I ordered a pair of them,I am now using Ecc83 should I move the jumper on the pcb to use 6N2P??
Now, however, one problem has arisen. the left channel is about 2 db. louder. what can I do. where do I go to look for a reason for this.
thanks again in advance.
Out of curiosity, if say I wanted to easily be able to change the input impedance of this phono stage, since the load inputs are in parallel with the onboard resistors, could I just leave those resistors out?
I think it's R1L & R1R for MC, and R3L & R3R for MM right? So if I just didn't install those, and always required the plugs to be installed I could just use the exact resistance I want in the plugs right? Or are there any implications to not installing the load resistors onboard?
Main reason I'm asking is because some of the mid to higher gain MC carts I've looked at in the past prefer a higher than 1K load as far as I can tell. So I'm just thinking it gives me a bit more versatility, since I can't increase the 1K load resistance if those 1K resistors are installed on board.
I think it's R1L & R1R for MC, and R3L & R3R for MM right? So if I just didn't install those, and always required the plugs to be installed I could just use the exact resistance I want in the plugs right? Or are there any implications to not installing the load resistors onboard?
Main reason I'm asking is because some of the mid to higher gain MC carts I've looked at in the past prefer a higher than 1K load as far as I can tell. So I'm just thinking it gives me a bit more versatility, since I can't increase the 1K load resistance if those 1K resistors are installed on board.
That will almost certainly be an imbalance in gain in V1 or V2.
Try different valves, or swap V1 and V3 and see.
This may seem a little counter intuitive but the resistors R1 and
R3 have other functions to permit simple switching between MC and MM using only a dual pole relay in each channel.
The design is using valve and Fet technology so the switching is a clever part of combining the two.
Without an R1 fitted you couldn't use the stage in MM mode and without R3 fitted the linearity of the Fet stage would be compromised in MC mode.
You could fit lets say up to 10K for R1 but the the HF performance on MM may suffer.
Most high output MC cartridges will work very well into an MM input at 47K. Adding a loading plug will bring this impedance down if needed.
Okay, thanks for the info.
Part of the issue for me, is that my preamp / amp combo needs a fairly large signal to reach full power output. I built the whole thing, and frankly the preamp/drive could be a bit beefier.
I need at an absolute minimum 0.5V input to the amp, so with 40db gain when the phono is set to MM I need at least 5mV output from the cartridge. With 60db of gain when set to MC, I need at least 0.5mV from the cartridge.
This means I can't really use a low output MC cartridge, as they're usually around 0.25mV, and high output MC cartridges which are in the 2 - 3mV range also won't work for me. But there are a few MC cartridges which operate between 0.5mV and 1mV, but most of the ones I've looked at do appear to want a load resistance more in the 1K - 2K range.
I can definitely just use 47K resistors for R3, as I wouldn't ever need a resistance higher than that, but if I were to use 2K resistors for R1 positions, would everything operate okay?
I recieved the pcc88 from post #665 today and first impressions are really good. Played some acoustic guitar and saxophone they really shine.
I can't see any problem with that 🙂
You can achieve a 'little' more gain by bypassing R13 with a quality electrolytic cap of say 220uF.
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Ohh! That's cool. Are there any bad side effects of doing this? I definitely will if it doesn't adversely affect anything.
And are you saying R13L & R13R? Or R13P?
R13L and R13R. Be sure to get the polarity right.
This isn't included in the original design as the quality/impedance of the cap may degrade the performance from the optimal reference level that was aimed at.
This isn't included in the original design as the quality/impedance of the cap may degrade the performance from the optimal reference level that was aimed at.
I'm looking at MM cartridge loading and would like to raise to 75K. But parallel resistors only lower total resistance. So my question is: can I swap the 47K for 100K and use the loading plugs to the desired value without any unforeseen side effects? My goal is to raise the top end a bit. Thanks, Vincent