think this preamp is up to all my expectation, but I could be biased.
1. Error in layout silkscreen, D8 in both sunt regulators should be reversed with cathode to the right.
2. I increased R13 and R15 from 2k2 to 3k3. The output bias was to high, about 150 mA(75 mA per leg), I suggest to have 100 mA. It could be because I used here BC549C/559C from Diotec Semiconductor, not BC550C/560C what I spare for input stage, lower noise.
3. I decrease R36 from 22k to 8k2, DC servo reaction was to slow.
4. In the Mouser order list some poste before I noticed to small (short) heat sinks. I used the ones in attachment from Fischer Elektronik.
Now you from the order list can send me a PM with yours PayPal email, and I will sent PayPal money request to you.
Damir
1. Error in layout silkscreen, D8 in both sunt regulators should be reversed with cathode to the right.
2. I increased R13 and R15 from 2k2 to 3k3. The output bias was to high, about 150 mA(75 mA per leg), I suggest to have 100 mA. It could be because I used here BC549C/559C from Diotec Semiconductor, not BC550C/560C what I spare for input stage, lower noise.
3. I decrease R36 from 22k to 8k2, DC servo reaction was to slow.
4. In the Mouser order list some poste before I noticed to small (short) heat sinks. I used the ones in attachment from Fischer Elektronik.
Now you from the order list can send me a PM with yours PayPal email, and I will sent PayPal money request to you.
Damir
Attachments
Hi Damir:
Thanks for updating us on the changes you've made.
p.m. sent
I'm curious about the servo changes.
I thought the "speed" of the servo was altered by changes in the 1M/1uF time constants (set by R38, R47, C12, C13) and R36 changes the "strength" of the servo to correct the circuit.
But you said you reduced R36 because the servo reacts too slowly.
So perhaps I misunderstand ?
Could you explain more ?
thanks,
mlloyd1
Thanks for updating us on the changes you've made.
p.m. sent
I'm curious about the servo changes.
I thought the "speed" of the servo was altered by changes in the 1M/1uF time constants (set by R38, R47, C12, C13) and R36 changes the "strength" of the servo to correct the circuit.
But you said you reduced R36 because the servo reacts too slowly.
So perhaps I misunderstand ?
Could you explain more ?
thanks,
mlloyd1
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Probably slow was wrong term I used. Actually when the preamp was switched on it take some time that DC servo corrects output DC offset and that time is shorter with lower value for R36 but stresses more the opamp. The higher its value the less DC servo influences audio, so there is some compromises to take. RC constant used(R38-C12 and R42-C12) in DC servo should be low enough to minimize that influence.
