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NYAL OTL 3

220.255.2.164

Posted on November 17, 2010 at 22:08:23
Posts: 63
Joined: July 31, 2007
I baught a pair of these amps a couple of months back and now need some help.

Although the amps came with the owners manual the biasing instructions were not included. I guess I have the earlier version of the amps as they come with 15 coupling caps and a test socket with 7 test points. The circuit diagrams available in the net are for versions with a larger no. of caps. If anyone has a copy of the biasing instructions could you pl send me a copy. Alternatively I am prepared to pay postage for a hard copy to Singapore.

Anpther issue is, valve 1 (6lf6) has a orange glow although there is signal to the speakers. Is the valve shot. Any coments on this would be appreciated. Currently I am not using the amp, need to resolve this first. If need be would replace with a matched valve.

All comments would be appreciated. Thanks

Nara

 

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RE: NYAL OTL 3, posted on November 18, 2010 at 11:44:31
Lew
Audiophile

Posts: 6870
Location: Bethesda, Maryland
Joined: December 11, 2000
I advise you to contact George Kaye Audio Lab, also maybe to be found under the trade name "moscode", via the internet. He and he alone can help, unless you are lucky enough to unearth another owner of a unit like yours.

 

RE: NYAL OTL 3, posted on November 19, 2010 at 20:25:57
airheadair
Audiophile

Posts: 135
Location: California
Joined: October 18, 2010
Contacting George Kaye is a good idea. He did tell me to beware of suspicious orange glows; it could mean that the tube is out of spec and in fact could damage the tube more. Ralph issues similarly warnings.

Biasing these amps is difficult. I have a hand-written set of instructions by Ted Hammond, a former NYAL employee. It includes a warning that lethal voltages in them can "KILL YOU DEAD." Still I could perhaps find a way to post these if you like. I will be out of town for a few days; I'm gong to Chicago to see Patricia Barber live. (My second pilgrimage within a year!)

May I ask how much you paid for these amps, what speakers you want to use them with, and where you got them? I use them with Stax F83's. They can play very loud indeed and sound very fast and pure. But I haven't auditioned anything seriously in decades.

 

RE: NYAL OTL 3, posted on November 19, 2010 at 23:26:23
Posts: 63
Joined: July 31, 2007
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

 

RE: NYAL OTL 3, posted on November 20, 2010 at 07:50:27
Lew
Audiophile

Posts: 6870
Location: Bethesda, Maryland
Joined: December 11, 2000
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.

 

RE: NYAL OTL 3, posted on November 21, 2010 at 13:50:32
decca4
Audiophile

Posts: 16
Joined: October 7, 2010
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.

 

RE: NYAL OTL 3, posted on November 22, 2010 at 13:50:58
Lew
Audiophile

Posts: 6870
Location: Bethesda, Maryland
Joined: December 11, 2000
"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.

 

RE: NYAL OTL 3, posted on November 22, 2010 at 17:18:37
decca4
Audiophile

Posts: 16
Joined: October 7, 2010
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

 

RE: NYAL OTL 3, posted on November 22, 2010 at 20:49:38
Posts: 63
Joined: July 31, 2007
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

 

RE: NYAL OTL 3, posted on November 22, 2010 at 21:04:59
Posts: 63
Joined: July 31, 2007
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

 

RE: NYAL OTL 3, posted on November 23, 2010 at 08:53:07
Ralph
Manufacturer

Posts: 2543
Location: Minnesota
Joined: April 24, 2002
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.

 

RE: NYAL OTL 3, posted on November 23, 2010 at 12:39:50
Lew
Audiophile

Posts: 6870
Location: Bethesda, Maryland
Joined: December 11, 2000
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.

 

RE: NYAL OTL 3, posted on November 24, 2010 at 20:04:24
airheadair
Audiophile

Posts: 135
Location: California
Joined: October 18, 2010
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).


 

RE: NYAL OTL 3, posted on November 25, 2010 at 05:41:16
Posts: 63
Joined: July 31, 2007
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

 

My take on PB, posted on November 27, 2010 at 22:59:51
Lew
Audiophile

Posts: 6870
Location: Bethesda, Maryland
Joined: December 11, 2000
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.

