OK, so here's the deal. Some time ago I built Jeremy Epstein's octal phono stage using 2 6SL7 and 2 6SN7 tubes with a voltage regulated power supply. (You can see the original design here, which I copied verbatim: Jeremy's Tube RIAA Phono Preamp)
Anyway, i hooked it up, and have been enjoying it, but I have two slight problems that I cannot diagnose...
First, since it was built I have noticed that one channel has a different EQ... the right signal seems to be very trebly and have almost no bass, whereas the left sounds normal. It's never been too noticeable in stereo, but it bothers the hell out of me just knowing that's the case.
Second, as of last night, i'm having an issue that's got me dead in my tracks– I work in the audio industry, so i deal with customer problems all the time and I've never even seen this happen myself. Anyway, I turned it on last night, and got silence in the left channel. Just the normal background hum that normally is there. Naturally, i went to diagnose it as anyone would– I swapped the cables to see if the problem persisted– bam! now the left channel worked. OK, I thought. Must be the cartridge lead or something in the table. So, in order to confirm, I hooked it directly up to my Marantz 1060's phono input, and to my shock, heard it sounding normal and perfect. I swapped back again to confirm... the right channel from the table works regardless of the input used in the phono stage, and the left RCA from the table works only on the Marantz. Again, regardless of the input/ channel I use on the phono stage, I can only get signal from the right RCA. If it makes any difference, I'm using an audio quest Big Sur from the table and it is grounded to my Monster conditioner. The cartridge is a Grado gold and I have confirmed it is working as intended and all leads are tight.
I'm at a loss here- is this an impedance issue? I really have no idea where to begin.
Thanks
Steve
Anyway, i hooked it up, and have been enjoying it, but I have two slight problems that I cannot diagnose...
First, since it was built I have noticed that one channel has a different EQ... the right signal seems to be very trebly and have almost no bass, whereas the left sounds normal. It's never been too noticeable in stereo, but it bothers the hell out of me just knowing that's the case.
Second, as of last night, i'm having an issue that's got me dead in my tracks– I work in the audio industry, so i deal with customer problems all the time and I've never even seen this happen myself. Anyway, I turned it on last night, and got silence in the left channel. Just the normal background hum that normally is there. Naturally, i went to diagnose it as anyone would– I swapped the cables to see if the problem persisted– bam! now the left channel worked. OK, I thought. Must be the cartridge lead or something in the table. So, in order to confirm, I hooked it directly up to my Marantz 1060's phono input, and to my shock, heard it sounding normal and perfect. I swapped back again to confirm... the right channel from the table works regardless of the input used in the phono stage, and the left RCA from the table works only on the Marantz. Again, regardless of the input/ channel I use on the phono stage, I can only get signal from the right RCA. If it makes any difference, I'm using an audio quest Big Sur from the table and it is grounded to my Monster conditioner. The cartridge is a Grado gold and I have confirmed it is working as intended and all leads are tight.
I'm at a loss here- is this an impedance issue? I really have no idea where to begin.
Thanks
Steve
Problem 1: You have an error somewhere in the EQ circuit wiring, probably in the shunt legs.
Problem 2: I'd be looking at a wire come loose from the input jacks or somewhere in the tonearm/TT wiring, almost certainly on the ground side. Are the grounds on the two input RCA jacks connected together? If not, do so with a clip lead and see if the sound comes back.
Problem 2: I'd be looking at a wire come loose from the input jacks or somewhere in the tonearm/TT wiring, almost certainly on the ground side. Are the grounds on the two input RCA jacks connected together? If not, do so with a clip lead and see if the sound comes back.
Yeah Conrad I had been thinking the same thing lately. May consider adding one.
OK, so. Update. I fixed the issue of only one channel working. Was related to a loose ground wire I didn't see before.
As for the EQ mismatch, I checked and double checked and all is wired correctly and the connections are good. I'm at a loss for this one. Tried swapping tubes and problem still persists. Definitely in the circuit or connections somewhere. Also tried swapping cables, inputs, etc. Still the right channel has less on the low end.
sk
OK, so. Update. I fixed the issue of only one channel working. Was related to a loose ground wire I didn't see before.
As for the EQ mismatch, I checked and double checked and all is wired correctly and the connections are good. I'm at a loss for this one. Tried swapping tubes and problem still persists. Definitely in the circuit or connections somewhere. Also tried swapping cables, inputs, etc. Still the right channel has less on the low end.
sk
It was the 0.01uF cap. It was wide open and has been since I built it. Never thought to measure that one before. Figures.- Status
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