edwinr Posted July 30, 2004 Share Posted July 30, 2004 ---------------- On 7/30/2004 6:04:03 PM paulparrot wrote: What you don't understand is it's all a matter of how a tube is used, in what circuit. Now, I would use a 2A3 in a push-pull amp, but people with other taste might prefer it in a SET amp. It's all really a matter of what floats your boat. There are no hard and fast rules in audio as there are so many variables. As always, your mileage may vary. Sincerely, The Parrot ---------------- Very profound statement Paul, and very true. In my brief experience in tube rolling I've just learnt that just throwing different 'better' tubes into a circuit designed with a budget in mind is not necessarily the right step towards audio nirvana. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted July 30, 2004 Share Posted July 30, 2004 < Very profound statement Paul, and very true. In my brief experience in tube rolling I've just learnt that just throwing different 'better' tubes into a circuit designed with a budget in mind is not necessarily the right step towards audio nirvana.[img src='http://forums.klipsch.com/idealbb/images/smilies/1.gif'> ---------------- Ditto, lots of wasted $$$ on nos tubes for naught, but I have lots of spares with no place to putem where should I stick them Quote Link to comment Share on other sites More sharing options...
mike stehr Posted July 30, 2004 Share Posted July 30, 2004 "where should I stick them" Leavin' yerself wide open on that one, aren't ya? Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted July 30, 2004 Share Posted July 30, 2004 ---------------- [/blockquote> Huh, I dont get it Quote Link to comment Share on other sites More sharing options...
mike stehr Posted July 30, 2004 Share Posted July 30, 2004 It's over your head..... Quote Link to comment Share on other sites More sharing options...
3dzapper Posted July 30, 2004 Share Posted July 30, 2004 Mike that's not his head. His head is bald! Rick Steve, no hit man please. My wife and daughter still love me. Quote Link to comment Share on other sites More sharing options...
edwinr Posted July 30, 2004 Share Posted July 30, 2004 ---------------- On 7/30/2004 11:41:24 PM 3dzapper wrote: Mike that's not his head. His head is bald! Rick --------------- So are tubes! And look how much we all love 'em! Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted July 31, 2004 Share Posted July 31, 2004 Go ahead, keep having fun at my expense maybe I should leave now Im so depressed I have no wit your full of sh@# Quote Link to comment Share on other sites More sharing options...
mike stehr Posted July 31, 2004 Share Posted July 31, 2004 Oh Wah. Poor Steve. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted July 31, 2004 Share Posted July 31, 2004 ---------------- On 7/31/2004 12:19:59 AM mike stehr wrote: Oh Wah. Poor Steve. ---------------- Quote Link to comment Share on other sites More sharing options...
mike stehr Posted July 31, 2004 Share Posted July 31, 2004 Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted July 31, 2004 Share Posted July 31, 2004 Hi, Dee: We had to go out yesterday, but I wanted to respond to your interest in some possible changes to your amps. I think part of what you decide you would like to do depends on how much of a financial investment you're willing to make to change them. I think the amps probably sound very good as is, but as some others have suggested, there are some things you can do to possibly improve what's already there. Some possibilities: 1) As soon as the VTV article on Jack Eliano's DRD came out, I incorporated one aspect of it, the so-called 'ultrapath' connection, into my Moondogs. This will provide some isolation between the audio and PSU aspects of the amps, and will permit the exclusion of the electrolytic cathode resistor bypass capacitor on the 2A3. In its place you would use your choice of a high voltage oil or film capacitor of about 50uf. One leg of the output transformer primary will connect to one end of this capacitor, and the other side of the cap will be returned to the cathode of the 2A3. I just performed this same modifcation to Edster's Horus parafeed monoblocks, and it works very well. You would very likely