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 Post subject: Re: Champlifier Mods
PostPosted: Fri Jan 13, 2012 3:24 pm 
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TNblueshawk wrote:
Ok Chris, follow up questions to be sure I understand.

First how am I connecting the bleeder resitor? From what to what here?

Second and if I understood correctly, I'm taking all the premap grounds and volume ground that you mentioned and starring them into one ground point using a terminal lug attached to the chassis next to the input jack an inch or so?

Ditto on the power ghttp://www.buildyourownclone.com/board ... 1923rounds you mention but where would you mount that terminal lug?

When starring in an amp, are you taking the wires and twisting them all together to make one big fat wire and then solder at once onto the term lug or are you taking each wire wrapping each one onto the lug and then soldering in that fashion?

Connect the bleeder across the first filter cap. From the + to -. 220K 2W is fine.

Correct about preamp ground. Attach all the preamp ground on the turret board then bring a single wire to the terminal lug.

Power amp ground mount it somewhere between the turret board and the PT.

In regards to your last question, look at this layout
http://img.photobucket.com/albums/v610/ ... 7May11.jpg *also note location of power amp ground *should also note input jacks are isolated here

Notice how all the power amp grounds and the preamp grounds are connected together on the turret board then taken to the ground terminal. This keeps the layout clean and avoids excess wires and runs.

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 Post subject: Re: Champlifier Mods
PostPosted: Fri Jan 13, 2012 3:25 pm 
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Morgan wrote:
From that valve wizard article:
Quote:
Perhaps some of the confusion surrounding ‘ground’ arises because when we start learning electronics we necessarily start with very simple circuits. So simple, in fact, that grounding isn’t a problem. We can make the ground connections to any old bit of metal or wire and, as long as they are all ultimately connected together, the circuit works. So we don’t bother to think or learn about grounding until we have already developed bad habits which, when we progress onto more advanced circuits, begin to cause problems, much to our surprise.

Wow - that hits right close to home!

Yep! :lol:
Pedals are great for grounding, cause they don't give a shi t!

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 Post subject: Re: Champlifier Mods
PostPosted: Fri Jan 13, 2012 3:43 pm 
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In the BYOC kit resistors R6 & R8 (pre-amp) cannot be grounded separately from R9 (power amp). They share a common turret for their ground connection.

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 Post subject: Re: Champlifier Mods
PostPosted: Fri Jan 13, 2012 3:45 pm 
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Stephen wrote:
In the BYOC kit resistors R6 & R8 (pre-amp) cannot be grounded separately from R9 (power amp). They share a common turret for their ground connection.

Indeed
With a bit of modding you could change that though.

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 Post subject: Re: Champlifier Mods
PostPosted: Fri Jan 13, 2012 8:18 pm 
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ChrisM wrote:
Now for this ground point I'd bring R4, C1, R6, R8, C7 and the ground connection of the Volume pot. These are all low current grounds and belong together. They are sensitive signals and should not be mixed with the power amp signals.


For the power amp I would do the same thing and install another terminal lug. The terminal lug must not use the PT bolts for mounting. To this ground pot I'd bring R9, C4, C5, C6 and the PT CT's for the HV winding and heater winding.
*If you really want to try to eliminate 60 Hz heater noise btw you can bring the heater CT to the output tube's cathode. Simple mod, no adverse effects on tone and easy to reverse.

There is a lot to say and read up on grounding in amplifiers but I'll just say
1. It's not good to use the chassis as a conductor for grounding
By grounding this way it appears like you have introduced ground loops (input jack/preamp/power amp), or if you want to break the ground loops, you must use the chassis as the signal ground between the input jack/preamp/power amp. Neither of those sound like good options to me (I'm not arguing that the original ground scheme is ideal). Thoughts?

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 Post subject: Re: Champlifier Mods
PostPosted: Fri Jan 13, 2012 8:48 pm 
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Quote:
All grounds tied together and grounded in one spot
For clarification, is that literally all grounds tied together at a single point, or just all grounds connected, like a bus wire? If it's a bus wire, the order the ground connections are made on the bus wire is significant. This is illustrated in the valve wizard ground PDF linked to earlier.

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 Post subject: Re: Champlifier Mods
PostPosted: Sat Jan 14, 2012 9:23 am 
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I was afraid I couldn't explain myself correctly. I'll have a go at drawing what I mean and in the meantime I'll delete my post because of confusion.

Unfortunately I'm not computer savvy so the drawing may be a dud. We'll see.


