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-   -   Hafler DH-101 Pre-Amp (http://www.diyaudio.com/forums/analog-line-level/185485-hafler-dh-101-pre-amp.html)

wally5 21st March 2011 11:10 AM

Hafler DH-101 Pre-Amp
 
Hi, what can I replace C12 with thats available, its a 15pf 1000v Ceramic.

https://picasaweb.google.com/1133366...NG5_dbT2qrlTA#

BobEllis 21st March 2011 12:41 PM

S150K25SL0N63L6R Vishay/BC Components Ceramic Disc Capacitors if you can't find a local distributor.

Without the schematic it's hard to tell, but I'd suspect that you don't need the 1000V rating. You can probably use a 15 pf mica cap, usually available rated at least 500V

stratus46 21st March 2011 03:10 PM

Quote:

Originally Posted by wally5 (Post 2511097)
Hi, what can I replace C12 with thats available, its a 15pf 1000v Ceramic.

https://picasaweb.google.com/1133366...49348/Desktop#

The power supplies in this unit are +/- 18 Volts. Any 15pF cap you'll find should be fine. Personally, the Mica suggestion from Bob Ellis would be very good, a C0G would also be good. Polystyrene are excellent but some flux removers attack the styrene.

What happened to the original cap?

Nice work on the unit though I wouldn't use an OSHA cord on it - especially if any other unit has a 3 wire power cord as it's the surest way to ground loop issues. It looks like you are not using the 3rd wire as I don't seem to see any solder on the terminal in the photo. Is that right?

A worthy mod to it improves the phono preamp and adds a needed high level input is to remove the phono 1/2 low level input switching and make phono 2 a high level input - in my case for the CD player. I did that back in '83 when I got the first CD player.

G≤

wally5 22nd March 2011 02:50 AM

Thanks for your replies, I thought the idea was to get rid of ceramics in the signal path, will Silver Micas sound better.
I was stuck on voltage rating, didnít know I could use 500v Silver Micas, which you can get quite easily.
The earth on IEC socket is not being used, just a floating ground like it was from original. Like the idea about Phono switch.

bobrown14 23rd March 2011 12:22 AM

Quote:

Originally Posted by wally5 (Post 2512113)
Thanks for your replies, I thought the idea was to get rid of ceramics in the signal path, will Silver Micas sound better.
I was stuck on voltage rating, didn’t know I could use 500v Silver Micas, which you can get quite easily.
The earth on IEC socket is not being used, just a floating ground like it was from original. Like the idea about Phono switch.

+1 - I replace the ceramic caps with those LOW pF requirements with mica.. Probably your only upgrade path. I've been looking for a 68pF 500V for my pre-amp (HK -17) replacement and found mica to really be the only easily available part here in the states.

Oh and Hi to all, I think my first post here (analog line level section).

Cheers,

Bob

wally5 23rd March 2011 01:32 AM

Quote:

Originally Posted by bobrown14 (Post 2513151)
+1 - I replace the ceramic caps with those LOW pF requirements with mica.. Probably your only upgrade path. I've been looking for a 68pF 500V for my pre-amp (HK -17) replacement and found mica to really be the only easily available part here in the states.

Oh and Hi to all, I think my first post here (analog line level section).

Cheers,

Bob

Hi, I get most of my parts from this company here in NZ.

Active Components ::

bobrown14 23rd March 2011 01:50 AM

Quote:

Originally Posted by wally5 (Post 2513200)
Hi, I get most of my parts from this company here in NZ.

Active Components ::

Ooohhhhh.....gotta thank you.


Cheers,

Bob

Jim W 23rd March 2011 03:01 AM

According to my schematic, C12 looks like it couples the preamp output to the inverting input of a differential pair, providing high frequency rolloff. I wouldn't guess that it would affect the sound quality greatly, and that any cap with good high frequency response and a reasonable tolerance would be fine.

Jim


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