notice a little more detail from this, as well. 2) It appears that there may be some direct coupling on the input and driver, but the amp uses AC coupling (hence the brown film capacitor)between the two stages. As a couple of others have pointed out, that cap could be replaced with a higher quality film and foil capacitor (lots to choose from)or a quality oil capacitor. The former might sound a little more detailed and bright, but the Jensens are very good here. 3) If you don't go the ultrapath route, you could substitute the primary B+ filter capacitor on the top of the amp with the same value in a very high quality Black Gate capacitor -- of which you would need two. Moreover, if that cap is only a single section filter capacitor, I would suggest one extra stage of filtering. In other words, instead of a single 100uf in conjunction with the 10H filter choke, you would use a 100uf/100uf capacitor at 450VDC, with one of the dropping resistors in the B+ supply connected between those two sections. However, the Black Gate capacitors are extremely expensive. If you used the Ultrapath connection, which is much cheaper to do, it would not really be necessary to go fo such an expensive capacitor, however I would still suggest an extra stage of filtering. 4) I'm going to go back and study the wiring you enclosed, but I'm not sure from the picture if the amp uses DC on the driver stage heaters. It may simply use a grounded, center-tapped filament transformer, which is a pretty classic way of doing that. If it does not use DC, I would suggest a small rectifier and filter circuit for even quieter performance. 5) Depending on what output tube you are using, you could also experiment with other 5 volt rectifiers. If I'm not mistaken, I think your amps use a 5Y3, is that right? The 5Y3 is a really good rectifier to use, and I set my Moondogs up to use the same tube when I was running some expensive RCA 2A3s. I would not want to impose over 250V max on vintage tubes, but you can certainly go higher than that if you are using something like a Sovtek or KR 2A3. Your amp could even be setup with a switch that can be used to switch between a higher and lower plate voltage. 6) If there is a cathode resistor bypass capacitor on the input, which would be an electrolytic, I (this has become a recent preference and is just my opinion)would leave it in place but, again, use one of good quality. An Elna or Black Gate would be good. The reason for this is that, IMO, it improves the overall frequency response of the amp, as well as provides more gain. There are some other things that go on, here, but better gain and very likely improved bass response (which SETs can sometimes need a little extra help with)can be expected. Some think that these gains are achieved at the cost of possible distortion, but more often than not, designers do bypass the cathode resistor with a capacitor. The Moondogs and DRDs both use one, but it's not critical to the circuit. I've experimented with this a great deal, and honestly think I prefer the bypass. The amp to me sounds faster, and more open at both frequency poles. Let me know if I can help in any way! Erik edit: Dee, studying the wiring again, it seems that the cathode resistor on the input stage is NOT bypassed the way it is in the DRD and Moondog amps. So, that would be fine left as-is, or it's something you can also experiment with to see what you prefer. The cap you would need for that would be in the range of $7.00, approx. Also: It seems that the bias for the 2A3 is taken off the center tap of the 2.5V filament supply, which implies that you probably don't have a hum-null potentiometer. Is that correct? If that is in fact the case, that is something I personally would like, and would be good to have in case you opt for the Ultrapath connection between the OPT primary and 2A3 cathode. Quote Link to comment Share on other sites More sharing options...
dubai2000 Posted July 31, 2004 Share Posted July 31, 2004 Erik, of course all this tech talk is far above my head (but still interesting to rad). Anyway, the Wrights do not have a hum pot, so your finding is correct (as usual ). Wolfram Quote Link to comment Share on other sites More sharing options...
