knight guitar amp conversion

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gja

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Joined 2005
mintyachts.com
I have a knight allied radio tube amp I purchased on ebay a while ago planning to make a guitar amp out of it.I changed the mic input to a standard guitar jack input,plugged an old peavey 12" 4 ohm speaker pulled from a 15w solid state guitar amp.It sounds great,suprisingly loud.BUT:it seems to cut the sound of after a while.(is this what one calls clipping?).I only play at half volume.amp has mic level pot,tone pot which works as on off and phono 1&2 level.3 tubes,12au7,6l6gt and I can´t remember the otherone.impedance is 4ohms on amp (could be 8 changing the wire between the screws.question is:where do I start to solve this problem?it seems the speaker can´t handle the power,if played to loud it just sounds ugly.could this be the reason? or is he input level of my guitar to high?(sinle coil pickup value 7.5K).
Any help would be greatly appreciated...nb:I am not en expert so please make t simple and step y step!
thanks everyone
 
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m6tt

Member
Joined 2007
If the signal is totally quiet a little while after you have been playing, you may have a cold solder joint that is heating up and disconnecting after the tubes and transformers get warm. I would carefully check the solders inside the amp & especially any modifications you made. I had a homemade harmonica microphone with a cold solder that made me think I had an oscillating amp, but just the right harmonica note inside the mic housing was resonating the joint and making it suck at audio frequencies. Good luck, I would say that amp will sound great, being single-ended, you could use a voltage divider off the speaker wires (check the interweb) to drive a larger system or PA to get more audio watts if you needed them. Have you tried it with a pedal? Low quality digital pedals sometimes make tube amps sound really crunchy if that's the tone you want (since SE is often not as grainy as PP) :) good luck and happy soldering!
 
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m6tt

Member
Joined 2007
no problem...
I just found a McGohan M503 at the local electronics recycling place...
I've been trying to convert it into a guitar amp myself, so hopefully you can send me some of that luck! I think it was thrown out because the fuse holder is loose and it works intermittently. It's a nice unit though, 50 watts from Sylvania big-bottle 6ca7s. It killed a 10" pretty fast when I first plugged it in. The output transformer is bigger than the power transformer and is set up to drive anything from a 4-ohm cabinet to a 70v PA line.
Did your amp come out 'too clean'? I don't play guitar (I play harmonica through an old organ amp w/a big accutronics reverb :), it's a project for my band...the sound was great but really, really HiFi-ish. Did you make any changes to your to give it more of a crunchy sound?
 
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