Saturday, October 15, 2011

Harp Amp Project - Fender Bassman RI


Today I bought a rather well used early Fender Bassman Reissue amp, which dates from April of 1991 by the production code. The amp has a tube rectifier (not solid state) and the original alnico blue speakers, which are re-branded Eminence 1028s. I paid $500.

The amp was playable when I got it home, but the tone was shrill and it had intermittent problems. A couple of the tubes were bad, so I replaced the 5881 power tubes with some Tung Sol new production tubes I had on hand, and swapped in a 5AR4 Sovtek rectifier. For now the preamp tube is an NOS JAN Philips 5751 and the 2nd gain stage tube is a vintage GE 12AY7. The phase inverter is a 12AX7.

I swapped out 3 of the 4 speakers: On top there is a pair of Weber 10A125-O speakers, and on the bottom is an Eminence Lil' Buddy ceramic speaker and one of the original alnico blues.

So far it sounds pretty good. I'm sure it will sound a heck of a lot better after I get it biased and tuned by Bruce Collins at Mission Amps in Denver. Since I tinker with amps a lot I had all the parts I used today laying around in my amp room, so there has been zero added expense on the amp so far. I was looking around for an old Bassman RI, partly because I recognized I already had a lot of the components I would need for the project.

I'll put up sound samples later. I plan to take the amp to a blues jam tomorrow night to see how it performs as it is now. I'll keep you posted.




UPDATES:

http://bluesharpamps.blogspot.com/2011/10/bassman-ri-harp-amp-project-update.html

http://bluesharpamps.blogspot.com/2011/11/bassman-tweed-rehab.html

http://bluesharpamps.blogspot.com/2012/05/playing-my-bassman-amp.html
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4 comments:

  1. tmfharpkingOctober 20, 2011 at 10:23 AM

    There is no bias pot on this amp-the bias is set from the factory. The LTD has adjustable bias.
    Those ARE eminence blue frame alnico speakers-they are not re-branded,and they are the best of the current speakers.

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  2. Rick DavisOctober 20, 2011 at 11:04 AM

    Adding a bias pot to this circuit is easy.

    Yes, I am aware they are Eminence speakers. However, they bear no Eminence branding, not even a rim code. They are OEM for Fender.

    ReplyDelete
  3. tmfharpkingOctober 20, 2011 at 4:02 PM

    The best upgrades I made to mine when I owned it,was to put a Hoffman Kit in it-point-to-point wiring,vintage NOS tubes,and a finger -jointed pine cab to replace the plywood.

    ReplyDelete
  4. Rick DavisOctober 21, 2011 at 10:19 AM

    Do you have a video example of that amp?

    ReplyDelete