Ross, Thumbs up on your video. I have built the same KT88 as yours and I’ve had some voltage problems, too. Your video has enlightening me. I never noticed the voltage disparity on the 33uF 450v caps until you pointed it out. Also, I thought I was the only one in the club that mounted my tube sockets on a 45° diagonal so that I could look at the gold lion logo. Very cool. Thank you!
Woah that’s some huge vacuum tube! I would love to build my own tube amp someday when I save a decent amount of money. I began to love a warm sounding music when I know that they massage my ear listening to them.
I made the same amp before Blueglow actually. Kegger helped me in the way. If I have to make it again I would use solid state rectification.. There is really not need for tube rectifier.
If you ever have that problem run a larger pair of caps in series. It doubles there voltage and half's there capacity. Also the 5y3 is way under sized for this amp. I would use a vintage 5ar4 or stick with 5u4
The 5AR4 was what the build called for, I used the 5Y3 to tame the b+ but that was never intended to be a long-term fix, and I have since switched back to the 5AR4. I think I put that in an update in the description. I agree that running two of those cheap cap's would have worked (although it isn't exactly half the capacitance?) but after I got burned, I decided to cut my losses ;-) Thanks for the comment!
Hello there Ross and thanks for your work,I'm gonna do one too, but in uk so using xpwr 144 transformer as have 240 volt supply. Also thanks to dan dee dee,useful comments. Any one else in the UK please chip in with info / experience. Cheers
Hi Ross, I know it was a while ago, but I was interested in your comments on this KT88 amp, I have recently completed one basically following Marks videos, although I used a slightly larger chassis and Hammond Transformer’s and choke. The mains Transformer is 373BX for UK supply! My voltages are a lot lower than what Mark was reading, but that is probably to do with my line voltage and different Transformer! My Rectifier tube is a Telefunken GZ34 After warm up I measured the Plate voltage as 400V DC Pin 8 Cathode 36V DC and pin 8 and pin 5 -36V DC I have uprated the 500 OHM Resistors to 25W, the amp sounds really nice to my old ears, the only other mod I may do, is fit some Diodes on the rectifier supply, I wonder if you have any comments on that, also how hot does the chassis’ get around the tubes on your amp, mine gets fairly hot, I’m thinking that this may be a cause for concern as regards components getting too hot! Thanks for any comments! Alex.
I just wanted to comment on the caps.. depending on the power transformer and Rect tube the B+ can be way to high after break in..I also build one and my voltages were off the charts after breaking it in..and the bias on the KT88s were 91ma .. so I changed the Bias resistor to find out when you lower the load.. the voltage goes up.!(491v) with a 600 ohm Bias resistor.SO keep the 500 ohm resistors and 10W is fine... although larger is ok to.. under normal load the load on the bias resistor is about 3.5W.. use a transformer with 360v-360V and the 5AR4 and the bias will end up after a few hours of 80ma on the KT88s... The parts diagram is wrong... 500 volt caps should be used.. and also when powering up the voltage can spike.
Totally agree with you. I settled for. 750 ohm resistor and am running the 88's at about 85% sounds good. I am putting in a thermistor as soon as I get one, more for the voltage drop than the spikes but that is a benefit also.
Hey Ross.. I also put in a thermistor .. I love the sound of this amplifier.. and with the Solid Cherry Altec19 clones I built,, together its amazing..I have to give credit to MARK.. He made it easy.
I rebuilt a couple of old silvertone hifi' into guitar amps.( one was a old medallion one was a longlegged record player . a head and a combo in the end both were stolen) but I wanted to ask another tubeamp person, WHY DID I LOVE THE SOUND OF THE HIFI TUBE AMPS WHEN I PLAYED GUITAR THROUGH THEM ??????????????????
Hadley Scott McIntyre i’m not sure if you mean that you liked the sound of the hi-fi tube amps better than Guitar tube amps. When most people think of tubes they think of richer harmonics, a certain degree of “sag” and other nuances. If I found an old hi-fi amplifier, especially if it was mono I would love to convert it for guitar use. Obviously unless you use a pedal in front of it, you would need something to bring the signal up to near line level. Maybe it’s time for us both to hit some estate sales!
William Yorston I guess it comes down to what your voltage really is. Mine was 462. In fact my voltages have always been pretty high. I went back to the 5AR4 rectifier and am just going to roll with the high current going through the KT88’s. I read a few things on the net that said the KT88 could handle high dissipation for extended times. If I were you, I would get some 500-600 volt caps and replace them since they are easy to get to probably. With the 750 ohm resistors, the current is a little lower. When I build the next one, I will up the wattage rating on the bias resistors.
