Count Bassie

Yep, this set goes back to the Mk V, and there are some significant differences between it and the Mk IV. Thank you for sending those though! I've downloaded them and I'll bet there will be another old tank added to the pile within the year, 😁. 👍

I'm all about it, I'll look them up. Thanks again Matt! (Sent him a mssg... Ashdown, Peavey and BAS next...)

Apparently there are some meaningful differences. The MK IV diverged from the MK V in the preamp I think, that's the report. He's been, as I say, reverse-engineering his way through some of it. I'm hoping to eventually get to someone who was part of the design team from that period.

Alright then... My tech has the amp opened up again, as the volume doesn't seem to be what it should. Apparently the signal travels from several points between the power section and the preamp, and the preamp is quite complicated. At this point the gain on the preamp has to be all the way up to get even moderately significant volume. The model I have, the MK IV, doesn't have a schematic or any kind of plan available, so I'm starting to dig in and see if I can talk to any of the people who had a hand in the early designs. So far my tech has been essentially reverse-engineering his way through the amp, and it's exhaustive. I'd be very interested in hearing about any sources of first-hand info about the MK IV'S design. Thanks! It's off to Ashdown...

Ready to receive... Went with gloss black, Rust-Oleum clear lacquer and #0000 steel wool.

So it's been cleaned up, which took a lot more work than anticipated. The fan was caked with some kind of mud or sludge, and the preamp module was taken apart and gone through methodically. I almost didn't want to know what went on in the life of the guy who owned it previously... Anyway it's working, but it's not putting out nearly the power it ought to be. The tech has it back again, and is going through the op amps that get signal from the power supply. It's got a surprisingly small power amp I'm told, due to the structure of this thing. It seems the 250 through 500 models used the same transformer and big blue caps, but the number of power transistors was the difference in the final product. But, it sounds like I expected it to, which is great... Hopefully the output comes up to spec, and I'll install it into the sleeve. Pix to prove it happened! (Typos fixed!)

Simply Ned

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Oh boy! Popcorn time! 😃

That I get! 😂 I'll give that info a little time tonight, thanks you guys, I appreciate the interest and help!

The math before me is like an irritating repellant before a garden-pillaging rodent. 😂 Ok, fair enough, I stand corrected.

The guy who's been repairing my amps the last 6 or so years there me that measuring at 1KHz takes less power than lower frequencies, so the rated power brings a higher number. This is incorrect?

Power is measured differently than it used to be. The numbers get blown up and it seems like power just ain't what it used to be. It is, it's just sold "differently"... Advertising...

I remember drooling over the SMX line in '95...

Old school dub reggae players could get with that I think.

Thanks everyone for posting. 😎👍

I like the presentation and then bringing in some mids with the graphic.

This about honest ratings hits the mark. My tech friend says similar about how power is now rated at 1k, which isn't really honest low end. It requires more power to reproduce low end, so you get higher, impressive numbers.

Thank you guys.

I've got a kind of prog-ish doom style original band, I play bass. I'm in process of getting a Mk IV head cleaned up and installed in a plywood sleeve I made, and I'm thinking about running it into an Ampeg PR410HLF cab, 600w @4 ohms. The Mk IV is rated at 250w, 4 ohms. In my experience, Trace heads seem to deliver more than that. I'm thinking this'll be loud as Godzilla with a stubbed toe in a mix with two loud guitars and big drums, playing some melodically complex bass lines. Can I get witness?

Dinosaur Sr...

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First word back in the amp is that the power section seems stable. The big blue caps are in good shape, so far so good. My tech guy had to clean up the fan, it was lousy with hardened crud- but once he got it free up it was working just fine. The preamp is next... And the sleeve is looking ok. I'm bringing it to the big panel saw to do a cut-back on the front panel section- like you see in a lot of these sleeves- so you can see the uv lit front panel from above. Then I'll rattle-can it with some black forest green and finish it up with some old hardware I've got in a box, somewhere around here...

😁