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#1
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Neutral header on OPTs
On Mon, 19 Jan 2004 09:01:43 +0100, Fritz Wuehler wrote:
Neutral header on OPTs rec.audio.tubes The other present transformer threads are too nastily muddied for me to enter. Mick, the RDH has been reprinted and is available from Heinemann-Butterworths in a facsimile edition of the last, 1968 RCA distribution of the famous fourth edition. Its a 1500 page book and therefore pretty pricey but eventually you will have to have one. lots of good stuff snipped Yep - I found the reprint for about £40 in paperback. I'll have to save up. :-) Thanks for all the info & advice. -- Mick http://www.nascom.info for Nascom & Gemini information Also at http://www.mixtel.co.uk where the collection started. Currently deserting M$ for linux... :-) |
#2
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On Mon, 19 Jan 2004 09:01:43 +0100, Fritz Wuehler wrote:
snip I am sure you are familiar with the famous series of cheap paperback electronics books published by Bernard Babani. There is actually a Mr B B Babani, and in 1960 he wrote a little book himself called Coil Design and Construction Manual. It is BP165, and my copy, fifteenth reprint of 1995, cost sterling pounds 3.95 from W H Smith, where they normally have a huge shelf of Babani Books. ISBN 0-85934-050-3. snip Sheesh! You had me scampering around the junk box (some people would call it a shed...) then... I had completely forgotten that I had that book! I've just checked, and it is the 1991 reprint (£2-50), so I've had it a while. That reminds me, I've a Radcom Handbook somewhere too... I can have a read now, while I listen to a bit of Eric Clapton via 6L6s... :-) |
#3
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Hello Andre,
just out of curiosity, if I remember correctly, you once had a very favourable article/review on the Velleman K4000 on your old homepage, so you might know what origin these toroid OPTs are from? I tried to get the answer from Velleman already (I have a very early K4000 in my living room, and my aim is to replace it with a completely homebrew amp) but they only wrote something like "made to Velleman specs" without getting any more precise. Tom -- Life: All in all a bad game, but graphics are really good. |
#4
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On Mon, 19 Jan 2004 20:59:11 +0100, Tom Schlangen wrote:
Hello Andre, just out of curiosity, if I remember correctly, you once had a very favourable article/review on the Velleman K4000 on your old homepage, so you might know what origin these toroid OPTs are from? I tried to get the answer from Velleman already (I have a very early K4000 in my living room, and my aim is to replace it with a completely homebrew amp) but they only wrote something like "made to Velleman specs" without getting any more precise. I always thought those amps looked rather nice in the pics... Have you considered swapping the OPTs with something else on flying leads, just to see what difference it makes? -- Mick http://www.nascom.info for Nascom & Gemini information Also at http://www.mixtel.co.uk where the collection started. Currently deserting M$ for linux... :-) |
#5
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Neutral header on OPTs
rec.audio.tubes I dont actually know where the Velleman K4000 trannies came from, Tom. But a good guess would be Antrim Transformers, in Northern Ireland. They are winders to just about everyone capable of defining a proper spec and who want a fair number of units. Quite a few of the famous European brand names have no windery of their own, only the Antrim works. What are you going to build in the case instead? Those trannies were designed for 3x EL34, so theres nothing commonplace about them. And the case is a nice piece of polished stainless, but there isnt space for big film caps in the bellypan, and even the plain painted steel bits are pretty substantial, so as little metalwork as a few extra holes will be a pain. (Listen to Mr Soft Ali speak!) I still have mine in a box in a store, just in case I ever want to put subs back in my system, or my son wants a proper big tube amp. Do you remember the primary impedance of the OPT? For the rest of you, Tom and I are discussing an early incarnation of the bestselling kit amp in the world, the Velleman K4040. I dont know what the procise configuration is now, but the K4000 was a PPP EL34 Class A/B with 18W in Class A and 96W in Class B into 8ohms. That was on the spec. Mine actually put out 101W at the spec input of 0V775 and could be substantially overdriven without adverse effects. It was like Jekyll and Hyde, a delicate enough amp into sensitive speakers but a monster when driving big bass bins. I loved it for being a lot of amp for a really very reasonable price. It cost about 500 quid when the best EL34 tube kit of the day, the Audio Innovations Classic 25, intended for an entirely different sort of owner and application (a purist EL34 PP amp, 25W strictly in Class A1), was 700 quid. The Chinese seem to me even today to be hard put to match Vellemans price, if you consider quality for quality. Andre Jute Tom Schlangen wrote: Hello Andre, just out of curiosity, if I remember correctly, you once had a very favourable article/review on the Velleman K4000 on your old homepage, so you might know what origin these toroid OPTs are from? I tried to get the answer from Velleman already (I have a very early K4000 in my living room, and my aim is to replace it with a completely homebrew amp) but they only wrote something like "made to Velleman specs" without getting any more precise. Tom -- Life: All in all a bad game, but graphics are really good. |
#6
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Mr. Jute said:
