dc offset at phono inputs

[mmerig]

A cap coupled phono input is still a sonic disaster. At uV levels electrolytic caps seem to be really non-linear.

At uV levels electrolytic caps seem to be really non-linear.

I have found any cap i had at hand at the input a serious degrader of sound.

And so on. . . .

I agree, I would not prefer a cap in series with the signal, but it was the safest, most expedient option to block dc. The amp is very quiet (less noisy than with a moving magnet cartridge and without the head amp), and sounds good.

And what I know, most modern RIAA Phono amp have no input cap.

This is because they are using dual supply, V+ V- and input at Ground level, 0V.

What I am dealing with is a pre-preamplifier, or a head amp, for a low-output moving coil cartridge. There is no RIAA EQ in it, and it has a dual supply rail (V+, V-).

I got it used for about $10 a few years ago, and just recapped it and replaced the gain switch. Now that I know it works, I will probably replace the NP electrolytic (Nichicon ES) caps with 10 uf Blackgate N, or something like that, and call it good for now (space is limiting for a film cap). The input cap may be unecessary, but I'm not sure, and don't want any DC going to my cartridge.

Thanks for the interest and help!

 

[fairlaneusa]

Hafler dh 101

Tested an estate sale dh 101 preamp- everything works good except for phono2. Any ideas what could be wrong.

 

[rayma]

There's just a switch, so clean the contacts, and check the connections between the RCA jacks and the phono PC-4 board.
https://hafler.com/pdf/archive/DH-101_preamp_man.pdf