My only concern with replacing the output transformers are the space constraints on the chassis. Push / Pull sounds like a fun change. Can’t say enough how grateful I am for your hard work creating these valuable videos !
Sweet! Stoked to follow you mods and make mine even better! I'd spend another 300 bucks to next level this thing. Juice has been worth the squeeze so far. Just want to keep thd as low as possible for clean power. Love how she sounds right now with your mods, a 5V4G, RCA grey glass 6SN7's and Soviet military "winged C" output tubes Thank you for these videos!!
All of the options mentioned sound interesting and would make for fascinating viewing. For my personal 6P1, which currently is completely stock, I would be willing to invest $300+ in upgrades, but I really like its SET sound. I am interested in refinements and it would be nice to get a bit more power, but I intend to keep mine a SET, so for me no ultra-linear and no to push-pull. I intend to make some of the changes upgrades you have already published, but haven't had the time to date.
Some one mentioned Switched UL too. That is a great idea. I wired my tubelab sse is in this configuration, but with massive 1628 OT's, the OT's are so large the power difference isn't realy noticeable though.
Double the stock price is so i guess for more power and even better sound. About this thing though because it was my first tube and instead of dealing with a bunch of used power amps that I couldn't tell were in proper operating condition or specs or whatever it seemed that I have found clearly a single-ended output amp and that was what I most importantly wanted I didn't want any any op amps or transistors or anything I wanted pure tube and although it wasn't going to be the best it was going to be different so that's part of why I got it
Skunkie, enjoy your channel, thanks so much for sharing your knowledge. Here's my immediate thought on what to do with the amplifier- how about a preamp?! A 6SN7 cathode follower preamp that is. Simple is good. Can you make 350+ volts without the present draw of the 2 x 2 PSE output tubes and front end tubes? Might have to go with SS rectifier? Pull the output tubes and see. Don't know what the primary inductance is of the output transfomers, maybe you have the means to measure that? Use the main PS choke as the 1st choke, then possibly split off and use the existing outputs as a following choke for each channel. Depending on the following amp you may or not need a 6.3 VDC supply to keep things quiet. From experience you will need a 330uf cap on the 6SN7 side of the choke to stabilize this cathode follower- this from a person who only wants as much capacitance as needed. Can't believe this manufacturer used what they did as an input cap, what were they thinking?! Scary. And a voltage divider off the power supply to stay within the 6SN7 cathode to heater spec. A simple 5W ?ohm series resistor will bring the 6.3 voltage to spec. Just a thought ... Posting this at 4AM though, may wonder what I was thinking later! Did you ever determine the primary impedance of the 6P1 ouput transformers? And curious. I've watched a lot of your videos, can't say I see you using square waves much. Wondering about the Reisong A12 and 100, 1K, 10K square wave final result ... and this one too. I know we don't "listen" to scopes, but they do tell a certain story. Thanks so much again.
I’d personally enjoy seeing it being turned into a PP amp. Also, from building guitar pedals, I know Hammond makes all kinds of different sized aluminum boxes you might be able to mount a transformer or a couple of transformers on a few of em that’d pretty easily be able to be screwed to the chassis. I dunno 🤷♂️ Just a thought. Really enjoy the channel. Keep up the great work 👍🔊😊🎶
I don’t typically leave comments, but I’m so excited to see more content on this 6P1! I bought it on your advise and so far have managed to change the caps but I’ve been struggling to follow how to change it over to a fixed resistance to get rid of the distortion, currently it’s buttery smooth to about 20% volume and just blearily loud after that. Have you noticed any difference in quality from removing the headphone out, when switching to the 4Ohm output from the 8s which the headphones are wired up to I could hear less of a noise floor. Can’t wait to see more on this, avidly watching along 😊
@@SkunkieDesignsElectronics I used a variable transformer to drop the voltage, couldn’t quite figure out the bucking transformer. Not sure if it’s helped the sound quality but I’ll be glad if it keeps these Sylvania tubes alive longer! I’ve got a dumb question if you’d be kind enough to answer, it’s what’s held me back from completing the fixed bias :) What Ohm rating should my 1W resistors be?