I dont actually know where the Velleman K4000 trannies came from, Tom. But a good guess would be Antrim Transformers, in Northern Ireland. I always thought they were made by Amplimo, a Dutch company specialized in toroidal transformers. The measured performance sure looks like it. Amplimo were the first to use vanderVeen calculations for their output transformers, and they're very good IMHO. Amplimos can also be found in the relatively scarce, but underestimated Miracle amplifier with 2 x EL34 PP UL/triode. To my ears one of the finest sounding EL34-based amps ever made, and I don't even like the EL34 :-) -- Sander deWaal Vacuum Audio Consultancy |
#7
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Hi Form@C,
I always thought those amps looked rather nice in the pics... They surely give a nice looking result after assembling the kit. Have you considered swapping the OPTs with something else on flying leads, just to see what difference it makes? No. Because of the simple reason that a pair of "assumed to be of decent enough quality to compare" OPTs will probably cost way to much "just for a try" ... Tom -- All the true gurus I've met never claimed they were one, and always pointed to someone better. -- Bill Vermillion |
#8
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Hi Andre,
I dont actually know where the Velleman K4000 trannies came from, Tom. But a good guess would be Antrim Transformers, in Northern Ireland. They are winders to just about everyone capable of defining a proper spec and who want a fair number of units. I see. No chance to obtain a single or a few pairs for us DIYers, I suppose. What are you going to build in the case instead? I don't intend to modify the K4000 further (I have nothing done what couldn't be undone easily), but I will try to sell it instead. I am aware that this doesn't make much sense moneywise, since for example new factory assembled K4040s in unopened original factory boxes with full factory guarantee go for the kit (!) price on Ebay ... Even when considering to store it away for a decade or two this will not make much sense to me moneywise, since nobody expects a used DIY assembled unit to rise an Euro or ten on profits. I am quite sure that I am able by now to construct and build an amp matching my (current) needs and interests much better than the K4000 does by now by investing the few money I will get from seeling it in a completely homebrew project. Those trannies were designed for 3x EL34, so theres nothing commonplace about them. I think you ment "4x" (a double PP pair) instead of "3x"? Well, OPTs capable of handling ~100 watts with a suitable Raa for a quad of EL34 /ch are not _that_ rare, I think. I mean, here in Germany there is even stock iron available from the then-famous Engel company (now HSGM) for the RIM industrial strenght amps ... without checking, I suppose suitable iron will be readily available from Sowter or even Hammond. Do you remember the primary impedance of the OPT? No. The old printed handbook doesn't elaborate, and currently downloadable docs on the K4040 from Velleman don't either. But I wouldn't be surprised to measure a reflected Raa in the range of, say, 1,5k to 2k :-) I dont know what the procise configuration is now, but the K4000 was a PPP EL34 Class A/B with 18W in Class A and 96W in Class B into 8ohms. Oh, mentioning "PPP" is dangerous, since there seems to be a completely other circuit type identified by this short name "PPP". In the case of K4000 and K4040, it definitely means "4 tubes in classical PP arrangement", two pushing and two pulling. A double PP pair. As far as I know, current K4040 and K4040B sport only few (but quite helpful) improvements from the original K4000 design, like an added LED chain for easy in vivo bias control/adjustment, and added power-on cycle and standby functionalities. I didn't compare the main amp circuit part by part, but changes over a decade obviously were minor, so the basic design obviously was quite good from the start :-) I loved it for being a lot of amp for a really very reasonable price. I agree regarding the sheer power per Euro ratio, but I have more and more doubts about the sonic qualities per Euro. Well, I think it wouldn't be fair to expect the sound of a refined and elaborated low power circuit from a mass production "power monster" like this amp. But all in all the K4000/K4040 surely gives excellent bang for the buck while maintaining a good sound - better than one would expect from the money asked compared to fashionable boutique stuff. As mentioned before, I made only very little "improvements" to this amp, like a better coupling cap here and a resistor of more adequate ratings there ... the most noticable and sonically obvious one was to plug eight carefully selected 70s production Tesla EL34 into it, which still (after some thousands of operating hours) beat some current production types out of their sockets sonically. Replacing the gain stage and PI stage tubes by "considered to be superior" types/brands didn't make a big difference, by the way. Tom -- Knowledge is power - knowledge shared is power lost. -- A. Crowley |
#9
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On Tue, 20 Jan 2004 20:54:08 +0100, Tom Schlangen wrote:
Hi Form@C, I always thought those amps looked rather nice in the pics... They surely give a nice looking result after assembling the kit. Have you considered swapping the OPTs with something else on flying leads, just to see what difference it makes? No. Because of the simple reason that a pair of "assumed to be of decent enough quality to compare" OPTs will probably cost way to much "just for a try" ... Yep... Tell me about it! :-( I was just wondering if you just happened to have parked a nice posh amp chassis next to it and cross-connected a few wires temporarily... You know what I mean! Is the sound quality something that you could tweak in the feedback? Perhaps stick a pot in and a couple of croc clips & a few little caps. Sod the reponse curve, tune it by ear until you like it! Just a suggestion, and you can always put it back. :-) -- Mick http://www.nascom.info for Nascom & Gemini information Also at http://www.mixtel.co.uk where the collection started. Currently deserting M$ for linux... :-) |
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