I'm so glad to see this little amp spected & documented. W-10 was a UTC designed amp using UTC iron. Back in the day this was a really desirable amplifier.
i do my negative feedback with a pot like you were doing. i too also like using separate power supplies with linkage lead. keep up the videos i learn so much watching you tutorials etc
Hi Ian, It does seem the manufacturers and the formula of 1200 times the sqrt of the output tap (for the value of the FB resistor) is a bit excessive for NFB and causes some strange LF issues. I have noticed that for years but never knew why until recently. I picked up an old Heathkit W1 (I believe that is the model) that is in really nice shape. Uses 807's and a very nice Peerless transformer. I just finished a power supply for it because another gentlemen bought the PS but not the amp ??? It was only $10 - whatever. I will start testing it tomorrow and post something on it. I am very pleased you enjoy my videos. As have said on a few occasions, I can do all this fun stuff in the solitude and vacuum of my workshop but sharing it with the world makes it much more valuable to me and I hope others enjoy it also. Stay safe.
I'm glad that you mentioned about the chassis ground. I built a 2A3 SE amp with a separate power supply. I Only have one ground between the two chassis's. I think I'll put a ground lug on each and run a piece of braided wire. Great video!
Yes, and this is especially true when building truly HV supplies for RF transmitters at 3 and 4 KV where the B+ lead is run separately from an control voltages umbilical cord, maybe using HV meter lead wire or even RG-8 category coax cable. You can also use two or three pins of the 8 pin octal socket (if that is what you use) to provide redundant ground paths between chassis. My moto has always been (1) stay alive and (2) do whatever it takes not to burn up the vacuum tube by (not) overloading the grid and screen. The plate can usually take care of itself but the screen grid is always vulnerable.
I'll be looking forward to another great year with ELPaso TubeAmps. The PP triode project using the inductor grid drive is especially interesting to me. The "Economy Power Supply" design featured in the 1960'ish Amateur Radio manual might be the ticket for this amp. It provides B++ for the triode plates, B+ for the driver/input stages, and B- for the grid bias. This may be overkill since I tend to over complicate things but it might be worth a look see. Nice looking transformers and great video. Bob H.
I am going to have to look for the economy power supply you mention. I am still totally taken away by the way you derived two voltages by using the Pi filter for the higher voltage and choke-input for the screen voltages. This amplifier uses a bridge. The 5U4 is half of the bridge and two diodes on the socket are the other half. Voltage comes up slowly (per the 5U4 warmup time) and the power supply filter is choke input to keep the voltage around 480 which I find that the 6L6/5881's seem to like and perform very well. My thoughts are to build a stereo version using the LS-61 transformers as they are 10K or 6K, with the Svetlana SV572-10 triodes. I did some changes last night that I have not posted yet and although the UTC transformers perform very well at or below their power rating, I have to say, so far, the James transformers and even the Acrosound transformers actually perform better at the higher powers at frequencies below 30 Hz. On the other hand, the UTC transformers perform exceptionally well even at 30KHz... wow... I love this stuff but it does get tedious and makes me step back often times and ask myself, what am I trying to prove...
Those Tek distortion boxes are still great.. I have 2 of them, one set up with a SG505 optioned with I-M 2 tone and balanced out in a TM500 rack, and the other paired with a 5000 series double wide generator single ended output in a TM5000 rack.
The Williamson design was published in 1947 in Wireless World. The design offered full band, full power at below 0.1% THD. Future versions used pentodes with the Blumlein OT tapping for 'ultralinear' operation. Harold Leak then offered a comparable design he called the 'Point One' amplifier, which had a long history eventually giving us the infamous Point One Stereo 20. EDIT: A quick check and the Leak predated the Williamson by 3 years..Kudos Harold Leak.
PPPS The difference mainly between Heathkit and UTC is the output stage - one is Triode as per original Williamson and Heathkit is 'ultralinear' as later designs. (The great Alan Blumlein who invented among many things, stereo in 1933ish and later the 45/45 system for vinyl invented ultralinear output stage).