Reasonable is subjective :) Looks like a 175ma transformer is just over $100 with $8 shipping and new OT are $80 each + $28shipping. So blew past $300 pretty quickly just on the iron. Oh well, if it turns out sounding good, it is worth it!
@@SkunkieDesignsElectronics That's actually not too bad. If You shine your light on the schematics, it will be a good amp with a small footprint. No pressure! 🤪
I'm looking forward to this. I would love to see a push-pull 6BQ5 topology implemented using Dave Gillespie's EFB scheme. Maybe ultra-linear using new Dynakit replacement Dynaco Z-565 OPT's (intended for Dynaco ST-35 and SCA-35). Triode USA also sells them. Gillespie swears that those are absolutely the best 6BQ5 OPT's on the market. People are selling these amps as fast as they buy them because they don't live up to the expectations that they had, which means prices are continually dropping. When they dip below 125 for a used one I will be looking to buy, because you can't get a nicely finished chassis, sockets, IEC socket, power switch, selector, and meters for that kind of money.
If you modify the amplifier, it would be interesting if you could switch the tubes into something that is more of a common tube, making it easier to tube roll and more powerful. The headphone output is an interesting part of the design and would be cool to keep that functionality.
Have you considered running dc on the heaters? The diodes would drop it a volt. In the same way a 5Y3 would drop an extra 20 volts compared to the 5AR4. Each of those would be $10 solutions compared to a new transformer which could be 5 times as much.
If you send the 7V AC through a bridge rectifier, you get 8.5VDC on the other side. And the main problem is the transformer can't supply the ma of current the output tubes are capable of, which because the transformer already runs toasty hot as is, would melt down if you run the output tubes any hotter biased. They are running at 1/2 their rated wattage, which likely is why the amp makes so little power.
@@SkunkieDesignsElectronics I was just talking about diode reduction, but you are correct that you would need some big diodes with the amperage. Most this size are sold as bridge rectifiers which would not work without other regulation. It just seemed a shame to spend half of what the amp cost on a new power transformer, and probably more than the total cost with two PP output transformers. I am glad that you are excited about the modifications. Your skills are definitely up to the challenge. In a different vein, if you are buying a new PT and OTs, then I would be interested in watching videos of you turning the chassis into the "High Fidelity Tube Junk Box Audio Amplifier" by Bruce Heran. This design let's a person use a variety of tubes because of the CSS bias. Also, the SS rectifier might let you get away without having to buy a big choke for the power supply. Edcore actually has Bruce Heran page in their amp kits section. I am looking forward to seeing what you decide.
Adding an external fan on top of power transformer reduces considerably it's temperature. Can this cooled transformer hold more current?. And if we also reduce the power tubes shared cathode resistors from 270 to 250ohms or even lower, how much power can we get?. I'm just thinking about a very easy tweak which does not require much time or money spent.
I can't in good faith tell people to overload a PT and then put a fan on it. Plus the rectifier tube is limited to 120ma as well. I'm not sure there is an easy, cheap, safe solution and it's why these have been collecting dust.
@@SkunkieDesignsElectronics Thank you. Yes, you are right. The rectifier tube is almost at maximum current. Mine measured 117mA total. What about a solid state rectifier? Definitely in Class A we are limited, that's why the idea of switching to class AB might squeeze more juice out of the amp, right?
Maybe turn it into a high quality headphone amp. Use simple solid state regs to adjust the B+ and heaters. Changing all the transformers just seems a bridge too far to me....
Please could someone explain to me what ohm rating does my 1W resistors that I need to buy to set a fixed bias on this, just a rookie trying to get some quality class A sound 😊
There is a resistance rating, which is in ohms and that determines it's actual resistance. The W rating is how much power the resistor can withstand. If you look at the schematic, the "fixed bias" mod is simply a voltage divider using a 1M and a 2M resistor. I used two 1M resistors in series for one leg of the divider, as they are easier to find.
I don't have a 6p1 nobsound, but by the time you have added 2 x PP, OT's thats some $$$ spent. There is foundation there for a much better SE amp with more voltage swing etc sfter the Power Trans upgrade. Would schade feedback help with bass response? plus better caps in the psu? Just a thought.
