BF/SF Bassman mods with V2

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jaysg
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BF/SF Bassman mods with V2

Post by jaysg »

Any standard gain mods using the unused half of V2? I'm trying not to reinvent the wheel, but I haven't come across any yet. Customer's amp already has a mid pot and a presence pot. I'm thinking a negative feedback pot or lift might be simpler.
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billyz
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Re: BF/SF Bassman mods with V2

Post by billyz »

Train wreck third stage. See my website for schematic, longhorn mod .
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jaysg
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Re: BF/SF Bassman mods with V2

Post by jaysg »

billyz wrote:Train wreck third stage. See my website for schematic, longhorn mod .
i see "Bassman head mod" but not anything about Longhorn. I'll look at the Express schematic...been a while. I built a Liverpool and didn't like it thAt much.
Teleguy61
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Re: BF/SF Bassman mods with V2

Post by Teleguy61 »

The bassman head mod is the longhorn mod.
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billyz
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Re: BF/SF Bassman mods with V2

Post by billyz »

Oh, yeah. Forgot what I did. That's normal. Anyway, I have done quite a few of these, even repeats for clients. The only issue is, its loud ! So get an attenuator.
I've tried all sorts of MV's and don't like any of them for this style circuit. The Clean channel becomes a stock Blackface normal ch. The Deep switch has lots of options, even leaving it (which is just a bass cut), I never understood fenders labeling of this switch. If a VVR can handle the heat , that would be best. Scale the entire amp though.
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jaysg
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Re: BF/SF Bassman mods with V2

Post by jaysg »

BillyZ, the tubes aren't marked. Did you rewire V1 as the parallel stage?
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billyz
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Re: BF/SF Bassman mods with V2

Post by billyz »

Yes, parallel v1a/b. See the 50k plate load. I often use two 100k's. Lowers the output impedance and reduces noise a little. Just a little more hair too.
ianm73
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Re: BF/SF Bassman mods with V2

Post by ianm73 »

A little late to the party but was wondering about the phase shift of the parallel triodes V1a & b. I've got it wired up and the cleans are much cleaner by eliminating that 3rd triode, but the bass channel is out of phase. any thoughts?

thx.
ianm73
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Re: BF/SF Bassman mods with V2

Post by ianm73 »

I have a pre PI MV installed and the sound was actually OK at paint peeling volume...is this typical of the circuit?
Mant
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Re: BF/SF Bassman mods with V2

Post by Mant »

I used the open half to make do a cathode follower into the tone section.
Kinda 6G6 topology.
Unbypassed cathode of v3 and made it variable Kept 1.5k and added 25k pot.
Marshall was 10k solodano is 39k.
Cool sounds
You sound more Like you do now then you did just a little while ago.
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