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Author Topic: DIY-Vacuum Tube Amps-looking for advice on transformers and capacitors Luciano Brigite Master Film Handler Posts: 277 From: Sao Paulo, SP, Brazil Registered: Jan 2002 posted 01-16-2003 07:28 PM                     Hello all, Before I start with the topic, I'm posting it here because ,although it's tech, has nothing to do with film. ( hmm.. hold on.. at some point it has something to do with me and Film Tech. was this little hobby of mine that brought me here . I found FT by "accident" while looking for tech tips N'tricks + schematics of tube amps on the net and one link I followed was leading to a Simplex amp schematic here on FT) Ok, I'm looking for some advice about winding my own output transformers for vacuum tube amps. find out the number of turns for each winding I believe I'm doing right ( looked for it before and found something in a book about transformers but it didn't say anything about building said component, only finding out the turns. wire gauge and lamination size)now I want to build it because I don't really want to pay some good $ to have it done somewhere. To me, it'll add some more "taste" to the project .Now what I'm not sure about how to do is the windings itself related to winding direction for primary/secondary and the lamination assembly. I know that some of these transformers are built with all the "E"'s to one side and all the "I"s to the other with a gap between them made of thin paper, plastic or other material and some others are built just like any common transformers ( "E" and "I" laminations mixed). Why are they build that way? Does it have anything to do with the UltraLinear thing? Oh BTW.. is the UltraLinear transformer design, just a normal winding with a tap for screen connection or it has a separate winding just for it or a totally different way to do the windings ? Another question I have is related to capacitors. there are many kinds available ( polyester, polypropilene , paper, oil,etc .. I think paper and oil are no longer made but some places may have them old stock) what kind is more suitable for this kind of aplication? I've used polyester and oil types ( but not mixed in the same circuit. or it's all poly or it's all oil) polyester are the common ones here and easy to find , oil caps are a little harder and I believe they're no longer made but some places still have them (NOS) Am I missing something better than these two kinds I'm using or are they ok? Any help, tips, tricks are welcome Thanks!  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 01-16-2003 08:03 PM                     Luciano, Go to the site www.diyaudio.com and there you will find everything, and everybody that knows everything about anything audio related. No joke!! If you have a tube related question just regester and post it under the Vacuum Tube section and someone will give you an answer. Some of these guys are real artists and build amazing stuff. You'll find me there under the Pass Labs section quite a bit. I recently built a pair of Pass Labs 100 watt, Class A, single ended power amplifiers. These things sound amazing to say the least. They idle as hot as some tube amps do! If you heard them, I'd bet that you'd completely abandon tubes all together. The only downside is that they make my power meter spin like the meat cutter at the Deli! I've attached a picture of mine...still need to finish the front panels, and have them all anodized though. Mark @ CLACO  |  IP: Logged Luciano Brigite Master Film Handler Posts: 277 From: Sao Paulo, SP, Brazil Registered: Jan 2002 posted 01-17-2003 07:34 PM                     Hello Mark, Thanks for pointing that website,I didn't take a good look at it yet but I believe I'll find a lot of useful information there. Your amps looks really nice, even without the panels. last time I saw heatsinks that size was when I had to replace the diodes of a xenon rectifier.Post some pictures of your amps when you get their covers done, i'd like to see it I tried a few solid-state amps before,using transistors or IC's because they were easier ( and somewhat cheaper) to build, but at the same time, I was getting more and more interested in tube amps and was getting a lot of tubes that were being sold in bags with 20,30 brand new in box tubes for about $5.00. got lots of them, selected the ones that'd be used for audio and the others that had no use for me, gave them away. Then started loking for their tech specs and slowly I came out with a few circuits.some worked, other didn't or not as I thought it'd do.. . Untill now my only problem was, and still is, find the output transformers.design them ( find out the number of turns, wire gauge and so on) I believe I learned how to do. the only problem now is wind the transformer.The places I know here that do that service are charging a quite a bit for it and I don't think all they want to wind a transformer is fair, unless there's something I'm missing about it. I'll find out where I put a few pictures of a pair of tube amps a friend gave me and I rebuilt them and one from the last tube amp prototype I finished yesterday . it's ugly as hell but worked fine.  