Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Colas LeGrippa on August 19, 2019, 02:46:30 pm
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Hola amigos !
Last year I have modded an old radio for guitar using the phono input if my memory is good.
All i had done is swapping the input jack accordingly. My friend who is the owner of that crap is. complaining about lit s low overall volume. I don't know much about this model of radio (nor other ones hey hey ) but I am sure something can be done to increase the volume.
Thanx
Colas
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6SQ7 driving a single 6K6. Ain't gonna be very loud. It is what it is. Put a mic in front of it. :icon_biggrin:
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Or a 100watter connected to the ot.....
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Sluckey, what about swaping the 6k6 by an el34 ? Modofyong the circuirt accordingly that s for sure
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I meant "modifying"....sorry my tel is f....small and my glasses are in the garage....
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Changing the power tube makes no difference. You need gain. Put a booster pedal in front.
Even then, it is "less than a Champ". Maybe he really wants something more than an antique radio?
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Is there not enough gain to drive the 6K6 to full output? It was a radio; there must have been other tubes in it that can be repurposed for more gain.
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I would throw this piece of.....radio in the garbage. He likes the vintage tone of it.
He is a doctor in literature....he doesn t even know how to play house of the rising sun....
Ok he s a friend of mine I wont blast him here my wife may read my post over my shoulder and tell her girlfriend I am a bullshitter....
Thanks folk for smart advices as usual.
Colas
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I don t know Tony Bones. All I know is 12a.....7 and el34. I will try to find mods for guitar on the net. Last time I checked didnt find nothing
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For a modest SE EL34 you want a PS that will do >300vdc @ ~150mA + on the 34, an OT ~ 3.5k
Need an RMS drive signal ~ 8-10Vac (pretty hard to get from 1 12…7) no TS will help.
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Od pedal and bigger speaker helped a lot thanks !
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You can rewire it for a 6SL7 ir a 2C52 in place of the 6SQ7 that way you have 2 gain stages or replace the 6SQ7 with a 6SJ7 pentode by copying an early champ 1st stage. Other wise you could put a 6v6 in there the current draw is similar and the give you maybe 20%more volume in my experience over a 6k6. If there's a way to get the spec for the power transformer you could see if it can handle a 6L6. Since you are not using any of the other tubes beside the audio ones take out the rf,and if tubes and this will help a little to expand the watt/volts of the transformer.in my experience in the older days they sometimes over engineered radios but it wasn't always the case and as it got into the 50s and 60s they were definitely cutting corners so the older the radio the better chance you ha e if it being over engineered with regard to power transformer capacity. Since it single ended it might be ok. If it was push pull Maybe not
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> rewire it for a 6SL7 ir a 2C52 in place of the 6SQ7 ... replace the 6SQ7 with a 6SJ7
Yeah but I doubt Colas wants to go that far:
"I would throw this piece of.....radio in the garbage. He likes the vintage tone of it. He is a doctor in literature....he doesn t even know how to play house of the rising sun...."
The least-hassle fix is a booster pedal. The more-work fix is to strip the IF tube of all but heaters, wire it as triode before the volume control-- not a huge gain but enough for guitar to push the power tube to max. At the other extreme we could chisel the chassis bare, new iron, 5F6 Bassman (followed by new speaker!!), BUT "He likes the vintage tone". If I like my 1967 Cougar, don't rebuild it into a Chrysler 300 Hemi.