I also noticed in the UTC design that they do not use a cathode bypass capacitor on the output stage as do the Heathkit designs. I did experiment with this amplifier inserting a 47 uF capacitor to ground off the cathodes and it did improve power output and lowered THD levels. I have also noticed that the later (Heathkit and other) designs do not use a maximum current pot (R20 in the UTC design) but all do use the balance pot (R15) which I found most sensitive to setting lowest THD around 20-30 Hz.
Hi David - Thanks so much for the video = always fun and educational. I was looking for the photos from New Mexico but I think you ran out of time! Question: how do you feel about separate bias pots for each output tube rather than using a master bias pot with a trimmer or balancing pot? Is there any advantage for separate B- rails for each output tube or does a master bias pot + balance or trimmer work better? BTW, I have learned so many usable tips from you - each one saves me a lot of trial-and-error time ( trial-and-error is my middle name!) and I am grateful. Gary in Albuquerque
Hi Gary, The McIntosh MA230 design uses separate bias pots for each output tube and I have built that very amplifier (1977) using their OPT which performs flawlessly, in my opinion, but I don't see any real advantage to doing it that way rather than any other simple way to balance the currents in the output tubes. Of course I am talking about fixed bias in this case and not cathode bias. From some of the oldest, higher quality, amplifier designs I see dating back to the 1930's, the designers realized how important this was for top performance to balance output cathode currents from a 6V6 to an 813. That simple little 50 ohm 3 watt pot I used the other day has really caught my attention for the easiest way of balancing cathode currents from a cathode biased design. I have some driver boards called, Poseidon, sold by TriodeElectronics, boards that use a 1meg pot, CT to ground, to try and balance fixed bias to the output tubes that does not work very well. I mention this in contrast to the separate pots you mention above. Back to the cathode bias design - the UTC W-20 design got it right with being able to set the overall cathode current plus balance with a couple of 50 ohm pots that I have built and posted that works great for a quad of 6L6's but I don't see the need for adjusting the exact cathode current - just the balance. Trial and error - that is me also - much of my success, if that is what I should call it - is empirical "design". I take inspiration from vintage designs that I trust and the max parameters from the RCA tube manuals and go for it... when it comes to RF high power amplifiers, I trust Eimac datasheets and designs. If you get it right, it will do exactly what Eimac says it will do. Not sure of the photos from NM? I made some beautiful pictures of the crescent moon yesterday but I don't know how to share them except by RUclips and a link to an unlisted posting. Please refresh my memory.
@@ElPasoTubeAmps David, thanks so much for your reply. I appreciate the material and the time you took to respond - it cleared up a bit of confusion on my part. I have copies of the Heathkit schematics you mentioned, and just love those circuits. I am going to try your suggestions regarding balancing the output tubes rather than setting the exact cathode current for each tube. One thing I like about your methodology, is that you strive for simplicity and uncomplicated circuitry and assembly. You also come from a position of personal experience and the empiricism you've gained from actual "real-world" working conditions. If you start this video (Jan 6, 2019) at about :45 in, you'll hear the comments you made about your trip with your grandson to NM to photograph the stars! Thanks again, David.
@@radiojet1429 I will be most happy to share my astronomy photos but it is much easier to share them via email. I just came in from photographing the crescent moon, again. Email me at my RUclips email and I will send you some nice one. TheAudioShop@SBCGlobal.Net I do try to make it simple. Simple not only is cheaper but it often times lasts longer, easier to understand and duplicate and easier to repair. I come from an era where we tried to make the very best that could be made and make it in such a way that it can be repaired in the field. We couldn't send $750,000 NASA mainframe CPU's back to the factory for repair. We had to fix them and that included the peripherals down to drilling and tapping and shimming mechanical parts as necessary. Simple is beautiful.
I hope you don't think this is rude of me but you are the man who might be able to answer this question for me. I have obtained a Stancor transformer and choke numbered 52C084 and 56C048 respectfully and I cannot find any information on them. I would like to incorporate them into a home built amplifier but without the specification, I'm stuck. If you or your followers can help me I would be very grateful.
www.bunkerofdoom.com/xfm/ This site is a good place to look. I recognize that part number style but I am not sure that is the number you should be looking for. I have been confused looking for Stancor transformers myself. It is out there somewhere and I have even found data on chokes/transformers by looking (and lucky finding them) on Ebay where they sometimes show data sheets and have the very one you are looking for. From what I saw on Ebay with that style number it seems to be an old one - possibly 1940's or even earlier? Good luck.
