Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: jordan86 on June 18, 2022, 02:06:05 pm
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I had to set this aside for a few weeks. I'm to the point of building out the preamp in my Hammond power amp conversion. Schematic at this link if interested. Its a fairly basic parallel 12ax7 stage 1 > tonestack > LTPI .
https://el34world.com/Forum/index.php?topic=28902.msg318739#msg318739
I've never flown components just point to point like this. But logic tells me the closer I can get my terminal strip to the 9 pin sockets the better. This means I need to put my B+ filter caps somewhere else. Would love feedback on whether this is a good layout. I hand drew my own garbage looking layout to make sure the terminal strips were placed right. I'll post it if you think it helps.
FWIW The red and white wires just above the terminal strip are B+ lines, going to the oil condenser (cap can). The black is the ground for the power amp. Orange will be the wire I run to the first 22uf filter cap, then run wires back to the marked B+ mounts on the terminal strip. I will ground the preamp filter caps and all the cathode/ground connections in one spot by the input jack. So a single ground point for all added preamp components.
Any red flags? Note the terminal strip will be properly stood up and screwed in, I just could get it to cooperate for the photo :icon_biggrin:
Note 1: The keen eyes will notice I do have turret strip that I bought just in case. Don't think I need it though, unless this layout is just way off. If that's a better choice though, I'm open to it.
Note 2: I don't think I need to use the outside common lugs of the 8 terminal strip. I considered using them though for cathodes/ground. I would probably lift them off the chassis with nylon washers under the strip just so I can pick my specific grounding points, and if somehow they did touch, it would just be a potential ground loop, not a short of B+ or grid. Is that crazy stupid? I guess they could crack/break which potentially could cause massive problems to the amp and my health :dontknow:
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Correction. Where I put V2 Ground, that should read V2 Tail. That will be the tail resistor on the LTP that I connect to the preamp ground chain.
I guess I could put in all the other components, if that would be more helpful. I’m just not real clear on if my scheme will be inherently noisy with the point to point layout. It seems I have audio/grid signals, and B+, and grounds all running amok.
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Just be neat. You'll be fine.
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Hi Jordan
If you do decide on the Pax 2x18 tag strip, they also make a neat project mod. (see my attachment).
I find these little tag boards very useful :laugh: In your case keep as far away from mains Tx as possible.
Kind Regards
Mirek