ba4x
New Member
Hi folks. Long time lurker / google searcher of the AudioKarma forums, this is my first post. Upon searching it seems there are some threads about this topic but none containing the specific guidance I am seeking.
I'm very happy to have put together a Yamaha stack for listening to records: P-751 turntable, C-80 preamp, and M-60 power amp. The speakers are B&W DM3000. This was all acquired over a few years through a close friend of mine who loves old Yamaha stuff, he has re-capped and cleaned up the components. I will say it sounds really great, if not a little bright at times. The phono cartridge is an Audio Technica VM540ML, which is an MM cart. I use the 47k 220pF setting on the preamp. I believe this cart + the C80 preamp pairing is the main source of the brightness, as excess capacitance can result in a spike in the HF range. The spike gets really annoying at times, and the EQ is only so good at mitigating it. I've done all I can to drive down the total capacitance (ie very short cables), and it now sits at ~290pF (220pF from the C-80, and about 60-70pF from the cables and turntable). This isn't terrible but I suspect the cart will be happier in the 100pF range. To achieve this, I'd need to get a new preamp with lower input capacitance. But here's an idea: Can I modify the input capacitance of the C-80? I realize this may be stupid or blasphemous in one way or another, and that's why I'm asking your advice.
From looking at the service manual for the C-80, I can identify a single 220pF cap which shunts from the input signal to ground. I'm hoping to replace this capacitor with a smaller one (maybe 100pF or 50pF).
The C-80 supports a 47k 330pF option, and I see a 100pF cap waiting to be run in parallel with the 220pF if the selector switch is set that way. So if I reduce the capacitance by any amount with my tinkering, I can always bump it up by 100pF by using this selector switch. This is my hypothesis.
Do I have my ideas right? Will I ruin or upset some system by replacing that 220pF capacitor with a smaller one?
I apologize if I'm muddying any concepts here. Perhaps this post should go in the DIY forum, but I thought to try here first. Thanks for your time.
I'm very happy to have put together a Yamaha stack for listening to records: P-751 turntable, C-80 preamp, and M-60 power amp. The speakers are B&W DM3000. This was all acquired over a few years through a close friend of mine who loves old Yamaha stuff, he has re-capped and cleaned up the components. I will say it sounds really great, if not a little bright at times. The phono cartridge is an Audio Technica VM540ML, which is an MM cart. I use the 47k 220pF setting on the preamp. I believe this cart + the C80 preamp pairing is the main source of the brightness, as excess capacitance can result in a spike in the HF range. The spike gets really annoying at times, and the EQ is only so good at mitigating it. I've done all I can to drive down the total capacitance (ie very short cables), and it now sits at ~290pF (220pF from the C-80, and about 60-70pF from the cables and turntable). This isn't terrible but I suspect the cart will be happier in the 100pF range. To achieve this, I'd need to get a new preamp with lower input capacitance. But here's an idea: Can I modify the input capacitance of the C-80? I realize this may be stupid or blasphemous in one way or another, and that's why I'm asking your advice.
From looking at the service manual for the C-80, I can identify a single 220pF cap which shunts from the input signal to ground. I'm hoping to replace this capacitor with a smaller one (maybe 100pF or 50pF).
The C-80 supports a 47k 330pF option, and I see a 100pF cap waiting to be run in parallel with the 220pF if the selector switch is set that way. So if I reduce the capacitance by any amount with my tinkering, I can always bump it up by 100pF by using this selector switch. This is my hypothesis.
Do I have my ideas right? Will I ruin or upset some system by replacing that 220pF capacitor with a smaller one?
I apologize if I'm muddying any concepts here. Perhaps this post should go in the DIY forum, but I thought to try here first. Thanks for your time.
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