Tom Mobley Posted January 2, 2004 Share Posted January 2, 2004 Erik, I will send you two new Hovland 2uf caps if you will help me build a version of your amps. All I really need is a schematic and a little hand-holding from time-to-time. Leo has agreed to sell me his original Monondog OPT's, they're Electraprint and will be pretty nice. I won't be able to do the para-feed output with them, so these would be the Non-Para-DRD 2A3 versions. Think it over, you've probably already got the schematic in your head if not on paper. I'll buy suitable PS trannies from Jack also. Tubes are not hard to find for this deal. I'll buy a couple plain-jane 5x13" boxes from AES, they're just across town from me. I'd like to go with a 5AR4 rectifier, soft start and all that. I'll consider the first iteration of them to be a bread-board type deal, appearance won't count for much. These will be for the Klipschorns, so I won't be paranoid about wringing out every last .1 watt out of them, make it a little easier. Tom Quote Link to comment Share on other sites More sharing options...
Deang Posted January 3, 2004 Share Posted January 3, 2004 Ha! I'll double that offer and give you FOUR Hovlands if can talk Tom out of this crazy plan! Seriously Tom, that's some nice wheeling and dealing there. You're definitely going to be starting out with some nice iron. Who sells nice chassis punches? Quote Link to comment Share on other sites More sharing options...
Guy Landau Posted January 3, 2004 Share Posted January 3, 2004 Quad II forty? I'm disappointed . Quote Link to comment Share on other sites More sharing options...
mike stehr Posted January 3, 2004 Share Posted January 3, 2004 http://www.0ne-shop.com/universal/Brands/Porter-Cable/Drills-Hammer-Drills/P-0000000a0000636b5a616b55577a6f77/Porter-Cable-18686-5-Step-Drill-Bit/Porter-Cable-18686-5-Step-Drill-Bit.php They are kinda spendy. But if a guy does a lot of chassis work it may not be, considering what a 3 or 4 sizes of chassis punches probably run cost-wise. Quote Link to comment Share on other sites More sharing options...
Deang Posted January 3, 2004 Share Posted January 3, 2004 Thanks Mike. "Quad II forty? I'm disappointed." Hmmm. If you don't mind, tell me why. I kind of thought I did pretty good. I landed the two monoblocks and the matching preamp for $2250. Not bad considering the three pieces retail for close to $6K. The amps were used in a second system, and belonged to a guy whose wife works for Quad. They were just bought last May, and have less than a 100 hours on them. Designed by Andy Grove of Audionote, the system was well received by most. Hard to complain here really: Potted transformers, 5UG4 tube rectified, 6SH7 input tubes, KT-88 output tubes -- all in glorious Ultra-linear with a touch of feedback. Pretty much what I like with the music I dig. These will probably end up in triode down the road. http://www.quad-hifi.co.uk/hfworld989.pdf http://www.quad-hifi.co.uk/quad_qc24_240audition.pdf Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted January 3, 2004 Share Posted January 3, 2004 Tom: You don't have to send me capacitors. I'd be glad to help anyway I can, short of having to do the chassis work! What you are essentially describing is a pretty straight-ahead 2A3 DRD. Except for the parallel-feed aspect, which is an important element, that's also what my amplifiers are. I had already inluded the DRD Ultrapath connection on the former Horus, and what I did was basically a complete makeover of the driver stage. The PSU also needed some modification, and the grid choke on the 2A3 taken out, as well. I have been very happy with the results, and the new amps, in my opinion, are more resolving and transparent than the Horus. The Horus is still an outstanding amp, though. I just think the DRD done in parafeed mode is a really nice combination. Having finished the changing of my AA networks into As, things sound better, still. Maybe Dean could explain why he thinks your plan isn't a good one, because I think it sounds like a great project. The DRD is a good SET amp. In addition to Electra Print as a source for the power transformer, you might also want to consider one of Hammond's Classis series. I am using the 374BX (I'm pretty sure that's the model number, but will check for you if you want.), and it's well-made and totally quiet. BTW: A tube rectifier is a sort of built-in soft-start feature on an amp or preamp, and is easier on downstream components than using SS rectification without a soft-start circuit. SS rectifiers have pretty strong in-rush, which is why on some designs such as the AES AE-1 preamp (SS rectification), it's beneficial to be able to let the tubes warm in standby before hitting them with B+. Which reminds me: If you used the Hammond PT mentioned above, you'll need a separate filament transformer for the 2A3. The Hammond doesn't have a 2.5 volt filament winding. If you wanted, it would be easy to install a standby switch, simply by putting a switch between the center tap of the power transformer and ground. With a tube rectifier, though, I don't really think it's necessary. I in fact don't have a schematic for the amp. I was able to have a close look at the DRD driver stage when building Kudret's amps, and took a few notes on part values, etc. Also: If you are going to do a DRD, you'll need a chassis about 3 inches deep (between top and bottom plate) in order to accommodate the large Ultrapath capacitor. edit: I can draw up a schematic in a few days if you would like one. I still want to experiment a little bit with the voltage divider/bias resistor combination on the 2A3, but things are working and sounding so good right now I might just leave things as they are. edit#2: Dean, maybe I've misunderstood you, but why is Tom's plan crazy? Quote Link to comment Share on other sites More sharing options...
