I would love to build a SET amp like this with a 6SN7 and a 6550. I need to look at what would change in the schematic (including potentially the OT) to make that happen. Thanks for detailing this so well! I have learned so much from you and I cherish every new video.
The voltage amplifier section could be the same. A 6550 should work just have to get the cathode bias resistor value correct for a proper amount of current thru the 6550.
For a 6550 tube in ultra linear, use around 440v on the plate, a 550R 10watt on the Cathode with a 220uF bypass cap, a 270k grid leak resistor, and a 1.2k G2 screen resistor connected directly to the 40% tap and it will bias at around 85% dissipation. For triode mode just change the G3 screen resistor from 1.2K to 100R and connect it directly to the plate lead. Bias will be about the same as UL.
A very simple design. Exactly how the tubes are supposed to run. That's great! I also made up some input cables out of rg58. Nice cables. I would use it in a chassis if I needed a longer run. Definitely don't have to worry about high audio frequency using it.
Love how this amp has come out. Thanks for sharing the schematic. I’ve done the same thing with pots in place of resistors when building and voicing guitar effects pedals, especially fuzz pedals due to the same transistors having different gain values from one to the next.
Great project, thanks for sharing. I do think you could make a few more videos on this 807 build going through build & your method philosophy, bit like lessons.
I had a scrap stereo amplifier chassis out of a record player, using two 6BM8's, where they forgot to install the ground wire to the speaker outputs. It didn't have negative feedback from factory. It probably sounded acceptable during its life if you didn't know differently, but it sure sounded better when I grounded those terminals.
Thanks for posting that, thought the two triode stages were DC coupled from your last comment in the last episode. I see things that could have been done differently, EG a 100r & 47r split V1 Rk with the 100r AC coupled to get more gain, same with the 500r 807 Rk. I'm sure though, that you considered all that, & as you said the you empirically tested the amp & tweaked the circuit to suit. The 100r B+ to screen grid resistor is used in a lot of Tektronix valve scopes, and numerous vintage test gear circuits. An interesting book if your not already familiar with it is "Some basic vacuum tube circuits - used in Tektronix instruments" which shows all the building blocks of valve design as used by Tek back in the 50's/60's. Lastly, noticed you use a stereo audio feed into mono when listening to audio & that you mostly build monoblocks. Is the amp building to you more about the building & testing? Thanks again for uploading. Best regards..DA.
I have built many amplifiers just for testing - crazy, huh? With that said, I have three that are stereo, two Williamson, one with Acrosound OPT and the other with UTC OPT and one SET with 300B. All of these were built to listen to and they are my main amps and my preference even over the McIntosh amps. The 300B mentioned will be getting posted soon as I change the circuit to one of the nice SE transformers, the same as in this video, that I bought from my friend in Poland. My 300B SET is a strange design and I will elaborate in the video but I am sure it can be improved considerably with a good SE OPT instead of the choke loaded plate circuit. It is the 300B where I did the testing and tweaking of the component values to my satisfaction and used that design in this amplifier. As you might have noticed, I find this one good enough I gave it a name, "Little Jewel". I hope it helps others experiment with SE amplifiers - a design amazingly simple and can perform beautifully if done correctly. I was totally against SE designs until the 300B and now this one that definitely sounds better than my 300B stereo version. Thanks for your comments. Lots of good information and the component values and design details of the vintage equipment like Tektronix, are hard to beat, to say the least.
