Sovtek 50H 6V6 - layout

KindCanuck

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Hey all! I’m back with my Sovtek 50H/Robrob JCM800 6V6 project. I’ve completed the layout with the changes from the schematic I posted about a month ago. Could some of you have a look and see if I made any mistakes? I only modified the preamp up until the master volume. PI and the rest are as per robrob's original.

Thanks!
 

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Phrygian77

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Edit: nevermind, I didn't realize there was a plate resistor there, not being very familiar with the Sovtek.
 
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radiocaster

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The "dirty" channel won't work at all if you use a stereo jack. You need jacks with switches.
 

KindCanuck

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The "dirty" channel won't work at all if you use a stereo jack. You need jacks with switches.
They are switching jacks, labelled S SW and T on the layout. I couldn’t find the proper symbol when drawing the schematic, so I used the trs.

B+3 doesn't pass the sniff test in your drawing.

Could you elaborate? I just put a new plate tap for the last preamp stage as the Sovtek schematic does.
 

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2L man

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It looks like pre amp return current flow thru chassis? You also use potentiometer case for operative current and now there is possibility go ground loop. There is no advantage using chassis a part of secondary operative voltage. Often it make amp hum more and it also increase noise on Mains Safety Earth wiring and make it less good to lessen all around electronics noise.
 

KindCanuck

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It looks like pre amp return current flow thru chassis? You also use potentiometer case for operative current and now there is possibility go ground loop. There is no advantage using chassis a part of secondary operative voltage. Often it make amp hum more and it also increase noise on Mains Safety Earth wiring and make it less good to lessen all around electronics noise.
I'm not sure I follow what you're saying, the chassis is ground. What current do you see flowing through it?
 

2L man

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On tube amplifiers Chassis has two roles, a Safety Earth and and somekind of Shield against electromagnetic noise. No current should flow there!!! Only when severe mains current leak fault happen the building Mains table/board fuse burn when mains current "short" to Earth. Building SE is connected to globe Earth, water blumps and concrete rebar etc.

On tube amp schematics the ground symbol is where secondary operative current flow back to power supply, either to PT Center Tab or Bridge rectifier Negative which are connect to first filter capacitor negative which on your layout reads GND. Best english term I have seen used for secondary return current is Common so I use it. I still wait someone who has studied electronics is USA tell what is correct english term? For me it has always been 0VDC where return current flow and a reference I measure voltages, currents, analog and digital signals and discretes.

On your layout I don't see a black wire between pre amp and PS. Also there are components soldered to potentiometers. Output jack neutral is not wired to Common. So these return current return thru Chassis!

You can wire all "ground symbols" to main capacitor Negative and it is a Star. Or make power amp ground lug a Common and wire "grounds" there and it is Star. Or install a single Common bus from PS and which go towards amp input and connect all ground symbols to it.

When you build you can verify there is no leak between Common and Chassis measuring resistance betwee them and it should be megaohms. Then when wiring is about to finish connect Common to Chassis close the input jack.

Amp input is best place to "short" Common to SE because it is the most sensitive making most gain. On input there also flow least return current so operative current "pollute" SE wire the least and this bebefit your guitar when it is Earthed thru instrument cable. You as well because you are also Earthed thru strings which are Earthed thru metal bridge. Also other band member amps and PA get less noise from SE. You benefit if their amps have proper "grounding" etc.
 

Lynxtrap

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I'm not sure I follow what you're saying, the chassis is ground. What current do you see flowing through it?

Current flows through every connection to ground/chassis. It's just that many of us are not used to thinking in terms of current. We often think in terms of voltage, and that leads us to think that ground=zero=nothing when it actually is part of the circuit.

When we connect circuit ground to different parts of the chassis, pots etc, we expect the chassis to function as a "wire". This is obviously not great - using an actual wire is better. The circuit really doesn't even need a connection to the chassis to work (called floating ground), but chassis is used for ground reference because it is at zero volts.

Having said that, Fender, Marshall, Vox and most others have never followed any such grounding rules.
 

KindCanuck

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On tube amplifiers Chassis has two roles, a Safety Earth and and somekind of Shield against electromagnetic noise. No current should flow there!!! Only when severe mains current leak fault happen the building Mains table/board fuse burn when mains current "short" to Earth. Building SE is connected to globe Earth, water blumps and concrete rebar etc.

On tube amp schematics the ground symbol is where secondary operative current flow back to power supply, either to PT Center Tab or Bridge rectifier Negative which are connect to first filter capacitor negative which on your layout reads GND. Best english term I have seen used for secondary return current is Common so I use it. I still wait someone who has studied electronics is USA tell what is correct english term? For me it has always been 0VDC where return current flow and a reference I measure voltages, currents, analog and digital signals and discretes.