No more $$$ than building a new amp from scratch though. I'm probably going to do this in "phases" and see what I can get with just the power transformer and biasing the tubes where they should be and go from there.
Yeah. Think that's a great idea, get as much as you can out of it in SE form. And then maybe try PP conversion. Then people can decide. I Notice you have two, a sound off would be interesting, one a PP conversion against the maxed out modded SE. In UK I struggle to get iron, of late I have been buying vintage gear to strip. Some nice small OT's in some of it too.
I bought this amp on your opinions . I am in the uk and have the updated version with the svetlana tubes. I have replaced the 5U4C with sylvania 6sn7 gtb short glass tubes. Huge improvement. I am just wandering what rectifier tube people are using ? Do I stick with the svetlana or is there something better ?
@@SkunkieDesignsElectronics thank you for your reply . To my ears it sounds great as it is. The sylvania 6sn7 gtb absolutely wipes the floor with the svetlana tubes. I was just wandering if the rectifier could be improved .
I've actually got a plan for 2 version and the parts sitting here. I keep heading off in other directions! Let me get these darn R300 amps done and maybe I can squeeze that in.
If you have to let go the output transformer and power one why not redesign it and make it something more powerful, something different and unique. Something that can bare the skunkie design stamp of approval /her own design/. Go for the P-P is my opinion.
My only concern with replacing the output transformers are the space constraints on the chassis.
Push / Pull sounds like a fun change.
Can’t say enough how grateful I am for your hard work creating these valuable videos !
Dang. Go for it!
Sweet! Stoked to follow you mods and make mine even better! I'd spend another 300 bucks to next level this thing. Juice has been worth the squeeze so far. Just want to keep thd as low as possible for clean power. Love how she sounds right now with your mods, a 5V4G, RCA grey glass 6SN7's and Soviet military "winged C" output tubes Thank you for these videos!!
All of the options mentioned sound interesting and would make for fascinating viewing. For my personal 6P1, which currently is completely stock, I would be willing to invest $300+ in upgrades, but I really like its SET sound. I am interested in refinements and it would be nice to get a bit more power, but I intend to keep mine a SET, so for me no ultra-linear and no to push-pull. I intend to make some of the changes upgrades you have already published, but haven't had the time to date.
Been waiting for this one to come back around. I say push/pull beast! Can't wait to see what you decide.
It's tempting :)
Looking forward to this. As far as money go give people options, but 300 bucks seems reasonable
Some one mentioned Switched UL too. That is a great idea. I wired my tubelab sse is in this configuration, but with massive 1628 OT's, the OT's are so large the power difference isn't realy noticeable though.
Double the stock price is so i guess for more power and even better sound. About this thing though because it was my first tube and instead of dealing with a bunch of used power amps that I couldn't tell were in proper operating condition or specs or whatever it seemed that I have found clearly a single-ended output amp and that was what I most importantly wanted I didn't want any any op amps or transistors or anything I wanted pure tube and although it wasn't going to be the best it was going to be different so that's part of why I got it
Skunkie, enjoy your channel, thanks so much for sharing your knowledge. Here's my immediate thought on what to do with the amplifier- how about a preamp?! A 6SN7 cathode follower preamp that is. Simple is good. Can you make 350+ volts without the present draw of the 2 x 2 PSE output tubes and front end tubes? Might have to go with SS rectifier? Pull the output tubes and see. Don't know what the primary inductance is of the output transfomers, maybe you have the means to measure that? Use the main PS choke as the 1st choke, then possibly split off and use the existing outputs as a following choke for each channel. Depending on the following amp you may or not need a 6.3 VDC supply to keep things quiet. From experience you will need a 330uf cap on the 6SN7 side of the choke to stabilize this cathode follower- this from a person who only wants as much capacitance as needed. Can't believe this manufacturer used what they did as an input cap, what were they thinking?! Scary. And a voltage divider off the power supply to stay within the 6SN7 cathode to heater spec. A simple 5W ?ohm series resistor will bring the 6.3 voltage to spec. Just a thought ... Posting this at 4AM though, may wonder what I was thinking later!
Did you ever determine the primary impedance of the 6P1 ouput transformers?