Hi David, i just caught up with the videos and what a neat amp you built! very jealous and a bit inspired, maybe i will steal your schematics :). i just got in to a rabbit hole of designing my own transformers and this would be a nice test bench, just finished writing a software to characterize BH curves and permeability if you are interested. keep up the good work and as you say stay safe! 73, IU3IRR
Hi Manuel, It sounds like you are doing well. I am truly surprised at the performance and sound of such a small amplifier. I built it on a burst of energy and knew to keep up the energy so I wouldn't drag it out or tire of it. My friend, Marko, as mentioned in the comments is a professional transformer winder. Maybe you two have something to share in your new endeavor. RF is still very much a big part of my hobby life and my last amplifier built and working is a 3-1000Z so I haven't lost the love for HV... 🙂 Stay safe and thanks for keeping in touch. 73 WA4QGA
Hi David, I have followed your TH-cam channel for some time and have been remiss in letting you know that I very much appreciate your efforts, always something good to learn. The 807 quick build series was terrific, something I suspect I am not alone in being eager to tackle. Two questions if I may; 1) Given the suggested similarities between the 807 and the 6L6GC, how difficult would it be to use the 6L6gc vs the 807? And what if any benefit might be realized? 2) As others have suggested, I would be pleased to see the schematic and would be glad to offer reasonable payment for a copy. Ha! Just noticed your recent upload, THANKS Thanks again, great channel, finally I would like to hear more about your background and how you got going with tube audio. Have a great Thanksgiving! Ken
Hi Ken, You should be able to substitute the 6L6GC without any circuit changes. In any case, the voltage amplifier section (6SN7) should work with any receiving class tube. How they might sound different - I wouldn't think there would be much if any difference - but, who knows... Thanks for your kind words. I needed this marathon build and all of you guys on TH-cam are a great bunch to work with and share experiences with. I decided long ago that building and enjoying all that I have in a silo would not be much fun but sharing it with the world opens up great learning and friendship experiences. I learn from you guys as much as you do from me. 🙂
Hi Dave. Thank you for this wonderful build and follow-up with the schematic. The amp sounds wonderful, even through TH-cam's digital compression! I have a question: Why is V2 DC coupled instead of capacitor coupled like the other two valves. I know it works perfectly, but I wonder if this decision to DC couple that stage is based on phase angle at certain frequencies that might be slightly off if we coupled via capacitor to V2's grid. I also see that V2 is the only valve with a bypass capacitor. Just wondering what audio changes we would expect to measure if the V2 circuit was built like the other two. PS. I downloaded LT Spice today. Thanks for the suggestion. 73 OM
I noticed lack of secondary winding to the ground. .As for me it is simple construction and needs at least two - three way speaker to boost edges of band and for such speakers may be short of power
The schematic will require finishing up electrically before it will simulate in LTSpice. You will also need to download the Norman Koren library so LTSpice can load the images of the tubes. Put the Koren library file in the same folder as LTSpice executable along with the image file. There is also a library called Ayumi Spice that is another library similar to Koren. www.normankoren.com/Audio/Tubemodelinstr.HTM www.diyaudio.com/community/threads/vacuum-tube-spice-models.243950/ Search for Norman Koren or Ayumi Spice. The second stage has it cathode raised well above ground and it a common second stage in the Williamson design where they take the opposite phase off the cathode. We don't need the opposite phase as it is not push-pull but I like that design detail and needs no grid blocking capacitor. The bias level between grid and cathode is proper with the raised cathode.
Thanks Dave. It was great watching you through this. I want to ask you.........Regarding making cables,, are you suggesting making interconnect cables for my audio system, say from phono stage or CD player or DAC to amplifier using 50 ohm coax? Red to center and white to braid?
RG-58 coax will make good interconnecting cables. I am thinking mostly using male RCA connectors on each end for stereo equipment and BNC for test equipment.
The 50-ohm impedance only matters for radio frequencies, not audio. For audio, it’s just wire, and it will work well, shielding against noise and help keep sound quality high.
That is why the cathode resistor is 22K instead of the typical low value for a cathode resistor. It is a proven design from Williamson amplifiers so I copied that detail.
What is the resistor called when you tied the output tube screen to the plate? its changing the Ultralinear of the output tube. The LOAD Resistors are the preamp tubes Cathode resistors, but what does the LOAD Resistor do? The LOAD resistor values adjust the asymmetrical clipping of the positive cycle and negative cycle
Glad to see the schematic. I'm not sure the Hammond Power transformer part number is current. Hammond's web site doesn't recognize the WO22772 number you provide. Can you give us the Hammond specs for it to allow matching to current Hammond numbering? And does the transformer have enough power for a stereo version or do I need two for that?
