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In Reply to: RE: NYAL OTL 3 posted by airheadair on November 19, 2010 at 20:25:57
Thanks for your reply.
Let me answer your questions first. Bid on ebay for US$2050 from vidlabtds in USA(Sr nos. BL005 and 007). Speakers are Tannoy HPD 385 (15 inches) in open baffles with side wings, these are 8 ohms speakers. Amps have not been used since purchase.
Would really appreciate it if you could post the biasing instructions to me. Willing to pay postage if you can send me a paypal invoice. Alternatively you could scan the instructions and email it to me, whichever is convenient.
Have removed the power cords and replaced them with IEC sockets. Intend to replace the WIMA caps as these would be out of spec by now. The amps come with different value caps which is rather odd. Any suggestions for suitable replacement caps. Also intend to eventually replace the 15 coupling caps (photoflash) with Panasonic TS ED caps as suggested by LEW (560uf 400v)with an extra pair to make up for total 9000uf in each amp.
I'm currently buying 6lf6 tubes from ebay to replace the faulty tube. What parameters should I look for in matching the tube.
I have also written to G Kaye but have not got a reply.
My postal add is:
V N Naidu
Block 497 J, Tampines St 45
#10-76
SINGAPORE 527497
Thanks for the help
Follow Ups:
Hi Naidu
I am in to my second pair of Futterman H3AA which has the basically the same circuitry as your OTL 3. In my first pair which I used many years ago there was a tendency for the anode plates to glow. The reason for this was most probably that to much current was going through the tubes. The funny thing was that when thy started glowing they sounded the best. The quick remedy was to shut them of for some minutes. In my case I believe as an afterthought that the bias was wrong. It could be that the problem that you have is the same and that the bias needs adjusting. If it is just one of the tubes that starts glowing then I would guess that that one needs replacing.
I have read in some old papers that the tubes should be matched. If this is true or not I don't know. However I think that each pair of tubes should be matched as the same current is expected to through them both. Maybe someone knows more about this than I do.
Good luck
Hi decca4(A),
I think the problem is with this particular tube (6lf6). When I interchanged it with tube 3 it still glowed in its new position while tube 3 was OK.
Yes according to the circuit diagram all the 6lf6 tubes need to be matched. I am in the process of getting a few tubes in the hope of finding one that matches. Following this and once I get a copy of the biasing instructions I would bias the amp.
Thanks,
Nara Naidu
Don't throw that tube out- get it tested on a tube tester. It might be that it conducts harder than the others but is otherwise OK.
It is a very good idea to use matched tubes BTW. This amp *should* have separate bias controls for each power tube. But is one thing to have all the tubes set properly at idle, its quite another to have them all working together at full power. That's why you want to use matched tubes.
Actually, film caps can last for quite a long time, not to say "forever", so your WIMAs are probably OK functionally. However, to my ears they are NOT a good sounding coupling cap, and this is a critical application. (Here I use the term "coupling" to refer to a cap that couples the input or driver stage to the output stage; I do not refer to the electrolytic caps that couple the output stage to the spkr, unique to Futterman types.) So I agree with your intention to replace the WIMAs, because IMO they are awful.
Adding more output stage-to-speaker capacitance might conceivably help lowest bass response, but there is no need to get crazy about it. More benefits could be gained by bypassing the spkr coupling electrolytics with a good film cap of the highest value and quality you can afford or find. (You only need a 200V rating for whatever you choose, so that usually saves some money vs high voltage caps.) Then you can bypass THAT cap with more and even better film caps of progressively lower value. There is no rule for that but I generally shoot for a 1:100 ratio of values, e.g., a 100uF film cap can be bypassed by a 1uF film cap and then again by a .01uF film cap.
Besides replacing and upgrading the speaker coupling electrolytics, you probably also should do the same for your power supply electrolytics, which are also pretty old by now.
Hi Lew,
Yes, I intend first to replace the WIMA caps. I plan to use Mundorf Supreme caps. Any other brand of caps that you think I should consider.