 

RE: My take on PB, posted on November 28, 2010 at 09:20:22
airheadair
Audiophile

Posts: 135
Location: California
Joined: October 18, 2010
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.

 

RE: My take on PB, posted on November 28, 2010 at 17:47:53
Posts: 63
Joined: July 31, 2007
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

 

RE: My take on PB, posted on November 28, 2010 at 18:06:58
airheadair
Audiophile

Posts: 135
Location: California
Joined: October 18, 2010
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.

 

RE: My take on PB, posted on November 29, 2010 at 18:44:24
Posts: 63
Joined: July 31, 2007
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

 

RE: NYAL OTL 3, posted on December 10, 2010 at 20:43:37
Mike Mount
Audiophile

Posts: 484
Location: midwest
Joined: September 25, 2004



I alway saw this variability (in [trans]conduction?) in my OTL3s
there were issues with getting (overpriced) tubes
and rarely ever matched one another.

My tubes would routinely pulse... purple.

I think that Ralph (as typically is the case) is correct
that some tubes under a dynamic load draw more
that others in the circuit.

The AS M60 (in background) was the best solution...

 

RE: NYAL OTL 3, posted on March 28, 2011 at 03:28:41
naidu


 
Hi,

I was not able to do much on the amp as I had been busy with other matters, however I managed to obtain some 6LF6 tubes from ebay in the meantime. Today I replaced the tube with the orange glow with 3 new tubes in turn and each tube started to also glow immediately upon switch on. Does this indicate something. I doubt it is a tube issue. Comments would be appreciated. Thanks.

Nara

 

RE: NYAL OTL 3, posted on May 23, 2012 at 02:01:01
Posts: 63
Joined: July 31, 2007
Hi,
Need to revive this thread as I still have not resolved the issue. To recap:

VI developes an orange glow upon switch on. It is similar when moved to V2 and V3 position. V1 is OK in V6-V8 position. V2 and V3 are OK in V1 position. V6-V8 also glow in V1-V3 position but are OK in their original postion. In addition to the glow the affected tubes get extremely hot.

I have since purchased 10 6LF6 tubes but each has a similar problem in V1-V3 position.

Have not attempted biasing in view of the overheating.

Inputs on what could be wrong would be appreciated.

As a last ditch measure, am considering converting the amps to OTL 3Q as I would then need only 4 6LF6 tubes. The lower power output is OK as dont need much power to drive the Tannoy HPD385(8 Ohms, 91db), previously driven by late Geroge Wright's 2A3 monos (3.5 Watts).

Assistance from members would be appreciated.

Thanks and Regards,
Nara

 

RE: NYAL OTL 3, posted on May 23, 2012 at 03:45:34
Banat
Audiophile

Posts: 329
Location: near Belgrade / Serbia / Europa
Joined: February 5, 2010
Hi !

Remove and check all trim pot`s with ohm meter , one by one , but without turning trim pot sliders .
I`m suspect that Amp upper bank of power tubes which plates glow orange have no correct G1/G2 bias beacose of bad bias trim pot .
Sign of incorrect power tube bias is that you don`t have exactly 1/2 of V1,2,3 B+ plate voltage on the lower bank of power tubes plates .
For example :
If you measure +300V on the upper power tube plates (V1,2,3) terminals than you have to measure exactly +150 V on the lower power tube plates terminals .

Best Regards !
__
Enlightened Evolution-Astral Projection

 

RE: NYAL OTL 3, posted on June 5, 2012 at 04:30:13
Posts: 63
Joined: July 31, 2007
Thanks for your comments Banat. Only 1 of the top bank of tubes glows. If there is an issue with the trim pots, should it not also affact the other 2 tubes in the upper bank. Yes I would check the trim pots anyway.

