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Hafler DH-101 Phono Mods

Macdude

Macdude

Hi /on/ Fidelity
I would like to do whatever upgrades I can to the phono stage in my pre-amp. I already ordered the recommended metal film resistors for the signal path.

As I understand it, the RIAA section could be improved upon a little bit. Does anyone have the info for doing this? I've searched and searched but all I can find is that it was done in the April, 1980 issue of Audio Amatuer (which I can't find). I also read there was a Musical Concepts mod available. I'd like to tackle it myself.

Thanks!
 
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There are two DH-101 mod articles in The Audio Amateur 4/1980, and a reference to power supply information in another. That's not the April issue, by the way; it's the last of four quarterly issues for that year. I don't have access to a scanner at the moment -- maybe someone else has a copy...
 
I have a DH-100 and would like to know if there's a source for a replacement for the RCA connector board. The original sockets were made of some sort of crap alloy that has corroded horribly over the years. It takes a lot of Cramolin to keep it working.
 
Thanks. I didn't find exactly what I needed in relation to specific RIAA parts, but I sent an email to John Hillig at Musical Concepts. I'm not in the market for an entire kit. I re-capped it and rebuilt the power supply with a kit I got from eBay.
 
In the article he talks about using single conductor, shielded wire between the phono RCAs and the phono stage. I used wiring from an RCA cable. Would it be correct to ground one end of the shield of each wire? It would make sense to me to do so.

Also, would wiring from a turntable have a lower capacitance than standard line-level RCA wiring and therefore be a better choice for the phono section mod?
 
I haven't seen one of these in a very long time, but in general, most preamps don't ground the phono input jacks at the rear panel. They rely on the internal cable shield instead, to make the internal phono ground connection to the preamp PCB.

TT output cables don't necessarily have lower capacitance than ordinary hookup cables. What's important is *matching* cartridge load requirements, not minimizing capacitive load.
 
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