coda Posted July 31, 2004 Share Posted July 31, 2004 the bias for the 2A3 is taken off the center tap of the 2.5V filament supply I loaned Kelly my Wrights for a weekend back in 2001, he took a few photos, the rest is history I suppose. Erik, you're correct, the 2001 photo actually drew George Wright onto the AA to make his one and only post ever. The vendor he was working with had placed the center tap on the 2.5 volt filament winding, as a result there was just a slight bit of background hum at the time. George's servicing results, before (bottom) and after (top), were excellent btw.. From George's notes: To correct the problem, cut the blue/white wire going to the terminal strip where the 100 uf cap, the 750 ohm 10 watt resistor and two 680 ohm .25 watt resistors are tied. Insulate the wire, and attach a new wire to this terminal posistion. Run the new wire over to the output socket area. Next,install two 22 ohm 2 watt resistors to this wire and insulate. The other end of one of the resistor leads goes to the junction of the orange and blue wire on the socket; the other resistor goes the the junction of the orange/white and the green wire also on the socket. These are pins 1 and 4 respectively of the output socket. Indeed, there's some room in that chassis to make a few mods, however generally I'm wary of making any changes to something that I'm happy with, as I give it very high marks for sounding harmonically correct. The current circuit design that gives the Wright amps its character works quite well with the Magnequest TFA-204 (originally designed by Peerless as a replacement for the famous Western Electric A171A transformer used in the WE91 300B amp). If George has made recent design changes to the WPA3.5 I'd be interested to hear further. Some interesting mod suggestions posted.. Of course, one of the advantages of sticking to tube rolling at this point is that they're easier to undo. Personally I can appreciate differences using the vintage RCA and Arcturus monoplates, and thoughtful tube matching in general can make a difference IMHO. Emission Labs makes a 2A3-Mesh that I've been curious to try out, Michael Klementovich (Co-Author Paul Wilbur Klipsch: The Life... The Legend) also owns the Wright WPA3.5 amps and WLA-12A preamp and has been taken by these output tubes (which are published as direct replacements for the original RCA 2A3 monoplate tube). Click on image below for further description. They are not inexpensive however.. take a look at these new 6SN7 globes..! Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted July 31, 2004 Share Posted July 31, 2004 Great! another picture. There is in fact a cathode bypass capacitor on the driver -- that little blue guy up towards the top of the chassis. (at least that what it looks like....) Edit: Thanks for the picture! Those two fixed resistors are another way of handling the filament supply. I would just prefer using something like a 50 ohm variable pot, with the center wiper connected to the bias circuit (without the bypass cap) and the opt returned to the cathode (wiper of the hum pot) by way of a 50uf high voltage oil or film capacitor. I also think using DC on the input/driver, filtered with 10,000-20,000uf would be better than using AC with a center-tapped supply. By 'better' I mean hopefully even quieter peroformance. Quote Link to comment Share on other sites More sharing options...
Daddy Dee Posted July 31, 2004 Author Share Posted July 31, 2004 ---------------- On 7/31/2004 8:26:52 AM mdeneen wrote: What does Mr. Wright suggest? mdeneen ---------------- That is a good question and Geo Wright's response would be most interesting. I'll see if can find out what he thinks this week. Had a couple of conversations with Mr. Wright around the time I purchased the amp... one of which was about upgraded tubes, which he no longer provided. He suggested that the best combination would be RCA blackplate 2A3 and Sylvania chrome dome 6SN7. Out of curiosity, I tried others and never had a better sound than his suggestion. Erik. Yep, 5Y3 rectifier tube. Thanks for your thoughts here. Are Friends Electric, Interesting story there, thanks. Quote Link to comment Share on other sites More sharing options...
Griffinator Posted July 31, 2004 Share Posted July 31, 2004 George really is a cool guy. Haven't had a chance to talk with him since he sent me my dealer kit, unfortunately. Too bad the damned financing fell through the first time, or I'd have brought a few of his dealer-only toys to Indy with me. Quote Link to comment Share on other sites More sharing options...
whodidit Posted July 31, 2004 Share Posted July 31, 2004 Keep it up trey!!!heh heh heh Quote Link to comment Share on other sites More sharing options...
Erik Mandaville Posted July 31, 2004 Share Posted July 31, 2004 ...then again, you could just leave it if it's sounding good to you. That's what matters, not a pile of mods listed by some weekend experimenter like me! ...I think the 2A3 filament supply could be quieted a bit, which is what is shown in the second picture. Erik Quote Link to comment Share on other sites More sharing options...
leok Posted August 1, 2004 Share Posted August 1, 2004 Interesting about the RCA blackplate 2A3 and Sylvania chrome dome 6SN7. That's the best combination I've found with my amps also. Leo Quote Link to comment Share on other sites More sharing options...
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