hi,can you tell me what is the voltage of the power transformer at the secondary if i put silicon rectifier diodes.i dont found your hammond reference on internet.i find weird that is no bypass cap on the cathode of 807 .Can i find shematic draw on internet i could do a clean copy .You indicate output R9 ,373V but i dont see R9 on your shematic.thanks a lot
hi interesting i have a question about negative feedback ,if i put a signal with my generator and i take the square wave at 1khz and if i turn the 10k pot to have the best square wave ,is it a good way to tune the negative feedback .thanks
The way I set the level of NFB is to (1) adjust the output of the amplifier for a clean sine wave at say, 4 watts. Then put a pot, maybe a 20K, in place of the 10K global NFB resistor and adjust it to say, 3 dB of NFB which would decrease the power by a factor of two or lower the power output to 2 watts. That would correspond to 3 dB of NFB. That does not mean you are decreasing your amplifier to a 2 watt amplifier as just a slight increase in the input signal will make the output come back up to 4 watts. Each 3 dB of NFB decreases the output by a factor of 2. If you want 6 dB of NFB you would adjust your 20K pot to have an output of 1 watts, etc. Then take the pot off and measure the resistance and put in a fixed resistor in place of the pot. As for a square wave, once you set the level of NFB with the fixed resistor, you can experiment with a capacitor across the resistor , something in the range of maybe 100 pF to 0.01 uF and watch the leading edge of a 1 KHz square wave and adjust for the best square corner on the leading edge. The goal being to attenuate overshoot but not so much to round the top leading edge of the square wave as that would start to attenuate high frequencies. Hope this helps.
hi if i understand well its the value of the capacitor that adjust the square wave .It would be interesting that you show the square wave to judge the quality of the output transformer in your future vidéos cause output transformer are not all the same for the quality of the square wave .i use hammond output transformer 1628 se its not bad but the square wave are not very good at 1khz and 10 khz. @@ElPasoTubeAmps
@@kubockferre5532 I don't want to bad-mouth Hammond transformers as I know a lot are in service and people are happy with them but... the (brand new) power transformer in this very amplifier shorted the secondary... dead... fortunately, I had a military transformer that I was able to install and it is working perfectly again. I may have to show a picture of it in a later video. I have noticed on pretty much every occasion, that the Hammond chokes do not measure advertised inductance - a 10H is likely to measure more like 8H. Not so with the surplus chokes I take out of military equipment - so much for that... as for the OPT, the square wave response is excellent - the tiniest bit of overshoot that can be taken care of with a small value capacitor. Too much capacitance and it rounds off the leading edge and HF response. I do not use a capacitor across the NFB resistor. Just my experience.
hi ,i do experiment with the negative feedback but i dont see the difference in the shape of the squarewave with my scope only the gain decrease so is it normal ! is the différence occurs only by ears ! thanks@@ElPasoTubeAmps
@@kubockferre5532 You are doing it right. If the NFB is (negative) you will see a gain decrease but it is compensated for by just raising the input driving voltage a bit more. It does not actually lower the power output capability of the amplifier. I highlighted (negative) because if the phase at the output of the OPT where the NFB resistor is connected is not negative with respect to the cathode it is being fed back to, the gain will increase instead of decrease as the value of the resistor is lowered. I have never noticed the shape of the square wave as NFB is increased but I don't think it would affect it at least not very much. In my opinion, a little NFB is a very good thing. I have heard one fellow say, "NFB is your friend". I agree. With no NFB at all, the frequency response is all over the chart and so is the power response. Some may prefer it that way but I don't. I was sitting around thinking of taking this amplifier to the shop and doing a video on NFB - I think that is what I am going to do and study square wave response also. Thanks 🙂
LOL.... actually up to 4 watts or so. Think about it... speakers that have SPL of 100 dB with one watt go to 103 dB with 2 watts and 106 with 4 watts. I will have the neighbors calling me in to the sound-police if I get it any louder. 🙂 Just have to experience it. Amazing how good - and loud - this power level can be.
There is a downloadable PDF file posted on the comment below and in several other comments, that is very nice. Hope it helps - I am listening to this little amplifier as I write and it is truly amazing sounding,
I would love to build a SET amp like this with a 6SN7 and a 6550. I need to look at what would change in the schematic (including potentially the OT) to make that happen. Thanks for detailing this so well! I have learned so much from you and I cherish every new video.
The voltage amplifier section could be the same. A 6550 should work just have to get the cathode bias resistor value correct for a proper amount of current thru the 6550.
For a 6550 tube in ultra linear, use around 440v on the plate, a 550R 10watt on the Cathode with a 220uF bypass cap, a 270k grid leak resistor, and a 1.2k G2 screen resistor connected directly to the 40% tap and it will bias at around 85% dissipation. For triode mode just change the G3 screen resistor from 1.2K to 100R and connect it directly to the plate lead. Bias will be about the same as UL.
A very simple design. Exactly how the tubes are supposed to run. That's great! I also made up some input cables out of rg58. Nice cables. I would use it in a chassis if I needed a longer run. Definitely don't have to worry about high audio frequency using it.