On your layout I don't see a black wire between pre amp and PS. Also there are components soldered to potentiometers. Output jack neutral is not wired to Common. So these return current return thru Chassis!

You can wire all "ground symbols" to main capacitor Negative and it is a Star. Or make power amp ground lug a Common and wire "grounds" there and it is Star. Or install a single Common bus from PS and which go towards amp input and connect all ground symbols to it.

When you build you can verify there is no leak between Common and Chassis measuring resistance betwee them and it should be megaohms. Then when wiring is about to finish connect Common to Chassis close the input jack.

Amp input is best place to "short" Common to SE because it is the most sensitive making most gain. On input there also flow least return current so operative current "pollute" SE wire the least and this bebefit your guitar when it is Earthed thru instrument cable. You as well because you are also Earthed thru strings which are Earthed thru metal bridge. Also other band member amps and PA get less noise from SE. You benefit if their amps have proper "grounding" etc.
Current flows through every connection to ground/chassis. It's just that many of us are not used to thinking in terms of current. We often think in terms of voltage, and that leads us to think that ground=zero=nothing when it actually is part of the circuit.

When we connect circuit ground to different parts of the chassis, pots etc, we expect the chassis to function as a "wire". This is obviously not great - using an actual wire is better. The circuit really doesn't even need a connection to the chassis to work (called floating ground), but chassis is used for ground reference because it is at zero volts.

Having said that, Fender, Marshall, Vox and most others have never followed any such grounding rules.

I didn’t touch the schematic beyond the input jacks and the preamp components, so I guess take it up with robrob or Marshall or Sovtek? Or if I have made a mistake by omitting a connection, please point it out, I’m new at this.

I merged the schematics to learn a bit and build a cool sounding amp for me.
 

sds1

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I didn’t touch the schematic beyond the input jacks and the preamp components, so I guess take it up with robrob or Marshall or Sovtek? Or if I have made a mistake by omitting a connection, please point it out, I’m new at this.

I merged the schematics to learn a bit and build a cool sounding amp for me.
You're fine, IMO it's a bit much to suggest you go optimizing ground schemes for classic/known working amp circuits when they are not known to have problems that might warrant optimizing. The implication that Marshall/Sovtek/robrob have made some huge mistake here is in itself confusing, especially to newcomers.

If you ever come to decide your build could somehow benefit from an optimized grounding scheme, just come back and ask. :)

You are lucky you didn't present a design with a standby switch, things could have gotten real rowdy in here.
 
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Lynxtrap

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I didn’t touch the schematic beyond the input jacks and the preamp components, so I guess take it up with robrob or Marshall or Sovtek? Or if I have made a mistake by omitting a connection, please point it out, I’m new at this.

I merged the schematics to learn a bit and build a cool sounding amp for me.

Yeah, that's cool. The grounding is really not an actual problem unless it turns out to be a problem (hum, etc).
I was trying to give an answer to your question about currents in the chassis and "the chassis is ground". It doesn't hurt to know these things when getting into amp building.
 

KindCanuck

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You're fine, IMO it's a bit much to suggest you go optimizing ground schemes for classic/known working amp circuits when they are not known to have problems that might warrant optimizing. The implication that Marshall/Sovtek/robrob have made some huge mistake here is in itself confusing, especially to newcomers.

If you ever come to decide your build could somehow benefit from an optimized grounding scheme, just come back and ask. :)

You are lucky you didn't present a design with a standby switch, things could have gotten real rowdy in here.

Hahaha @ standby. I’ll for sure come back, I’ve built a Princeton reverb delete before so this is my second build, and first time working with diylc so I didn’t want to get too complicated. Thanks for the reassurance!

Yeah, that's cool. The grounding is really not an actual problem unless it turns out to be a problem (hum, etc).
I was trying to give an answer to your question about currents in the chassis and "the chassis is ground". It doesn't hurt to know these things when getting into amp building.
For sure, like I said above, I’m not looking to get complicated or into the weeds yet. Right now I’ll settle for an amp that makes sound and doesn’t kill me when playing it. Thanks for the help!
 

2L man

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You guys have lots of freedom and "polluting" electric network is one of them :) I understand preventing it must first have e federal law. I did recommend building amp better because it is easy when building. Changing it better later takes more work.
 

wangdaning

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You guys have lots of freedom and "polluting" electric network is one of them :) I understand preventing it must first have e federal law. I did recommend building amp better because it is easy when building. Changing it better later takes more work.
I could only imagine you seeing fuse boxes wired to plywood and exposed. This happens and I have seen it many times. That said, I agree, do it right the first time if you can.
 




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