what probelm about this hard wiring amps

[kldguitar]

Our new amp 100 w tube guitar amp. 5 12ax7,4 el34.
hard wiring. but the noise little larger. who can help us and tell me how to reduce the noise

[MWJB]

Working backwards from the power tubes try and isolate the stage where the noise is getting into the circuit & what kind of noise it is.

Tube shields on the preamps may help, shielded cable in sensitive areas (grid wires), heater wiring around the preamp tubes looks somewhat "loose".

Without more specific info it's hard to make specific suggestions.

[cbarrow7625]

I think in your case it's all going to be about lead dress and cable routing.

1.) Tightly twist together your heater wires. That will at least reduce the AC induction hum. It looks like you have some of them twisted (although loosley). But where you really need them twisted tight is going from preamp tube to preamp tube.

2.) Pay careful attention to which wires you have running next to each other. Don't have wires from successive stages run parallel to each other. The one from the later stage can capacitively couple noise (and signal) back through the wire to the previous stageand make the noise far waorse than it needs to be. Same thing goes for cathode wires. Don't let them run in parallel with plate wires.

3.) Lead dress - Do whatever you can to run all of your wires at right angles to each other. Wires crossing each other perpendicularly will have far less chance of coupling than wires run either parallel, 45 degree angles or randomly (like yours appear).

I don't know what that large bundle of wires is that is going out to the tone stacks but, intuitively, I would say that is probably a bad idea. I can't give you any specifics without knowing what those wires are but see my comments above & see if that doesn't help you sort it out.

Looks like you have AC filament wires running directly beneath your "presence" & "depth" controls. That's not a good idea. That's going to induce num & noise. Are the presence & depth connected to the negative feedback circuit? If so, how are those wires routed? Man, they are a long way away from the output jacks! I wouldn't be surprised if you couldn't do something better with those as well.

It looks like one of your power tubes is directly underneath your fuse socket. That doesn't seem like a good idea. Any AC noise will get amplified by that tube only (the push-pull configiration of the output tubes won't cancel it). Keep all AC away from any & all signals wherever possible!! This goes double for routing signal wires near and/or past any of the transformers or chokes. The magentic fields will induce noise & hum.

Speaking of transformers, have you tried rotating the orientation of the transformers & chokes to see if that reduces any of the noise? It looks like you probably have them turned the proper way, but you never know. You may find that magnetics don't always do what your eyes tell you they should be doing. I would try rotating those a little bit.

How are your grounds run? Looks like you have some hybrid star / linear ground scheme going on there. There is one obvious thing I would change - the only ground wire that should be connected to the chassis next to the input jack is the input jack itself. Run the rest of your grounds directly to the earth ground point where your ground wire / transformer secondary ground are attached to the chassis. Oh, yeah, and move that ground point if it causes you to have to route those grounds over the power transformer.

MWJB's suggestions are good too but it looks to me like you could make some real improvements just by paying attention to your wire routing & lead dress a little more.

Chris

[kldguitar]

thanks. We will study your advices

I think in your case it's all going to be about lead dress and cable routing.

1.) Tightly twist together your heater wires. That will at least reduce the AC induction hum. It looks like you have some of them twisted (although loosley). But where you really need them twisted tight is going from preamp tube to preamp tube.

2.) Pay careful attention to which wires you have running next to each other. Don't have wires from successive stages run parallel to each other. The one from the later stage can capacitively couple noise (and signal) back through the wire to the previous stageand make the noise far waorse than it needs to be. Same thing goes for cathode wires. Don't let them run in parallel with plate wires.

3.) Lead dress - Do whatever you can to run all of your wires at right angles to each other. Wires crossing each other perpendicularly will have far less chance of coupling than wires run either parallel, 45 degree angles or randomly (like yours appear).

I don't know what that large bundle of wires is that is going out to the tone stacks but, intuitively, I would say that is probably a bad idea. I can't give you any specifics without knowing what those wires are but see my comments above & see if that doesn't help you sort it out.

Looks like you have AC filament wires running directly beneath your "presence" & "depth" controls. That's not a good idea. That's going to induce num & noise. Are the presence & depth connected to the negative feedback circuit? If so, how are those wires routed? Man, they are a long way away from the output jacks! I wouldn't be surprised if you couldn't do something better with those as well.

It looks like one of your power tubes is directly underneath your fuse socket. That doesn't seem like a good idea. Any AC noise will get amplified by that tube only (the push-pull configiration of the output tubes won't cancel it). Keep all AC away from any & all signals wherever possible!! This goes double for routing signal wires near and/or past any of the transformers or chokes. The magentic fields will induce noise & hum.

Speaking of transformers, have you tried rotating the orientation of the transformers & chokes to see if that reduces any of the noise? It looks like you probably have them turned the proper way, but you never know. You may find that magnetics don't always do what your eyes tell you they should be doing. I would try rotating those a little bit.

How are your grounds run? Looks like you have some hybrid star / linear ground scheme going on there. There is one obvious thing I would change - the only ground wire that should be connected to the chassis next to the input jack is the input jack itself. Run the rest of your grounds directly to the earth ground point where your ground wire / transformer secondary ground are attached to the chassis. Oh, yeah, and move that ground point if it causes you to have to route those grounds over the power transformer.

MWJB's suggestions are good too but it looks to me like you could make some real improvements just by paying attention to your wire routing & lead dress a little more.

Chris

Good advices. We will study it and discuss later

[kldguitar]

The advantage of hand wiring

Good advices. We will study it and discuss later

The important advantage of hand wiring is it has good ground,PCB has larger ground loop, so it easy casue noise from other power component, But hand wiring concel this loop, so the noise of hand wiring might be lower

[stokes]

The important advantage of hand wiring is it has good ground,PCB has larger ground loop, so it easy casue noise from other power component, But hand wiring concel this loop, so the noise of hand wiring might be lower

I used to think this was the case,and am a big fan of point to point or hand wiring as you call it,I still think it gives a "purer" tube tone,but as for noise,if you look at some of these high gain monsters like Mesa and such,with all that gain they generate,noise was surely a problem when they were developing them,but they can be as quiet as anything,they sure have solved that issue.When played clean,these amps can tend to be somewhat harsh to me,but I do have a MKIIC+ that has a great sounding clean channel,but I did have to install an adjustable bias pot to tweak the power tubes to get it to sound good to me.But for ground loops and noise,I gotta disagree,the PCB's dont necessarily cause it,maybe bad construction and or design using them,but there are a lot of very quiet PCB designed amps out there.I still would rather work on or build PTP over PCB's but that is more because of the extra steps it takes to get at things and the all the bells and whistles they cram into a PCB amp.Just lazy,I guess.Oh,and all the lead dress issues and such pointed out by cbarrow are just as important in a PTP as a PCB amp,so thinking the same amp with PTP and bad dress/routing wont make noise is wrong.