Outstanding build. Your tone was great and the steps were clear, concise and easy to follow. Very clean throughout. I even enjoyed how you built the chassis using TIG welding. Sounds great.
Thanks for commenting, I really appreciate it! It was a fun build. I liked it so much I'm making a High Gain and a JTM version using this output section. Cheers.
@@MikeFreda Don't laugh, but I got into fiddling with amps. I would find these old tube amps on eBay that didn't work. Through the grace of God and help from a guy I befriended, (Jon Besent, who was an amp builder that started "Austone"), I never blew myself up. I bought a tube PA amp at the swap meet for $5.00, and converted into a amp head. It had 2 EL-84s and 1 12AX7. Believe it or not it rocked.
We all have to start somewhere. I started building tube amps in my late 20's when I came across a Fender Amp book that had a Schematic of a Champ in it. I said to myself, "is that all it is?" I bought the book and took it to work. An old guy I worked with was into ham radios. He laughed when I showed him the book and told him I wanted to make this Champ amp. He then proceeded to educate me a bit. The one major thing he told me was to always keep on hand in my pocket when testing. I still do that today. Cheers
@@MikeFreda Very cool to have a mentor. The electronic guys are not around anymore, or at least in my neck of the woods. I live in the desert area of California, and when I was in high school we had electronics class. I wish I took it, but being a 16 year old kid with a 68 Dodge Super Bee, I dove into auto shop 100%, and we cruised the main drag in Palm Springs. It was a great time to be alive. Wish I would have picked up a guitar way back then too.
Thank you for your comment and kind words. UA-cam has a lot of content for people to filter through. I often wonder why some channels don’t have a lot of Subs and some do.
The amp does have a wide range and the speaker and cabinet does make it project. Adding a bit of reverb livens up the sound a bit as well. I’d say it’s almost as loud as a real Fender Princeton. Cheers.
I just finished my first amp build thanks to the inspiration of your 1 watt tube video series and it sounds great. You do a excellent job. Keep up the good work!
Another great video! I like how the circuit has a range of sounds, not just overdriven. Looking forward to the upcoming video on the lightbulb limiter.
I built one with a tmb tone stack built in, marshall jtm values. Raw switch and a nfb pot. The donor amp was a black heart little giant 5 watt amp. I really love it. A 1 watt version would be fun too.
You are a wizard and you did an amazing job, so thorough and I appreciate the knowledge I've gained and can return to. The only thing I wouldn't do is 1 watt, seems like a crayon drawn half mustache on the mona lisa. cheers
Thanks for your comment. A lot of people do make a 6V6 or EL84 power section in these amps but I wanted to do something different to see how loud it actually is and to try something with tubes I had in my tubebin. To my surprise, its way louder than I thought it would be. As I mentioned, it is a practice or a studio recording amp. Cheers.
@@MikeFreda well all I'm really saying is if you ever build a 100w monster and document your build, I'll be right there when you blow down your neighbor's house 😉 🤙🏼
Just a quick safety tip. Always run the source or line to the rear terminal of a fuse holder. The load goes to the ring. The reason is the ring is exposed when the fuse cap is removed.
You didn't test the negative feed back loop?!?! But what great video I definitely want to do the same thing but I'm thinking maybe put two output tubes ( I had thought of maybe using four 12 ax7s as I'll put tubes but I don't know if that's even feasible) and maybe a full tone stack. Put a potentiometer on the feedback loop and put it on the front of the amp as well That would be really cool. I'm definitely going to build this again thank you so much for posting this video and all the work you put into it and the schematics and everything Great job.
Thanks for commenting. Part 3 has some more test tones near the end. I was planning on a making a Part 4 with just playing but I never got around to it. It's still in the works. Output tubes typically have a low MU and are able to drive more current. I don't think a 12AX7 is suitable for that sort of job. 12BH7 and even a 12AU7 is a better option in the output section. Adding a pot on the feedback is basically make a presence knob. Yes, that will work if the values are right. To be honest, I didn't hear much difference wit it on or off. I may have to revisit my values. Cheers.
