Electronics is a hobby I have a passion for. Up until recently I thought it was too deep a subject and required many college level or even graduate classes. But it is liberating for me to know thanks to these videos that the operation and tweaking of amplifier designs can be learned online or thru the right books.
It doesn't, if you are willing to read and study + ask questions on a solid forum like audiokarma.org/, you can absolutely learn enough to at least be dangerous lol
Just wanted to say how I really appreciate an honest review here. Much more educational and down to earth than all those YT “audiophiles” with their sponsored goods and overly positive reviews. We need more like you!
Please do not forget that we are still looking for your final schematic of your 300B and BoM to see if we can find all parts locally. Thank you for your great videos and i consider myself a fan of them. Greetings from Bulgaria and have a wonderful day.
Thank you for your very interesting videos. I have an A50 and was about to sell it, but now I will keep it until you have finalized your mods and try to implement them. There are two things that I would love to see: 1. Could you make sure that your mods also work for the European main voltage of 230V (in case any specific considerations are needed) and 2. could you also look into any mod to the circuit of the V-meters, so that they do something more meaningful. Currently they hardly move at all. I am looking forward to the next video in the series. Greetings from Germany.
At 3:45 when you mention 33uF in series is will be the same. Is it support to be 1/2 instead? Like 16.5uF total? I thought parallel is double and series is 1/2.
Good catch. I forgot besides increasing their voltage tolerance, it halves their value. Not something I would normally do and not 100% sure why they added the complexity of this.
@@SkunkieDesignsElectronics Thank you, I am learning at the moment so I was confused then used digitkey website to check with the formula to make it's correct. :) Waiting for next video.
It's also funny that the design targets 5H+5H then uses large resistors for an RC network. Current + high resistances = noise. Although paralleling resistors helps reduce thermal noise, it would probably be better to run larger chokes (with low DCR) and reduce the RC resistor values. Voltage drop is going to be key for the cascode.. and with low PSRR you'll need that low Vripple.
On the use of LEDs - they have been shown to increase THD by 0.x% compared to a resistor in the cathode circuit. I think removing that 5W PSU resistor, it's part of an initial LPF that is reducing Vripple as part of a RCLCLC pi filter.. A nice schneider mains PI filter would also probably not go amiss for any mains transients.
If you replace a un-bypassed resistor it will increase THD (reduced negative feedback), but also it increases the amplification like bypassing it with a cap would, and in my experience sounds better than a bypassed resistor. Also the type of LED matters on what they sound like too. I normally use a LED + smaller value resistor and tune the sound via the resistor value. I'm pretty sure I can remove any ripple caused by removing that first PS resistor by adding a small cap between the chokes. The B+ need to be brought up a lot given the output tube is running at 50% plate dissipation and no where near it's voltage limit. I'm not really concerned about resistor noise in the PS RC network feeding the driver stage as there is very low current there. That said, I'm a fan of having a separate RC network for each driver channel. And at this point it's all theoretical until it's built and listened too. And as I noted in another video, THD in a tube amp isn't always a bad thing :) If you are looking for how to build something with 0.1 THD to hit a paper measurement, you're watching the wrong channel :P
If the PSU is unregulated then you probably need to take into account the mains variation (in the UK that's 230V ±10%) and the regulation of the power supply transformer (say 8%). So they're probably making a safe decision that the +18% with the final B+ value not going above the maximum voltage of the tube before arc over. So assuming the viewer is in the US, then the changes should target their supply.
Hey Skunkie Designs Electronics. I have a question. Out of all the amps your have built or modded which one is the best sounding amp in your opinion. Thanks and I love the channel!!
I don't see grid stop resistors to avoid oscillations? It shaves of high hiss I the highest frequenties. Maybe it isn't Required I use it in my Amp at grid end tube and input first stage wich you have a potmeter wich act like a gridstoper I use 1k metaalfilm 0,5 watt
Oh... I need to go back and look lol. Nope just looked, 8200uf 16V caps. I do see orange drops being used and they don't sound bad, for HIFI I like the Mundorf alum/oil better.
Thanks for the videos! Can the preamp section be feasibly taken out of the loop so that the unit functions only as an amplifier? I need remote control of volume.
@@rndm4642 Your preamp or whatever you are using does not have the "Drive" to feed the 300b tubes without the 6SN7 tubes being in the circuit. A 300b needs 140-160V peak to peak signal drive. Also when you have the volume knob turned all or most of the way up, it's bypassed and is no longer in the signal path.
