I have an old ('72 - 74 era) V4 (not a V4B). I got it early last Spring. I promptly took it to a local tech who is really good with vintage tube stuff, but mostly works on guitar amps and has not had that much experience with Ampeg heads in general. Anyway, he serviced the head, replaced some blown caps, etc., and pronounced it good to go. It appears to have all original tubes, or at least American made tubes from that time period. When he gave it back to me, he did comment that he particularly liked it because it didn't have the shrill scream (or words to that effect) that a lot of high powered guitar amps have. While he had it, I did have him modify Channel 2 to V4B specs. That just involves replacing 2 caps, so it was cheap and easy. Since them, I have also acquired a '72 Traynor YBA-3 Custom Special head, which is an all-tube bass amp only rated for a little bit more power (135 vs 100 in the Ampeg). Comparing them, I noticed, and a guitarist friend commented, that the Traynor sounded warmer and we both like it better. Also, it seems like the Traynor would play a fair bit louder before starting to distort. The Traynor is rated for a little more power, but it seems like they should be a lot closer in output level (at the point of distortion onset) than they are. And, with the Ampeg, I have had it where the Midrange control was turned up to the 3:00 position, the Bass rolled off to 9:00, and the Treble boosted slightly, just to get a sound I thought was okay. But, it still seemed to be lacking some midrange cut (cut, as in presence in the mix). So, yesterday, I took it over to my new amp tech's place. He has a V4B from the same era hooked up to an Ampeg 810 cab. We tried playing both amps, back to back, through the same cab, using the same P bass. Using Channel 2 on my V4 should have resulted in identical sound (in theory, of course). In reality, the bottom notes sounded about the same. But, if I played up around frets 10 - 12 on the G string, on his V4B, it sounded good. And on my V4, it sounded like I was playing with several wet blankets thrown over the cab. I left the amp with the tech (a new guy - not the one that worked on it 6 months ago) to check out. But, I would really like to know what some of you experts here think might be the problem. Thanks for any help!