Champ 5F1 wiring?

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Mark
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Champ 5F1 wiring?

Post by Mark »

I have a question for Champ builders out there. What wiring do you consider the most critical in an 5F1 Champ?

My Champ is a Kendrick Roughneck which is a 5F1 clone. Over the years, I have modified it, I replaced the 10" speaker, put Large core Mercury output transformer in (made a big difference to the bass response), and I got rid of the Kendrick mods bringing it in line with a standard Champ.

The amp was always okay but it lacked top end, one day I noticed the pot was noisy and the cause was the wiper wire from the pot to the 12AX7. I put a piece of shielded cable in and suddenly the amp was brighter and more transparent sounding.

Has anyone else had this experience?

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Re: Champ 5F1 wiring?

Post by Stevem »

Yes, all of that preamp circuit/ component, and or the speaker output jack so close to the input jacks is the cause!
Signal bleed out of one wire and ( that wire which you replaced) and the input jacks was phase canceling your signals high end responce.

On circuit board type amps like all of those Orange amps and other amps cramed into a small chassis that I mod for more gain I have to make Aluminum and card board sheilds for the input and speaker output jack to stop them from oscillating and or phase canceling .

This phase canceling technique can also be used to trouble shoot a oscillating amp issue on a build of mod session!

Shielded wire should always be used on the grids of atleast the first 2 gain stages of any amp.
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Re: Champ 5F1 wiring?

Post by xtian »

Stevem wrote: Thu Apr 27, 2017 12:39 pm
Shielded wire should always be used on the grids of atleast the first 2 gain stages of any amp.
Respectfully disagree.
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Re: Champ 5F1 wiring?

Post by M Fowler »

In a 5F1 amp the most critical is the filament wiring, being single ended amp, the filament supply will buzz.

In all amps keeping the preamp filter ground separate from the PT center tap and reservoir filtering.
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Re: Champ 5F1 wiring?

Post by pompeiisneaks »

xtian wrote: Thu Apr 27, 2017 2:48 pm
Stevem wrote: Thu Apr 27, 2017 12:39 pm
Shielded wire should always be used on the grids of atleast the first 2 gain stages of any amp.
Respectfully disagree.
I agree with xtian here, I've not done hundreds of amps, but I've done about 6 now, and every one only had shielded from the input jack to the first triode. Some did have hum, and in every case it was due to me doing a poor job connecting grounds, or having heater wiring lead dress issues. Upon resolution of those they've all been silent. I've also repaired a few, but I'm still pretty new. One of my builds a Gibson EH185, I used a lot of shielded wire because I screwed up and did the tube sockets and transformers mirrored from how they should have been so my pre made turret board was backwards to the order of things. I used the shielded wire to help stop noise from the other nearby stages, it didn't seem to help a ton, and I'm planning on gutting the turret board and making the amp P2P to remove the noise problems, all related to lead dress, not shielded or not. Everything I've read also indicates that the only stage that is sensitive really to the external noise is the first gain stage of the first preamp tube and this is why that's normally the main one to use shielded wire on. I know the dumbles tend to use a lot more shielded wire, but I think in those cases they're for the drive which is also one of the noisier parts of the circuit (or so it seemed to me looking over the layouts). I'd be curious if careful routing of those wires in a dumble without shielding would still create a nice quiet amp.

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Re: Champ 5F1 wiring?

Post by JazzGuitarGimp »

pompeiisneaks wrote: Thu Apr 27, 2017 5:04 pm
xtian wrote: Thu Apr 27, 2017 2:48 pm
Stevem wrote: Thu Apr 27, 2017 12:39 pm
Shielded wire should always be used on the grids of atleast the first 2 gain stages of any amp.
Respectfully disagree.
I agree with xtian here, I've not done hundreds of amps, but I've done about 6 now, and every one only had shielded from the input jack to the first triode. Some did have hum, and in every case it was due to me doing a poor job connecting grounds, or having heater wiring lead dress issues. Upon resolution of those they've all been silent. I've also repaired a few, but I'm still pretty new. One of my builds a Gibson EH185, I used a lot of shielded wire because I screwed up and did the tube sockets and transformers mirrored from how they should have been so my pre made turret board was backwards to the order of things. I used the shielded wire to help stop noise from the other nearby stages, it didn't seem to help a ton, and I'm planning on gutting the turret board and making the amp P2P to remove the noise problems, all related to lead dress, not shielded or not. Everything I've read also indicates that the only stage that is sensitive really to the external noise is the first gain stage of the first preamp tube and this is why that's normally the main one to use shielded wire on. I know the dumbles tend to use a lot more shielded wire, but I think in those cases they're for the drive which is also one of the noisier parts of the circuit (or so it seemed to me looking over the layouts). I'd be curious if careful routing of those wires in a dumble without shielding would still create a nice quiet amp.