Agree that RG-58 is better than most of the audio cables.
Love how this amp has come out. Thanks for sharing the schematic. I’ve done the same thing with pots in place of resistors when building and voicing guitar effects pedals, especially fuzz pedals due to the same transistors having different gain values from one to the next.
Thank you for the schematic
Great project, thanks for sharing. I do think you could make a few more videos on this 807 build going through build & your method philosophy, bit like lessons.
I had a scrap stereo amplifier chassis out of a record player, using two 6BM8's, where they forgot to install the ground wire to the speaker outputs. It didn't have negative feedback from factory. It probably sounded acceptable during its life if you didn't know differently, but it sure sounded better when I grounded those terminals.
That looks great. Thanks for running through this design.
Nice clean drawing looks good soundcheck
Brilliant thanks from England
Thanks for posting that, thought the two triode stages were DC coupled from your last comment in the last episode. I see things that could have been done differently, EG a 100r & 47r split V1 Rk with the 100r AC coupled to get more gain, same with the 500r 807 Rk. I'm sure though, that you considered all that, & as you said the you empirically tested the amp & tweaked the circuit to suit.
The 100r B+ to screen grid resistor is used in a lot of Tektronix valve scopes, and numerous vintage test gear circuits. An interesting book if your not already familiar with it is "Some basic vacuum tube circuits - used in Tektronix instruments" which shows all the building blocks of valve design as used by Tek back in the 50's/60's.
Lastly, noticed you use a stereo audio feed into mono when listening to audio & that you mostly build monoblocks. Is the amp building to you more about the building & testing? Thanks again for uploading. Best regards..DA.
I have built many amplifiers just for testing - crazy, huh? With that said, I have three that are stereo, two Williamson, one with Acrosound OPT and the other with UTC OPT and one SET with 300B. All of these were built to listen to and they are my main amps and my preference even over the McIntosh amps. The 300B mentioned will be getting posted soon as I change the circuit to one of the nice SE transformers, the same as in this video, that I bought from my friend in Poland. My 300B SET is a strange design and I will elaborate in the video but I am sure it can be improved considerably with a good SE OPT instead of the choke loaded plate circuit. It is the 300B where I did the testing and tweaking of the component values to my satisfaction and used that design in this amplifier. As you might have noticed, I find this one good enough I gave it a name, "Little Jewel". I hope it helps others experiment with SE amplifiers - a design amazingly simple and can perform beautifully if done correctly. I was totally against SE designs until the 300B and now this one that definitely sounds better than my 300B stereo version. Thanks for your comments. Lots of good information and the component values and design details of the vintage equipment like Tektronix, are hard to beat, to say the least.
Thanks Dave, well done!
Hi David, i just caught up with the videos and what a neat amp you built! very jealous and a bit inspired, maybe i will steal your schematics :). i just got in to a rabbit hole of designing my own transformers and this would be a nice test bench, just finished writing a software to characterize BH curves and permeability if you are interested. keep up the good work and as you say stay safe!
73, IU3IRR
Hi Manuel,
It sounds like you are doing well. I am truly surprised at the performance and sound of such a small amplifier. I built it on a burst of energy and knew to keep up the energy so I wouldn't drag it out or tire of it. My friend, Marko, as mentioned in the comments is a professional transformer winder. Maybe you two have something to share in your new endeavor. RF is still very much a big part of my hobby life and my last amplifier built and working is a 3-1000Z so I haven't lost the love for HV... 🙂 Stay safe and thanks for keeping in touch. 73 WA4QGA
Thanks, and a litle question, is there a connection to the return of negative fedback ?
The bottom of the secondary must be grounded. As careful as I was I made a few mistakes. I noted them in a comment.
Hi David,
I have followed your TH-cam channel for some time and have been remiss in letting you know that I very much appreciate your efforts, always something good to learn.
The 807 quick build series was terrific, something I suspect I am not alone in being eager to tackle. Two questions if I may;
1) Given the suggested similarities between the 807 and the 6L6GC, how difficult would it be to use the 6L6gc vs the 807? And what if any benefit might be realized?
2) As others have suggested, I would be pleased to see the schematic and would be glad to offer reasonable payment for a copy.
Ha! Just noticed your recent upload, THANKS
Thanks again, great channel, finally I would like to hear more about your background and how you got going with tube audio.
