johnt@sdd.hp.com (John Thomas) (05/06/91)
Does anyone know any modications for a Halfer DH-101 preamp. Please post responses. Thank you.
moskowit@paul.rutgers.edu (Len Moskowitz) (05/08/91)
Audio by Van Alstine out in Minnesota has a few levels of upgrade for Hafler -101s. Give them a call. (612-890-3517) Len Moskowitz
tmurphy%peruvian@hellgate.utah.edu (Thomas Murphy) (05/08/91)
In article <11819@uwm.edu> johnt@sdd.hp.com (John Thomas) writes: >Does anyone know any modications for a Halfer DH-101 preamp. Please post >responses. Thank you. I most highly recommend the Musical Concepts modifications for the DH-101. The supermod IIIN is $175 kit and $270 installed. It consists of a major power section over-haul, and several changes to the amplification sections. You will find your pre-amp to be much more musical, focused, and with a new found sense of staging. You can call MC at 314-831-1822. Or mail me for more comments. ------------------------------------------------------------------------------- Murph "Government that governs the least
gap5444@lims01.lerc.nasa.gov (Greg Priddy) (05/11/91)
In article <11946@uwm.edu>, moskowit@paul.rutgers.edu (Len Moskowitz) writes... > >Audio by Van Alstine out in Minnesota has a few levels of upgrade for >Hafler -101s. Give them a call. (612-890-3517) > While it may or may not be of concern to the original poster, Audio by Van Alstine does not modify Hafler products as much as they engineer their own designs from the ground up and install them in Hafler chassis'. They do make use of the original switches, pots and power transformers. AVA would rather leave the expense of fabricating the sheet metal to someone else and design and build the guts themselves. Nothing wrong with that... -Greg -*---*---*---*---*---*---*---*---*---*---*---*---*---*---*---*---*---*---*-- DISCLAIMER: Please don't hold | Greg A. Priddy Analex Corporation my employer responsible for | (216) 977-0143 3001 Aerospace Pkwy *my* opinions. | -Supporting NASA LeRC- Cleveland, OH 44142 -*---*---*---*---*---*---*---*---*---*---*---*---*---*---*---*---*---*---*--
sbhattac@cmcl2.NYU.EDU (Shankar Bhattacharyya) (05/13/91)
In article <11819@uwm.edu> johnt@sdd.hp.com (John Thomas) writes: >Does anyone know any modications for a Halfer DH-101 preamp. Please post >responses. Thank you. In addition to the modifications provided by commercial establishments, there was a pair of articles in 1980 in Audio Amateur. One dealt with rewiring parts of the DH-101. That was mostly about eliminating a ground loop, and shielding the phono leads, reducing the length of wiring involved in the two-phono-source setup (which sacrifices one phono input), and other such things. These reduced hum rather substantially, and essentially eliminated cross-talk between high-level sources and the phono signal, which is pretty bad in a stock DH-101. The other article was about the guts of the preamp, and covered alteration of the RIAA equalization, bypassing of coupling capacitors at various points, and increasing the bias current in the phono section. This increased bias was standard in the DH-101 from about 1980 on. The article also recommended an improved power supply, and suggested some options. I have done this to a couple of DH-101's, and the owners were rather pleased with the results. My own preamp is a scratch-built implementation, with on-board regulators, good capacitors, and most of the other obsessive doo-dads. It is not the state of the art, but I'm pretty happy with it. I'm not inclined to worry too much about the equalization. It makes a difference, but I think that is generally pretty trivial compared to what a pair of loudspeakers or a room can do. If you are comfortable with a soldering iron, you can do all the modifications in about one long afternoon. Collecting supplies is not included. Incidentally, if you do reach into the DH-101, you will find that some of the transistors run distinctly hot. I suggest making yourself familiar with that before you start messing around. They run hot enough that if you don't know that it is normal, it can perturb you . It perturbed me, anyway. - Shankar
mhk@racer.HQ.Ileaf.COM (05/15/91)
I'll second the reccommendation of Musical Concepts. but... instead of the modification kit, get the MC-III board installed. It does cost more, but sounds better. It is a dual-mono design with seperate regulated power supplies for each channel. My DH110 sounded very good after all the mods, matched transistors, and teflon capacitors, but my MC-IIIT(eflon) sounds better. And if you really want to do it right, do what I'm doing: putting the board in my own chassis with Cardas jacks, EVS stepped attenuators, Cardas hook-up wire, and an 8-amp outboard power supply. If you want a really simple and cheap mod to the DH101, look in some (far) back issues of Audio Amateur. There was at least one article and the numerous follow-up letters. It won't sound as good as the Musical Concepts mods, but it will sound better than stock. Keep in mind that the DH101 is a cheap pre-amp (good for a spare) and you won't be able to sell a modified unit for what's invested in it.