I just picked up a single NYAL OTL1 from California that I plan to use in a mono system. This is basically an OTL3 with a seperate regulated power supply in its own case. It has some voltage issues. The actual measurements I have taken are below: (where I say "incorrect" I mean that the measurement is most likely not what is required by design and the reverse for the comments containing "correct")
Input Tube Voltages
PLATE VOLTAGE - 75vdc (this I believe is correct)
SCREEN VOLTAGE - 23vdc (this I am sure is incorrect)
Phase Splitter Tube Voltages
PLATE VOLTAGE - 88vdc (this I am sure is incorrect)
SCREEN VOLTAGE - 154vdc (this I am sure is incorrect)
CATHODE VOLTAGE - 75vdc (this I am sure is incorrect)
V1, 2, 3 Upper 6LF6's Voltages
PLATE VOLTAGE - 335vdc (this is close to correct which should be 320vdc)
SCREEN VOLTAGE - 150vdc (this I am sure is incorrect)
CATHODE/RAIL VOLTAGE - 84vdc (this I am sure is incorrect as it should be 160vdc)
V6, 7, 8 Lower 6LF6's Voltages
PLATE VOLTAGE - 84vdc (this I am sure is incorrect as it should be 160vdc)
SCREEN VOLTAGE - 165vdc
BIAS VOLTAGE - At PS side of R47 39vdc (this I believe is correct)
Incoming PS Voltage measurements (I believe all of these measurements are all correct)
Probes across A & H gets 200vdc
Probes across H & Ground 335vdc
Probes across A & Ground 535vdc
I have attached a pdf of the OTL1 amp schematic. I do not have the power supply schematic and if anyone does that would be great. I have heard that the regulated power supply in the NYAL OTL1 is basically the same as the Moscode 600 so if anyone has that schematic that would be great if you could post it. I have also posted the NYAL OTL3 amp schematic for comparison. As you can see the B+ is regulated. I have confirmed that the regulated power supply is supposed to puts out 2 amps of current. I have a pair of NYAL OTL3's that I will check these measurements against sometime this week and post them.
I generally feel that the regulated power supply is not the problem for the following reasons:
1. The measurements coming out of the Reg. PS are all basically the required voltages in comparison to the original Futterman H3 which the nYAL OTL's were not that far removed from.
2. I have ran the amp and PS for several minutes each time I have tested her and the Reg. PS never blew a fuse or even basically got hot and in my experience with Reg. PS is that would occur if there was a problem inside of it.
I should also say that I have tested all the tubes and they are all good. Just for the heck of it I took another set of known good tubes as well and replaced the original set and the same problems still occurred.
Any help would be greatly appreciated.
Input Tube Voltages
PLATE VOLTAGE - 75vdc (this I believe is correct)
SCREEN VOLTAGE - 23vdc (this I am sure is incorrect)
Phase Splitter Tube Voltages
PLATE VOLTAGE - 88vdc (this I am sure is incorrect)
SCREEN VOLTAGE - 154vdc (this I am sure is incorrect)
CATHODE VOLTAGE - 75vdc (this I am sure is incorrect)
V1, 2, 3 Upper 6LF6's Voltages
PLATE VOLTAGE - 335vdc (this is close to correct which should be 320vdc)
SCREEN VOLTAGE - 150vdc (this I am sure is incorrect)
CATHODE/RAIL VOLTAGE - 84vdc (this I am sure is incorrect as it should be 160vdc)
V6, 7, 8 Lower 6LF6's Voltages
PLATE VOLTAGE - 84vdc (this I am sure is incorrect as it should be 160vdc)
SCREEN VOLTAGE - 165vdc
BIAS VOLTAGE - At PS side of R47 39vdc (this I believe is correct)
Incoming PS Voltage measurements (I believe all of these measurements are all correct)
Probes across A & H gets 200vdc
Probes across H & Ground 335vdc
Probes across A & Ground 535vdc
I have attached a pdf of the OTL1 amp schematic. I do not have the power supply schematic and if anyone does that would be great. I have heard that the regulated power supply in the NYAL OTL1 is basically the same as the Moscode 600 so if anyone has that schematic that would be great if you could post it. I have also posted the NYAL OTL3 amp schematic for comparison. As you can see the B+ is regulated. I have confirmed that the regulated power supply is supposed to puts out 2 amps of current. I have a pair of NYAL OTL3's that I will check these measurements against sometime this week and post them.