Thankyou for the info. I have managed to work out the transformer by trial and error with the help of a vaiac. 0-120v, 0-120v, 310v-0-310v, 5v and 6.3v. The weight is about 12 pounds so I'm assuming around 0.3A for HT and around 6A each for LT. The choke is about half that weight with DC resistance across 3 terminals of 0 - 84 - 310 ohms.@@ElPasoTubeAmps
What model Triplett meters do you hanging? I have the one like yours with the voltage divider, 630 NA I believe and I have a 630 APLK. Update, saw the closeup of your meters, 630NA and 630PL. Virtually the same as my setup. I have Simpson 260 series 7, nice but not like a Triplett.
When I was a kid back in 66 I used to get magazines and go read them in the baseball dug out when they caught me they could not figure out what to punish me for when they saw that I was reading popular electronics and electronics illustrated and not Playboy 😂🤣😂🤣😂🤣😂🤣
Any time I travel with work or vacation, and still today retired and at the age of 69, I take data sheets and schematics on electronics, math, telescopes, etc. and people have seen me looking at them and pronounced me weird. Maybe they are right but that is OK. BTW - I never got caught reading the intellectual articles in Playboy either... :-)
Thanks for noticing. I didn't realize I said 120 instead of 1200. RUclips took away the option of the speech bubble because they say it can not be seen on mobile devices so they decided it was of no use. My comment to the UTC method of determining the resistance value of the FB resistor is that I have noticed that is the maximum amount (lowest resistance/maximum NFB) of feedback before the amplifier may become unstable at low frequencies as can be see with the cathode current fluctuating at about one Hz and the trace on the oscilloscope bounding up and down with no input. I have found on many amplifiers that the FB resistor may be best set at a value a bit higher than derived from that calculation. That has been my experience.
@@ElPasoTubeAmps I really enjoyed watching - I got carried away and started talking to the screen. It's often better to use less feedback than the standard value used. Manufacturers often went as close as they could toward instability to improve bandwidth, noise and distortion figures.
Have you come across a W-3AM? Also, just curious to see if you have looked into the R-Core transformers which started out a while back in Japan for use as low noise power transformers in pre-amplifiers. I have not seen a lot on RUclips about these transformers, or whether they would be viable as a tube power transformer, or maybe even an output transformer... They seem to get around the issue (in EI Core Transformers) where you get air gaps between the E and I lamination causing inefficiencies. They also seem to be easier to make than toroidal... Cheers, - Eddy
Hi Eddy, at one time many years ago, I do remember having at least two of the series of Heathkit amplifiers. Probably the W3 and W5 if I can remember that far back. I did not appreciate them at the time like I do now. I am not familiar with the transformers you mention but they sound very interesting. I have been very lucky so far to have access to these vintage transformers like the Acrosound, James and UTC and even the big KW level ones I used with my 3-400Z and 813 amplifiers. I do these builds and measurements just to see if these transformers do perform as people seem to think they so. I have not been disappointed so far. On the other hand, I have built a McIntosh MA230 amplifier using a new McIntosh transformers I purchased directly from them in 1977 and it out performs all other transformers pure and simple and will deliver 25-30% more power at low distortion than they rate the transformer for. I don't know if Mac would even sell their output transformers directly anymore.
@@ElPasoTubeAmps - Yeah the older transformers can be using custom metal formulations, for increasing permeability, that modern manufactures just don't use, due to the higher cost of using a custom molecular mix for the laminations. There was an older 3-part series that Mark (another tube RUclipsr) put out a few years back where this topic came up for a set of moving coil type phono cartridge SUTs (step up transformers) I believe they were vintage Triad models. This is what got me thinking about the viability of using R-Core style transformers for high efficiency applications like moving coil SUTs. Anyways, thanks for replying. Cheers, - Eddy
I agree with your thoughts. I did test the amplifier with a 47uF capacitor across the cathode resistor and it did improve the performance. I don't remember the exact numbers but I believe the power increased by a couple of watts for the same THD level without the bypass capacitor.