A complete build document will be uploaded with the part 3 video. I’ll include alternate parts as well (like the Hammond chassis) I’m working on that video right now. The chassis I built in these videos is 11.5”x 6.5”x2”.
Thanks for the reply,@@MikeFreda. The dimensions are quite helpful. Just out of curiosity, if a person wanted to simply build a 1 watt power amp, assuming they already had a viable preamp, would it be feasible to simply feed the output of the preamp thru the 0..022µf/600v bypass capacitor, connected to the grids of the 12BH7?
Yes/no. Most preamp sections will work with this output stage. Just have to be careful you have the coupling caps installed and you are not pushing/driving the tube too hard. The other issue is the output transformer. You need to have the correct primary impedance and it needs to be a a push/pull OT. You just can’t take a champ OT for a 6v6 or Deluxe OT and try to make that work.
Great build, looks similar to my Princeton clone I built last year! Few questions: 1) have a part number for your impedance selector? 2) what software did you use to make up your schematic?
Thanks. It’s coming together. Next video will be out shorty. The switch is a Alpha 4H2. On the final version of the amp I actually decided to remove the selector switch and go with a line out instead. I used AutoCAD for the schematic. One could use Draw.io as well.
Thanks. I've built amps using both types of metal. I don't think it really makes a difference. Aluminum is easier to drill holes into and steel is easier to weld (if you need to weld the chassis) Some people feel that the metal can affect the RF and magnetic field of the output transformer/amp. Ken Fisher (Trainwreck amps fame) only built his chassis out of Aluminum because of this. My ears can't hear a difference. Cheers
Thanks. To make a higher wattage amp, you will need a different power tube and output transformer and possibly a larger power transformer to handle the extra current. You could use one EL84 or a 6V6. You are then basically making a Fender Champ or Princeton. Cheers
Hey Mike :)) After some deliberation I decided to convert a cheap practice amp into a 1w tube amp. So a couple of questions arose. I'm not a purist, and would rather have a functional amp (because I have no other tube amp and where I live, shipping and import tax might cost you as much as the amp itself). I'm fine with the tone of your build, but: 1. The 6K49VG power transformer works for US power (110v), I had difficulty finding an EU-compatible alternative (220v) 2. If I were to add a 3-band EQ instead of just the tone pot, do you think it is doable? 3. Is using a trim pot to bias the amp a good idea with this build? Would be grateful if you had advise at least for the first part. I can live with an EQ pedal going into the amp, and desoldering a resistor every time I swap tubes is annoying, but guess I can just socket it.
Thanks for commenting. I hope the project works out for you. Hammond makes the equivalent 220V transformer in their "300" series. It has dual primary taps. Just find one that has the same secondary voltage and current ratings. Yes, just follow the Fender Blackface Champ (AA764 circuit and layout) Mind you, a TMB Tone stack can rob some of the mojo over a simple tone stack. This is a Cathode bias amp. It's not common practice to install a trim pot. You do find trim pots on a fixed bias amp. If you are worried you can just install a larger bias resistor and it should be good for most 12BH7's. Up to 680ohm as recommend on the schematic. The larger the bias resistor, the cooler is runs. The circuit does have NFB, just install a switch like I show in the video. I have found that its hard to hear a difference. You may need to lower the size of the NFB resistor. I hope that helps?
@@MikeFreda thanks for the quick reply. I'll look at the Hammond website, see if I can find something usable. I actually already changed the negative feedback loop in my schematic. 1. 10k resistor, the recommended minimum, and a 50k pot in series. Should give me a range of 10-60k ohms. I would expect 10k to be quite clean and 60k to somewhat break up. 2. A presence control, 5k pot with a 0.1uF cap connected to the ground. Both are described in "Negative feedback loops and the Fender presence control" video by Uncle Doug. I can share the result if you're interested. As for the treble-mid-bass controls, I agree that they take certain peaks and you do lose tone in between. The way I'd go about it, add another 12AX7 in parallel, filter the inputs, use pots to add certain frequencies. I could use an op-amp to do it too, but that might be seen as cheating, and I'd need a separate power supply for the op-amp. But it still feels like overcomplicating something that is unlikely to be used in studio or live, this is a practice amp after all. After some research, I decided not to implement an fx loop because most of the distortion happens in the power amp, so the fx loop would likely sound like crap.
