Twin Reverb

[Phil Lamprecht]

I purchased a 1972 Fender Twin Reverb Amp from a friend of mine and the Amp works fine but lacks in volume. I need to turn the master on 10 and the pre gain on 8 to get enough volume to practice with in my basement.The tubes are OK but the caps have never been replaced. It has a 15" JBL K 130 8 ohm speaker. This amp calls for a 4 ohm speaker and I am thinking about a Black Widow 1501-4 ohm speaker. I would appreciate any coments from anyone who has used this speaker in a Fender twin. Would this BW 4 ohm speaker increas the volume ?
Thank you Phil

[Ken Fox]

Phil, are both channels equally weak? If so I would be suspicious of the inverter tube (12AT7 near the power tubes). To test swap it with tube #3 from the right, as you face the back of the amp.

Also, are the power tubes newer JJ tubes? If so they run cold and would require the amp to be converted to an adjustable bias (it has bias balance if it is stock).

Many more things could cause low volume.

[Bill Yoder]

Phil,i have a "74" s.f.twin,with a 15"jbl,d130,it is an 8 ohm speaker,and i could take the glass out of the door if i cranked it open.plenty of volume.i play the average size clubs on about 5 volume.this is on steel or lead.

[Donny Hinson]

Would this BW 4 ohm speaker increase the volume ?

Very little. I suspect you have bad or wrong tubes in it. Often, people swap tubes in these old amps to get a certain "sound", and it just winds up degrading the sound (to anyone but them)!

It's an old amp; take it to a tube amp specialist ! It's worth a few hundred dollars to get the amp back to original specs. Plan on spending that amount about every 3-5 years to keep it sounding right.

P.S. If the tube amp guy doesn't know what a pedal steel is, say "thank you" and walk away. The LAST thing you want is to have it worked on by a rock-head or blues-freak.

[David Doggett]

Donny is right of course. But if there is no steel amp guy in your area, and you don't want to ship it to one, you can get a knowledgeable rock/blues/metal tube amp tech to set a tube amp up decent for steel. Just tell him to reverse his usual thinking and give you the maximum amount of clean headroom the amp is capable of. You want cold and clean. Most pedal steels have a high impedance pickup, and you don't want it to overdrive the preamp. And you want both the preamp and power amp to be cold and clean, with maybe some bloom and just a little grit (or maybe not) only at the very top of the volume range with both channel volume and master volume (if it has one) maxed. They can do it if they know what you want. And that old Twin will be a glorious steel amp.

[Marvin Born]

Someone as already suggested the phase inverted tube. Also check that the input preamp tube is correct. It should be a 7025 or 12AX7. If a 12AT7 is in that socket you will have low gain.

However, there could also be an open coupling cap somewhere, as this is a common problem.



Turn the reverb up and the master gain up and move the amp and let the reverb bang gently. If it is loud then the problem is ahead of that circuit in the pre amps. If it is weak then you have possible phase inverter or power tube problems.

There two output jacks. One marked internal speaker and the other external speaker. Make sure the speaker is plugged into the internal and not the external. Twins have a shorting lug in the internal speaker jack to protect the output transformer from no load.

That amp will be very loud on 5 with the master up near 8, so if you can stand to be in the same room with it on 10, its needs service.

[John Billings]

" if you can stand to be in the same room with it on 10," YOU'RE STONE DEAF!

[Doyle Weigold]

Well, I feel "Big John" and I was right on this one. Here is a good example of what happens when somebody that don't know what they are doing switches things around, then somebody else ends up with the headaches. I will always think Fender, Peavy, Webb, etc. know more about our equipment than we do. Doyle