December 18, 1998

Here's How to Fatten a Fender Deluxe for Harp

This discussion originally appeared in a slightly different form in a message posted to the Harp-L List in August 1998. Don's advice is aimed, in this case, at mods for a blackface 1965 Fender Deluxe amplifier.


The non-reverb Fender Deluxes and Princetons differ from their reverb cousins in having one less gain stage, with the result that they are a bit thinner sounding than the reverbed versions of the same amps. (This is the main reason why the Princeton and Deluxe Reverbs are much more highly prized than the non-reverb models.)

Here’s a few tips on how to fatten the sound on non-reverb blackface Fenders.

Bridge the two channels
Tube swaps
Speaker Swap
Microphone

Bridge the two channels


1) Plug into the normal channel with your mic cord.
2) Use a short shielded patch or guitar cord and patch from the other input of the normal channel into the input of the vibrato channel.
3) Adjust the tone and volume controls of the normal channel (with the volume turned down on the vibrato channel) until you get the amp sounding the way you like.
4) Remember where you have the volume set on the normal channel, then
turn it all the way down.
5) Now set the tone and volume controls on the vibrato channel and get that sounding good.
6) Bring the volume control back up on the normal channel.

That’s the basic procedure. You can also fiddle with all the knobs, if you like, to find different combos that sound good. I’d start by setting the bass controls all the way up and treble all the way down, then slowly bring up the treble control to where you like it. On the Deluxe, the vibrato channel is voiced a bit "brighter" than on the normal channel, so you'll find that keeping the treble and volume down a bit on that channel will help cut feedback.

Please note that channel bridging will have the opposite effect if it is done on reverb amps, due to the two channels being out of phase to one another.

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Tube swaps

1) Try 12AY7 tubes in the first gain stage of each channel. Looking at the back of the amp, the tube all the way to the right is the normal channel tube and the tube to the left of it is the vibrato channel tube. Replacing these two with 12AY7s will cut the gain and warm up the response of the amp a bit, helping to reduce feedback.
2) Power tubes: try US manufactured NOS 6V6 tubes. When it comes to 6V6 tubes there really aren’t any currently manufactured that are completely satisfactory. My Deluxe used to eat Sovtek 6V6's on a weekly basis. Only NOS stuff can take the high plate voltages that are generated in Deluxes.
3) Rectifier tube: I'm currently using a 5Y3 rectifier tube in my Deluxe. This swap should be done under the advice of a knowledgeable amp tech. The current draw of a 5Y3 is different than that of the stock GZ34, and you may risk overheating the power transformer of your amp. Have a tech try it and monitor the amp to see if there is a problem. I have not had any problems with mine when using a 5Y3. The 5Y3 will lower the output of the amp a bit, but the amp will compress more and sound "crunchier." A bias adjust would also be a good idea. If the power tubes are biased cold, it will sound thinner.

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Speaker Swap

What kind of speaker do you have in your Deluxe? Most likely it's an Oxford. I would look into one of the Jensen Alnico replicas. I have a Mojo MP12R in my Deluxe, and it’s really improved the sound. A more expensive choice is the Weber VST P12Q. The Mojo has a more midrangy sound and a bit more breakup; the Weber P12Q has better bass response. An even hipper speaker mod is removing the stock baffleboard and making a new one with a pair of 8 inch speakers. I haven't done it, but a pair of Weber P8Q's in a Deluxe sounds to me like a killer harp rig. You could use either a pair of 16 ohm speakers wired in parallel or a pair of 4 ohm speakers wired in series. Finding a pair of 4 ohm, 8" Champ replacement speakers would probably be easiest. If you do try that mod, remember to save the original baffleboard and speaker assembly! A ‘65 Deluxe is a collector’s piece, and you wouldn't want to ruin the value of the amp.

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Microphone

What kind of mic are you using? I find that Shure Green Bullets tend to sound better with blackface Fenders. I like Astatic JT30s for tweed amps. Sometimes finding the right mic can make an amp sound a whole lot better.

Richard Hunter adds: When you go to a store to check out the mics, bring your amp! A mic that sounds great with one amp may sound very different with another amp of the same make and model.

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