Not really. The input impedance will not match and there is no RIAA equalization in this circuit. This is a guitar amp, not a HiFi amp. Would it work? Probably. Will it sound good? Probably not. Cheers.
I love point to point wiring, they sure don't make them like they used to. I have electrocuted myself in excess of 5 times perusing this hobby. Even with the Variac and light bulb i still get the odd bang now and then. Ah well in the words of Peter Green.
Thanks for commenting. Yes, there is an inherent risk when working with high voltage tube amps. I like to use the “one-hand-in-pocket” method when testing. Stay safe, cheers.
Hi Mike, This is a great build. I have a question if you don't mind? What made you choose eyelet board instead of turret board. Any particular reason? Thanks
Hello, thanks for your comments. I use eyelets because they are easier for me to obtain, install and wire especially under the board. Fender uses eyelets well into the 70’s. I’ve used turrets a couple times and they work okay, nothing really wrong with them. You do need a thicker mounting board. It’s not something that stuck with me since it was awkward for me to purchase.
@@MikeFreda Hi, that makes perfect sense now you’ve explained it. I think I’ll look into eyelet board. Love the amp you made so might attempt my own version 👌
Thanks for commenting, I'm not too familiar with what is available globally for 230V PT's but I do know Hammonds 300 series have dual primaries for 120 and 240V. They are a little expensive but are available. Another option is to find something in your area that you can a salvage. Cheers.
Hello, this amp is intended for guitar mono operation. There is overdrive/distortion in the preamp circuit. yes, you could plug in some headphones and listen while you play guitar but its not a HiFi headphone amp. That being said, you could take the output section of this amp and mirror it for stereo usage and graph on a hifi preamp section. (1 triode section of a 12AT7 per channel, 150v at the plate @ 1-2ma bias would suffice.) This would drive any headphones as long as the output impedance sort of matches the headphone impedance. That would be an interesting circuit to make... hmmmmm
I currently have a 7 dollar iron I got from walmart, and no multimeter, do you know of any decent irons and meters that arent too expensive? I've already put together a distortion pedal pcb kit but I don't think I'd get away with my current set up for long 😂😂
I'd recommend getting a Solder Station with adjustable heat. Weller makes a entry level one of these. (i.e. WLC100CUL) I used one of these for years when I first started. As for a DMM, I'd get one rated for at least ~500volts. When dealing with Tube amps, you can see voltages that high. You want to make sure the unit and the probs are rated for that. I would not cheap out on this aspect. A base Fluke will work just fine for hobby tube amp building. (i.e. Fluke 101) Cheers.
Not really but if you want to spend the money, go fo it. You will get the hang of what works best and what does not. I find maxing the temp of the iron and getting the components up to heat fast and adding solder better than a lower heat and holding the iron for a longer period of time waiting for things to flow. Cheers.
Thanks. As per my Documented voltages on my build schematic (link in the description) each triode is drawing 12mA ~4 watts. The listed max values are 20mA. This 12BH7 appears to be in the wheelhouse of its Typical Characteristics.
Hi, so I built the amp - and all the voltages check out except I get very low volume output from the amp. I checked everything and ya.....stumped to be honest. Any suggestions??