I generally feel that the regulated power supply is not the problem for the following reasons:
1. The measurements coming out of the Reg. PS are all basically the required voltages in comparison to the original Futterman H3 which the nYAL OTL's were not that far removed from.
2. I have ran the amp and PS for several minutes each time I have tested her and the Reg. PS never blew a fuse or even basically got hot and in my experience with Reg. PS is that would occur if there was a problem inside of it.
I should also say that I have tested all the tubes and they are all good. Just for the heck of it I took another set of known good tubes as well and replaced the original set and the same problems still occurred.
Any help would be greatly appreciated.
I finally got a chance to get back to this amp and work on it so I thought I would report back my findings for those of you who are interested in NYAL Equipment, Futterman Amps & OTL's of this nature in general.
First thing I know is that the "mystery" surrounding these amps and there design and how they really work seems only to exist because no one really wants to say how they were built. Not sure why that is but no matter who I talk who was involved in designing, building and marketing these amps from the various vendors who produced one version or another of the futterman it is all a mystery. I think everybody knows that the futterman design is in the public domain at this point and could be used b anyone for any reason and there would be no legal issues.
Getting back to the amp and its seperate regulated power supply.
I started with the power supply on the OTL1. In the attached schematic of my first post you can see the amp with its seperate regulated power supply not shown but noted. Well I reverse engineered the power supply this past week and I found a few things.
1. It only regulates about 2 amps not 10 as noted in other lit. out on the web.
2. The screens are not regulated from the power supply box as shown in the OTL1 schematic only the B+ is regulated from this box. The screens are regulated inside the amp box off of that transformer exactly as shown in the OTL3 schematic.
3. Also it appears you could add the screen regulator supply to the power supply box as the PC board has the burned section for it on the board but the components are not added and I need to check further but it appears the transformer has the secondaries for the screen supply but they are not used inside of the power supply box they are just capped. (I will check this further over the next few days and post).
4. Also the AC power for the amp box passes through the regulated power supply box via a relay. I suspect to let the power supply get to full working voltage and stable before it turns on the amp itself.
I will be venturing into the amp box this weekend and report more shortly but let me tell you what I think is the case so far from what I can see.
1. In the amp box the transformer used is exactly like the transfromer used in OTL3 which means all of the secondaries are in the amp box transformer for a full and complete power supply. I will confirm this by Monday but this means in an OTL1 amp if the regulated B+ box had issues you could just put the B+ section into the amp box just as it is in an OTL3 and keep going. Of course unregulated B+ but I am not so sure how much this really matters other then to say hey I have a regulated B+ power supply on my OTL. I say this because I also have a pair of the NYAL OLT3's which does not have a regulated B+ and they sound excellent once rebuilt (which they are).
If anyone else knows these amps and there design and would like to comment that would be great.
Post more early next week.
A lot of the NYAL amps used a photoflash filter cap that was old when the amp was produced. Harvey would strip the outside plastic coating off the caps to make them look like they were USA made. They are tall (~5") and narrow- about 1" diameter. If you have any of these in your amps just be advised that they are a good 30 years old- older than the amp itself. I think the value was 1200uf @ 360V- I might be wrong about the capacity but not the voltage.
I don't think anyone is concerned about legal issues in talking about this amp. The main problem that you run into with them is reliability. Some of that comes from the parts used and some from the design itself- if overloaded they can oscillate if not set up correctly. Several manufacturers have marketed Futterman amps since the demise of NYAL- Prodigy, Silvaweld, Fourier and a servo-controlled version by Counterpoint, to name a few. Reliability of the amplifiers seemed to have played a role in the demise of either the company or the product. However, the Futterman-built amps seemed to hold up a bit better, perhaps because Julius knew the circuit better than most, and knew how to tweak the feedback circuits.
