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Hello all! First post, sorry if this is in the wrong section, but Theory seemed to be the best place for a schematic discussion.
Okay so I have this Blackheart BH5H I'm not using, because it is too clean and the cleans aren't anything special. Certainly not on par with my 78 Tweedified Fender Champ. I thought about doing a few mods to increase the gain, but then I thought, why not do something completely original with the amp? So here's what I came up with, and I was hoping for some input.
Concept: Convert a Blackheart BH5H to a real Vox AC4 + an extra gain stage
Execution: Replace PCB with Eyelet board, PCB Sockets with Normal Sockets
Features:
Original AC4 Schematic:
My Modified Schematic:
I apologize for the lack of tube symbols, the program I'm using doesn't have tube libraries. Here are the relevant tube pinouts for reference:
To Do:
Concerns:
What does everyone think?
To answer the questions I anticipate you'll have:
Why not buy the new AC4TV? Well, first of all, the reissue uses a 12ax7 which isn't true to the original. Second, I already HAVE the black heart, and nobody local seems to want to buy it. Third, I think I can do this mod for ~$80-120 including new tubes.
Why not do the Bitmo mods? I'd only use it on the vox section, which doesn't really nail the vox sound anyway, and doesn't do enough to increase gain IMO. Basically the amp will be a chassis, cab, and Transformer donor.
Okay so I have this Blackheart BH5H I'm not using, because it is too clean and the cleans aren't anything special. Certainly not on par with my 78 Tweedified Fender Champ. I thought about doing a few mods to increase the gain, but then I thought, why not do something completely original with the amp? So here's what I came up with, and I was hoping for some input.
Concept: Convert a Blackheart BH5H to a real Vox AC4 + an extra gain stage
Execution: Replace PCB with Eyelet board, PCB Sockets with Normal Sockets
Features:
- 2 EF86 Gain Stages
- 1xEL84 Power Tube
- 3/5 Watt switch retained from Blackheart
- Diode Rectifier with Standby Switch
- 2 Gain Controls, Tone Control
Original AC4 Schematic:
My Modified Schematic:
I apologize for the lack of tube symbols, the program I'm using doesn't have tube libraries. Here are the relevant tube pinouts for reference:
To Do:
- Implement Pentode-Triode Switch into Schematic
- Investigate output of Blackheart PT
- Design Eyelet Board Layout
Concerns:
- Could someone verify my schematic for sanity/viability?
- Will the PT have enough juice to power the heaters on 3 tubes?
- The PT should be enough to power 3 tubes, since the EF86’s (other than the heaters) have the same number of plates and cathodes as a single 12ax7.
- What changes need to be made to the filter caps/power resistors to ensure proper voltage to the two EF86’s?
What does everyone think?
To answer the questions I anticipate you'll have:
Why not buy the new AC4TV? Well, first of all, the reissue uses a 12ax7 which isn't true to the original. Second, I already HAVE the black heart, and nobody local seems to want to buy it. Third, I think I can do this mod for ~$80-120 including new tubes.
Why not do the Bitmo mods? I'd only use it on the vox section, which doesn't really nail the vox sound anyway, and doesn't do enough to increase gain IMO. Basically the amp will be a chassis, cab, and Transformer donor.
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