Thank you Ross. This is one amp I am considering building. Do you know what wattage and distortion figures this amp produces. Also linearity across the audio spectrum? Thanks!
Glad to hear you might build it! As for the testing, sadly I don't have the testing equipment needed to get these figures. However toward the end of the series, Mark goes into some details about power ratings and harmonic distortion etc. As far as power output, I have done some testing with the oscilloscope at various frequencies. I'm planning on doing a second video where I update all that information, so stay tuned for that
Great job, Ross. I have yet to build mine, I am at the fabrication stage, ready to drill but I am hesitating. I am tossed up on the same exact issues you would change. Do I want a volume pot and why not just run it in ultralinear. Once I drill...I have 450V Nichicon caps also but am wondering if your problem was mainly being cheap caps? I imagine the voltage ratings are understated by a certain percent, so I am hoping the 450V caps will be fine. If not I guess I will be replacing them too...
The transformer that Blueglow electronics used is 380V / 380V that's going to set the bias at 91ma after break in..KT88s are running at 38W.. mine was spot on same as marks when built.but after a few days I noticed the tubes being hotter than normal.. so I took it back to the bench and started measuring. 485V B+ 91ma on the KT88s..so I had a old 5U4 that I tried and the voltages were back to normal.. put in the 5AR4 CRAP.! 485V ! so. I think the correct transformer with the 5AR4 is 360v / 360v and the correct transformer with the 5U4 is 380v /380v. my bias runs at 80ma each KT88 and it sounds great.. 1 more thing.. I tried different preamp tubes..the 6N1P works best in that circuit, as designed..
@@dandee5018 Thank you for this information! I have completed drilling my chassis, I will start wiring it. It is a slow process as I work long hours and don't have much time for it. Anyway, I will build mine like the Blueglow version and watch my voltages. It will be interesting to see the differences in all these builds. Mine will be an exact cookie-cutter with even the same brand components Mark used. If my voltages jump after break-in I will just follow your lead. It is good to learn from the experience of others. I did swap out those 450V caps too. I mean, they are cheap, why even install them if questionable, right?
Hey.. you should use the 360v/360v power transformer.. the 380v is on the edge! if you already have that one.. I used a 5U4 rect.. that solved my problem.. if you change the bias resistor on the KT88s the B+ goes up when the current goes down.. I found that out the hard way. I don't know if there is a way to exchange emails? I have photos and I also built a set of Altec 19s. that really sing with the KT88 amp... I have a listing in craigslist kt88.. Cleveland.@@turnersparadise8368
if I built another KT88 amp.. I had built mine in only ultralinear.. which is awesome.. and I leave the volume at max.. so I would delete that control and cost.. but I would put 100K across each input.. the line input needs a good preamp to drive the amplifier.. also the other preamp tubes need lower plate voltages.. use a 6N1P.. that seems to work best with the parts in the parts list...
Not really a Kit, but Blueglow electronics made it a virtual kit by supplying the expertise and parts list with his video series, check it out. I love SE amps, but my next one will be P-P just because I want to try it out.
@@rossharrell6218 I’m not a fan of blue glows work he does a lot of modifications to original designs I keep things buy the book and I don’t like his method of using thermistors simple resistors and simple math are used to reduce higher voltages I would only do a scratch build with transformers I have laying around I don’t see the cost return in dumping about 800 dollars mosty in transformers for a 10 -14 watt amplifier that doesn’t even have a preamp And not to sound like a jerk but my Scott 222c would probably sound a lot better then that amplifier you made and for half the cost It’s hard to get all your money back on a amplifier that you made
If you watch one of the later Blueglow videos (in the KT88 series) he plays some music through it. Sorry but I didn’t want to hassle with all the legal hoops of playing copyrighted music.
Not really in any qualitative way. However as with most things stereo, if the same tube is handling different channels you want to make sure that both sides of the triode are matched. I had to make sure that my preamp tube and my power tubes were well matched so that I didn’t get differences in channel output. If I had a guitar amplifier with significantly different amplification stages in each of the triodes I wouldn’t care much.
I just didn't want to look into the whole copyright thing. I could set up a stereo pair of mics and record something but it didn't seem worth the hassle. I suppose if there is desire for it could do it. I have since put in a thermistor and changed the rectifier, so it might be worthwhile.
While it is not an in-depth demo, I did use this amp for a video where I restored my Knight preamp (just look at my channel to find it). After I found out that copyrighted music only becomes an issue if you get paid for the video (which I will never be ;-) I posted a video with the amp in action, if only for a few seconds.