I have a couple of W-10 also that I took the LS transformer off for a stereo version I built. If it has the UTC LS-57 or 61 or 63 transformer on it, it is worth some money - maybe $250 maybe more. It it has the original power supply also - wow... it could sell for quite a price. Be careful selling such items on Ebay, is my advice. Its price probably also depends on if it has 6SN7 or 7N7 drivers and ... does it work...
Hi Simon, good to hear from you. I hope you are doing well. I am very partial to the Triplett meters. I prefer them to the Simpson for two reasons. One is they have a 100K ohm scale (which requires a special 30 volt battery that you can still get) and they also measure very high AC and DC voltages. The one on the left in my video is a 630-NA and will do 6KV and the one on the right is a 630-PL which does 5KV. As far as I am concerned, there is no difference between the two. I purchased the PL version brand new around 1972 and it works perfect. Naturally, if you buy one used, you may have to replace the Rx1 thru Rx1000 scale resistors as they may be damaged from applying voltage while on the ohms scale. I have seen people rotate the dial with voltage on the probes, going thru the ohms scales and current scales so be careful what you buy on Ebay. There is good documentation on the Internet so they can be repaired. When all the resistors in the ohms scales are correct, you can switch between the ohms scales and probably not have to touch the zero dial. I love these big Triplett meters and do recommend them as one of the best analog meters around.
www.antiqueradios.com/forums/viewtopic.php?t=338628&view=previous You can also search for the Heathkit W3, W4 and W5 schematics and get their complete manual.
I'm so glad to see this little amp spected & documented. W-10 was a UTC designed amp using UTC iron. Back in the day this was a really desirable amplifier.
i do my negative feedback with a pot like you were doing. i too also like using separate power supplies with linkage lead. keep up the videos i learn so much watching you tutorials etc
Hi Ian,
It does seem the manufacturers and the formula of 1200 times the sqrt of the output tap (for the value of the FB resistor) is a bit excessive for NFB and causes some strange LF issues. I have noticed that for years but never knew why until recently.
I picked up an old Heathkit W1 (I believe that is the model) that is in really nice shape. Uses 807's and a very nice Peerless transformer. I just finished a power supply for it because another gentlemen bought the PS but not the amp ??? It was only $10 - whatever.
I will start testing it tomorrow and post something on it.
I am very pleased you enjoy my videos. As have said on a few occasions, I can do all this fun stuff in the solitude and vacuum of my workshop but sharing it with the world makes it much more valuable to me and I hope others enjoy it also.
Stay safe.
I'm glad that you mentioned about the chassis ground. I built a 2A3 SE amp with a separate power supply. I Only have one ground between the two chassis's. I think I'll put a ground lug on each and run a piece of braided wire. Great video!
Yes, and this is especially true when building truly HV supplies for RF transmitters at 3 and 4 KV where the B+ lead is run separately from an control voltages umbilical cord, maybe using HV meter lead wire or even RG-8 category coax cable. You can also use two or three pins of the 8 pin octal socket (if that is what you use) to provide redundant ground paths between chassis. My moto has always been (1) stay alive and (2) do whatever it takes not to burn up the vacuum tube by (not) overloading the grid and screen. The plate can usually take care of itself but the screen grid is always vulnerable.
I'll be looking forward to another great year with ELPaso TubeAmps. The PP triode project using the inductor grid drive is especially interesting to me. The "Economy Power Supply" design featured in the 1960'ish Amateur Radio manual might be the ticket for this amp. It provides B++ for the triode plates, B+ for the driver/input stages, and B- for the grid bias. This may be overkill since I tend to over complicate things but it might be worth a look see. Nice looking transformers and great video. Bob H.
