mike stehr Posted December 20, 2003 Share Posted December 20, 2003 Yeah, I shoud have figured the Bench supply didn't have a 2.5 filament tap. Now that I remember... Dan doesn't have a 2.5 filament tap on his DC tube supply either, he used external 2.5 volt filament transformers. His DC tube bench supply was a "Employee Discount" item when he worked for Magnavox back around 1966. It's a 500 volt supply at 200 milliamps, it uses 6550's. He said that supply would be the last to go if he ever gives up audio. I think they should just bury it with him, 'cause I don't see him giving up on audio. That's my plan when the money isn't as funny, a DC tube bench supply! Why not?! Quote Link to comment Share on other sites More sharing options...
NOSValves Posted December 20, 2003 Author Share Posted December 20, 2003 Mike, Tell him he doesn't need 500V and that I will trade him for mine and even throw in a buck or two Yes a 2.5V filament transformer is cheap as heck so no big deal there. Craig Quote Link to comment Share on other sites More sharing options...
NOSValves Posted December 20, 2003 Author Share Posted December 20, 2003 ---------------- On 12/20/2003 2:58:01 PM DaddyDee wrote: Craig, Well, since I've been a customer whom you know all too well doesn't have much tech knowledge or skill, my response is definitely non technical. It's a cool looking amp, for sure. A couple of things I'd mention are: Wouldn't there have been some pretty significant improvements over a design from 1929? Of course, I'd do well to assemble a kit, but I'd also be inclined to build from a tried and true circuit design like JFL's Horus. my $.02---------------- Dandydee Exactly where do you think the circuit for the Horus really came from ?? Where do you think all the SET circuits in use today really came from. Don't kid yourself there are no completely new designs that come out on the market today. This stuff was researched out long ago and far away in another galaxy. Everyone is just tweaking old circuits or doing a variation of a variation of a variation of something that was designed years ago. Craig Quote Link to comment Share on other sites More sharing options...
arco Posted December 21, 2003 Share Posted December 21, 2003 Another Loftin-White idea that plays both 300B's and 2A3's, can be capacitor or transformer coupled and is very synergistic with KHorns... Quote Link to comment Share on other sites More sharing options...
arco Posted December 21, 2003 Share Posted December 21, 2003 And the finished amp looks like this.. Quote Link to comment Share on other sites More sharing options...
NOSValves Posted December 21, 2003 Author Share Posted December 21, 2003 Arco, nice post ! I'll have to study that one ! Wish it was a formal schematic but beggars can't be choosers LOL !! Craig Quote Link to comment Share on other sites More sharing options...
Wardsweb Posted December 21, 2003 Share Posted December 21, 2003 ---------------- On 12/20/2003 4:43:33 PM mdeneen wrote: welcome---short question regarding the 6SL7 bypass. It looks like 220uF is much larger than would be required - maybe by 10X. Did you do that because of what you had in the stash? And, was the extra 6dB or so of gain required? Again, welcome! mdeneen ---------------- Sure, you can use a smaller cathode bypass cap, or an unbypassed cathode resistor. It happens that I have a bag of really good 220uF Sprague Extralytics that I like for this function, so that got used. The bigger the bypass cap, the less the low frequency phase shift. Other concerns of cap quality and availability really predominate over numeric value in this setting. It isn't "wasteful" or shameful to use "too big" a cathode bypass cap. I usually prefer the sound of a bypassed cathode. Theoretically, you get less "distortion" with an unbypassed resistor contributing degenerative feedback. Resistor quality and sound then become very important. I would use 1/2 Watt or 1 watt carbon comp if I did that, or expensive bulk foil, like Vishay, not metal film; maybe a high quality wirewound if it sounded good. That's the final arbiter, how it sounds, not theoretically "lower distortion". Quote Link to comment Share on other sites More sharing options...
3dzapper Posted December 21, 2003 Share Posted December 21, 2003 Aristidis, I just visited your web site and must say that you did a suberb job with it. Totally readable and enjoyable. Thanks. Rick Ps: Say hi to max for me. Is he as much a character in real life as he is on the forum? Quote Link to comment Share on other sites More sharing options...
Wardsweb Posted December 21, 2003 Share Posted December 21, 2003 Here are a couple of pics for easy reference: Click Here For My 2A3 Page Quote Link to comment Share on other sites More sharing options...
Parrot Posted December 21, 2003 Share Posted December 21, 2003 Wardsweb, That is a great site you have. Quote Link to comment Share on other sites More sharing options...
mike stehr Posted December 22, 2003 Share Posted December 22, 2003 Nice work Wardsweb! Really nice! What are you using to strap those Capacitors down? Curious to how you went about it. Quote Link to comment Share on other sites More sharing options...
