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Author Topic: Amp Conversion?
MattS

Posts: 1
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Post Amp Conversion?
on: October 3, 2013, 12:40
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Hello everyone,

I am a newb here. I found this site recently and saw Joe's video about "Any old Crap" and thought that old PA amp sounded cool. I emailed Joe about the old amp I have and he referred me to all of you for advice.

I have an old Knight tube amplifier that I believe is an old amplifier for a phonograph and or stereo. I pulled the top off and saw these old tubes. There are two 12AX7's (Mullard and Westinghouse), one 6V4, and two 6BQ5's (I think) (Mullard and Westinghouse). When I plugged the unit in, they all started warming up.
I am wondering if I should attempt to convert this into a guitar amp. I've had it checked out by an electrician and he said everything is functioning well and doesn't need anything replaced. He said it could be converted for guitar by adding an input jack, but it would mainly be clean (no distortion?). Would do you think?

I hope the pictures I will try to include come through so you can see what it is.

Any advice or recommendations you might be able to give me would be greatly appreciated.

Thank you,
Matt

https://s1326.photobucket.com/user/emtshaw/media/Matt011_zps333fbe66.jpg.html
https://s1326.photobucket.com/user/emtshaw/media/Matt012_zpsf61c318e.jpg.html
https://s1326.photobucket.com/user/emtshaw/media/Matt013_zps23b71fe4.jpg.html
https://s1326.photobucket.com/user/emtshaw/media/tubeamp007_zps4762423f.jpg.html
https://s1326.photobucket.com/user/emtshaw/media/tubeamp006_zpsa2707fe1.jpg.html
mwseniff

Posts: 149
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Post Re: Amp Conversion?
on: October 3, 2013, 17:43
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You might get power amp distortion at stage volume this probably sort of equivalent to a Vox AC15 power wise. It should work with FX pedals pretty well for fuzz. The tuner input would definitely need rework to be a guitar input. The phono input would have a lot of bass and no high end due to the RIAA curve for records. You might want to check on Ebay as it might be worth something to someone as is. You could also use it for a mono system if you dig old 78's. I have a mono setup to check mixes for my studio as mono really shows whats up sometimes. This may well have been a kit but if so it was a good job from the pics. I would be hesitant to make it a guitar amp as it is kinda cool. You may also find the filter caps will need replacement after some use, they dry out over time as usage and heat may finish them off (shelf life of electrolytic caps is 10 years let alone add heat and volts).

smgear

Posts: 170
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Post Re: Amp Conversion?
on: October 3, 2013, 18:25
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I think I have to +1 that. It certainly could make a fine clean amp - though without reworking the input stage, you'll either get uber low/muted highs (slightly more appropriate if you play jazz or bass) or a pretty brittle harshness depending on the input you choose. However, just looking at it I can hear how amazing it would sound driving an 8" bookshelf speaker. Turning it into a mono ipod/laptop dock would sound awesome. I've got one similar back in the states and it has such a nice fat sound - it makes me actually listen to the radio because am sounds so fantastic through it. Or, back to the guitar option, if you happen to use any digital multi's, then this would probably make a nice 'warmer' amp for those. Given the relatively flat and normalized signal coming out of most of the digi line outputs, I think the tuner input would probably sound decent with minimal, if any, mods. But I'll defer to the pro's in that regard.
Digital-
Larry

Posts: 192
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Post Re: Amp Conversion?
on: February 8, 2014, 09:26
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I didn't follow through on all of my planned tube amp restorations (yet), but the one I did, I just replaced a carbonized tube socket and the electrolytics and ok to be honest most of the (very small number of) components. It's something like a 5 watt class A amp. It's fairly blah to just plug a guitar into directly, though it does give off a decent clean tone. It has no tone controls and by the time you hit it hard enough to overdrive it (e.g. using a boost pedal), the resulting distortion is not my favorite.

I'd start simple - just get it working and see where your inclination leads you.
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