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!
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!
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!
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!
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
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
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
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
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
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.
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.
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.
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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.
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Hi Stenks, what are you doing for the balance control? It looks like the Alps is just a stereo volume control, or am I missing something? Does the Alps fit the Hafler knobs, or did you need to change anything? Would you happen to have the Alps part number?
I need to replace my volume and balance controls, and I'm looking for a nice potentiometer...Thanks!
I need to replace my volume and balance controls, and I'm looking for a nice potentiometer...Thanks!
I am currently at work but I'll answer you later, have not missed anything I turned off the balance control and make modification of the wheel for volume because of deterioration of the potentiometer, the potentiometer is blue Alps valvet 2 x 100k with a 6mm shaft. I finally say that I found an article from Audio Amateur and demanded that I will put it here I hope it will be useful.
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I found this: DH-101 Volume Mod
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Hi Stenks,
I recently finished a complete overhaul of a DH-101 and I'm extremely satisfied with the sound of this preamp. I basically followed the suggestions in those posted articles from the 70's. I also replaced the resistors with Dale metal film. I rewired with Kimber TCSS. I used shielded cable for the phono inputs. I also elliminated the equalizer loop and wired the outputs direct, as well as wiring the phono inputs direct instead of through the switch. I followed the grounding scheme shown in those articles. The high level inputs are dead silent even with the volume all the way up. The phono section starts to get an ever so touch of hum at about 3:30 on the volume contol, but if I listened that loud I would blow any speaker as well as my ears, so it's basically non existant. And it sounds fantastic. I decided to go direct coupled, so I put in some 25 turn pots to replace R4 as per John at Musical Concepts recommendation to allow DC offset adjustment. My amp has an input cap so it doesn't cause a problem.
As I said, I love the results. It was like night & day when compared to a stock DH-101. Those old articles are great. And John at Musical Concepts was very helpful with sourcing some hard to find parts.
Best Wishes,
Bob
I recently finished a complete overhaul of a DH-101 and I'm extremely satisfied with the sound of this preamp. I basically followed the suggestions in those posted articles from the 70's. I also replaced the resistors with Dale metal film. I rewired with Kimber TCSS. I used shielded cable for the phono inputs. I also elliminated the equalizer loop and wired the outputs direct, as well as wiring the phono inputs direct instead of through the switch. I followed the grounding scheme shown in those articles. The high level inputs are dead silent even with the volume all the way up. The phono section starts to get an ever so touch of hum at about 3:30 on the volume contol, but if I listened that loud I would blow any speaker as well as my ears, so it's basically non existant. And it sounds fantastic. I decided to go direct coupled, so I put in some 25 turn pots to replace R4 as per John at Musical Concepts recommendation to allow DC offset adjustment. My amp has an input cap so it doesn't cause a problem.
As I said, I love the results. It was like night & day when compared to a stock DH-101. Those old articles are great. And John at Musical Concepts was very helpful with sourcing some hard to find parts.
Best Wishes,
Bob
Thank you very much for your detailed response u1022186 i am very grateful for that, I must say that I partly do to the signal using an ordinary plated wire which I have mentioned, or shielded cable. I also replaced the existing resistors with metal film resistors, I replaced the old one with toroidal transformer, I've made the exchange electrolytic capacitor with high quality Nichichon MUSE in line and phono stage, replece diode with shotky also I am waiting the upgrade kit from Ebay coupling polypropilene and silver mica capacitor, replace old RCA with gold plated RCA change the potenciometre with ALPS blue valvet 2 x 100K ohm /log. I have question whether in this case would be better to use plated wire or shielded cable as you can see in my picture I use WDH CS 18 wires, whether this short wires can affect signal and make some hum. Tell me if you are using shielded cable for signal or something otherwise. Yesterday I experimented a bit and I noticed that there is crosstalk between the left and right channels, you simply turn off one channel (RCA connector log off from the back) and move the volume knob to the end, the channel that was quietly expelled hear music, whether it is a problem with wiring or the buttons to switch inputs.
Thank you in advance
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Thank you in advance
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An externally hosted image should be here but it was not working when we last tested it.
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Mods
Hi all, just been reading The Audio Amateur articles about coupling capacitors in this thread. Just wondering if C2, C8, C11, and C20 coupling capacitors really benefit being bypassed by a cap, and if so what value, 0.1 uf be ok also what type of cap would be suitable and sound the best. You can see some images attached to link of what coupling caps I used on my DH-101, are these ok or shall I swap these out too. The RIAA Equalisation mods, are they worth doing, does it make it sound better. Reading these Audio Amateur articles made me see some of the design faults of this pre amp. Crap push buttons switches, poor wire routing etc. Can anybody see anymore small mods I could do to make it sound better? Don’t what to drastically modify it. I accept this pre amp for what it is and I like it.
https://picasaweb.google.com/113336685910601049348/Desktop?authkey=Gv1sRgCNG5_dbT2qrlTA#
Hi all, just been reading The Audio Amateur articles about coupling capacitors in this thread. Just wondering if C2, C8, C11, and C20 coupling capacitors really benefit being bypassed by a cap, and if so what value, 0.1 uf be ok also what type of cap would be suitable and sound the best. You can see some images attached to link of what coupling caps I used on my DH-101, are these ok or shall I swap these out too. The RIAA Equalisation mods, are they worth doing, does it make it sound better. Reading these Audio Amateur articles made me see some of the design faults of this pre amp. Crap push buttons switches, poor wire routing etc. Can anybody see anymore small mods I could do to make it sound better? Don’t what to drastically modify it. I accept this pre amp for what it is and I like it.
https://picasaweb.google.com/113336685910601049348/Desktop?authkey=Gv1sRgCNG5_dbT2qrlTA#