NOSValves Posted January 3, 2004 Share Posted January 3, 2004 Dean, Some may be disapointed but I'm darn proud of you ! Now if I can just get you to wire those babies in Triode ! Quote Link to comment Share on other sites More sharing options...
Guy Landau Posted January 3, 2004 Share Posted January 3, 2004 ---------------- On 1/3/2004 2:51:11 AM DeanG wrote: Thanks Mike. "Quad II forty? I'm disappointed." Hmmm. If you don't mind, tell me why. I kind of thought I did pretty good. I landed the two monoblocks and the matching preamp for $2250. Not bad considering the three pieces retail for close to $6K. The amps were used in a second system, and belonged to a guy whose wife works for Quad. They were just bought last May, and have less than a 100 hours on them. Designed by Andy Grove of Audionote, the system was well received by most. Hard to complain here really: Potted transformers, 5UG4 tube rectified, 6SH7 input tubes, KT-88 output tubes -- all in glorious Ultra-linear with a touch of feedback. Pretty much what I like with the music I dig. These will probably end up in triode down the road. http://www.quad-hifi.co.uk/hfworld989.pdf http://www.quad-hifi.co.uk/quad_qc24_240audition.pdf ---------------- That was a good deal. I hope that I'm wrong and they'll sound great. I'll wait for your review. Are you still buying the AVA T7? Quote Link to comment Share on other sites More sharing options...
Tom Mobley Posted January 3, 2004 Author Share Posted January 3, 2004 I think possibly Dean was referring to my SET path, probably in jest. Or semi-jest. If that's a word. Tom Quote Link to comment Share on other sites More sharing options...
Tom Mobley Posted January 3, 2004 Author Share Posted January 3, 2004 http://www.hammondmfg.com/300series.htm Either one of the first two would work, but if I used the 300BX I could go to 300B tubes easily if the 2A3 thing didn't work out. Mouser has the 300BX for like $137 per and the 302AX for $110. Any issues with using a resistor to break the 5V filament power of the 300BX down to 2.5 for the 2A3? What if a guy ran that through a little silicone rectifier and an RC network, feed DC to the 2a3 filaments? Anything to gain there? Tom Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted January 3, 2004 Share Posted January 3, 2004 Oh, maybe you're right. That's such a tiresome, way-overworked issue. It's just not worth getting so upset about. SET or PP -- who cares!? Or why not both? I'm starting to look around for a PP option, simply because I want to learn more about it. Maybe I'm missing something! ...and thanks very much for your generous offer of those capacitors. I'm happy to help as I can. Quote Link to comment Share on other sites More sharing options...
Tom Mobley Posted January 3, 2004 Author Share Posted January 3, 2004 Erik, See my heavily edited double post above. Anything to gain there? Tom Quote Link to comment Share on other sites More sharing options...
Deang Posted January 3, 2004 Share Posted January 3, 2004 Completely in jest guys, really. Most of you listen to a lot of music that probably really benefits from these circuits. As for me, I've just made the decision to trade some of that midrange transparency for bottom end control and dynamics. Guy, based on what I've been reading over the last couple of days, I may be short-changing that Quad preamp. Still, I called Frank and gave him the go ahead on the T7. The problem with ALL of this stuff, is you just don't know what you have until you actually get it into your system. I'm not sure, but I don't think these Quads have much more in them than even some SET amps. When you get right down to it, they are basically like some of the Quicksilvers with better iron and tube rectification. Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted January 3, 2004 Share Posted January 3, 2004 I'll tell you one thing, Dean: They look really nice! Quote Link to comment Share on other sites More sharing options...
Deang Posted January 3, 2004 Share Posted January 3, 2004 That's my motto Erik -- better to look good than to sound good. Quote Link to comment Share on other sites More sharing options...
NOSValves Posted January 3, 2004 Share Posted January 3, 2004 ---------------- On 1/3/2004 1:44:52 PM DeanG wrote: That's my motto Erik -- better to look good than to sound good. ---------------- I know that is right !! I can't count the times he has said on the phone "I realize the such and such may sound better but this looks great" Quote Link to comment Share on other sites More sharing options...
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