Hello, tell me what to do? I turned on the amplifier, it played for 7 minutes, I turned it off, then the next day I wanted to turn it on, but it doesn't turn on.I checked the preheater everything is fine, but the amplifier still doesn't turn on anymore?what should I do? thank you in advance
series cap cut the cap value in half . Ripple can be reduced with the cap between the chokes making it a 12db roll off 6db as is. I would go at least 100mfd between the chokes.
Yeah I brain farted on the series cap cut in half and was thinking a 100uf cap between the chokes would be a good plan but need to sim it out. Thanks for the note!
Thanks for this! I'm trying to help a friend fix his broken A20 which is in the same series as the A50 but has KT88s in SE ULmode. Unfortunately I can't get hold of a schematic! So any insight is helpful. He inserted the KT88s incorrectly with pin 1 in pin 5 of the sockets and blew a couple of caps by the sound of his description!
@@SkunkieDesignsElectronics I'd send you this if I was not so far away!😁 If anyone knows where to get a schematic it would be helpful as when I contacted the manufacturer they weren't very helpful! They seem a bit protective of their plagiarized designs😂. I'm hoping it will be a simple repair or I may have to back engineer the circuit which will take me a while! Hopefully I'll have it fixed by the time you get your hands on one. If so I'll be watching your mods with bated breath in the hope I can follow along!
Electronics is a hobby I have a passion for. Up until recently I thought it was too deep a subject and required many college level or even graduate classes.
But it is liberating for me to know thanks to these videos that the operation and tweaking of amplifier designs can be learned online or thru the right books.
It doesn't, if you are willing to read and study + ask questions on a solid forum like audiokarma.org/, you can absolutely learn enough to at least be dangerous lol
Just wanted to say how I really appreciate an honest review here. Much more educational and down to earth than all those YT “audiophiles” with their sponsored goods and overly positive reviews. We need more like you!
This is so cool. You really know your stuff. Can't wait to see what you can get out of it!!!
Im struck by your loveliness. Great vid.
Please do not forget that we are still looking for your final schematic of your 300B and BoM to see if we can find all parts locally. Thank you for your great videos and i consider myself a fan of them. Greetings from Bulgaria and have a wonderful day.
It's all on my website www.skunkiedesigns.com/300b
Good video and summary of this amp's internals, great work!
This is gold! 🙌🙌🙌
Thank you for your very interesting videos. I have an A50 and was about to sell it, but now I will keep it until you have finalized your mods and try to implement them. There are two things that I would love to see: 1. Could you make sure that your mods also work for the European main voltage of 230V (in case any specific considerations are needed) and 2. could you also look into any mod to the circuit of the V-meters, so that they do something more meaningful. Currently they hardly move at all.
I am looking forward to the next video in the series. Greetings from Germany.
Yup, I plan to do this :)
At 3:45 when you mention 33uF in series is will be the same. Is it support to be 1/2 instead? Like 16.5uF total? I thought parallel is double and series is 1/2.
Good catch. I forgot besides increasing their voltage tolerance, it halves their value. Not something I would normally do and not 100% sure why they added the complexity of this.
@@SkunkieDesignsElectronics Thank you, I am learning at the moment so I was confused then used digitkey website to check with the formula to make it's correct. :) Waiting for next video.
Just excellent. Thank you.
It's also funny that the design targets 5H+5H then uses large resistors for an RC network. Current + high resistances = noise. Although paralleling resistors helps reduce thermal noise, it would probably be better to run larger chokes (with low DCR) and reduce the RC resistor values. Voltage drop is going to be key for the cascode.. and with low PSRR you'll need that low Vripple.
On the use of LEDs - they have been shown to increase THD by 0.x% compared to a resistor in the cathode circuit. I think removing that 5W PSU resistor, it's part of an initial LPF that is reducing Vripple as part of a RCLCLC pi filter.. A nice schneider mains PI filter would also probably not go amiss for any mains transients.
If you replace a un-bypassed resistor it will increase THD (reduced negative feedback), but also it increases the amplification like bypassing it with a cap would, and in my experience sounds better than a bypassed resistor. Also the type of LED matters on what they sound like too. I normally use a LED + smaller value resistor and tune the sound via the resistor value.
I'm pretty sure I can remove any ripple caused by removing that first PS resistor by adding a small cap between the chokes. The B+ need to be brought up a lot given the output tube is running at 50% plate dissipation and no where near it's voltage limit. I'm not really concerned about resistor noise in the PS RC network feeding the driver stage as there is very low current there. That said, I'm a fan of having a separate RC network for each driver channel.
And at this point it's all theoretical until it's built and listened too. And as I noted in another video, THD in a tube amp isn't always a bad thing :) If you are looking for how to build something with 0.1 THD to hit a paper measurement, you're watching the wrong channel :P
caps in series the voltage doubles the capacitance half's 16,5 uf cap at 800 volts etc
Someone already pointed out this error, thanks.