I watched marks UA-cam channel on Blue Glow for years and this is the very same amp that I want to build. But I currently have serval Nelson Pass amplifiers I’m working on. Could it be your voltage is higher because in your part of the country your line voltage is higher. Also the tolerance and resistors even though you and Mark may have picked the exact same resistor value plus or minus a few percent. Marks resistor value example could be plus a few ohms your exact same resistor value could’ve been minus a few ohms. Stack that up with a few extra volts on your line voltage plus a few arms on your resistors then multiply that going through your transformer would make a big difference on your secondary voltage. Different parts of our country have different voltage even though the standard is supposed to be 120 parts of our country only have 114 or 118 in other parts of our country have 129. This will make a huge difference on the secondary output voltage. I always like to add a lot extra voltage rating on my caps just for the peace of mind and the extra life. Example if it called for 400V I would put in 600V. Excellent build I can’t wait until I make mine.
Thanks for the comment. I agree that there are many variables, and they add up. My line voltage is spot on 120V +/- .3v However, who knows what is is at Mark's place. The truth is, my voltages agreed with his off the b+ rails, but after the plate resistor and a few other places, mine went higher than his. I can live with it the way it is, and you are right to build in some margin on high-voltage caps. Like I said in the video, I got anxious and ordered the caps that were available at the time. I am glad you will be building yours soon, I listen to mine almost every day.
Big fan of blueglow. Great to see a real world follow up on this amp.
Ross,
Thumbs up on your video. I have built the same KT88 as yours and I’ve had some voltage problems, too. Your video has enlightening me. I never noticed the voltage disparity on the 33uF 450v caps until you pointed it out. Also, I thought I was the only one in the club that mounted my tube sockets on a 45° diagonal so that I could look at the gold lion logo. Very cool. Thank you!
Hah! Glad I am not the only one.
Woah that’s some huge vacuum tube! I would love to build my own tube amp someday when I save a decent amount of money. I began to love a warm sounding music when I know that they massage my ear listening to them.
I made the same amp before Blueglow actually. Kegger helped me in the way. If I have to make it again I would use solid state rectification.. There is really not need for tube rectifier.
You're using Chinese-ium caps?!?! You're a braver man than I.
Like the big blue guys at the back. Transform...ers. 😊😊
Beautiful
If you ever have that problem run a larger pair of caps in series. It doubles there voltage and half's there capacity. Also the 5y3 is way under sized for this amp. I would use a vintage 5ar4 or stick with 5u4
The 5AR4 was what the build called for, I used the 5Y3 to tame the b+ but that was never intended to be a long-term fix, and I have since switched back to the 5AR4. I think I put that in an update in the description. I agree that running two of those cheap cap's would have worked (although it isn't exactly half the capacitance?) but after I got burned, I decided to cut my losses ;-)
Thanks for the comment!
Hello there Ross and thanks for your work,I'm gonna do one too, but in uk so using xpwr 144 transformer as have 240 volt supply. Also thanks to dan dee dee,useful comments. Any one else in the UK please chip in with info / experience. Cheers
There are some 220/240v builders on the AudioKarma discussion thread, just search Kegger/Blueglow. Have fun!
Hi Ross, I know it was a while ago, but I was interested in your comments on this KT88 amp, I have recently completed one basically following Marks videos, although I used a slightly larger chassis and Hammond Transformer’s and choke. The mains Transformer is 373BX for UK supply! My voltages are a lot lower than what Mark was reading, but that is probably to do with my line voltage and different Transformer! My Rectifier tube is a Telefunken GZ34 After warm up I measured the Plate voltage as 400V DC Pin 8 Cathode 36V DC and pin 8 and pin 5 -36V DC I have uprated the 500 OHM Resistors to 25W, the amp sounds really nice to my old ears, the only other mod I may do, is fit some Diodes on the rectifier supply, I wonder if you have any comments on that, also how hot does the chassis’ get around the tubes on your amp, mine gets fairly hot, I’m thinking that this may be a cause for concern as regards components getting too hot! Thanks for any comments! Alex.
I just wanted to comment on the caps.. depending on the power transformer and Rect tube the B+ can be way to high after break in..I also build one and my voltages were off the charts after breaking it in..and the bias on the KT88s were 91ma .. so I changed the Bias resistor to find out when you lower the load.. the voltage goes up.!(491v) with a 600 ohm Bias resistor.SO keep the 500 ohm resistors and 10W is fine... although larger is ok to.. under normal load the load on the bias resistor is about 3.5W.. use a transformer with 360v-360V and the 5AR4 and the bias will end up after a few hours of 80ma on the KT88s... The parts diagram is wrong... 500 volt caps should be used.. and also when powering up the voltage can spike.