I am going to have to look for the economy power supply you mention. I am still totally taken away by the way you derived two voltages by using the Pi filter for the higher voltage and choke-input for the screen voltages. This amplifier uses a bridge. The 5U4 is half of the bridge and two diodes on the socket are the other half. Voltage comes up slowly (per the 5U4 warmup time) and the power supply filter is choke input to keep the voltage around 480 which I find that the 6L6/5881's seem to like and perform very well. My thoughts are to build a stereo version using the LS-61 transformers as they are 10K or 6K, with the Svetlana SV572-10 triodes. I did some changes last night that I have not posted yet and although the UTC transformers perform very well at or below their power rating, I have to say, so far, the James transformers and even the Acrosound transformers actually perform better at the higher powers at frequencies below 30 Hz. On the other hand, the UTC transformers perform exceptionally well even at 30KHz... wow... I love this stuff but it does get tedious and makes me step back often times and ask myself, what am I trying to prove...
Love your test gear
Those Tek distortion boxes are still great.. I have 2 of them, one set up with a SG505 optioned with I-M 2 tone and balanced out in a TM500 rack, and the other paired with a 5000 series double wide generator single ended output in a TM5000 rack.
The Williamson design was published in 1947 in Wireless World. The design offered full band, full power at below 0.1% THD. Future versions used pentodes with the Blumlein OT tapping for 'ultralinear' operation. Harold Leak then offered a comparable design he called the 'Point One' amplifier, which had a long history eventually giving us the infamous Point One Stereo 20.
EDIT: A quick check and the Leak predated the Williamson by 3 years..Kudos Harold Leak.
Wonderfull!!
PPPS The difference mainly between Heathkit and UTC is the output stage - one is Triode as per original Williamson and Heathkit is 'ultralinear' as later designs. (The great Alan Blumlein who invented among many things, stereo in 1933ish and later the 45/45 system for vinyl invented ultralinear output stage).
I also noticed in the UTC design that they do not use a cathode bypass capacitor on the output stage as do the Heathkit designs. I did experiment with this amplifier inserting a 47 uF capacitor to ground off the cathodes and it did improve power output and lowered THD levels. I have also noticed that the later (Heathkit and other) designs do not use a maximum current pot (R20 in the UTC design) but all do use the balance pot (R15) which I found most sensitive to setting lowest THD around 20-30 Hz.
Hi David - Thanks so much for the video = always fun and educational. I was looking for the photos from New Mexico but I think you ran out of time! Question: how do you feel about separate bias pots for each output tube rather than using a master bias pot with a trimmer or balancing pot? Is there any advantage for separate B- rails for each output tube or does a master bias pot + balance or trimmer work better? BTW, I have learned so many usable tips from you - each one saves me a lot of trial-and-error time ( trial-and-error is my middle name!) and I am grateful. Gary in Albuquerque
Hi Gary,
The McIntosh MA230 design uses separate bias pots for each output tube and I have built that very amplifier (1977) using their OPT which performs flawlessly, in my opinion, but I don't see any real advantage to doing it that way rather than any other simple way to balance the currents in the output tubes. Of course I am talking about fixed bias in this case and not cathode bias. From some of the oldest, higher quality, amplifier designs I see dating back to the 1930's, the designers realized how important this was for top performance to balance output cathode currents from a 6V6 to an 813. That simple little 50 ohm 3 watt pot I used the other day has really caught my attention for the easiest way of balancing cathode currents from a cathode biased design. I have some driver boards called, Poseidon, sold by TriodeElectronics, boards that use a 1meg pot, CT to ground, to try and balance fixed bias to the output tubes that does not work very well. I mention this in contrast to the separate pots you mention above. Back to the cathode bias design - the UTC W-20 design got it right with being able to set the overall cathode current plus balance with a couple of 50 ohm pots that I have built and posted that works great for a quad of 6L6's but I don't see the need for adjusting the exact cathode current - just the balance.
Trial and error - that is me also - much of my success, if that is what I should call it - is empirical "design". I take inspiration from vintage designs that I trust and the max parameters from the RCA tube manuals and go for it... when it comes to RF high power amplifiers, I trust Eimac datasheets and designs. If you get it right, it will do exactly what Eimac says it will do.
Not sure of the photos from NM? I made some beautiful pictures of the crescent moon yesterday but I don't know how to share them except by RUclips and a link to an unlisted posting. Please refresh my memory.