And curious. I've watched a lot of your videos, can't say I see you using square waves much. Wondering about the Reisong A12 and 100, 1K, 10K square wave final result ... and this one too. I know we don't "listen" to scopes, but they do tell a certain story. Thanks so much again.
Some neat ideas! Thanks.
Since you have limited power supply, what about redesigning it as a headphone Amp (you can ditch the output transformers).
I’d personally enjoy seeing it being turned into a PP amp. Also, from building guitar pedals, I know Hammond makes all kinds of different sized aluminum boxes you might be able to mount a transformer or a couple of transformers on a few of em that’d pretty easily be able to be screwed to the chassis. I dunno 🤷♂️ Just a thought. Really enjoy the channel. Keep up the great work 👍🔊😊🎶
I don’t typically leave comments, but I’m so excited to see more content on this 6P1!
I bought it on your advise and so far have managed to change the caps but I’ve been struggling to follow how to change it over to a fixed resistance to get rid of the distortion, currently it’s buttery smooth to about 20% volume and just blearily loud after that.
Have you noticed any difference in quality from removing the headphone out, when switching to the 4Ohm output from the 8s which the headphones are wired up to I could hear less of a noise floor.
Can’t wait to see more on this, avidly watching along 😊
Switching to "fixed bias" on the input tube does make a huge difference in the audible distortion.
@@SkunkieDesignsElectronics I used a variable transformer to drop the voltage, couldn’t quite figure out the bucking transformer. Not sure if it’s helped the sound quality but I’ll be glad if it keeps these Sylvania tubes alive longer!
I’ve got a dumb question if you’d be kind enough to answer, it’s what’s held me back from completing the fixed bias :)
What Ohm rating should my 1W resistors be?
Of You can replace the iron for a reasonable prise, I like to go to with the PP option.
Reasonable is subjective :) Looks like a 175ma transformer is just over $100 with $8 shipping and new OT are $80 each + $28shipping. So blew past $300 pretty quickly just on the iron. Oh well, if it turns out sounding good, it is worth it!
@@SkunkieDesignsElectronics That's actually not too bad. If You shine your light on the schematics, it will be a good amp with a small footprint.
No pressure! 🤪
I'm looking forward to this. I would love to see a push-pull 6BQ5 topology implemented using Dave Gillespie's EFB scheme. Maybe ultra-linear using new Dynakit replacement Dynaco Z-565 OPT's (intended for Dynaco ST-35 and SCA-35). Triode USA also sells them. Gillespie swears that those are absolutely the best 6BQ5 OPT's on the market. People are selling these amps as fast as they buy them because they don't live up to the expectations that they had, which means prices are continually dropping. When they dip below 125 for a used one I will be looking to buy, because you can't get a nicely finished chassis, sockets, IEC socket, power switch, selector, and meters for that kind of money.
Also a lot people are keeping them. Why don’t you put the link where they are being sold at the price you are talking about.
If you modify the amplifier, it would be interesting if you could switch the tubes into something that is more of a common tube, making it easier to tube roll and more powerful. The headphone output is an interesting part of the design and would be cool to keep that functionality.
But then it wouldn't be a 6P1 :)
@@SkunkieDesignsElectronics you do have a good point.
For 100 years there are such amplifiers, but no one has invented anything against the dust....but thx for the vid.
Have you considered running dc on the heaters? The diodes would drop it a volt. In the same way a 5Y3 would drop an extra 20 volts compared to the 5AR4. Each of those would be $10 solutions compared to a new transformer which could be 5 times as much.
If you send the 7V AC through a bridge rectifier, you get 8.5VDC on the other side. And the main problem is the transformer can't supply the ma of current the output tubes are capable of, which because the transformer already runs toasty hot as is, would melt down if you run the output tubes any hotter biased. They are running at 1/2 their rated wattage, which likely is why the amp makes so little power.
@@SkunkieDesignsElectronics I was just talking about diode reduction, but you are correct that you would need some big diodes with the amperage. Most this size are sold as bridge rectifiers which would not work without other regulation. It just seemed a shame to spend half of what the amp cost on a new power transformer, and probably more than the total cost with two PP output transformers. I am glad that you are excited about the modifications. Your skills are definitely up to the challenge.
