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Post subject: Re: My Modded Champion 600
Posted: Mon Nov 21, 2016 11:53 am
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mud wrote:
Luxter wrote:
Hi,
I decided to modify my C600 following what you did. I do not have a lot of experience so I really appreciate you documenting all this.

I have found pretty much everything needed but I was wondering what's the voltage of the 0.022 mF Orange Drop cap you soldered across R5.

Thanks


FYI, bluesky636 kind of jumped off the radar a while back, hopefully and maybe this will bring him in for a little bit
Bill is missed
mud


Thanks for the information! I hope he's alright.


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Post subject: Re: My Modded Champion 600
Posted: Sun Jun 25, 2017 9:37 pm
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Joined: Mon Apr 05, 2010 2:37 pm
Posts: 8708
Location: Natural Bridge, Virginia
Replaced the ceramic 6" Jensen Mod speaker with a Weber Alnico Signature 6S. Much smoother sounding with a nicer breakup compared to the ceramic version.

Also decided to modify the circuit by adding a tone control ala a Harvard. Single coils were OK through the amp but humbuckers were too dark. Both sound really nice now with the control afforded by the tone control. I removed the low gain input and installed the tone pot in its place with a matching chicken head.

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Post subject: Re: My Modded Champion 600
Posted: Fri Jan 26, 2018 7:51 am
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I do not understand why the schematic shows two 12AX7 tubes when there is only one?


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Post subject: Re: My Modded Champion 600
Posted: Thu Feb 08, 2018 4:04 am
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Joined: Tue Jun 29, 2010 1:20 pm
Posts: 9640
Location: Indiana
All 12AX7s have two triodes, each triode is one half of the tube, and the schematic is showing the two halves seperately. So yes, only one preamp tube, each half as indicated by “V1A” (1, 2, 3) and “V1B” (6, 7, 8 ).

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---> "The amp should be SWITCHED OFF AND UNPLUGGED before you do this!" <---

Por favor, disculpe mi español, no se llega a la práctica con mucha frecuencia.


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Post subject: Re: My Modded Champion 600
Posted: Tue Dec 04, 2018 10:43 am
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Hi,

I got this nice little amp a month ago. Amp was used but in very good original condition. The sound was to my ears quite good but the hum - it was - horrible. I see that SE amps hum always but this much is not acceptable.

I googled threads of the mod of this amp and found this best. Thanks bluesky636 and others. There are also several threads especially of the hum reduction in web. After reading this a couple of times through I began to mod it.

I put a choke - capacitor and a resistor - capacitor filters in the power line. That helped very much but still there was too much hum and noise present.

I thought that the preamp stage is not well built. I have built a KT88SEUL map some years ago, point to pint wiring and my own layout design (see if you will: https://www.diyaudio.com/forums/tubes-v ... -seul.html). There is not hum at all. I see that in that amp preamp signal in line level but still. I do not accept that much hum and noise. Background noise at my home is only 35dB. I like it, i live in Finland in a small town.

I built the preamp wiring point to point. Assembled new input jacks and a new volume pot and shielded/grounded signal wires. I also removed the tone stack, reduced by resistors the signal level 6db (100k/100k voltage drop) and put some more resistors to the circuit. Cap across R5 too. Now it is quite ok. Noise and hum not hearable in silent room up to vol pot setting 7-8. Fine tuning of the filament virtual 100R resistors, I think, should cancel the rest of the hum but I have not yet done it. After all I think that preamp wiring should generally be planned better in these amps.
https://aijaa.com/bCzATT
https://aijaa.com/9uIZXY


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