Totally agree with you. I settled for. 750 ohm resistor and am running the 88's at about 85% sounds good. I am putting in a thermistor as soon as I get one, more for the voltage drop than the spikes but that is a benefit also.
Hey Ross.. I also put in a thermistor .. I love the sound of this amplifier.. and with the Solid Cherry Altec19 clones I built,, together its amazing..I have to give credit to MARK.. He made it easy.
Mark's under chassis wiring was much tidier looking
Gee, ya think ;-)
I rebuilt a couple of old silvertone hifi' into guitar amps.( one was a old medallion one was a longlegged record player . a head and a combo in the end both were stolen) but I wanted to ask another tubeamp person, WHY DID I LOVE THE SOUND OF THE HIFI TUBE AMPS WHEN I PLAYED GUITAR THROUGH THEM ??????????????????
Hadley Scott McIntyre i’m not sure if you mean that you liked the sound of the hi-fi tube amps better than Guitar tube amps. When most people think of tubes they think of richer harmonics, a certain degree of “sag” and other nuances. If I found an old hi-fi amplifier, especially if it was mono I would love to convert it for guitar use. Obviously unless you use a pedal in front of it, you would need something to bring the signal up to near line level. Maybe it’s time for us both to hit some estate sales!
Ross, both my builds have 450v caps, many many hours on the first no issues yet, but you made me nervous so may replace mine.
William Yorston I guess it comes down to what your voltage really is. Mine was 462. In fact my voltages have always been pretty high. I went back to the 5AR4 rectifier and am just going to roll with the high current going through the KT88’s. I read a few things on the net that said the KT88 could handle high dissipation for extended times. If I were you, I would get some 500-600 volt caps and replace them since they are easy to get to probably. With the 750 ohm resistors, the current is a little lower. When I build the next one, I will up the wattage rating on the bias resistors.
@@rossharrell6218 This build is at 449.3
with the 5AR4 the current on the preamp tube is at max.. when using the 380v/380v transformer....@@rossharrell6218
What's the power difference in these tubes vs 6LQ6 tubes?
Thank you Ross. This is one amp I am considering building. Do you know what wattage and distortion figures this amp produces. Also linearity across the audio spectrum? Thanks!
Glad to hear you might build it! As for the testing, sadly I don't have the testing equipment needed to get these figures. However toward the end of the series, Mark goes into some details about power ratings and harmonic distortion etc. As far as power output, I have done some testing with the oscilloscope at various frequencies. I'm planning on doing a second video where I update all that information, so stay tuned for that
Great job, Ross. I have yet to build mine, I am at the fabrication stage, ready to drill but I am hesitating. I am tossed up on the same exact issues you would change. Do I want a volume pot and why not just run it in ultralinear. Once I drill...I have 450V Nichicon caps also but am wondering if your problem was mainly being cheap caps? I imagine the voltage ratings are understated by a certain percent, so I am hoping the 450V caps will be fine. If not I guess I will be replacing them too...
The transformer that Blueglow electronics used is 380V / 380V that's going to set the bias at 91ma after break in..KT88s are running at 38W.. mine was spot on same as marks when built.but after a few days I noticed the tubes being hotter than normal.. so I took it back to the bench and started measuring. 485V B+ 91ma on the KT88s..so I had a old 5U4 that I tried and the voltages were back to normal.. put in the 5AR4 CRAP.! 485V ! so. I think the correct transformer with the 5AR4 is 360v / 360v and the correct transformer with the 5U4 is 380v /380v.
my bias runs at 80ma each KT88 and it sounds great.. 1 more thing.. I tried different preamp tubes..the 6N1P works best in that circuit, as designed..
@@dandee5018 Thank you for this information! I have completed drilling my chassis, I will start wiring it. It is a slow process as I work long hours and don't have much time for it. Anyway, I will build mine like the Blueglow version and watch my voltages. It will be interesting to see the differences in all these builds. Mine will be an exact cookie-cutter with even the same brand components Mark used. If my voltages jump after break-in I will just follow your lead. It is good to learn from the experience of others. I did swap out those 450V caps too. I mean, they are cheap, why even install them if questionable, right?
Hey.. you should use the 360v/360v power transformer.. the 380v is on the edge! if you already have that one.. I used a 5U4 rect.. that solved my problem.. if you change the bias resistor on the KT88s the B+ goes up when the current goes down.. I found that out the hard way.