In a different vein, if you are buying a new PT and OTs, then I would be interested in watching videos of you turning the chassis into the "High Fidelity Tube Junk Box Audio Amplifier" by Bruce Heran. This design let's a person use a variety of tubes because of the CSS bias. Also, the SS rectifier might let you get away without having to buy a big choke for the power supply. Edcore actually has Bruce Heran page in their amp kits section. I am looking forward to seeing what you decide.
How about a high bias PP ultralinear design, not quite class A but close?
Nice project!
Triode or ultralinear two classical options. Why not Pentriode mode?
Will you consider it?
Congratulations for your amazing work!
Poll. With different pricing/power options.
Adding an external fan on top of power transformer reduces considerably it's temperature. Can this cooled transformer hold more current?. And if we also reduce the power tubes shared cathode resistors from 270 to 250ohms or even lower, how much power can we get?. I'm just thinking about a very easy tweak which does not require much time or money spent.
I can't in good faith tell people to overload a PT and then put a fan on it. Plus the rectifier tube is limited to 120ma as well. I'm not sure there is an easy, cheap, safe solution and it's why these have been collecting dust.
@@SkunkieDesignsElectronics Thank you. Yes, you are right. The rectifier tube is almost at maximum current. Mine measured 117mA total. What about a solid state rectifier? Definitely in Class A we are limited, that's why the idea of switching to class AB might squeeze more juice out of the amp, right?
Maybe turn it into a high quality headphone amp. Use simple solid state regs to adjust the B+ and heaters. Changing all the transformers just seems a bridge too far to me....
Please could someone explain to me what ohm rating does my 1W resistors that I need to buy to set a fixed bias on this, just a rookie trying to get some quality class A sound 😊
There is a resistance rating, which is in ohms and that determines it's actual resistance. The W rating is how much power the resistor can withstand. If you look at the schematic, the "fixed bias" mod is simply a voltage divider using a 1M and a 2M resistor. I used two 1M resistors in series for one leg of the divider, as they are easier to find.
I don't have a 6p1 nobsound, but by the time you have added 2 x PP, OT's thats some $$$ spent. There is foundation there for a much better SE amp with more voltage swing etc sfter the Power Trans upgrade. Would schade feedback help with bass response? plus better caps in the psu? Just a thought.
No more $$$ than building a new amp from scratch though. I'm probably going to do this in "phases" and see what I can get with just the power transformer and biasing the tubes where they should be and go from there.
Yeah. Think that's a great idea, get as much as you can out of it in SE form. And then maybe try PP conversion. Then people can decide. I Notice you have two, a sound off would be interesting, one a PP conversion against the maxed out modded SE. In UK I struggle to get iron, of late I have been buying vintage gear to strip. Some nice small OT's in some of it too.
I bought this amp on your opinions . I am in the uk and have the updated version with the svetlana tubes. I have replaced the 5U4C with sylvania 6sn7 gtb short glass tubes. Huge improvement. I am just wandering what rectifier tube people are using ? Do I stick with the svetlana or is there something better ?
The rectifier tube these come with works fine, on a class A amp, they don't really make any difference as far as audio quality anyway.
@@SkunkieDesignsElectronics thank you for your reply . To my ears it sounds great as it is. The sylvania 6sn7 gtb absolutely wipes the floor with the svetlana tubes. I was just wandering if the rectifier could be improved .
Leave it as a class a remember you can use 6n6 tubes witH adapters or 6v6 both of whic i have use and provide lots of juice
Have you given up on this 6PI ?
I've actually got a plan for 2 version and the parts sitting here. I keep heading off in other directions! Let me get these darn R300 amps done and maybe I can squeeze that in.
If you have to let go the output transformer and power one why not redesign it and make it something more powerful, something different and unique. Something that can bare the skunkie design stamp of approval /her own design/. Go for the P-P is my opinion.
250-300? I'd have to save up... but i'd do it...
Just don't change the tubes, lol, i stocked up.
Honestly, I bet 90% of the difference between these amps and high end amps is the iron.
Keep it as class A. There are those who think it sounds better.