@@MikeFreda I used the hammond 125A, I suspect it's because I'm running it off mains AC - kinda figured while I wait for the power transformer to be wound I would like to hear what the amp sounds like. (I have 230VAC for mains, which I thought would work seeing that the transformer gives 230vac) I am using a 20VA 0-230 0-6.3v for the heaters. Apparently you need a transformer or I needed to adjust the rectification to simulate a center tap.....first amp build so still learning
Thanks for your comment. Figuring this out can be a bit convoluted and can get a bit confusing. When designing from scratch you need to look at the tubes load sheet/graph and see where its optimal performance is for the application being used. Once you figured out what that voltage and current is, use ohms laws to figure out the bias and load resistor. You also need to know what your PSU is supplying. What a lot of people do is use a known current value from an existing circuit that has been figured out and use ohms law (V=IxR) and adjust the resistors to suit.
Thanks for your comment. Yes/no. At lower volume or changing the input tube to a 12AY7 or 12AU7, it would be great. As it stands, the 12AX7 / circuit design does over drive the power tube when you turn the volume past 5/6.
PART 1: ua-cam.com/video/JKoEprk4eaU/v-deo.html
Outstanding build. Your tone was great and the steps were clear, concise and easy to follow. Very clean throughout. I even enjoyed how you built the chassis using TIG welding. Sounds great.
Thanks for commenting, I really appreciate it! It was a fun build. I liked it so much I'm making a High Gain and a JTM version using this output section. Cheers.
@@MikeFreda Don't laugh, but I got into fiddling with amps. I would find these old tube amps on eBay that didn't work. Through the grace of God and help from a guy I befriended, (Jon Besent, who was an amp builder that started "Austone"), I never blew myself up. I bought a tube PA amp at the swap meet for $5.00, and converted into a amp head. It had 2 EL-84s and 1 12AX7. Believe it or not it rocked.
We all have to start somewhere. I started building tube amps in my late 20's when I came across a Fender Amp book that had a Schematic of a Champ in it. I said to myself, "is that all it is?" I bought the book and took it to work. An old guy I worked with was into ham radios. He laughed when I showed him the book and told him I wanted to make this Champ amp. He then proceeded to educate me a bit. The one major thing he told me was to always keep on hand in my pocket when testing. I still do that today. Cheers
@@MikeFreda Very cool to have a mentor. The electronic guys are not around anymore, or at least in my neck of the woods. I live in the desert area of California, and when I was in high school we had electronics class. I wish I took it, but being a 16 year old kid with a 68 Dodge Super Bee, I dove into auto shop 100%, and we cruised the main drag in Palm Springs. It was a great time to be alive. Wish I would have picked up a guitar way back then too.
Just by watching the video I was expecting this channel to have at least 100k subscribers, you definetely deserve more
Thank you for your comment and kind words. UA-cam has a lot of content for people to filter through. I often wonder why some channels don’t have a lot of Subs and some do.
Great vid! I agree
What I like about a one watt tube amp is the sound doesn't come out of a box it fills the room.
The amp does have a wide range and the speaker and cabinet does make it project. Adding a bit of reverb livens up the sound a bit as well. I’d say it’s almost as loud as a real Fender Princeton. Cheers.
I just finished my first amp build thanks to the inspiration of your 1 watt tube video series and it sounds great. You do a excellent job. Keep up the good work!
I always wanted to build at tube amp !
Cool Mike! I ever would have thought of winding the wires using a drill. Clever!
Another great video! I like how the circuit has a range of sounds, not just overdriven. Looking forward to the upcoming video on the lightbulb limiter.
Thank you. Yes, I’m surprised how dynamic it actually is with the tone, volume and pick attach. Current Limiter video will be up soon.
I built one with a tmb tone stack built in, marshall jtm values. Raw switch and a nfb pot. The donor amp was a black heart little giant 5 watt amp. I really love it. A 1 watt version would be fun too.
Sounds like a cool project. My next guitar amp project will be a ~2-3 watt JTM45…. On a budget! Cheers.
@@MikeFreda look forward to a video on that one!
You are a wizard and you did an amazing job, so thorough and I appreciate the knowledge I've gained and can return to. The only thing I wouldn't do is 1 watt, seems like a crayon drawn half mustache on the mona lisa. cheers
Thanks for your comment. A lot of people do make a 6V6 or EL84 power section in these amps but I wanted to do something different to see how loud it actually is and to try something with tubes I had in my tubebin. To my surprise, its way louder than I thought it would be. As I mentioned, it is a practice or a studio recording amp. Cheers.