These days most of the OTLs you see use the Circlotron approach, which is simpler and a lot more stable.
I don't think anyone is concerned about legal issues in talking about this amp. The main problem that you run into with them is reliability. Some of that comes from the parts used and some from the design itself- if overloaded they can oscillate if not set up correctly. Several manufacturers have marketed Futterman amps since the demise of NYAL- Prodigy, Silvaweld, Fourier and a servo-controlled version by Counterpoint, to name a few. Reliability of the amplifiers seemed to have played a role in the demise of either the company or the product. However, the Futterman-built amps seemed to hold up a bit better, perhaps because Julius knew the circuit better than most, and knew how to tweak the feedback circuits.
These days most of the OTLs you see use the Circlotron approach, which is simpler and a lot more stable.
The cap is 680uf at 360v.
I have to say that all of my futterman and NYAL amps have run with zero issues for years and often for hours per day. I agree that they need to be used correctly (16 ohms or higher) and that the set up of the amps takes time and clear understanding on how to do that, but I must say once past that I find them easy to work with and steady amps. Rebuilding is highly recommended of course since all the parts are old by now and heat has usually caused these parts to age poorly and it leave you with a high level of potential failure.
I guess what I am saying is no one that was involved in these initial designs has ever been that willing to help the diy communitity fully IMHO. Do a web search on these amps and all you find is old marketing material or articles from guru's and such. You will find more info on Futterman himself then the amp. If your lucky an occassional thread with bits and peices on the design comes up and if you read closely you can use some of the info to help you with a rebuild. Or you could pay extreme amounts for manuals, schematics, set up procedures, etc. No real product support and the funny thing is most of these guys copied the design after the patent went public. There are many other product suppliers in the high end audio world that are more helpful and certainly with products that are no longer in their main line up then those that have copied this design and made money.
I started this thread to see if more who have touched these amps would step up and add some real info as I know that the amp in the thread needs a rebuild to work correctly and caps are the problem I was just hopeful for a real discussion on a rebuild, set up, usage experience, etc. Just does not seem to exist on these amps and it in frustrating because they are fantastic.
I don't know who you've been able to contact concerning the Futterman/NYAL amps but that capacitor value reminded me of somebody that worked there and IS still around. This person used that exact same value in his Dynaco mod kits and I'm staring at a Polaroid of an OTL he was building close to 20 years ago. Andy Fuchs of Fuchs Audio Technology, GSI and Tube God might be worth getting in touch with. How much he knows or remembers I can't tell you but it can't hurt to try. Brian Clark is another one that might be worth hunting down, maybe Andy knows his whereabouts. Send Andy an email and see what he says. Andy once published an OTL Compendium which had many different OTL designs in it, from the US, Japan, and Europe. I will try to dig mine up and see if there is anything different from what you posted. Of course there is always George Kaye but I imagine he's the first you thought of, right?
Craig
Craig
Yes, 680uf. That's the one. The trick is that they are an unusual form factor and hard to find replacements.
Years ago I used to buy them from Bill Godbout Electronics for use in modifying Dyna ST-70s. When I realized that he was about the only place I was going to find that part cheap, I bought out his entire inventory. Years later I was speaking to Harvey Rosenburg, and he told me how he used to buy this part from the same supplier, but one day when he went to order the part was nla. I didn't have the heart to tell him that it was because I beat him to it. One thing I learned early on though- don't use that part in a capacitor input supply. They lasted about 15 years before they all started dying.
You might also look over at the OTL Asyum on audioasylum.com There is at least one guy there that goes by the name of Lew that has a set of Futterman amps and has been keeping them alive for many years.
