Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Eulipian on May 14, 2019, 04:58:40 pm
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I bought a Bell Sound 2215 circa 1959, with the idea of converting it into a Fender circuit (Tweed Deluxe or Vibrolux or Blackface/Brown Princeton). Signal path is 1 - 12ax7 --> tone stack --> 1 - 6cq8 ---> 2 - 6v6 The 6cq8 tetrode is the second amplification stage and the triode serves as the phase inverter. The 6cq8 is a mystery to me.It is medium-mu triode-sharp cutoff tetrode.I have read that the beam tetrode can be operated as a triode by connecting its screen grid to its plate. I could simply replace it in its current position with a 12ax7 with appropriate circuit mods. I wonder if there's any advantage to trying to work with it where it is in the circuit, either as is or operating both halves as triodes? Please delete or ignore not appropriate, but feel free to say "that's not a good idea b/c ......."
Thanks,
Carl Varady
Honolulu HI
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Do you intend to use the original Bell chassis and modify it to be guitar friendly? If so, I have a suggestion...
Leave everything (including the power supply) to the right of the volume control exactly as it is. Rewire the phono preamp (12AX7) to your favorite Fender preamp. May I suggest any AB763 preamp?) Play it for a while and evaluate. I think you will be pleased and will only have changed a little bit of the Bell.
That power amp structure looks very similar to all the Sunn power amps. Compare your Bell power amp to this Sunn…
https://el34world.com/charts/Schematics/files/Sunn/Sunn_200s_only_schematic.pdf
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Thanks Steve. I'll look at the Sunn amp. I'm fundamentally lazy and not very skilled so leaving most of it alone sounds good to me.
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Hey, do you know Tua?
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No. He lives with his family in AL, but his roots are in the 5-O. We'll see if he's got the smarts to make the grade in the NFL. Also, he's not big enough to scramble like he does and not pay a price with DE and LB looking for free lunch.
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Agree: this amp was designed to be musical, but not set up for guitar.
Here is a *simple* hack to play guitar on it. Two snips, one jumper. (The iPod stuff on the bottom is a frill for later.)
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Very cool. I'm going to try Steve's suggestion with some Robinette mixed in and will post some progress notes--hopefully not involving sirens and flashing lights.
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Aloha Carl!
Funny when we visited the sports news was all about the St. Louis Cardinals? It was like being at home! We couldn’t figure it out.... Ah yes, Kolten Wong (Hilo), our awesome second baseman! That explains it! Even more coincidental, our guide at Kualoa Ranch played lacrosse with my daughters fiancé at college here in St Louis. Small world after all!
Jim
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It's a very small world Ritchie, and in Hawai`i, you're always going to see someone you know wherever you go.
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Do you intend to use the original Bell chassis and modify it to be guitar friendly? If so, I have a suggestion...
Leave everything (including the power supply) to the right of the volume control exactly as it is. Rewire the phono preamp (12AX7) to your favorite Fender preamp. May I suggest any AB763 preamp?) Play it for a while and evaluate. I think you will be pleased and will only have changed a little bit of the Bell.
That power amp structure looks very similar to all the Sunn power amps. Compare your Bell power amp to this Sunn…
https://el34world.com/charts/Schematics/files/Sunn/Sunn_200s_only_schematic.pdf (https://el34world.com/charts/Schematics/files/Sunn/Sunn_200s_only_schematic.pdf)
Steve, I'm looking at your 2007 rev. of the Deluxe Lite - BF and would like to use it for the initial pre-amp and tone stack of this project. But I see there are significant differences in the power supply--filter choke for example--and wonder if that will affect incorporating the pre-amp and tone stack you've designed into my 2215 circuit?
Thanks and "talofa" to Tua.