Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: gtrplayr1976 on January 11, 2017, 10:32:38 am
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I'm looking to convert a Blues Jr for a friend. He would like it to have a cleaner sound for pedals. He has the chassis in a custom 2x12 cab ,but the original OT has the wrong impedance. I replaced it with a TO22 from Allen amps ,and did some mods that Lyle Caldwell posted on Tube amp builders page on FB that should have cleaned it up. I think it did some ,but has a nasty overtone distortion that I can't find. I was thinking getting rid of the circuit boards ,and rebuilding on Dougs turret boards. Any thoughts on this ?
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I installed Doug's board for a friend and it is a much easier mod platform. As you found out the PCBs are fragile and ribbon cable is brittle. Doug re-engineered the layout with adjustable bias as well. The factory board had bias set real hot so there was very little headroom. When you get your build working well, then do your mods. EL-84M Sovteks will increase clean headroom quite a bit and are ideal with pedals. Doug's circuit board replaces the crappy reverb with a resonance circuit. This helps to get rid of the "boxy" sound. The Fender speaker is s fine--no need to replace it. Love this little amp. Jim
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I installed Doug's board for a friend and it is a much easier mod platform. As you found out the PCBs are fragile and ribbon cable is brittle. Doug re-engineered the layout with adjustable bias as well. The factory board had bias set real hot so there was very little headroom. When you get your build working well, then do your mods. EL-84M Sovteks will increase clean headroom quite a bit and are ideal with pedals. Doug's circuit board replaces the crappy reverb with a resonance circuit. This helps to get rid of the "boxy" sound. The Fender speaker is s fine--no need to replace it. Love this little amp. Jim
Thanks Jim. I was also told the bigger OT will help with headroom. I'll mention the tubes to the owner also. He bought a custom 2x12 combo cabinet. It has a Hellatone ,and an Alnico Blue. I had already added a bias pot. The bias is set around 60%?
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David Allen http://allenamps.com/parts.php#transformers (http://allenamps.com/parts.php#transformers) sells upgraded OTs for Blues JR (TO20 and TOB) for about $64 to $69. He will also crimp the connectors on for you if you call him when you order. Have used a couple of these in Blues Jr. mods and have sounded great. Seemed to increase the headroom a bit also.
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David Allen http://allenamps.com/parts.php#transformers (http://allenamps.com/parts.php#transformers) sells upgraded OTs for Blues JR (TO20 and TOB) for about $64 to $69. He will also crimp the connectors on for you if you call him when you order. Have used a couple of these in Blues Jr. mods and have sounded great. Seemed to increase the headroom a bit also.
Thanks. I have a TO22 I got from Allen. :)
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Who made that Blues Jr. custom 2X12 cab for you? Jim
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Who made that Blues Jr. custom 2X12 cab for you? Jim
I'll ask him Jim. I think he got it off EBay unfinished.
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Who made that Blues Jr. custom 2X12 cab for you? Jim
This is where he got it ,but I think he first saw them on EBay.
http://carlscustomguitars.com/ (http://carlscustomguitars.com/)
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Mojotone has a 1 x12 and a 2 x 10 cabinet that fits the Fender chassis. They are very nice.