SFDR Just Not "Right" - Fix it?

[jpastras]

I've got two SFDRs. One, a 1972 w/ Blackface conversion and 12F150, sounds remarkably good. I would never part with it.

The other, a 1973 w/ a 12F150 and Blackface conversion by the same tech, just isn't "right". It lacks the bass of the 72, and it's nowhere near as loud. "3" on the volume of the 72 is louder and fuller than "7" on the '73.

It had a problem in the past with intermittent crackle and approximate 50% volume loss, but that seems to have been rectified after the blackface conversion (must've changed the right part).

I've checked both channels.

I've tried the weak one with the strong one's speaker.

To eliminate pot taper as a potential issue, I've rolled off all bass, turned treble all the way up, and cranked the volume.

The '72 has more bass and volume. It sounds like a good deluxe reverb. The '73 sounds anemically weak - not nearly as good as a DRRI.

Here's my question: should I bother spending the money to attempt to get the "73 sounding right, or do y'all think, from your technical experience, that some of these amps "got it" and some don't?

Will this be too costly a goose-chase? If I have to spend $200, I'd rather just sell it.

[Blue Strat]

Have you swapped all tubes or asked the amp tech (since he's seen at least one of your amps)?

[jpastras]

I've swapped every tube.Also, it's important to mention this: I bought it. It sounded pretty good, although somewhat "silverfacey"(a little cold/stiff). It started with the intermittent crackle and volume loss. I took it in to have it repaired, but the cause was so hard to find, I just decided to do a total cap job/blackfacing (buckshot approach to problem resolution). It came out sounding pretty good, until I compared it to the other. I never really compared it to the other before, so I really can't say for sure if it was always comparatively deficient.

[jay42]

Check to see that they both have the original power and output transformers.

[tlpruitt]

Could be component drift in either amp. I have been amazed at how far off spec some of the old carbon comp resistors are in some of my old amps. Just the other day I had a 1.5k cathode resistor that measured almost 2.4k and a 100k plate load resistor that was up to around 180k.

Sometimes when the components drift the amp can change for the better but sometimes not. Anyway, if the transformers are correct and you tried swapping speakers and tubes the next step may be to start checking component values.

-Tim

[soldersucker]

I've got three and they are all slightly different +- 10% with 100% being the "best" one sounds like you need a better teck rather than a different amp.The fact that they are so consistantis shown by thier continued disireability after all these years.He's missing something most likely.btw my favourite is lower left:BEER
http://i163.photobucket.com/albums/t289/stn23/2008_0309camselldelx0242.jpg

[Blue Strat]

Sounds like the problem was never fixed and should be revisited.

If you really want a 2nd DR, let your tech take a crack at it and set a time/money limit. You could get another one and have to invest as much or more making it "right".

[jpastras]

Thanks for the input, fellas. Like two of y'all, I'm a sfdr afficianado. I have two, and have always been on the lookout for a third really good one for a reasonable price.The tech is definitely very good. We both wanted save bench time by just recapping and hoping for the best. It was always a possibility that we'd have to revisit the issue. I was just concerned that my expectations of consistency between amps might be too high.Thanks again for the input.