~Phil
Phil, it's too bad it's not an eyelet board. If it were, you could strip it and flip it. Problem solved. Did you install the turrets youself, or were they preinstalled? If you have the punch down tool, you could carefully remove the turrets and install new ones on the other side of the board.
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Re: Champ 5F1 wiring?

Post by pompeiisneaks »

I bought it from Hoffman amps. I don't currently have the tools to redo it, but that's not a bad idea! I've got a drill press and was going to build a dumble using turret board instead of eyelet board and build them myself anyway, may be worth it to buy some more turrets and strip those out like you suggest. I'll have to give that a go.

As an additional note to this topic, the last build I did was a champ and we only used shielded on the input and it sounds super clean. The heaters weren't done fender style on top but instead I like to follow the method Merlin Blencowe suggests where you run them way away and run up the lines directly over the pins themselves and back out.

Here: Image the smiley one on the right but with the wires back against the edge like in the first sadface one :)

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Re: Champ 5F1 wiring?

Post by xtian »

I avoid shielded wire if at all possible, to avoid dulling the amp with extra capacitance. Even on the input run. Even on my high-gain builds. Just keep the leads short.
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Re: Champ 5F1 wiring?

Post by pompeiisneaks »

Oh interesting, you just put the first preamp right next to the input jack. That's not a bad idea at all. How do you keep the heaters away from the other components though? I guess I should look at that pic again for a bit :)

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Re: Champ 5F1 wiring?

Post by xtian »

I've certainly fought raging "hum" battles in my builds, but it's almost always grounding issues.

In fact, I got so disgusted with efforts to prevent hum from heater wiring and getting no results, I did a "worst case" experiment. I attached some extra long heater wires in the circuit, maintaining the current flow thru these wires, but loose, so I could move these heater wires around. With the amp running, I moved these heater wires around, close to V1, input, other places, and I couldn't cause any increase in hum, even with the worst lead dress you've ever seen.
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Re: Champ 5F1 wiring?

Post by pompeiisneaks »

Very interesting. I've also seen a few guts of really high end amps with the heater wires literally done as bare wires in a straight line with some shrink tube put between each tube... guess it's pretty likely not that hard to avoid hum from them. I've been able to use a humdinger to make the tiny amount of heater hum dissipate completely anyway.

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Re: Champ 5F1 wiring?

Post by Mark »

Thanks for your replies, so I gather you guys have encountered this rolling off of the upper frequencies.
This amp does hum a bit. I'm fairly sure it is the heaters, I seem to remember removing the 12AX7 and the hum was still there at the same volume.
Last edited by Mark on Fri Jun 09, 2017 5:48 am, edited 1 time in total.
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Re: Champ 5F1 wiring?

Post by Stevem »

In a build done right and your plate leads are longer than your grid leads then no high end loss in the 7k wide audio range of guitar will take place from using shielded wire.
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Re: Champ 5F1 wiring?

Post by didit »

pompeiisneaks wrote: Thu Apr 27, 2017 5:04 pm
xtian wrote: Thu Apr 27, 2017 2:48 pm
Stevem wrote: Thu Apr 27, 2017 12:39 pm
Shielded wire should always be used on the grids of atleast the first 2 gain stages of any amp.
Respectfully disagree.
I agree with xtian here, [...]
Agreement? Is it that shielding is unnecessary, or actually harmful. Could consensus be -- shielding inputs eliminates a few possible day-one hassles & longer term risks, and the modest addition capacitance makes no difference? Or is there harm binding up an otherwise naked wire in wire mesh & black vinyl?

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Re: Champ 5F1 wiring?

Post by Blackburn »

The 5F1 is my favorite amp to build and I've never had any hum issues due to internal circuit wiring. The only hum I've had issues with is transformer coupling on those steel chassis. When I stop playing and mute the strings it sounds like the amp is off. And I personally wouldn't use shielded wire in a 5F1, primarily because I've never even come close to seeing it as necessary. My $.02

Here's a pic of my last one I did....
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