I don't remember much about version 1.2. I think Valery had fixed the op amp issue. I'm don't remember why he added the feedback but I think there was some issue after running 1.1 version of the amp for a while.
I can send you some Simpelstark+ boards if you want to build the latest version.
I can send you some Simpelstark+ boards if you want to build the latest version.
I have troubles with the ver.1.3 too but after one year sporadically using.
Recently i discovered that i have used fake 2sk 246.All my stock of k246 is fake.
I don't know that problem was due to fake k246 but placing new original matched pair jfet i have a functional amplifier again.....up to now!
Now I'm curious to see how this channel (ver 1.2) will be.
Thank you very much for your offer. Yes, if I don't get you in big troubles I would like to have the latest version. I have already made the enclosure, I have engraved it and I would not like it to host another amplifier.
thimios
Recently i discovered that i have used fake 2sk 246.All my stock of k246 is fake.
I don't know that problem was due to fake k246 but placing new original matched pair jfet i have a functional amplifier again.....up to now!
Now I'm curious to see how this channel (ver 1.2) will be.
Thank you very much for your offer. Yes, if I don't get you in big troubles I would like to have the latest version. I have already made the enclosure, I have engraved it and I would not like it to host another amplifier.
thimios
C21 and C22 don't need to be 160V, that was just out default cap we used on most amps.
Valery layed out V1.3 to fit parts he had available to him in Russia. Many of the capacitors were hard to find throughout the rest of the world so I reworked the boards for more easily available parts.
Valery layed out V1.3 to fit parts he had available to him in Russia. Many of the capacitors were hard to find throughout the rest of the world so I reworked the boards for more easily available parts.
It's best to stick with 470uF caps there. Snap ins fit nice there. LGU2C471MELZ would fit and are in stock at Mouser.
I have an older ver.pcb 1.2
This version use Latterals as drivers for BJT.
As i had most of parts in home,i did not resist to assemble this.
Using the design values bias was zero.
I placed a 1k resistor parallel to R27=910ohm
This version use Latterals as drivers for BJT.
As i had most of parts in home,i did not resist to assemble this.
Using the design values bias was zero.
I placed a 1k resistor parallel to R27=910ohm
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Amplifier is death silent,as you can see on the grapf.
Sound is awaysome BUT up to 10v RMS.
Power supply is +/-45v.
Increacing volume even farther,distortion becomes huge 5-10%.
Please any sugestion?
I have an mp3 recording ,using an UMIK1 micropfone and the audacity software.
Room acoustic is terrible but i hope that you can hear amplifier character.
Sound is awaysome BUT up to 10v RMS.
Power supply is +/-45v.
Increacing volume even farther,distortion becomes huge 5-10%.
Please any sugestion?
I have an mp3 recording ,using an UMIK1 micropfone and the audacity software.
Room acoustic is terrible but i hope that you can hear amplifier character.
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That actually makes sense. Both feedback and the ODNF circuit would be trying to correct the error in the output at the same time but the feedback circuit would be attenuating the output as well causing the ODNF circuit to try to boost the output. I wonder if Valery added the feedback expecting to use one or the other?
Resuming,using the printed circuit ver.1.2 we have 3 different options.
1 usege of the error correction circuit.Install U1,U2 and the periferals.NOT install R40,C21.
2 usege of the negative feedback network.Install R40,C21.NOT install U1,U2
3 without feedback,NOT install NOITHER U1,U2 NOT R40,C21.Connect TP2 to TP3.
I will post THD measurements for 3nd option soon.
1 usege of the error correction circuit.Install U1,U2 and the periferals.NOT install R40,C21.
2 usege of the negative feedback network.Install R40,C21.NOT install U1,U2
3 without feedback,NOT install NOITHER U1,U2 NOT R40,C21.Connect TP2 to TP3.
I will post THD measurements for 3nd option soon.