Have a great Thanksgiving!
Ken
Hi Ken,
You should be able to substitute the 6L6GC without any circuit changes. In any case, the voltage amplifier section (6SN7) should work with any receiving class tube. How they might sound different - I wouldn't think there would be much if any difference - but, who knows... Thanks for your kind words. I needed this marathon build and all of you guys on TH-cam are a great bunch to work with and share experiences with. I decided long ago that building and enjoying all that I have in a silo would not be much fun but sharing it with the world opens up great learning and friendship experiences. I learn from you guys as much as you do from me. 🙂
Hi Dave. Thank you for this wonderful build and follow-up with the schematic. The amp sounds wonderful, even through TH-cam's digital compression!
I have a question: Why is V2 DC coupled instead of capacitor coupled like the other two valves. I know it works perfectly, but I wonder if this decision to DC couple that stage is based on phase angle at certain frequencies that might be slightly off if we coupled via capacitor to V2's grid. I also see that V2 is the only valve with a bypass capacitor. Just wondering what audio changes we would expect to measure if the V2 circuit was built like the other two.
PS. I downloaded LT Spice today. Thanks for the suggestion. 73 OM
I noticed lack of secondary winding to the ground. .As for me it is simple construction and needs at least two - three way speaker to boost edges of band and for such speakers may be short of power
The schematic will require finishing up electrically before it will simulate in LTSpice. You will also need to download the Norman Koren library so LTSpice can load the images of the tubes. Put the Koren library file in the same folder as LTSpice executable along with the image file. There is also a library called Ayumi Spice that is another library similar to Koren.
www.normankoren.com/Audio/Tubemodelinstr.HTM
www.diyaudio.com/community/threads/vacuum-tube-spice-models.243950/
Search for Norman Koren or Ayumi Spice.
The second stage has it cathode raised well above ground and it a common second stage in the Williamson design where they take the opposite phase off the cathode. We don't need the opposite phase as it is not push-pull but I like that design detail and needs no grid blocking capacitor. The bias level between grid and cathode is proper with the raised cathode.
Thanks! Very nice.
Thanks Dave. It was great watching you through this. I want to ask you.........Regarding making cables,, are you suggesting making interconnect cables for my audio system, say from phono stage or CD player or DAC to amplifier using 50 ohm coax? Red to center and white to braid?
RG-58 coax will make good interconnecting cables. I am thinking mostly using male RCA connectors on each end for stereo equipment and BNC for test equipment.
@ElPasoTubeAmps thanks Dave. I have some high quality RG-58/U to do this. The only question I have is that the 50 ohm impedance won't affect anything?
@@dtg474 It will work great. It is only 50 ohms to RF and to audio it is just a piece of wire little more than lamp cord but with a shield from noise.
The 50-ohm impedance only matters for radio frequencies, not audio. For audio, it’s just wire, and it will work well, shielding against noise and help keep sound quality high.
Many thanks.
Any reason you did not use a coupling cap before the 2nd 6SN7 stage? wouldn't this introduce DC onto the grid of that stage? Isn't that bad?
That is why the cathode resistor is 22K instead of the typical low value for a cathode resistor. It is a proven design from Williamson amplifiers so I copied that detail.
What is the resistor called when you tied the output tube screen to the plate? its changing the Ultralinear of the output tube. The LOAD Resistors are the preamp tubes Cathode resistors, but what does the LOAD Resistor do? The LOAD resistor values adjust the asymmetrical clipping of the positive cycle and negative cycle
Glad to see the schematic. I'm not sure the Hammond Power transformer part number is current. Hammond's web site doesn't recognize the WO22772 number you provide. Can you give us the Hammond specs for it to allow matching to current Hammond numbering? And does the transformer have enough power for a stereo version or do I need two for that?
