Tube through a SS effect loop amp,suggestions?

[Le Basseur]

There's this young fellow who asked me yesterday about a possible "tube li'l box" insert in his SS amp's send/return,"just for the sake of a little more tube colouring". .This device should look like a separate box,not incorporated in the amp itself.
This guy plays electric bass through an Ampeg B1-RE amp w/ B410HLF box.
I suggested a simple gain stage (eventually followed by a cathode follower/buffer) with as little as possible amplification (maybe a 12AU7?...or any other triode w/ small Mu).
The guy wants nothing else but "tube coloration",without any of the possible benefits of such an "insert" (a little more compression,sag,etc) in the signal chain.
What would you do to achieve that?
TIA for any ideas (though,this thread might sound silly enough).
Regards,

[Don Moose]

If they were handy (local), I'd probably try on some tube-based overdrives - just because the gain and overdrive are available doesn't mean you have to use them.

Next choice might be a tube-based preamp like an Alembic F2-B.

What I'm implying is that a pre-existing product might be a better choice than designing and tuning something new ... unless you just want to.

Hope this helps!

[drlowlow]

He wants tube coloration but doesn't want extra compression or sag. It sounds like he wants a tube operating in a linear zone which I think he will be disapointed in it not altering the sound so much. The economics of building such a circuit so that the tube operates in it's manufactuers recomended parameters would be quite an expense when compared to other ready made products on the market. I think it will take some fine tuning to get something that will work well in this location. I think you are on the right path with the circuit you desribed but there will be alot of variables to be adjusted. I would set it up with a gain and master volume sceme so that he can push the tube or tubes non linear if he decides that is what he is really after.

I would feel a bit bad if I tried to sell him something without first explaining to him that there are many companys that have done alot of research and development and build in bulk and can more economically build a device that may have more features than requested but will ultimately be less of an investment and might be more of the tone he is after. This isn't saying you can't build an excelent quality device for him, I am sure you can, and if that is what he wants there is no reason you shouldn't.

Good luck with it, and I am interested in how it turns out.

[Le Basseur]

Don and drlowlow,
Thanks for your comments,you both nailed it at it's best!

If they were handy (local), I'd probably try on some tube-based overdrives

Unfortunately,they're not as handy/popular as they'd have to be (there's a big market gap between botique effects and newer Boss/Behringer digitals).However,your suggested approach IS what I thought at in the first place.Also,the Alembic F2-B is definitely a good point to start from.

I would feel a bit bad if I tried to sell him something without first explaining to him that there are many companies that have done alot of research and development

My point exactly.This issue isn't a simple "build/sell" thing but AFAIK implies alot of tweaking wich may raise the overall costs up to a level that makes it,well,unprofitable for both parts.Aside of the regular repair jobs that I do where the timing/prices are clear enough,when I tweak something I try to keep the costs as low as possible though there are certain limits...my time,and,very often,the obvious undecision of the customer who drives me nuts.

This isn't saying you can't build an excelent quality device for him, I am sure you can

Thanks for the credits!

Good luck with it, and I am interested in how it turns out.

Again,thanks for your good toughts.I'll keep you informed as the subject goes,though I guess that a "cost-no-object" thingy wouldn't be acceptable by the customer's side.
Anyway...even without a predicted "happy end",both you helped a lot.
Regards,

[Don Moose]

The F2-B is a fairly simple circuit, and I'd expect it to be happy with a wide enough range of supply voltages to make it work with the back-to-back transformers PSU trick using a couple of 15-25VA trannies. You're in a 230VAC/50Hz country, right?

[Shea]

One of those reissue Fender outboard reverb units would fit the bill.

Shea

[Le Basseur]

The F2-B is a fairly simple circuit, and I'd expect it to be happy with a wide enough range of supply voltages to make it work with the back-to-back transformers PSU trick using a couple of 15-25VA trannies.

Thanks for the suggestion!
Alembic is one of the few choices after I eliminated a bunch of them for various reasons.
Also,thanks a lot for reminding me of the back-to-back trannies idea,as a "real",smallish pwr xfr is a PITA to aquire.

You're in a 230VAC/50Hz country, right?

That's right.

One of those reissue Fender outboard reverb units would fit the bill.

Shea,I'm not sure I know the stuff you've mentioned here.
Is it a standalone effect,or a PCB module,or what?
Thanks!

[Don Moose]

Shea is referring to the 6G15 or the Silver Face outboard reverb units Fender used to do.

(I hope these links work - if not, go to www.ampwares.com/ffg hit the Schematics and Layouts link and look for 'Reverb Unit')

[Le Basseur]

Thank you!