I don't know if there is a way to exchange emails? I have photos and I also built a set of Altec 19s. that really sing with the KT88 amp... I have a listing in craigslist kt88.. Cleveland.@@turnersparadise8368
if I built another KT88 amp.. I had built mine in only ultralinear.. which is awesome.. and I leave the volume at max.. so I would delete that control and cost.. but I would put 100K across each input.. the line input needs a good preamp to drive the amplifier.. also the other preamp tubes need lower plate voltages.. use a 6N1P.. that seems to work best with the parts in the parts list...
keep me informed.. I always like to see progress of the builds.. kt88 craigslist cleveland
What are those speaker stands holding the bookshelf Klipsch?
Yes R 15M's
have you worked out the plate dissipation
could you be using the wrong primary on your power transformer? Some transformers have taps for Japan where the voltage is about 105 VAC, 60 Hz.
Not in this case, the PT only has on primary winding. I am going to do an update on this project any day now. Thanks.
@@rossharrell6218 too bad, it would be an easy fix.
Nice job kinda was this a kit or a design from the internet and why did you choose this design?
Not really a Kit, but Blueglow electronics made it a virtual kit by supplying the expertise and parts list with his video series, check it out. I love SE amps, but my next one will be P-P just because I want to try it out.
@@rossharrell6218 I’m not a fan of blue glows work he does a lot of modifications to original designs I keep things buy the book and I don’t like his method of using thermistors simple resistors and simple math are used to reduce higher voltages
I would only do a scratch build with transformers I have laying around I don’t see the cost return in dumping about 800 dollars mosty in transformers for a 10 -14 watt amplifier that doesn’t even have a preamp
And not to sound like a jerk but my Scott 222c would probably sound a lot better then that amplifier you made and for half the cost
It’s hard to get all your money back on a amplifier that you made
I wanted to hear it playing.
If you watch one of the later Blueglow videos (in the KT88 series) he plays some music through it. Sorry but I didn’t want to hassle with all the legal hoops of playing copyrighted music.
@@rossharrell6218 got you thanks . You did a good job. I hope to keep in touch and show you some of my system.
It probably don’t even work
What is the size of output transformers please?Or producer and code please?
Edcor CXSE25-5K. Is that what you needed? I believe Mark's earlier videos go into detail regarding alternative examples. Thanks for the interest.
Are hifi preamp tubes different than the guitar preamp tubes?
Not really in any qualitative way. However as with most things stereo, if the same tube is handling different channels you want to make sure that both sides of the triode are matched. I had to make sure that my preamp tube and my power tubes were well matched so that I didn’t get differences in channel output. If I had a guitar amplifier with significantly different amplification stages in each of the triodes I wouldn’t care much.
BTW, BlueGlows B+ is a little too high for my taste..
👋🏻👍🏻
Why no demo of sound?
I just didn't want to look into the whole copyright thing. I could set up a stereo pair of mics and record something but it didn't seem worth the hassle. I suppose if there is desire for it could do it. I have since put in a thermistor and changed the rectifier, so it might be worthwhile.
While it is not an in-depth demo, I did use this amp for a video where I restored my Knight preamp (just look at my channel to find it). After I found out that copyrighted music only becomes an issue if you get paid for the video (which I will never be ;-) I posted a video with the amp in action, if only for a few seconds.
Just did a follow up with demo!
Who cares what he did
I watched marks UA-cam channel on Blue Glow for years and this is the very same amp that I want to build. But I currently have serval Nelson Pass amplifiers I’m working on. Could it be your voltage is higher because in your part of the country your line voltage is higher. Also the tolerance and resistors even though you and Mark may have picked the exact same resistor value plus or minus a few percent. Marks resistor value example could be plus a few ohms your exact same resistor value could’ve been minus a few ohms. Stack that up with a few extra volts on your line voltage plus a few arms on your resistors then multiply that going through your transformer would make a big difference on your secondary voltage. Different parts of our country have different voltage even though the standard is supposed to be 120 parts of our country only have 114 or 118 in other parts of our country have 129. This will make a huge difference on the secondary output voltage. I always like to add a lot extra voltage rating on my caps just for the peace of mind and the extra life. Example if it called for 400V I would put in 600V. Excellent build I can’t wait until I make mine.
Thanks for the comment. I agree that there are many variables, and they add up. My line voltage is spot on 120V +/- .3v However, who knows what is is at Mark's place. The truth is, my voltages agreed with his off the b+ rails, but after the plate resistor and a few other places, mine went higher than his. I can live with it the way it is, and you are right to build in some margin on high-voltage caps. Like I said in the video, I got anxious and ordered the caps that were available at the time. I am glad you will be building yours soon, I listen to mine almost every day.