Sorry to interrupt your tweaking Merlino+Salas. I continue to follow this thread although most of it doesn't concern my circuit or build. As I get more used to the sound of my Salas njfet riaa I notice that the signal is a wee just too strong. Not even my cdp puts out the same sound volume. No big deal really but I'd like the volume to go up slowly because right now it responds quickly to a slight increase in the volume pot. I'd like to tame it a bit to avoid overdriving it and running into early distortion. Would lowering the input voltage to the preamp help or is more drastic action needed?
decide how much you would like it lower.
Salas will then tell you (if you ask nicely) which resistors to change to get that lower gain.
Can you give me your final bias voltages and resistors values, also tell me how much lower in % output you would need? There must be enough gain in your CJ preamp and the Nagaoka can be 5mV in reality also. What amp and speakers?
These are the voltages:
Vin : 24.1 / 24.1
Q6-R1: 23.2 / 23.1
Q2 coll: 12.86 /10.15
Q2 base: 7.03 /7.04
Q1 dr : 6.3 / 6.3
R2 = 4.7R / 4.7R
Q3-R9: 11.5 / 9.47
R6 = 11.1R / 17.6R (trimmer)
R8-R9: 20.7 / 20.2
My 170GRs (1st and 2nd stage) were not particularly well-matched and 2 pairs of BLs were used in the 2-buffer positions. My CJ line gain is quoted at 26dB. Power amp is a Kingrex T20 driving Yams 1000 (90dB/1V).
Hope this helps.
JA
Hi Salas! I adjusted the trimmers to get the voltage bias you suggested on the second stage )Q3-R9) and the sound did mellow down. But I could still detect some hardness in the upper mid to high freq. I thought it was due to burining-in issues or the components used (mainly MF resistors and russian caps) or even (perhaps) the signature of Class D amps.
Then today, out of curiosity I hooked it up to a valve power amp (Eli Duttman's "El Cheapo" with 6BW6 outputs) and it sounded just fine!! Much more than I expected. In fact I didn't like it that much with my SB phono and switched to the T-amp. My impression so far is that your njfet riaa complements valves very well.
An exciting journey indeed!!
Joe A
Then today, out of curiosity I hooked it up to a valve power amp (Eli Duttman's "El Cheapo" with 6BW6 outputs) and it sounded just fine!! Much more than I expected. In fact I didn't like it that much with my SB phono and switched to the T-amp. My impression so far is that your njfet riaa complements valves very well.
An exciting journey indeed!!
Joe A
Did it tame volume control action with your pre as you were looking for?
System matching is to taste, and your internal parts play a role too, but its true this phono pre is designed in a structure like if it was a tube one. I also use it in a tubes line control and power amp environment.
OK I will do: 1st I will check the connection & after I will check the parts, thanks again x kind support
It did, but not as much as I expected or wished for, tbh. But I didn't change R2. It's already better now with the valve amp. Could be something to do with its input sensitivity. But I'll change it when I come to do the next step.
Talking of components I was thinking of changing to Russian teflons FT-2 in the C4 position, which, as Merlin has found, sound very nice indeed. Currently I have PIOs K40Y9. While at it I'll replace R2 to 10R.
From my limited experience and judging by my ears only, I'd say you have a CHAMP there and we are all very lucky to have you not only sharing it on this forum but also helping us out (incl. inexperienced builders like me). So a Big Thanks and Well Done!!
Joe A