On a new MC/MM pre I am working on I’ve provided switched resistive loading to flatten out the response. It’s amazing how much peaking you can get with a standard 47 k load.
Hi Bonsai,
Your Powerpoint presentation on curing hum is absolutely the best exposition ever! I used it on a couple of power amps (using LM3886 modules) and they are beautifully quiet. I think the Akitika amps (very highly regarded by Stereophile) use the same approach.
I'm behaving like an unsupervised kid in a candy store with this forced stay at home period. I have so many "in-progress" projects that it is difficult to focus. And, like the kid, I'm also gaining weight!
If you can have an option for no additional load C and print on the case what the input C is you will get a gold star from me. In many cases the tonearm cable has more than enough capacitance already!
The arm is very clever! Thanks for sharing, and last night I was off line for the entire evening watching movies so I missed it.. 😀
Bill raises an important point, my few investigations seemed to point mostly at excessive loading capacitance as being a common problem. A low capacitance input stage seems de rigeur with most MM and many MI cartridge types, and does not hurt where SUTs are concerned - particularly higher ratio transformers. Think about the capacitance reflected back to the cartridge using an SUT which is C x N^2 of all of pre-amp input capacitance (strays + inter-electrode or Ceb and C miller) and transformer interwinding and winding to core capacitances.
Bill raises an important point, my few investigations seemed to point mostly at excessive loading capacitance as being a common problem. A low capacitance input stage seems de rigeur with most MM and many MI cartridge types, and does not hurt where SUTs are concerned - particularly higher ratio transformers. Think about the capacitance reflected back to the cartridge using an SUT which is C x N^2 of all of pre-amp input capacitance (strays + inter-electrode or Ceb and C miller) and transformer interwinding and winding to core capacitances.
> excessive loading capacitance as being a common problem.
Large capacitance was unavoidable with long cheap cables and high-Mu triodes. The C had to be designed into the total system.
Today we can make C about zero. The flip-side is that we should increase R about as much as we reduced C. Keep the R*C product about the same.
So if 47k+300pFd is specced, but 100pFd is possible, try it with 141k (+/-10%). 30p suggests 470k. And the off-vinyl noise level may drop.
Large capacitance was unavoidable with long cheap cables and high-Mu triodes. The C had to be designed into the total system.
Today we can make C about zero. The flip-side is that we should increase R about as much as we reduced C. Keep the R*C product about the same.
So if 47k+300pFd is specced, but 100pFd is possible, try it with 141k (+/-10%). 30p suggests 470k. And the off-vinyl noise level may drop.