Thanks,
Nara
Arguing the sound of capacitors is kind of like arguing about religion; I never quibble with anyone else's preference. From all that I know, Mundorfs are very good. I also like MIT RTX and most teflon caps, altho the latter are quite expensive. MITs take a long time to break in and sound plastic-y until they do. For lower values, the Russian teflon caps available on eBay may be a very good choice to save lots of money and if you have space. (They are quite large.) But by all means do try the Mundorfs. Another good cap I have heard of lately is the Clarity line of caps, particularly the MR. I personally do not like traditional paper in oil caps; many swear by them.
Lew
When you say bypassing the electrolytic output capacitors do you then mean replacing the output capacitors or mounting the new film capacitors in parallel with the output capacitors?
By the way has anyone had a chance to compare the original Futterman H3AA with the NYAL OTL 3? I have at one occasion and the Original came out on top.
As I recall it when studying the respective circuitry many years ago the only difference is really in the power supply. The screen grids were fed with a different regulator circuit. Also the originals were hard wired.
"Bypass" means film caps are in parallel with electrolytic caps, in this case.
It was claimed once that George Kaye modified the Futterman circuit in a way that greatly improved bass response. Although I owned many "real" Futtermans and liked all of them, I never heard an NYAL product and so cannot comment on the comparison. George Kaye is very knowledgeable, however.
I'm back from my trip to Chicago, where I heard f Patricia Barber
for the second time at her home base, the Green Mill (I've seen her two other times as well). Absolutely utterly fantastic. Everyone should grab everything this woman has ever produced. The recorded sound is usually really good too.
Anyway I have scanned Ted Hammond's hand-written instructions on biasing the OTL3 c.
I am reluctant to post it for various reasons, but I will email it if you send me your email address. (I think you did once already but I lost it).
Yesterday i purchased a DIY OTL 3 set and they just sound amazing.
They are hooked up to my DIY ELS speakers.
But I will like to have the info regarding BIAS adjustment, as I expect this to come in handy when the time comes.
Can I please have a copy send to my e-mail?
Best regards
Skjold
Whats your email add
Hi
Email : t.skjold.petersen@gmail.com
Skjold
Best regards
Skjold
I like her style. I like her voice. I think she is an excellent musician. Plus, she is the beneficiary of some of the finest quality recordings I have ever heard. I just don't like most of the music she has written for herself. A little of it goes a long way with me. I like her a lot when she sings standards, but I am a fogey, I admit.
Interesting: I tend to feel the other way. For example, on her most recent album,
The Cole Porter Mix: although she sings the Cole Porter songs with precision and beauty,
I think her style is too intense for their light-hearted wit. Her own songs on that album,
Snow, I Wait for Late Afternoons and You, and the January Song are simply exquisite. Nightclub,
which consists of all standards, is my least favorite of her albums. On the other hand,
I can see why her album "Mythologies" is hard to appreciate. It's pretty far from jazz.
Post Modern Blues (from "Modern Cool") is rather far out but lots of fun.
Actually I do like a lot of her standards too, especially in her early work (Split, Distortion of Love).
I also like her piano playing a lot; this hasn't shown up yet as much on her recordings as it does in her live performances.
Hi Airheadair,
Any update on the instructions. I was not able to contact you directly as I do not have your email add. However I had given my email add in an earlier post. Anyway it is: v_n_naidu@hotmail.com. Hope to hear from you soon. Thanks
Nara
I sent you a copy on November 25. Didn't it show up?
I aso sent you another copy today. Please let me know
if you don't get this one either.
Good luck, and BE CAREFUL.
Thanks for all the comments and help. I am in the process of obtaining 6LF6 tubes for current and future replacements and would like to seek comments on the parameters to be used for matching of tubes for replacement. Gm, Mu and Rp have been mentioned in various asylum posts. Are there any other parameters that should be used in matching of 6LF6 tubes.
Thanks,
Nara
Hi,
Glad you enjoyed the Patricia Barber session.
Yon can email the instructions to me at
v_n_naidu@hotmail.com.
George has also given me a reply but does not have a copy of the instructions. Thanks for you help, realy appreciate it.
Rgds,
Nara
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