The Steel Guitar Forum

I just acquired a 67 blackface super reverb amp. The height of the cabinet has been cut down about 4 inches and a 15" JBL D130 installed. The D130 is 16 ohms and the schematic for the 4 10" spkrs is 2 ohms. My questions are as follows:
1. Due to the impedance mismatch, what kind
of sound and volume would you expect?
2. Staying with a 15" spkr, what kind of
spkr would you suggest to get a better
impedance match?
3. I know this amp has been played by a lead
guitarist for 30 yrs just as it is.
Would you expect any damage to the amp?
4. Who can rework and rebias this amp?

Thanks
Gene Piper

Try calling or writing Gerald Weber at Kendrick Amplifiers for starters. I don't have their number on me but they're in Pflugerville, Texas. I believe their area code is 510.

510 is my area code here in California.

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Carter D10 8p/10k
www.sinkler.com

Gene, I'm not a great electronics man but I've used old Fender amps as long as just about anybody. That 16 ohm load is not going to hurt anything, it's only going to reduce the power. Are you sure it's 16 ohm? something doesn't jive. JBL numbered their 16 ohm speakers different. The 12 inch 16 ohm is a 131. That super reverb sure sounded good with the 4x10s for guitar, but wasn't very good for steel.
Jim

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Jim,
The speaker nameplate reads 15" JBL D130 Impedance 16 ohms. Any opinions on what kind of 15" speaker to use? Would a 4 ohm speaker improve the output power? Could I use 2 15" 4 ohm speakers in parallel to reduce the total impedance to 2 ohms? Thanks.
Gene

Tube type amps aren't that picky about the load, but you can overdo it. I'm not sure that the 4X10s that came in the amp were wired in parallel. I'd try to keep the load at about 8 ohms. If you've got another 16 ohm JBL, there's your answer.Put it in parallel with the one you've got. If you get the load too low the output tubes will run too hot, making it allmost like the output transformer was shorted. Anyway if the amp sounds good at 16 ohms, leave it that way. IIABDFI {if it ain't broke}
Jim

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Super Reverbs ARE wired for 2 ohms (assuming a stock output transformer). The 16 ohm speaker load is a pretty gross mismatch which is cutting your already marginal (for steel) power by at least half. It would be fine around the house or maybe in the studio, but you will never get your volume over other electric instruments and/or drums that way. If you do want to use the amp on a bandstand, replace the speaker with a 4-ohm Peavey Black Widow 1501 or JBL (D, K, or E)130. Another alternative is to replace the output transformer with an aftermarket multitap (multiple output impedance) transformer to match the 16-ohm JBL you have. Along with that, I'd also have a tech install a solid-state rectifier (if it doesn't already have one) and re-bias the amp to increase its headroom.

Gene, the number for Kendrick Amps is (512) 990-5486 or e-mail at:

kendrick@inetport.com

Good luck!