@@ElPasoTubeAmps David, thanks so much for your reply. I appreciate the material and the time you took to respond - it cleared up a bit of confusion on my part. I have copies of the Heathkit schematics you mentioned, and just love those circuits. I am going to try your suggestions regarding balancing the output tubes rather than setting the exact cathode current for each tube. One thing I like about your methodology, is that you strive for simplicity and uncomplicated circuitry and assembly. You also come from a position of personal experience and the empiricism you've gained from actual "real-world" working conditions. If you start this video (Jan 6, 2019) at about :45 in, you'll hear the comments you made about your trip with your grandson to NM to photograph the stars! Thanks again, David.
@@radiojet1429 I will be most happy to share my astronomy photos but it is much easier to share them via email. I just came in from photographing the crescent moon, again. Email me at my RUclips email and I will send you some nice one. TheAudioShop@SBCGlobal.Net
I do try to make it simple. Simple not only is cheaper but it often times lasts longer, easier to understand and duplicate and easier to repair. I come from an era where we tried to make the very best that could be made and make it in such a way that it can be repaired in the field. We couldn't send $750,000 NASA mainframe CPU's back to the factory for repair. We had to fix them and that included the peripherals down to drilling and tapping and shimming mechanical parts as necessary. Simple is beautiful.
I hope you don't think this is rude of me but you are the man who might be able to answer this question for me. I have obtained a Stancor transformer and choke numbered 52C084 and 56C048 respectfully and I cannot find any information on them. I would like to incorporate them into a home built amplifier but without the specification, I'm stuck. If you or your followers can help me I would be very grateful.
www.bunkerofdoom.com/xfm/
This site is a good place to look. I recognize that part number style but I am not sure that is the number you should be looking for. I have been confused looking for Stancor transformers myself. It is out there somewhere and I have even found data on chokes/transformers by looking (and lucky finding them) on Ebay where they sometimes show data sheets and have the very one you are looking for. From what I saw on Ebay with that style number it seems to be an old one - possibly 1940's or even earlier? Good luck.
there is stancor specs out there online otherwise tube diy asylum will help you.
Thankyou for the info. I have managed to work out the transformer by trial and error with the help of a vaiac. 0-120v, 0-120v, 310v-0-310v, 5v and 6.3v. The weight is about 12 pounds so I'm assuming around 0.3A for HT and around 6A each for LT. The choke is about half that weight with DC resistance across 3 terminals of 0 - 84 - 310 ohms.@@ElPasoTubeAmps
What model Triplett meters do you hanging? I have the one like yours with the voltage divider, 630 NA I believe and I have a 630 APLK. Update, saw the closeup of your meters, 630NA and 630PL. Virtually the same as my setup. I have Simpson 260 series 7, nice but not like a Triplett.
When I was a kid back in 66 I used to get magazines and go read them in the baseball dug out when they caught me they could not figure out what to punish me for when they saw that I was reading popular electronics and electronics illustrated and not Playboy 😂🤣😂🤣😂🤣😂🤣
Any time I travel with work or vacation, and still today retired and at the age of 69, I take data sheets and schematics on electronics, math, telescopes, etc. and people have seen me looking at them and pronounced me weird. Maybe they are right but that is OK. BTW - I never got caught reading the intellectual articles in Playboy either... :-)
PS the feedback resistor is 1200 x squareroot of speaker voice coil imp (tapping secondary) NOT 120x.
Thanks for noticing. I didn't realize I said 120 instead of 1200. RUclips took away the option of the speech bubble because they say it can not be seen on mobile devices so they decided it was of no use.
My comment to the UTC method of determining the resistance value of the FB resistor is that I have noticed that is the maximum amount (lowest resistance/maximum NFB) of feedback before the amplifier may become unstable at low frequencies as can be see with the cathode current fluctuating at about one Hz and the trace on the oscilloscope bounding up and down with no input. I have found on many amplifiers that the FB resistor may be best set at a value a bit higher than derived from that calculation. That has been my experience.
@@ElPasoTubeAmps I really enjoyed watching - I got carried away and started talking to the screen. It's often better to use less feedback than the standard value used. Manufacturers often went as close as they could toward instability to improve bandwidth, noise and distortion figures.
