New 2 channel KT88 based P/P design. Check my work?

[Gainzilla]

Thanks Mark,

The power supply is the least concrete for me and the biggest area I was hoping to learn about through this build. The values of the bias circuit came from the JCM800 Kerry King sig amp which has kt88s (It was a bit difficult for me to find examples to study). Same for the Power Amp values. I'll update the design to a more traditional value. That one seemed a bit unusual to me as well. I hate not knowing everything. lol

Obviously, I could do a more tried and true power section and just paint by numbers, but I'm trying to learn. I may still go that route for the actual build. I do appreciate all the help here though, so thanks for taking the time (everyone else as well!).

Also, 560k pots are a typo. I'll fix those. I actually already have the 500k dual pots.

[Gainzilla]

I hear you on trying more tried and true designs, but I'm not just trying to build my own amp. I'm trying to learn, and the only way to do things is to try, fail, ask questions. I do respect your expertise and willingness to help (you've helped me in the past, thank you), however I don't think there's a need to rip me. I'm being respectful of the forum and it's rules, and politely asking for help. True, my schem had dozens of errors. Most of those are from translating the "design" into a program I'm unfamiliar with, but others are definitely showing I still have a lot to learn. But that's why I'm here. If you don't want to help, then fine. Actually, if you feel like you want to rip me I suppose you're welcome to that as well. Everyone starts from zero.

Cheers

[Alan0354]

Not even 1N5408 will be enough, PIV there is 1400V , way above 1N5408 specs, so at least 2 in series each are needed (8 to complete a bridge).

This bridge rectifier only see 500V X1.414= about 700V max reverse. This is not like the old fender with CT grounded. BUT it is always safer to use two in series anyway.

[Alan0354]

I hear you on trying more tried and true designs, but I'm not just trying to build my own amp. I'm trying to learn, and the only way to do things is to try, fail, ask questions. I do respect your expertise and willingness to help (you've helped me in the past, thank you), however I don't think there's a need to rip me. I'm being respectful of the forum and it's rules, and politely asking for help. True, my schem had dozens of errors. Most of those are from translating the "design" into a program I'm unfamiliar with, but others are definitely showing I still have a lot to learn. But that's why I'm here. If you don't want to help, then fine. Actually, if you feel like you want to rip me I suppose you're welcome to that as well. Everyone starts from zero.

Cheers

Don't worry about it, all I can suggest is to stop and think about it stage by stage. Why people doing what they do.

Circuit in guitar amp follow a very few design trend, if you read enough schematics from Marshall, Fender, Soldano, Dumble etc. You'll start to see they follow very closely to each other.

1) I would concentrate on the power supply to start out as this can be critical. Think about why they do what they do, ask question here.

2) Then study the power amp. I found most power amp are quite similar.

3) Last, look at the preamp. This is where you shape the sound. Every change in the resistor/capacitor value can change the sound completely. But the basic circuit is mostly common cathode design with a cathode follower mix in here or there. You first need to get the basic operating voltage in the ball park, then you experiment with different value of the components in between stages. It takes time to get the feel of how different circuit gives you different sound.

That's why I suggested you stop and think about the circuit, don't just build the complete amp because if something goes wrong, you don't know where to start. Build the power supply first, then the power section. Build the preamp last. That's how I design my amps.


FYI, I am planning to design and build two audiophile power amp. They are a lot more complicated, more involved and very different from guitar amps. This is what I have been doing:

I got myself one tube power amp and one SS power amp. I just finished studying the SS amp. I chop up the amp into small section and ask more specific questions on the forum. I have been doing this for about a month, I think I still need another month to read through the tube book, study more establish schematics to even start on the design.

[MarkusBass]

With corrected schematics you are now ready to start building the amp. It seems that you don't have much experience with tube amps but this is the time for you to learn. I will not be easy but with correct schematics and help from the forum you will make it.

Mark

[gui_tarzan]

Sometimes we write things and don't consider the "tone" in which they're written. That appears to be the case here but it could be someone is just not having a good day. As a definite amateur when it comes to building amps, I do know the safety concerns because I have been repairing tube amps for a long time. As far as negative attitudes, rightly or wrongly they're based on a concern for your safety above all else and from reading the thread so far, I would strongly suggest you do a lot of reading about the proper safety procedures you must use while working with tube amps so you don't harm or worse, kill yourself. Think about the voltages you're working with - 120v hurts, 220v messes you up or can kill you, 500v will stop your heart in a millisecond.

One thing that stood out to me immediately in your power supply is the "A" cap - you will need to run two caps rated at 350v or more in series to get the necessary max voltage requirement so you don't blow them up when you turn the amp on. And the suggestion of building a simple amp first is solid - once you understand how the components work with each other and what they do it'll be easier to design your own. Experience is talking here and there are a lot of guys here with a lot more experience and knowledge than I have.

[gui_tarzan]

I hear you on trying more tried and true designs, but I'm not just trying to build my own amp. I'm trying to learn, and the only way to do things is to try, fail, ask questions. I do respect your expertise and willingness to help (you've helped me in the past, thank you), however I don't think there's a need to rip me. I'm being respectful of the forum and it's rules, and politely asking for help. True, my schem had dozens of errors. Most of those are from translating the "design" into a program I'm unfamiliar with, but others are definitely showing I still have a lot to learn. But that's why I'm here.

Yes, that's how most of us learn, but you have to be able to do it safely.

[Gingertube]

Preamp - after you fix the problems noted above you will also want to add a gate stop resistor of say 1K to the IRF820 gate to prevent parasitic oscillations.
Cheers,
Ian