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 Post subject: Re: Champlifier Mods
PostPosted: Sat Jan 14, 2012 9:48 am 
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Actually, your post was pretty good, it was just that one line that was a little ambiguous. I wouldn't let not being computer savvy hinder you, just pen/paper sketch and take a picture of it.

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 Post subject: Re: Champlifier Mods
PostPosted: Sat Jan 14, 2012 12:41 pm 
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defaced wrote:
ChrisM wrote:
Now for this ground point I'd bring R4, C1, R6, R8, C7 and the ground connection of the Volume pot. These are all low current grounds and belong together. They are sensitive signals and should not be mixed with the power amp signals.


For the power amp I would do the same thing and install another terminal lug. The terminal lug must not use the PT bolts for mounting. To this ground pot I'd bring R9, C4, C5, C6 and the PT CT's for the HV winding and heater winding.
*If you really want to try to eliminate 60 Hz heater noise btw you can bring the heater CT to the output tube's cathode. Simple mod, no adverse effects on tone and easy to reverse.

There is a lot to say and read up on grounding in amplifiers but I'll just say
1. It's not good to use the chassis as a conductor for grounding
By grounding this way it appears like you have introduced ground loops (input jack/preamp/power amp), or if you want to break the ground loops, you must use the chassis as the signal ground between the input jack/preamp/power amp. Neither of those sound like good options to me (I'm not arguing that the original ground scheme is ideal). Thoughts?

No ground loops this way. Not sure why you think that.

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 Post subject: Re: Champlifier Mods
PostPosted: Sat Jan 14, 2012 5:47 pm 
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ChrisM wrote:
No ground loops this way. Not sure why you think that.
Here's a sketch of how I'm interpreting your ground scheme.

The red bars are the ground connections between the sections of the amplifier.
With the red bars intact, there are ground loops
With the red bars removed, the chassis is being used as part of the signal ground

To make the schematic easier to follow in this discussion, I've taken the liberty of incorporating the filter caps/dropping resistors into the pre/power amp schematic.
Image

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 Post subject: Re: Champlifier Mods
PostPosted: Sat Jan 14, 2012 6:44 pm 
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The red bars are just the chassis

That's not a ground loop. Read Merlin's article on group loops.

To give an idea...
A ground loop on the input would be not insulating the input jack then again running a wire from it to the preamp ground. A double ground if you will.

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 Post subject: Re: Champlifier Mods
PostPosted: Sat Jan 14, 2012 6:46 pm 
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Quote:
A ground loop on the input would be not insulating the input jack then again running a wire from it to the preamp ground. A double ground if you will.
Obviously, I included that in my illustration :wink:

Quote:
With the red bars removed, the chassis is being used as part of the signal ground

Which as you stated, and I agree, is not a good thing.

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 Post subject: Re: Champlifier Mods
PostPosted: Tue Jan 17, 2012 11:37 am 
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Just finished my amp Sunday. Love it so far, but haven't been able to play it wide open for more than 5 minutes.

On the subject of mods though...does anyone have any extremely strong opinions on capacitor type for C2&C3? I think Mallory's came with the kit, but I hear good things about Sozo Mustard's as well. Wonder if its worth experimenting.


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 Post subject: Re: Champlifier Mods
PostPosted: Sun Nov 25, 2018 12:22 pm 
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I was having an issue with my guitars sounding like the tone was rolled off through this amp. I replaced the coupling capacitors with half the original value (.001uf i think), and it helped but not enough.

Today i installed a bright cap of .022uf from the middle to right lug of the volume pot and it made the exact change i was hoping for. Took the woolly-ness away and gave it a chime that i expected from a fender.

It may be to extreme for people with single coils, but my humbuckers love it.


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 Post subject: Re: Champlifier Mods
PostPosted: Wed Jul 15, 2020 8:52 pm 
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I'd have to say, after trying all these mods the only one worth while is the negative feedback loop. The rest don't work with the amp that well. I changed the coupling caps, and put a screen resistor and all that jazz. None of it sounded good. I changed everything back to stock but the feedback I put on a 50K pot and replaced the 22K to a 10K, giving me 10K to 60K to play around with. 10K is great for pedals giving me more head room, especially for overdrive/distortion pedals. Anyways, just my 2 cents. I'm glad I messed around with the circuit a bit so at least I know what everyone is talking about. Just not for me. I think it just depends on the gear you have, speaker used, etc. Using your ears is the ultimate test to all these mods.


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