As a last ditch measure I'm seriously considering converting the amp to the 3Q version with only 2 tubes in the upper and lower banks respectively. Would like to seek inputs from members on what other changes if any that need to be made to the circuit other than just removing 2 tubes. If I am not wrong, the photo in Mike Mounts post shows the OTL3 Q. Would Mike like to confirm and comment please. Comments from others using the 'Q' version would be appreciated
The few comments on the OTL3 Q that I have read, state that 1 tube in the upper and lower bank are removed and capacitors added to roll off the base at @100hz. The capacitors bit would not apply as I would not be using the amp to drive the Quadb

Rgds,
Nara

 

RE: NYAL OTL 3, posted on June 5, 2012 at 09:26:22
Banat
Audiophile

Posts: 329
Location: near Belgrade / Serbia / Europa
Joined: February 5, 2010
If only one of upper bank three power tubes glows than check the value of G1 grid stop resistor on that glowing tube first , since that grid stop resistors is only non common element of upper power tubes bank negative bias network , but is separate for each power tube , check for bad solder points around that glowing tube socket to .
BTW , NYAL OTL 3 is not very complex electronic unit and some factory service manual which include voltage and current chart , adjusting points ,... etc , well be very helpful for quick service and quick malfunction diagnose .

Best Regards !


__
Enlightened Evolution-Astral Projection

 

RE: NYAL OTL 3, posted on June 6, 2012 at 01:17:04
Posts: 63
Joined: July 31, 2007
Thanks for your comments Banat,
Checked all the resistors when I received the amps and they were all within specs. The problem is not with a particular tube position in the upper bank.
Only 2 of the original tubes in the upper bank do not glow in any position in the upper bank. One tube in the upper bank glows in all the 3 positions in the upper bank. Also all the 3 tubes from the lower bank glow in all the 3 positions in the upper bank. All the six tubes do not glow in the lower bank.
Also all the 10 tubes that were purchased subsequently glow in all the 3 positions in the upper bank. Frankly I'm puzzled. If the problem is with a particular tube position in the upper bank,then it would be easier to find a solution.
This is the reason why I am considering using the amp with 2 tubes in each bank if this does not require any change to the circuit.

Rgds,
Nara

 

RE: NYAL OTL 3, posted on June 8, 2012 at 02:48:12
714rhino


 
How much plate current are you drawing? Lift the positive leg of the bridge rectifier and insert a meter, if you are over 500ma dial it back to around 350, sounds like you are running them too hard and the ones that do not glow can withstand the high current and the glowing tubes cannot.
Buy a set of tubes from Roger Modjeski, (ram tubes) they are the best you can get.

 

RE: NYAL OTL 3, posted on June 11, 2012 at 01:18:00
Posts: 63
Joined: July 31, 2007
Hi 714rhino,
Thanks for your reply. To date it appears to be the most appropriate solution to the problem with the OTL3.
Would like to check with you, instead of lifting the positive leg of the bridge rectifier to measure current, could I set the current (350mA) and center balance by adjusting R16 and R23 as indicated in para 9 of the biasing instructions.

Thanks & Rgds,
Nara

 

RE: NYAL OTL 3, posted on June 19, 2012 at 21:27:37
714rhino


 
Sorry not to get back with you sooner, I will send the alignment procedure to your e-mail tomorrow.

 

RE: NYAL OTL 3, posted on June 20, 2012 at 06:40:55
Posts: 63
Joined: July 31, 2007
Thanks 714rhino but I do have a copy of the instructions. I am not up to it to bias the amp and would be getting a tech competent friend to do it for me soon. I was just wondering if in the meantime I could just set Ip and balance as indicated in para 9 of the instructions and see if the glowing stops.

Rgds,
Nara

 

RE: NYAL OTL 3, posted on June 20, 2012 at 19:25:17
714rhino


 
Do the full alignment procedure as described in your manual, if you cannot get the amp to align properly you know that there is a problem either with the tubes or a passive component causing a problem, cap/res...etc.

 

RE: NYAL OTL 3, posted on July 18, 2012 at 05:40:39
t.skjold.petersen
Audiophile

Posts: 2
Location: Roskilde
Joined: July 18, 2012
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

 

RE: NYAL OTL 3, posted on July 18, 2012 at 16:10:56
Posts: 63
Joined: July 31, 2007
Whats your email add

 

RE: NYAL OTL 3, posted on July 19, 2012 at 00:49:26
t.skjold.petersen
Audiophile

Posts: 2
Location: Roskilde
Joined: July 18, 2012
Hi
Email : t.skjold.petersen@gmail.com

Skjold
Best regards
Skjold

 

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