Have you come across a W-3AM?
Also, just curious to see if you have looked into the R-Core transformers which started out a while back in Japan for use as low noise power transformers in pre-amplifiers. I have not seen a lot on RUclips about these transformers, or whether they would be viable as a tube power transformer, or maybe even an output transformer... They seem to get around the issue (in EI Core Transformers) where you get air gaps between the E and I lamination causing inefficiencies. They also seem to be easier to make than toroidal...
Cheers,
- Eddy
Hi Eddy, at one time many years ago, I do remember having at least two of the series of Heathkit amplifiers. Probably the W3 and W5 if I can remember that far back. I did not appreciate them at the time like I do now.
I am not familiar with the transformers you mention but they sound very interesting. I have been very lucky so far to have access to these vintage transformers like the Acrosound, James and UTC and even the big KW level ones I used with my 3-400Z and 813 amplifiers. I do these builds and measurements just to see if these transformers do perform as people seem to think they so. I have not been disappointed so far. On the other hand, I have built a McIntosh MA230 amplifier using a new McIntosh transformers I purchased directly from them in 1977 and it out performs all other transformers pure and simple and will deliver 25-30% more power at low distortion than they rate the transformer for. I don't know if Mac would even sell their output transformers directly anymore.
@@ElPasoTubeAmps - Yeah the older transformers can be using custom metal formulations, for increasing permeability, that modern manufactures just don't use, due to the higher cost of using a custom molecular mix for the laminations.
There was an older 3-part series that Mark (another tube RUclipsr) put out a few years back where this topic came up for a set of moving coil type phono cartridge SUTs (step up transformers) I believe they were vintage Triad models. This is what got me thinking about the viability of using R-Core style transformers for high efficiency applications like moving coil SUTs.
Anyways, thanks for replying.
Cheers,
- Eddy
You need to do a cathode bypass in the output tubes me thinks
I agree with your thoughts. I did test the amplifier with a 47uF capacitor across the cathode resistor and it did improve the performance. I don't remember the exact numbers but I believe the power increased by a couple of watts for the same THD level without the bypass capacitor.
I have a W-10 that I’m trying to figure out what it’s worth. Could you tell me if I send you a pic ?
I have a couple of W-10 also that I took the LS transformer off for a stereo version I built. If it has the UTC LS-57 or 61 or 63 transformer on it, it is worth some money - maybe $250 maybe more. It it has the original power supply also - wow... it could sell for quite a price. Be careful selling such items on Ebay, is my advice. Its price probably also depends on if it has 6SN7 or 7N7 drivers and ... does it work...
On a different subject, are they Triplett meters ? ~I have been looking at them on ebay, what model would you recommend? Happy new year to you too!
Hi Simon, good to hear from you. I hope you are doing well.
I am very partial to the Triplett meters. I prefer them to the Simpson for two reasons. One is they have a 100K ohm scale (which requires a special 30 volt battery that you can still get) and they also measure very high AC and DC voltages.
The one on the left in my video is a 630-NA and will do 6KV and the one on the right is a 630-PL which does 5KV. As far as I am concerned, there is no difference between the two. I purchased the PL version brand new around 1972 and it works perfect. Naturally, if you buy one used, you may have to replace the Rx1 thru Rx1000 scale resistors as they may be damaged from applying voltage while on the ohms scale. I have seen people rotate the dial with voltage on the probes, going thru the ohms scales and current scales so be careful what you buy on Ebay. There is good documentation on the Internet so they can be repaired. When all the resistors in the ohms scales are correct, you can switch between the ohms scales and probably not have to touch the zero dial. I love these big Triplett meters and do recommend them as one of the best analog meters around.
ruclips.net/video/S00c_qQB-hA/видео.html
I think you might enjoy this video on the Triplett 630. I agree with it 100%.
Ship ??
AMERICAN parts have always been the best, and only on Chinese crap today
Where can I find the schematics?
www.antiqueradios.com/forums/viewtopic.php?t=338628&view=previous
You can also search for the Heathkit W3, W4 and W5 schematics and get their complete manual.
@@ElPasoTubeAmps Thank
bit.ly/2VP5nUY