Wardsweb Posted December 22, 2003 Share Posted December 22, 2003 The caps are held down with waxed cotton cord used in lacing wiring harnesses. Something I learned while working on a deep space satellite for NASA. You are not allowed to use tie wraps and must hand lace all harnesses. Quote Link to comment Share on other sites More sharing options...
mike stehr Posted December 22, 2003 Share Posted December 22, 2003 What have you laced the capacitors to? That filament transformer looks like my old Jefferson, except mine doesn't have a 5 volt winding. Nice! Quote Link to comment Share on other sites More sharing options...
Wardsweb Posted December 22, 2003 Share Posted December 22, 2003 Caps are secured to the chassis with tie mounts The transformers are new Hammond. All the part numbers are on the schematic. Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted December 22, 2003 Share Posted December 22, 2003 Hey, Wardsweb: I love the chassis work -- that IAG is the same one I used for my parallel feed Horus amps. You did some really fine metal work on that! I should have gone to that Bottlehead meeting to see these (and meet ya!) in person! I'm curious: Have you tried the Ultrapath/G.E. connection with a larger capacitor and an unbypassed resistor? I'm using a 47mf. Solen cap. in this position, and the 2A3 cathode resistor is all by itself -- very much like the conventional DRD approach. Speaking of DRD, the Horus amps used to be AC-coupled (with .1mf Jensen PIOs), and I am just about finished with a revision of the input/stage. This will include paralleled sections of a 6N1P (lower output drive impedance), and a plate suppy via a choke-reactor. This will be direct-coupled to the 2A3 grid. I think a parallel (or shunt) feed output would be something you would like very much -- I have built and used both types of outputs, and really prefer the latter. Combined with the Ultrapath out put as Leo described above, it is fantastic -- very quiet, detailed, and as you mentioned, provides good isolation from PSU artifacts. Just for kicks, you might also try taking off one leg of the cathode R bypass cap on the input. As Leo has done, and also mentioned to me via email, it is perhaps a slightly less than 'pure' design; however you are using very good quality electrolytics to do the job. I have done this for the second time on the Moondogs as an experiment, and plan on not using a capacitor in that position on the Horus input revision. That should be finished possibly later today-tomorrow. Really excellent post, thanks for joining us here! I will add a follow-up post to show how I set up the chassis -- Again, your metal work is just superb, Wardsweb! Where are you in Texas, again? Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted December 22, 2003 Share Posted December 22, 2003 I think this is the right one!? Too small -- anyway, that's the general idea. This will be probably tiresome for everyone else: These guys have heard enough banter about Horus/s, Moondogs, and DRDs to last a life time! Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted December 22, 2003 Share Posted December 22, 2003 And Craig: This DOES look like an interesting design. What's neat about it all is that SETs like this, the Horus, Moondogs, DRDs, etc are such (simple) that they make great platforms for experimentation, revision, etc. If something doesn't work out, go back to what does! Quote Link to comment Share on other sites More sharing options...
Wardsweb Posted December 22, 2003 Share Posted December 22, 2003 Erik thanks for all the accolades. As you may suspect, I have a passion for audio. Tie this to a life spent in electronics and I have the perfect hobby, shall I dare say, obsession. The next Bottlehead meet will be Jan 17th in Terrell Texas, just east of Dallas. You may read more about it on at Official Lone Star Bottleheads Website As for me, I'm in San Antonio. Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted December 22, 2003 Share Posted December 22, 2003 Wardsweb: The compliments are deserved. Everyone who comes to this forum has a passion for audio -- and sure! describe it as an obsession. Once one gets going with it, it's hard to put on the breaks. I tell myself weekly that I'm going to stop with the fiddliing and tweaking... and the new output or input/driver topology, or the different coupling capacitors, or the PIO/FI issue, or the PP-SET-Watt battle ground...or the whatever crazy idea I happened to get into my head. I'm just about done with the new choke-loaded, direct-coupled driver on the former Horus (I'm not sure what to call the thing, anymore). I hope I like this better than the original design, because it's been quite a bit of work! The Horus was already a very quick, great sounding amplifier, but once I finished and heard the DRDs, I couldn't help but wonder how the DRD driver stage would do in a parallel-feed, ultrapath output 2A3 amp! Quote Link to comment Share on other sites More sharing options...
Wardsweb Posted January 4, 2004 Share Posted January 4, 2004 Ok, you have now seen my Custom DIY direct coupled ultra path 2A3. Well I will show for the first time my Bottlehead Paramour 2A3's at the meet just outside of Dallas. Here is a sneek peak of them on the bench during assembly last week. Quote Link to comment Share on other sites More sharing options...
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