Years ago I used to buy them from Bill Godbout Electronics for use in modifying Dyna ST-70s. When I realized that he was about the only place I was going to find that part cheap, I bought out his entire inventory. Years later I was speaking to Harvey Rosenburg, and he told me how he used to buy this part from the same supplier, but one day when he went to order the part was nla. I didn't have the heart to tell him that it was because I beat him to it. One thing I learned early on though- don't use that part in a capacitor input supply. They lasted about 15 years before they all started dying.
You might also look over at the OTL Asyum on audioasylum.com There is at least one guy there that goes by the name of Lew that has a set of Futterman amps and has been keeping them alive for many years.
Craig,
I also have a copy of it, so if you can't find yours I'll look for mine.
Andy is a close friend of a close friend of mine. He is very clever with modern tube design and produces products that are stable and last a long time.
I have a pair of enormous OTL monoblocks with 10-12 sweep tubes per amp that Andy custom built. I haven't used them in years inasmuch as I'm in a multi-year SET phase these days. They are chrome plated and quite something to look at.
If anyone wants them, let me know. I'm open to trades or whatever. I have 3000 SF of gear stacked to the 10'-12' ceilings. I turned 55 the other day and decided it's time to seriously downsize.
Sorry, I wasn't trying to high-jack the thread, I was just looking to offer my OTL Compendium if it would help. The OTL's I have were an afterthought....
I also have a copy of it, so if you can't find yours I'll look for mine.
Andy is a close friend of a close friend of mine. He is very clever with modern tube design and produces products that are stable and last a long time.
I have a pair of enormous OTL monoblocks with 10-12 sweep tubes per amp that Andy custom built. I haven't used them in years inasmuch as I'm in a multi-year SET phase these days. They are chrome plated and quite something to look at.
If anyone wants them, let me know. I'm open to trades or whatever. I have 3000 SF of gear stacked to the 10'-12' ceilings. I turned 55 the other day and decided it's time to seriously downsize.
Sorry, I wasn't trying to high-jack the thread, I was just looking to offer my OTL Compendium if it would help. The OTL's I have were an afterthought....
I know Andy's OTLs were Futtermanish but don't know how close they really were/are. I have a simple hand drawn schematic he sent me years ago but not enuff info to help. From the NYAL schematics available on the net everyone interested knows the basics but not the little details, and that's where people in the know are quiet, that's fine if they are trying to make a living at it. A friend of mine had some of the Fourier products that I was hoping to get a crack at but he sold them before I had a chance to check 'em out. Atmaspheres are the only OTLs I've had the pleasure to geek with.
Craig
Craig
Last edited:
I guess my issue is that there really is not enough of these Futterman/Nyal style otls out there to make any real money off of at this point and in general whenever i have been in conversations with some who were involved in the past with these amps during there hey day I am almost always told "why don't you just sell these and get something else" usually one of there newest products and that does not work for me as I feel these amps are great when restored and running correctly and yes I completely agree it is those devil details that they keep close whenever you ask questions.
On another note does anyone have a NYAL or Futterman power trans avail for sale?
Last edited:
DrRick,
I would love to get a copy if you fine it. Also I would be interested in seeing what you have and possibly take some things off your hands.
Please PM me about Andy's OTL compilation. My first thought was to find it (hard part) scan it (easy part) and post it on-line. Upon further reflection, I want to check with Andy prior to doing so.
I may be thinking too much about this, inasmuch as I think it was just a collection of things already in the public domain.
If Andy objects to my posting it online or making copies (at the cost of whatever Kinkos or Staples charges) for people, perhaps I'll just gift you my copy.
Also, please PM me or email me about the extra goodies I have. If you provide me with an email address I'll send you pictures of the OTL's and anything else you have an interest in. It would be a help to let me know where your interests beyond OTL's lie. I have an awfully large amount of stuff. My collection is 90%+ tube audio related stuff including some vintage tube recording/pro audio gear. The remaining 10% is quite varried.
