Dean Markley CD60 reissue Any Schematics Available? Reverb Problem

[Scomodeals]

recently picked up 8 ( yes 8) Dean Markley CD-60 from the early 2010's (actually 2 are cd30 but pcb is virtually identical). They came without output tubes ( 6l6GC). Once output tubes are installed and fired up, everyone of the amps has a loud hissing that can be lessened or increased via the reverb control knob. So , effectively these amps have no reverb. Everything else works nicely. I have no schematic and it is a 2 sided board. I'm flying blind here. The reverb is generated in a Belton digital module (BTDR-1h). These amps were made when the belton modules had a very high failure rate, so I naturally assumed that a bad batch of module had been installed in these amps. Also, it appears that the reverb send/return is handled by a TL072cp, which I have found to be a high failure part. I changed out both and.... Zilch, no change. ... I am not a fan of random part swapping but I cant find a schematic to this beast. It is marked "made by Ultrasound amplifiers on the PCB.... any help is appreciated... thx Scott In Mesa Arizona.. One additional note, the hissing sounds very much like a preamp tube with open grid resistor. But I have never heard of a digital reverb with send/return handled by a 12ax7 preamp tube...

[drewl]

They actually reissued these?

I've worked on a few originals and there are hand drawn schematics for those, but I didn't see any for newer ones.
Maybe someone else has.

[nosaj]

I'm pretty sure ChuckH had a hand in the reissues of the cd60. Maybe he will chime in.

nosaj

[g1]

The re-issue is supposed to be pretty much the same as the original. The original had a tank, but it was solid state drive and return, so maybe these schematics could help:
https://music-electronics-forum.com/...813#post732813

[Scomodeals]

Thank you everyone. I'll look into the original schematic. I have not been successful messaging Chuck H. I'm new to this board. It may be because I am not a "contact of his

[g1]

We can put up a bat-signal.
Chuck H

[Scomodeals]

ah yes... thank you... I do not know the ways of this board

[g1]

In case you missed it, I linked some of the schematic in post #4 above.

[Scomodeals]

I did see that. G1 . thank you... perusing them now

[Chuck H]

We can put up a bat-signal.
Chuck H

Oh NOOooo!...

I didn't have much to do with the CD series amps other than telling Dean that they had a bit of a cult following and I suggested that reissuing the line was a possibility (alternative to manufacturing MY original design). I did examine and critique the design and build. But not much of that had to with the circuit actually. More about the physical aspects and the speakers. But I'm subscribed here now so I'll follow and help where I can .

EDIT: Dean would have been better off with my amp at the time. Direct competition for the Orange Tiny Terror and Double Terror line (Contemporary at the tine but mine had better performance and tone!) but it was the more complicated option. Dean chose the reissue suggestion and the current owners of DMS continued it after Dean sold the company too. We could have made a much bigger noise with my amp ideas and carried it into a roll with a little effort, But whatcha gonna do!?!

[g1]

But whatcha gonna do!?!

Shop it around to somebody else?

[Chuck H]

Shop it around to somebody else?

I had thought about it. But I had a "working relationship" with Dean and was going to be part of the whole process. Meaning I'd be getting paid. Not much patentable in a guitar amp and I'd already sold a couple so it's now "in the public domain" anyway. So shopping it around would have amounted to giving the design to away for nothing. Also, the whole simple circuit/18W thing is sort of passé now. I figured out long ago that there's not much money to be made in designing and building amps anymore. With the exception of a handful, most boutiquey amp builders are just getting by.

[Chuck H]

Since all the amps do it I think there's a possibility that it's a design flaw. Hiss is a normal byproduct of gain, and not often much else. Since reverb circuits require a lot of gain amplifying a very tiny signal I could imagine some hiss being generated. The older tube and tank circuits usually make their share of background noise in one way or another.

If this is the case it may be possible to modify the circuit for more drive to the Belton brick and lower amplification after. I never had a copy of the new design. The modifications for the brick were done by Greg Farres of UltraSound amps. He designed and managed the acoustic amps that Dean sold. Dean has since sold the company and at last check I think Greg has moved on. But I'll check again and if I can reach him I'll try to get a current schematic.

[g1]

I guess it's a question of how much hiss. The review of the re-issue in Premier Guitar did not mention anything, so I'd imagine it on par with other amps.
But like Chuck said, if all 8 amps do it, you would think it's a design issue or maybe a board fault. What is the history of the amps and why were 8 together like that? Could they have been a batch of defects/returns ?

[Chuck H]

Well I found Greg Farres. He's still working for a couple of other places but started his own business selling a few gadgets and pedals that he designed.

THIS IS NOT SPAM! But I will say to everyone here that if you're in the market for a good sounding DI box I know this one, designed by Greg, has an excellent reputation. And I had the honor of trying out some of his early stomp boxes about ten years ago. All sounded great. Especially the dirt box. So...

I actually have a matter that I need to contact Greg about and I don't really want to preempt that with a different matter (for my own reasons). So here's a link to his company website. Just go to "support" and Greg's contact email is right there. You could write him about acquisition of a current, Belton brick loaded CD series schematic and I'm sure if he has one he'll send it to you. He's kind of a Boy Scout that way. Helpful by nature. Still, it wouldn't hurt to say something like "Love the site and considering one of your products." or something like that. And anyway, like I mentioned, you can only do well with one of his products.

www.gmfamps.com