@@SkunkieDesignsElectronics re design the PSU will work much better
Nicely done.
If the PSU is unregulated then you probably need to take into account the mains variation (in the UK that's 230V ±10%) and the regulation of the power supply transformer (say 8%). So they're probably making a safe decision that the +18% with the final B+ value not going above the maximum voltage of the tube before arc over. So assuming the viewer is in the US, then the changes should target their supply.
I plan to sim all of this and also measure, but the B+ is no where near the limits of these tubes, which is part of the problem.
Caps in series divide in parallel add up.
Hey Skunkie Designs Electronics. I have a question. Out of all the amps your have built or modded which one is the best sounding amp in your opinion. Thanks and I love the channel!!
My fav is my 6SQ7/EL34 UL SE
@@SkunkieDesignsElectronics Are you still planning to make a few of them for sale ??? If so, any guess on cost?? Great videos !!!
I don't see grid stop resistors to avoid oscillations? It shaves of high hiss I the highest frequenties.
Maybe it isn't Required I use it in my Amp at grid end tube and input first stage wich you have a potmeter wich act like a gridstoper I use 1k metaalfilm 0,5 watt
I plan to add them to the grid of the 300B, 6sn7 usually is fine without them.
Great stuff. Can you change a Gemtune X1 that uses 2 el34 tubes in single ended to 300b. Am wanting to get that 300B midrange!
Highly doubt it, 2 very different output tubes. With the right tubes and amp design, an EL34 amp can sound very sweet.
Please design 6SN7 45 2 watts Parafeed using 50H choke. 45 is good to build too.
I have used orange drop decoupling capacitors with on my guitar tube amps with success. Also, 8200uF caps on the filaments!? That has to be a typo :)
Oh... I need to go back and look lol. Nope just looked, 8200uf 16V caps. I do see orange drops being used and they don't sound bad, for HIFI I like the Mundorf alum/oil better.
6SN7 at B2 should change resistor to make 265VDC on anode instead of 230 it is about 4mA on that Anode.
Thanks for the videos! Can the preamp section be feasibly taken out of the loop so that the unit functions only as an amplifier? I need remote control of volume.
Simply turn the volume knob up and control it with a pre-amp or whatever you plan to use to do it remotely.
@@SkunkieDesignsElectronics Thanks! That’s what I’m doing now but I figured that would mean unnecessary signal path and corresponding degradation?
@@rndm4642 Your preamp or whatever you are using does not have the "Drive" to feed the 300b tubes without the 6SN7 tubes being in the circuit. A 300b needs 140-160V peak to peak signal drive. Also when you have the volume knob turned all or most of the way up, it's bypassed and is no longer in the signal path.
@@SkunkieDesignsElectronics thank you!
Can you suggest a model that you felt good in a lower price range?
A "Skunkie modded" A10/A12 is a good option, and IMHO sounds better then even a modded A50.
Hello, tell me what to do? I turned on the amplifier, it played for 7 minutes, I turned it off, then the next day I wanted to turn it on, but it doesn't turn on.I checked the preheater everything is fine, but the amplifier still doesn't turn on anymore?what should I do? thank you in advance
That's not a lot to go on, send me a message at my website contact page and I'll try to help.
series cap cut the cap value in half . Ripple can be reduced with the cap between the chokes making it a 12db roll off 6db as is. I would go at least 100mfd between the chokes.
Yeah I brain farted on the series cap cut in half and was thinking a 100uf cap between the chokes would be a good plan but need to sim it out. Thanks for the note!
@@SkunkieDesignsElectronics After the second choke up the value there also . What sim are you using ?
I wonder about my Audio Space AS-3i
Sorry, not familiar with that one.
Thanks for this! I'm trying to help a friend fix his broken A20 which is in the same series as the A50 but has KT88s in SE ULmode. Unfortunately I can't get hold of a schematic! So any insight is helpful. He inserted the KT88s incorrectly with pin 1 in pin 5 of the sockets and blew a couple of caps by the sound of his description!
Wish I could help, I don't know anything about an A20. I'm sure at some point someone will send me one to review/mod.
@@SkunkieDesignsElectronics I'd send you this if I was not so far away!😁 If anyone knows where to get a schematic it would be helpful as when I contacted the manufacturer they weren't very helpful! They seem a bit protective of their plagiarized designs😂. I'm hoping it will be a simple repair or I may have to back engineer the circuit which will take me a while! Hopefully I'll have it fixed by the time you get your hands on one. If so I'll be watching your mods with bated breath in the hope I can follow along!
Caps in series halves the capacity!
You are correct, thanks for the comment.