Simplistic NJFET RIAA

[RCruz]

Cool

[Salas]

Originally Posted by df_genius

I got my V1.2R regs debugged this morning (I tried to keep the layout as compact as possible), and have finished the phono section. I wanted to keep the regs as close as possible to the the phono section so used one board for everything. Using my old 15Mhz BK scope I can't detect any oscillation at all, I just get the noise of the scope itself at the highest frequency setting. I'm going to start installing into my pre-amp (using the baseplate as the heatsink) this evening, and have short a connection as possible to the input sockets. Here is a (bad quality) photo

A good try. Now let's see if they will give you some subjective difference. Let us know.

[df_genius]

Almost there, I think. I just seem to have one issue, the voltages on Q4 are wrong. Both channels measure 1.0/2.0/0.8V on BCE pins. Both B and C pins start higher and then quickly drop to those values. The LEDs light momentarily and then go off. I've re-checked R13 and R12 and they are the supplied values. Supply voltage is a steady 45V. Any ideas please?

[altek]

Nice, cool work, hmm.... I'm was beginning to think that's what I did too difficult...

[Salas]

Originally Posted by df_genius

Almost there, I think. I just seem to have one issue, the voltages on Q4 are wrong. Both channels measure 1.0/2.0/0.8V on BCE pins. Both B and C pins start higher and then quickly drop to those values. The LEDs light momentarily and then go off. I've re-checked R13 and R12 and they are the supplied values. Supply voltage is a steady 45V. Any ideas please?

Is R2 OK value? Also recheck that the connections are following the schematic around the cascode. Q4 orientation also.

[Salas]

Originally Posted by altek

Nice, cool work, hmm.... I'm was beginning to think that's what I did too difficult...

Your build was busy and compacted too with VU meters even. Not easy. How is it going with it, listened to more records and systems? All well?

[altek]

Yes, many times, and listened, liked, well-staged scene of a nice warm sound and no sharp, Jazz, Rock, very good
Compared with the phonostage Primare R 32 - took another for comparison from my friend.
It seems to me that my best (subjectively) - my softer more "articular"
It is best scene is particularly felt in the middle of the range (trumpet, vocals, bass string...)
Long struggled with the noise (ground) but in the past
The only thing that remains is that a strongly heated MOSFETs in a shunt regulator but not critical (63 C)
UV meter were made only for the beauty -))

[Salas]

You use PIO caps also, they should be easy on the ear. What circuit do you use for driving the VU? Has op-amp, parallel capacitor to slow down needle ballistics etc?

[altek]

Originally Posted by Salas

You use PIO caps also, they should be easy on the ear. What circuit do you use for driving the VU? Has op-amp, parallel capacitor to slow down needle ballistics etc?

Good idea thanks. To control the VU meter I have get circuit from reel to reel tapedeck in the Soviet - K157DA1
(This is a special IC designed for analog indicators) and picked off caps for more spectacular reverse arrows.
Corrective capacitors and resistors , are connected directly to the chip and they determine the transmission coefficient.

[df_genius]

Originally Posted by altek

Nice, cool work, hmm.... I'm was beginning to think that's what I did too difficult...

Your build looks really good. This will be going in my pre-amp with DC-B1, AK3493 DAC and headphone stage all in the same case. I had a different stage in mine previously using polystyrene RIAA caps and V1.0 regs, but wanted to build the best Salas phono stage I could for it. I had a few grounding issues but got the stage quiet eventually.