Reverb Tone Improvement?

[Diablo]

I've got a BF Deluxe Reverb clone I built from a Mojo/Marsh kit. Everything is working fine to my ear, but I had another guitarist play it and he didn't like the sound of the reverb. To my ear, the reverb doesn't sound as good as the reverb on my Ampeg V4. So what are the things responsible for the tone of a reverb? Is there anything I can look at on the BFDR to improve the reverb tone, or is it the nature of the Fender design? The reverb tank on the BFDR is identical to the one in my Fender Hot Rod Deluxe. Could the reverb tank being "out of the vinyl bag" have a bad effect on the reverb tone? Does tube selection have a large impact on the reverb tone?

[Chuck H]

Is the tank made by the same MFG with the exact same part # on it? Unless you have a problem with distortion, not enough reverb volume, or your using an unusual reverb circuit, the reverb tone is in the transformer and the tank. Be sure of your tank ID. I used a Beldon tank once that was "a direct replacement part". What a mistake. Supposedly the "same tank". Not even close. I had to replace the reverb tranny in that amp too. I bought the parts from...Well, I won't say. But it was my first reverb amp build and I was taken for a ride. Crappy transformer and crappy tank = crappy tone.

Chuck

[Diablo]

I didn't check the numbers on the tanks, but it was the same manufacturer and they looked identical as far as I could tell. I took a good look at the "in" and "out" transducers and they looked the same too. I took a look at the driver tube (12AT7), and realized that I was using one of my "good used" tubes, that may not really be all that good. So, I stuck in a brand new tube. I think I convinced myself that it sounds better with the new tube.

The transformer is a Mojo, so I think they have that right....knock on wood. The reverb circuit design is all 1965 blackface Fender, and I made no changes.

[Chuck H]

With all else being equal, and it sounds like it is, I would try swapping the tank from the amp with the "good" reverb with that tank to see if it makes a difference. There are differences from tank to tank, new to old, steel type used in the springs, etc.

Other than that you should check to see that the voltages on the driver tube and recovery tube are the same or close to the amp with the good sounding reverb. Higher or lower voltages with change the bias requirements for those tubes. This makes the biggest difference on the driver tube, which is being used as a tiny power tube. But even with the bias set correct higher voltages could sound harsher and lower voltages could sound mushy or muddy.

Chuck

[Diablo]

Thanks Chuck for the ideas. I played around with the tank mounting and found out it makes a huge difference. The reverb sounded best with the tank removed from the cabinet. I tried putting the tank in the vinyl bag and inside the cabinet, and it sounded muffled like it lost most of the reverb - I think the vinyl must have been touching the springs. Removed the tank from the vinyl bag and used a "Fender-style" piece of cardboard under the tank and mounted it back in the cabinet and layed the vinyl on top of the tank. Now sounds very good. Every time I mounted the tank, I was using rubber grommets in the mounting holes to isolate the tank from cabinet vibration. I have the tank sitting up on 3/4 inch thick hardwood blocks that are glued to the floor of the cabinet.

[jrfrond]

Reverb tanks, being electromechanical, are subject to the same vibratory principles as anything else, and wrapping the tank in a bag can muffle the highs somewhat, as can incorrect mounting position, for which the retainer springs that hold the reverb spring frame are optimized.

There is wiggle room to play with reverb response within the return circuit, but sometimes just swapping out for another identical pan can mae the difference. Or, swapping a 9-spring pan for the common 4-spring version. As long as the other parameters remain constant, you can swap-in pans with longer or shorter decay, shorter or longer springs (provided you have the cabinet space), etc., and not hurt anything in the process.

[Mark Hammer]

The pleasingness of reverb tone can often be a function of the manner in which one pushes or tickles the springs. The, in turn, can be a function of the toneshaping in the drive stage, and the amount of drive. The original Fender reverb has a "dwell" control to adjust the drive, but a great many amps lack any such control.

ALL components, even when new, are built to fall within a certain tolerance, and it is not at all unreasonable to suggest that the actual component values used in amp X might be a poor match for the spring's qualities. Add to that the vicissitudes of time on things like caps (which doesn't apply in the current example), and the reverb tone can fall outside the perimeter of what the user seeks.

Using this schem as the point of reference ( http://www.thevintagesound.com/ffg/s...a763_schem.gif ), things to consider might include the 2k2 cathode resistor and 25uf cap on the 12AT7 driver stage, the 500pf series cap leading up to that stage, the 25uf cap on the 7025 recovery stage, and .003uf cap in series with the reverb level control. The series caps can be used to include, or attenuate, bass content in the reverb signal. The cathode caps can be used to adjust where the gain is applied, with smaller values appying the gain less to the bass end.

While not the same type of amp at all, I had a solid-state late 60's Gibson amp some years back that had an atrocious reverb sound. I identified the series cap leading up to the driver stage and replaced it with a newer component of smaller value. The result was reverb bliss. It went from sounding like a parking garage with stainless steel walls to yielding a nice ambient wash.

[Enzo]

I would have to say that expecting the reverb circuit in a Fender Deluxe Reverb - clone or for real - to sound the same as the one in an AMpeg V4 is not very likely.

The Ampeg drives the pan through a cap off the plate of a triode and into a high impedance pan. The Fender drives a low impedance pan with a transformer. The recovery circuits are not the same either. Of course they will sound different. ANd not only that, but the sound being reverberated comes from the rest of the amp, and those are not very similar either.


My initial reaction though was that it sounded OK to you at first, what happened?

[Diablo]

I would have to say that expecting the reverb circuit in a Fender Deluxe Reverb - clone or for real - to sound the same as the one in an AMpeg V4 is not very likely.

The Ampeg drives the pan through a cap off the plate of a triode and into a high impedance pan. The Fender drives a low impedance pan with a transformer. The recovery circuits are not the same either. Of course they will sound different. ANd not only that, but the sound being reverberated comes from the rest of the amp, and those are not very similar either.


My initial reaction though was that it sounded OK to you at first, what happened?

It sounded OK at first to me, but then I had someone else listen to it. His ears said it didn't sound typical of a Fender. He was hearing some sort of "delay or echo sound" that shouldn't have been there. After I changed out the driver tube and remounted the pan on cardboard, Mr. golden-ears said it now sounds like a Fender. I still don't think it sounds as good as my V4 reverb, but you've explained nicely why that is, and there's probably not a lot I can do about that.

[Diablo]

And while I have all the reverb experts present, I'm thinking of building a stand alone reverb 5G15 kit from Weber. I see where the kit sticks to the Fender schematic except for the driver tube. The kit uses a 6V6. Should I use a 6K6 like the Fender? I assume this is a reliable and tone-full reverb unit design? The reverb would be for my tweed amps.