Re: [Harp-L] 5C3 tweed deluxe mods

Wire the volume controls as regular voltage dividers with 270K mixer resistors off the wipers (See 5F6A bassman), tone pot connects to the junction of the 270Ks. Leave out the 500pf bright cap off the tone pot.

Split the cathodes on V1 and wire one of the channels as "cathode biased", installing a 1.8K to 2.2K cathode resistor on that channel's cathode, bypass the input cap for that channel (I'd go 0.022uf rather than 0.1uf) with a very large value resistor, I use 33meg.

The 6N9P tubes that come with the Weber kit can be subbed for 6SN7 (low gain), or 6SL7 (medium gain). However, if it were me, I would use a 5E3 chassis (9pin sockets in the preamp) and build around 12A#7 tubes because this gives you more options tonally.

I'd suggest a 10" baffle board cut out, rather than a 12", perhaps an Eminence 102, maybe an Alpha (might be on the dark side). Money no object try a Kendrick Blackframe. Those with more experience with Weber speakers will no doubt have their preferences.

Amps don't really know, or care what kind of mic you use as long as it has a big enough signal to drive the amp & not so big as to leave you with no sweep on the vol pot...that said, "grid-leak biased" inputs (like the 5C3 has stock) seem to prefer crystal & ceramic mics over CM/CR/Dynamics. But if you have one channel grid leak and one channel cathode biased, you are not limited to one type of input. I would not buld the amp with 2 grid leak biased channels.

Also experiment with cathode bypass caps, both in the preamp & power amp, sometimes taking them off increases headroom, sometimes the amp might go muddy. Try one at a time & see how you go. Which brings me on to an idea for a bit more flexibility/different voices - if the 250K & 25K resistors in the PI are grounded out (grounding the grid of the 'out of phase' 6V6, nearest the rectifier) then the amp is now running single-ended for 1/2 power/dirtier tone. However, if you do this same trick, but leave the 6V6 cathode resistor unbypassed, the amp is now 'self-split, push-pull' which sounds different to either stock, or single-ended. Both can be achieved with simple switches, perhaps even an on/off/on DPDT.
Feel free to mail me if you have questions/need clarification.
Regards, Mark.

From: Lare Sattler <lmsattler@xxxxxxx>
To: harp-l@xxxxxxxxxx 
Sent: Monday, 12 March 2012, 3:58
Subject: [Harp-L] 5C3 tweed deluxe mods

I'm about to start building a 5C3 tweed deluxe kit from Weber and am interested in harp-specific mods I might do while building, rather than afterwards, since the amp will primarily be for bluesharp. Any and all input will be greatly appreciated.
Lare Sattler    The Little Chicago Band     Canton Ohio

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