I think you got an "O" instead of a zero for the first number. Here it is: www.tedweber.com/w022772/
hi,can you tell me what is the voltage of the power transformer at the secondary if i put silicon rectifier diodes.i dont found your hammond reference on internet.i find weird that is no bypass cap on the cathode of 807 .Can i find shematic draw on internet i could do a clean copy .You indicate output R9 ,373V but i dont see R9 on your shematic.thanks a lot
hi interesting i have a question about negative feedback ,if i put a signal with my generator and i take the square wave at 1khz and if i turn the 10k pot to have the best square wave ,is it a good way to tune the negative feedback .thanks
The way I set the level of NFB is to (1) adjust the output of the amplifier for a clean sine wave at say, 4 watts. Then put a pot, maybe a 20K, in place of the 10K global NFB resistor and adjust it to say, 3 dB of NFB which would decrease the power by a factor of two or lower the power output to 2 watts. That would correspond to 3 dB of NFB. That does not mean you are decreasing your amplifier to a 2 watt amplifier as just a slight increase in the input signal will make the output come back up to 4 watts. Each 3 dB of NFB decreases the output by a factor of 2. If you want 6 dB of NFB you would adjust your 20K pot to have an output of 1 watts, etc. Then take the pot off and measure the resistance and put in a fixed resistor in place of the pot. As for a square wave, once you set the level of NFB with the fixed resistor, you can experiment with a capacitor across the resistor , something in the range of maybe 100 pF to 0.01 uF and watch the leading edge of a 1 KHz square wave and adjust for the best square corner on the leading edge. The goal being to attenuate overshoot but not so much to round the top leading edge of the square wave as that would start to attenuate high frequencies. Hope this helps.
hi if i understand well its the value of the capacitor that adjust the square wave .It would be interesting that you show the square wave to judge the quality of the output transformer in your future vidéos cause output transformer are not all the same for the quality of the square wave .i use hammond output transformer 1628 se its not bad but the square wave are not very good at 1khz and 10 khz. @@ElPasoTubeAmps
@@kubockferre5532 I don't want to bad-mouth Hammond transformers as I know a lot are in service and people are happy with them but... the (brand new) power transformer in this very amplifier shorted the secondary... dead... fortunately, I had a military transformer that I was able to install and it is working perfectly again. I may have to show a picture of it in a later video. I have noticed on pretty much every occasion, that the Hammond chokes do not measure advertised inductance - a 10H is likely to measure more like 8H. Not so with the surplus chokes I take out of military equipment - so much for that... as for the OPT, the square wave response is excellent - the tiniest bit of overshoot that can be taken care of with a small value capacitor. Too much capacitance and it rounds off the leading edge and HF response. I do not use a capacitor across the NFB resistor. Just my experience.
hi ,i do experiment with the negative feedback but i dont see the difference in the shape of the squarewave with my scope only the gain decrease so is it normal ! is the différence occurs only by ears ! thanks@@ElPasoTubeAmps
@@kubockferre5532 You are doing it right. If the NFB is (negative) you will see a gain decrease but it is compensated for by just raising the input driving voltage a bit more. It does not actually lower the power output capability of the amplifier. I highlighted (negative) because if the phase at the output of the OPT where the NFB resistor is connected is not negative with respect to the cathode it is being fed back to, the gain will increase instead of decrease as the value of the resistor is lowered.
I have never noticed the shape of the square wave as NFB is increased but I don't think it would affect it at least not very much. In my opinion, a little NFB is a very good thing. I have heard one fellow say, "NFB is your friend". I agree. With no NFB at all, the frequency response is all over the chart and so is the power response. Some may prefer it that way but I don't. I was sitting around thinking of taking this amplifier to the shop and doing a video on NFB - I think that is what I am going to do and study square wave response also. Thanks 🙂
Is it 300-0-300?
1watt ?
LOL.... actually up to 4 watts or so. Think about it... speakers that have SPL of 100 dB with one watt go to 103 dB with 2 watts and 106 with 4 watts. I will have the neighbors calling me in to the sound-police if I get it any louder. 🙂 Just have to experience it. Amazing how good - and loud - this power level can be.
Make a *.pdf file for the schematic Hommie. ❤❤. Screen shots & GIFs. Are for pud knockers, Amigo
There is a downloadable PDF file posted on the comment below and in several other comments, that is very nice. Hope it helps - I am listening to this little amplifier as I write and it is truly amazing sounding,
I had trouble finding it as well when comments were sorted by "top comments", but it showed up near the top when sorted by "newest". Hope this helps!
Research the power transformer, Fender Champ, Vibro Champ and Princeton. Pretty sure
I didn't know that. The power transformer was given to me.
Switchcraft!
I'm going to write that name down before I post another video... 🙂
That 500 Ohm cathode bias resistor would dissipate 10.8W at 60 mA.
I^2 * R = 0.06^2 * 500 = 1.80 watts
Man, I messed that one up. 😮
@@K5HJ No more than I do sometimes... 🙂 Thanks and 73 WA4QGA