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Old 30th September 2008, 10:05 PM   #21
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I did a search on the Hafler DH-101 and this old thread came up. I've changed the jacks, recapped and changed some strategic resistors over to metal film. What a great old preamp! It is driving a pair of Phase Linear 400s, one for each channel and I'm listening to Dark Side of the Moon right now. I rebuilt the 400s from old junkers and my system is really sounding great. The cool thing is that except for the CD player, no component is younger than 35 years. I'm running a rebuilt Soundcraftsmen RP-2212 equalizer too, and I've donned my flame proof suit (I know, I should wear it all the time anyway with the amps I like)...
I have a question, though, about the coupling caps that Hafler used. The original had 10uf tants back to back, in series, with the + leads joined, for 5uf. I think I might try to find some 5uf poly caps. Does anyone have any suggestions or better ideas?
Thanks!
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Old 9th October 2008, 12:42 AM   #22
ViperZ is offline ViperZ  Canada
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Hi all,

I got a DH-101 in a very poor shape. Someone tried to "mod" it with old AA article mods and really didn't do a good job.

I replaced the electrolytic caps, replaced the most important resistors with metal film ones. Now I am trying to rebuild the TONE circuitry, which was really butchered, not removed.

Does anybody know how the numbering on the button contacts work? i.e. where is the contact 1? For example, when it says in the manual "connect the green wire to the SS Lug #8" - which lug is #8? There is two rows of "lugs" on the back of each button, but I can't find any marking, which would identify lug #1 to start counting.

I basically need to rebuild the "tone" button wiring - there are 6 wires, which were cut off.

I also have the original audio amateur article, which directs on how to disable the tone circuit, so I'll just work backwards .

Thank you!
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Old 9th October 2008, 01:12 AM   #23
anatech is offline anatech  Canada
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Hi VintageDave,
Yes, lose the tantalum capacitors. If you see wet tantalum capacitors, leave them in. They are totally different and very expensive to replace. Film capacitors are an excellent way to go.

Hi ViperZ,
Don't you just hate when equipment has been "audiophileized"? I sure do!

If you get yourself in a real bind, I'm in Georgetown. Not so far away. I may be able to help you out. Contact numbering may have to be traced out, or simply wire per the schematic. If there are four switch sections, you can sometimes get away by mixing them up. You can not if there is a PCB on the switch, but then you can trace it out. Also, active sections may be staggered to decrease crosstalk.

-Chris
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Old 8th July 2009, 02:21 PM   #24
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Hi. I'm also using the DH-101 preamp and would love to try some of these mods. Would it be possible for anyone to send me a copy of the schematic and also the old AA articles on the mods. I am a new member but my email address is bobjan1@optonline.net
I no longer have any of the original paperwork. I built the kit back in the 70's. Also, I see that putting it into a new case with new wiring and switches was mentioned. Could anyone recommend a good USA source of enclosures. I also want to rebuild my old amps into new encloseres. Thanks
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Old 15th July 2009, 07:55 PM   #25
Glowbug is offline Glowbug  United States
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Quote:
Could anyone recommend a good USA source of enclosures. I also want to rebuild my old amps into new encloseres. Thanks
http://www.par-metal.com/

Those guys seem like they can do some cool stuff...

There's also the common Hammond boxes from Parts Express, Parts Connexion, AES, etc, etc
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Old 15th July 2009, 08:28 PM   #26
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Thanks for the info. Turns out the're in NJ and only about 40 minutes from me. so I can pick up any cases they make and save on shipping. I'm ordering new cases for my amps from them. Once I finish with the amps, I'll start on the preamp. Thanks again, Bob
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Old 15th July 2009, 09:35 PM   #27
Glowbug is offline Glowbug  United States
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NP.

I might be picking up a DH101 sometime too, I'm seeing a couple non-working ones out there and I'm itching for a solder slinging project I need any preamp, anyway...not having my main system working is killing me.
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Old 16th July 2009, 09:18 AM   #28
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I'm loving mine. I replaced all the jacks with ones that I got from RS, they come 4 to a pack I think, and all I did was unsolder and remove the old ones from the phenolic strip, screwed the new ones in place, and soldered them. Took an hour or so. Then all new electrolytics, and I put film caps, big polyester ones I think, in place of the tantalum coupling caps, and it sounds great.
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Old 19th May 2012, 09:11 PM   #29
stenks is offline stenks  Serbia
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Hi all admirers,
I am the owner of Hafler DH-101 and I perform some mods described here, I would be grateful if someone put pictures from magazines Audio amateur how to modified DH-101 thank in advance.
Few days ago I replaced the volume poteciometar with blue ALPS nice improvement.

Click the image to open in full size.

Last edited by stenks; 19th May 2012 at 09:32 PM. Reason: Pictures
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Old 19th May 2012, 10:51 PM   #30
stenks is offline stenks  Serbia
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Made a new plexiglass carriers for the Gold-plated RCA connectors, the new quality PCB board, the wiring will be Van Den Hul CS-18, mains filter and torus transformer will be installed. After the completion of the modification will put new pictures.




Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

Last edited by stenks; 19th May 2012 at 11:05 PM.
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