@@MikeFreda well all I'm really saying is if you ever build a 100w monster and document your build, I'll be right there when you blow down your neighbor's house 😉 🤙🏼
Just a quick safety tip. Always run the source or line to the rear terminal of a fuse holder. The load goes to the ring. The reason is the ring is exposed when the fuse cap is removed.
Yes, you are correct. Good catch. That was corrected upon final assembly.
You didn't test the negative feed back loop?!?!
But what great video I definitely want to do the same thing but I'm thinking maybe put two output tubes ( I had thought of maybe using four 12 ax7s as I'll put tubes but I don't know if that's even feasible) and maybe a full tone stack. Put a potentiometer on the feedback loop and put it on the front of the amp as well That would be really cool. I'm definitely going to build this again thank you so much for posting this video and all the work you put into it and the schematics and everything Great job.
Thanks for commenting. Part 3 has some more test tones near the end. I was planning on a making a Part 4 with just playing but I never got around to it. It's still in the works. Output tubes typically have a low MU and are able to drive more current. I don't think a 12AX7 is suitable for that sort of job. 12BH7 and even a 12AU7 is a better option in the output section. Adding a pot on the feedback is basically make a presence knob. Yes, that will work if the values are right. To be honest, I didn't hear much difference wit it on or off. I may have to revisit my values. Cheers.
amazing!
I appreciate what you're doing, but I really would been nice to at least get a peek at the wires on the back of the board.
Good Night my Youth A beautiful project Can you share the schematics? Thanks
Sure would be nice to have that link to that Hammond chassis.
A complete build document will be uploaded with the part 3 video. I’ll include alternate parts as well (like the Hammond chassis) I’m working on that video right now. The chassis I built in these videos is 11.5”x 6.5”x2”.
Thanks for the reply,@@MikeFreda. The dimensions are quite helpful.
Just out of curiosity, if a person wanted to simply build a 1 watt power amp, assuming they already had a viable preamp, would it be feasible to simply feed the output of the preamp thru the 0..022µf/600v bypass capacitor, connected to the grids of the 12BH7?
Yes/no. Most preamp sections will work with this output stage. Just have to be careful you have the coupling caps installed and you are not pushing/driving the tube too hard. The other issue is the output transformer. You need to have the correct primary impedance and it needs to be a a push/pull OT. You just can’t take a champ OT for a 6v6 or Deluxe OT and try to make that work.
Great videos! I subbed!
Awesome, glad you like the video. Thanks for the sub. Cheers.
Great build, looks similar to my Princeton clone I built last year!
Few questions: 1) have a part number for your impedance selector? 2) what software did you use to make up your schematic?
Thanks. It’s coming together. Next video will be out shorty. The switch is a Alpha 4H2. On the final version of the amp I actually decided to remove the selector switch and go with a line out instead. I used AutoCAD for the schematic. One could use Draw.io as well.
Great video! I’m fixing to build the same amp using a hammond chassis. Any issues using an aluminum chassis vs steel? Thanks!
Thanks. I've built amps using both types of metal. I don't think it really makes a difference. Aluminum is easier to drill holes into and steel is easier to weld (if you need to weld the chassis) Some people feel that the metal can affect the RF and magnetic field of the output transformer/amp. Ken Fisher (Trainwreck amps fame) only built his chassis out of Aluminum because of this. My ears can't hear a difference. Cheers
@@MikeFreda thank you!
Awesome build!! Just out of curiosity, what components would make the amp a higher wattage?
Thanks. To make a higher wattage amp, you will need a different power tube and output transformer and possibly a larger power transformer to handle the extra current. You could use one EL84 or a 6V6. You are then basically making a Fender Champ or Princeton. Cheers
Hey Mike :))
After some deliberation I decided to convert a cheap practice amp into a 1w tube amp.
So a couple of questions arose.