BTW, I think the compilation includes the schematics and data on the OTL's I have. One very clever thing Andy did on these OTL's was using the 40 volt heater version of a popular sweep tube, i.e. the 20FL6 instead of the 6LF6. By doing so the cost of re-tubing is very low.
I may be thinking too much about this, inasmuch as I think it was just a collection of things already in the public domain.
If Andy objects to my posting it online or making copies (at the cost of whatever Kinkos or Staples charges) for people, perhaps I'll just gift you my copy.
Also, please PM me or email me about the extra goodies I have. If you provide me with an email address I'll send you pictures of the OTL's and anything else you have an interest in. It would be a help to let me know where your interests beyond OTL's lie. I have an awfully large amount of stuff. My collection is 90%+ tube audio related stuff including some vintage tube recording/pro audio gear. The remaining 10% is quite varried.
BTW, I think the compilation includes the schematics and data on the OTL's I have. One very clever thing Andy did on these OTL's was using the 40 volt heater version of a popular sweep tube, i.e. the 20FL6 instead of the 6LF6. By doing so the cost of re-tubing is very low.
Sorry, I forgot to ask where you're located. I'm also in the NE US, specifically Monmouth County, NJ.
The issue with the Fourier is it had a severe problem with its filter caps. They were marked 'Bindu' and were run 40 volts **over** their ratings! As you might expect, they had a tendency to explode.
The Futterman circuit was tricky enough that nearly every company that has ever tried to do business making it has been driven out of business. Of course, I don't know the real reasons why companies that made Futterman amps would fail, but its a correlation that cannot be ignored!
I think that is why the Circlotron OTL approach has been a little more successful. Not only is it possible to build an amplifier that will be reliable, without a lot of tweaking, but its output impedance is 1/2 of what it would be with a totem-pole output.
I am in NY just north of the city. I will PM you my personal email. I am interested in the OTL's and the paper.
Thx
Well its not the caps as I changed them and no change. I did find a dead resistor (243K) in the upper screen regulator and felt like this required that I pull the board and do a complete rebuild. Maybe burn some new boards at the same time
Anyone interested?
I will keep you posted
Well its not the caps as I changed them and no change. I did find a dead resistor (243K) in the upper screen regulator and felt like this required that I pull the board and do a complete rebuild. Maybe burn some new boards at the same time
Anyone interested?
I will keep you posted
Ok I took he board out over the last week and pulled evey cap off the board and replaced them. I checked every resistor for value and they were all in great tolerence except the ones around the 2 regulator tubes (6LU8). From what I can gather something crashed in the regulators, either a regulator tube, a resistor, a solid state component, something and that caused the overall problem. I then replaced all the solid state components as well and cleaned every pot on the board and checked there values and all was good.
I then pulled the small board that runs the front meter as well as carrying the bias, balance & AC pots. I checked the resistors and all were good. I checked and cleaned the pots and all were good. I changed all of the solid state components and cleaned the rotarty switch and put the board back in the face plate.
With both boards in and all pots on both boards set to 50% value I put tubes in the amp, attached it to the regulated B+ supply box and plugged it in and turned it on with a 16 ohm load attached and she powered up and I was now able to get her to maintain bias and balance as well as adjust the AC signal to their respective positions on the meter.
I checked a few voltages and they were all close and she sounded fantastic so I felt that I should just let her play for a while and then later on (read 3 or 4 days from now) I would go crazy getting every pot to the exact voltages as all were within 1 to 3 volts of where they needed to be anyway.
She was/is attached to my Tannoy Westmeister copy which has a 15" Calrad 50 watt 16 ohm Triaxial Speaker in it that I use as a mono system and I played the new Dave Matthews Band album as well as some old Doors and David Byrne. So about a hour and a half she played.
When I shut her off I touched all 3 TIP50's as well as all the zeners and they were all running cool so I was very happy.
While I had the board out I scanned both sides so I can make replacement boards. The reason is the traces were lifting in almost every area that I had to touch and you definately would not be able to refill the board a second time.
Well that is the end of this saga. Thanks for all your info.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.