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 01-17-2003 08:57 PM                     Luciano, If you can suscessfully wind your own output transformers you have suceeded in performing a major feat!! Winding output transformes is an art in itself, and even some black magic is occasionally thrown in for good measure. It would be difficult to do, but something I would encourage you to explore in great depth. Can't remember if I've ever seen any books on the subject, but there are probably some out there someplace. The amps I built, although large to disipate the large amount of heat genberated, are actually quite simple. The audio signal only passes thorough two semiconductors, and as a result the signal remains very pure. The amps sound really good and primarily only generate second order harmonic distortion, like a good tube amp does....this type is the least bothersome type audibly. The distortion level is also very low to begin with. This type of output stage is 50% more efficient than a straight class A amp as it uses an active current source. The green colored pcb is 4X6 inches to give you some scale as to the size of these amps. Mark  |  IP: Logged Luciano Brigite Master Film Handler Posts: 277 From: Sao Paulo, SP, Brazil Registered: Jan 2002 posted 01-19-2003 12:28 AM                     Well, I looked at that site again but didn't find anything about output transformers. I didn't want to register there and ask about it at the time, will leave it for another time. After looking there I did a search on the web for any information about these transformers and found a few things I believe will be usefull for me for a while. ( one of the other sites I visited suggested reverse engineering on damaged/junk transformers and I think i'll do that sometime since I have a few bad transformers somewhere and one other showed some drawings of two kinds of windings for PP transformers, a bit different from what I was thinking.) I remember seeing a few of Pass's amps somewhere in the net,I got it bookmarked but I ended losing the link to the pages. Could you point me to the site/page for that amp you built? I'd like to take a look at it.  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 01-19-2003 11:29 AM                     Sure, Go to www.passlabs.com and then go to products, and then to Aleph. Look for the Aleph 2 service manual PDF, and download that. It has the circuit description, and schematics. If you are going to build any of the Aleph amplifiers there is a universal circuit board available through the forum to allow you to build any of them...depending on what power level you require....30 watts up to 200. Its a nice pcb.....has 2 oz copper traces, and is all silkscrened and solder masked. Building anyone of them does require matching the input devices and output devices so they all share the current equally...this is however really easy to do with a 4 1/2 digit DVM. I got to .01 volt very easily from devices that were all from the same date batch. I ended up building a pair of Aleph 2's, they're Rated at 100 watts, but they actually clip out at about 140 or so into 8 ohms. With the supply I built into them peak power is huge. Also, I use all teflon covered silver wire in my units. The added cost was trivial as compared to the time involved in building them. Nelson's stuff is always very consertively rated. There is also a very long thread at DIY about the Aleph X which is the current Pass Labs design. A number of people there have gotten together and backwards engineered it from the original patent(with help from Nelson himself!). Basically it consists of two Aleph amplifiers that are cross coupled, this reduces noise and distortion to limits that are almost unmeasureable. More important though is the sound quality, which so far no one has come close surpassing. Nelson approves of others using his unique patents and supports the forum all the time. He is an interesting person...a physisist by degree, not an engineer!! Its amazing that a number of his amplifiers have already achieved classic status along with stuff from Marantz, Audio Research, and Krell. But, like some of the Marantz and Audio Research stuff, some of his older Threshold, and Pass Labs products command quite high resale values. Mark @ CLACO www.clacoequipment.com  |  IP: Logged Luciano Brigite Master Film Handler Posts: 277 From: Sao Paulo, SP, Brazil Registered: Jan 2002 posted 01-22-2003 06:03 PM                     Thanks again for the link Mark I downloaded the manual for the model you built and two others, one of them is for a 30W amp and I think it'll be the one I'll try after the tube amps. 100W I think it's too much for me, specially if it's RMS.. I believe the 30W one will be ok. I'm trying to stop listening music too loud.. but will do it sometimes About the output transformers.. well.. I reviewed all the calculus (sp?) I did before and redid a few of them , specially the ones for the two amp projects I'm building and based on all the information I read on the net, I believe they're right. Since they're SE amps, the transformer's winding is as I was thinking and will give it a try as soon as I find a place that will sell me small quantities of lamiantion and wire, it won't be easy but I'm not going to give up on it so easy, and wind it up by hand using... a handcrank film rewind. I was going to put here a picture of a breadboard prototype of the amp I'm building now but I just lost the file well.. next post,maybe  |  IP: Logged

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