I'm not a purist, and would rather have a functional amp (because I have no other tube amp and where I live, shipping and import tax might cost you as much as the amp itself).
I'm fine with the tone of your build, but:
1. The 6K49VG power transformer works for US power (110v), I had difficulty finding an EU-compatible alternative (220v)
2. If I were to add a 3-band EQ instead of just the tone pot, do you think it is doable?
3. Is using a trim pot to bias the amp a good idea with this build?
Would be grateful if you had advise at least for the first part. I can live with an EQ pedal going into the amp, and desoldering a resistor every time I swap tubes is annoying, but guess I can just socket it.
Also, what if I want to add a switch to the negative feedback loop?
Thanks for commenting. I hope the project works out for you.
Hammond makes the equivalent 220V transformer in their "300" series. It has dual primary taps. Just find one that has the same secondary voltage and current ratings.
Yes, just follow the Fender Blackface Champ (AA764 circuit and layout) Mind you, a TMB Tone stack can rob some of the mojo over a simple tone stack.
This is a Cathode bias amp. It's not common practice to install a trim pot. You do find trim pots on a fixed bias amp. If you are worried you can just install a larger bias resistor and it should be good for most 12BH7's. Up to 680ohm as recommend on the schematic. The larger the bias resistor, the cooler is runs.
The circuit does have NFB, just install a switch like I show in the video. I have found that its hard to hear a difference. You may need to lower the size of the NFB resistor.
I hope that helps?
@@MikeFreda thanks for the quick reply. I'll look at the Hammond website, see if I can find something usable.
I actually already changed the negative feedback loop in my schematic.
1. 10k resistor, the recommended minimum, and a 50k pot in series. Should give me a range of 10-60k ohms. I would expect 10k to be quite clean and 60k to somewhat break up.
2. A presence control, 5k pot with a 0.1uF cap connected to the ground.
Both are described in "Negative feedback loops and the Fender presence control" video by Uncle Doug.
I can share the result if you're interested.
As for the treble-mid-bass controls, I agree that they take certain peaks and you do lose tone in between. The way I'd go about it, add another 12AX7 in parallel, filter the inputs, use pots to add certain frequencies. I could use an op-amp to do it too, but that might be seen as cheating, and I'd need a separate power supply for the op-amp.
But it still feels like overcomplicating something that is unlikely to be used in studio or live, this is a practice amp after all.
After some research, I decided not to implement an fx loop because most of the distortion happens in the power amp, so the fx loop would likely sound like crap.
can i use this for a phono signal? thank you great vids mann
Not really. The input impedance will not match and there is no RIAA equalization in this circuit. This is a guitar amp, not a HiFi amp. Would it work? Probably. Will it sound good? Probably not. Cheers.
tank you so much for your information friend @@MikeFreda
Are you using a tube rectifiers ? What is the desired B plus voltage for the tube plates ?
No. Solid state. Please have a look at the Build Schematic in the Description.
I love point to point wiring, they sure don't make them like they used to. I have electrocuted myself in excess of 5 times perusing this hobby. Even with the Variac and light bulb i still get the odd bang now and then. Ah well in the words of Peter Green.
Thanks for commenting. Yes, there is an inherent risk when working with high voltage tube amps. I like to use the “one-hand-in-pocket” method when testing. Stay safe, cheers.
Hi Mike, This is a great build. I have a question if you don't mind? What made you choose eyelet board instead of turret board. Any particular reason?
Thanks
Hello, thanks for your comments. I use eyelets because they are easier for me to obtain, install and wire especially under the board. Fender uses eyelets well into the 70’s. I’ve used turrets a couple times and they work okay, nothing really wrong with them. You do need a thicker mounting board. It’s not something that stuck with me since it was awkward for me to purchase.
@@MikeFreda Hi, that makes perfect sense now you’ve explained it. I think I’ll look into eyelet board. Love the amp you made so might attempt my own version 👌
Can you tell me what kind of transformer should i use for 230V
Thanks for commenting, I'm not too familiar with what is available globally for 230V PT's but I do know Hammonds 300 series have dual primaries for 120 and 240V. They are a little expensive but are available. Another option is to find something in your area that you can a salvage. Cheers.
