Simplistic NJFET RIAA

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Salas

Salas

diyAudio Chief Moderator
Joined 2002
Paid Member
wanders said:
I finished my build late last year (last post #15548); and the FSP has been delivering great sound. I decided to try my hand at building a 6SN7 tube pre. That's now in the cake pan stage and has been making superb digital sound for about a week. This morning, I hooked it up to the vinyl side. My AT ART9 started jumping around and chattering. I screwed around with it too long and now there is no output and it's probably damaged. I tried it again with a Denon DL-301-ii, which, like the ART9, started chattering and jumping around; but, I stopped that test immediately and the denon seems to be ok. Both carts worked properly with my Mcintosh c-27. (I know, should have tried the denon first; but I didn't expect an issue.)

Anyway, that's my problem. But it seems pretty likely that the FSP and the 6SN7 are not going to be happy together until something gets modified. So, I'd sincerely appreciate ideas on what I should be checking into - on either piece. I can post some specifics on the pre if appropriate.

Thanks,
Click to expand...

Check if there is voltage leaking to your 6SN7's signal ground side and from there all the way to the cartridges. There is no normally expected reason for the cartridges to have anything to do with using different line level preamps. I used my FSP hooked to a 6V6 line preamp that's having a 340 VDC PSU and been listening for ages.
 
alexkosha

alexkosha

Member
Joined 2013
Two things:
a. I installed 10uF 50V Wima MKS parallel to C8. Very nice extension in sound clarity. Did not do reverse to compare backwards, but I believe the change is obvious.
b. I have very old Pioneer CS-G7001 speakers for my general tests needs (got them for $20) and I'm trying to replace Ele caps in crossovers (40 years old caps). I find some part that I do not know what is it. I thought it is ceramic cap, but it is not. No capacitance on it. R=0.67 Ohm. Thought it might be Thermistor or Varistor, but can find any similarly looking piece on internet.
So, may you know what it is...
 

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Salas

Salas

diyAudio Chief Moderator
Joined 2002
Paid Member
PTC "resistor" maybe. For protection like a resetting slow blow fuse. PTC thermistors are in essence resistors with a positive temperature coefficient.
Although you probably wanted to post (b) in some other thread in the multiway section for more opinions. :)

Regarding (a) there are 5mm pitch 1uF MKS 63V that may come handy too to tuck under C8 if you would fancy the effect with those also. Or just as extra to the 10uF. Or a 0.1uF MKP1837 as extra.
 
H

HH

Member
Joined 2002
I am in the final stages of building my simplistic RIAA. Yesterday I thought I had completed the build, all measurements were fine for hours, and I was getting ready to do some listening. I mounted connecting wires with phono plugs, and just before connecting the phono stage to my amplifier, I re-measured all the voltages.

One channel was still measuring fine, but on the other, the DCV rail had increased to 44V. The TP1-TP2 had decreased to -0.7V.! All solderings seems to be fine, and I could really use a couple of suggestions on what to look for.

All help will be greatly appreciated.
 
P

PJN

Member
Joined 2004
Hi Salas,

I've been living with your pre for a while now and really enjoying listening to vinyl again. The other day I used it to convert some LPs to digital for a friend with my PC(Magix Audio Cleaning Lab). All I can say is WOW, really excellent. In the past I had used the phono pre in a nice 1970's vintage Sony V5 to do conversions. Using your pre and recording in 24 bit is a major step up, and it's really nice to be able to clean up all of that surface noise digitally. Kudos again on a great design.

Paul
 
Salas

Salas

diyAudio Chief Moderator
Joined 2002
Paid Member
HH said:
I am in the final stages of building my simplistic RIAA. Yesterday I thought I had completed the build, all measurements were fine for hours, and I was getting ready to do some listening. I mounted connecting wires with phono plugs, and just before connecting the phono stage to my amplifier, I re-measured all the voltages.

One channel was still measuring fine, but on the other, the DCV rail had increased to 44V. The TP1-TP2 had decreased to -0.7V.! All solderings seems to be fine, and I could really use a couple of suggestions on what to look for.

All help will be greatly appreciated.
Click to expand...

Hey HH did you solve it by now?
 
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