HI from Brooklyn,NY;Happy New Year; Would this amp for be good enough for high -end headphones,Monoprice M1570 planar headphones? Thanks for help.
Hello, this amp is intended for guitar mono operation. There is overdrive/distortion in the preamp circuit. yes, you could plug in some headphones and listen while you play guitar but its not a HiFi headphone amp. That being said, you could take the output section of this amp and mirror it for stereo usage and graph on a hifi preamp section. (1 triode section of a 12AT7 per channel, 150v at the plate @ 1-2ma bias would suffice.) This would drive any headphones as long as the output impedance sort of matches the headphone impedance. That would be an interesting circuit to make... hmmmmm
I currently have a 7 dollar iron I got from walmart, and no multimeter, do you know of any decent irons and meters that arent too expensive? I've already put together a distortion pedal pcb kit but I don't think I'd get away with my current set up for long 😂😂
I'd recommend getting a Solder Station with adjustable heat. Weller makes a entry level one of these. (i.e. WLC100CUL) I used one of these for years when I first started. As for a DMM, I'd get one rated for at least ~500volts. When dealing with Tube amps, you can see voltages that high. You want to make sure the unit and the probs are rated for that. I would not cheap out on this aspect. A base Fluke will work just fine for hobby tube amp building. (i.e. Fluke 101) Cheers.
@@MikeFreda will there be any problems with not having temperature readout on that iron? Or does it not really matter?
Not really but if you want to spend the money, go fo it. You will get the hang of what works best and what does not. I find maxing the temp of the iron and getting the components up to heat fast and adding solder better than a lower heat and holding the iron for a longer period of time waiting for things to flow. Cheers.
great build what was the current you ended up with through the 12BH7
Thanks. As per my Documented voltages on my build schematic (link in the description) each triode is drawing 12mA ~4 watts. The listed max values are 20mA. This 12BH7 appears to be in the wheelhouse of its Typical Characteristics.
Where's the final schematic?
Hello, there are Google drive links to all the documents in the video description. Cheers.
Hi, so I built the amp - and all the voltages check out except I get very low volume output from the amp. I checked everything and ya.....stumped to be honest. Any suggestions??
I suspect you have a wiring issue, wrong resistor value. What OT did you use? PM me a few pictures and voltages and I can have a look.
@@MikeFreda I used the hammond 125A, I suspect it's because I'm running it off mains AC - kinda figured while I wait for the power transformer to be wound I would like to hear what the amp sounds like. (I have 230VAC for mains, which I thought would work seeing that the transformer gives 230vac) I am using a 20VA 0-230 0-6.3v for the heaters.
Apparently you need a transformer or I needed to adjust the rectification to simulate a center tap.....first amp build so still learning
@@MikeFreda Oh and on the layout if the 13.6v is a negative, I'm only getting positive voltages, but in line with the schematic and layout
Interesting. I don't recommend doing any of this. Doing this is very dangerous. I recommend waiting until you have all the proper components.
I'm curious how do you find the load resistance for preamp tubes?
Thanks for your comment. Figuring this out can be a bit convoluted and can get a bit confusing. When designing from scratch you need to look at the tubes load sheet/graph and see where its optimal performance is for the application being used. Once you figured out what that voltage and current is, use ohms laws to figure out the bias and load resistor. You also need to know what your PSU is supplying. What a lot of people do is use a known current value from an existing circuit that has been figured out and use ohms law (V=IxR) and adjust the resistors to suit.
Do you have the final layout?
Working on it right now. New video (part 3) in the works.
does this work well with pedals?
Thanks for your comment. Yes/no. At lower volume or changing the input tube to a 12AY7 or 12AU7, it would be great. As it stands, the 12AX7 / circuit design does over drive the power tube when you turn the volume past 5/6.