EF86 Amp with Dumble Overdrive Circuit?

[rsalinger]

I'm new to Amp Garage... and already, I've learnt so much.

I've asked this on a few other boards and received a lot of input (thanks mcinku)...

Seeing as the Bluesmaster is an Overdrive Special with a Bassman-style preamp, I'm wondering if anyone could tell me if an AC-30 type preamp (pre-Top Boost) could be "Dumblized" by adding the overdrive circuit (and V2) with a relay? Or, if the noise issues inherent with many modern production EF86's make this an impossibility. Currently, I'm using a EF806 tube... which is a modern high-grade EF86 replacement, with ZERO issues. Quiet as sin.

The reason that I'm asking is that I've recently built a Stangray Clone and have a lot of space left over in the chassis... Additionally, I'm a huge Brad Paisley fan and I know that he uses a Dumble-style pedal (Zendrive) with his Stangray. I was hoping to get something similiar without pedals.

Thanks,

Rob

[M Fowler]

You can built the RxES or the Maz GT to get the extra gain your looking for in a similiar package as the Stangray.

[rsalinger]

You can built the RxES or the Maz GT to get the extra gain your looking for in a similiar package as the Stangray.

Thank you for the reponse.

I thought about the Maz GT, but decided against it because it has to be really "opened up" to crunch... and what I've been wanting to do is install a "lead channel" with a relay. Something that is refined and "sings" (and at lower volumes, too).

The RxES sounds interesting... but, I know that Dr.Z's schematics are closely guarded secrets because his amps are still in production.

Any other ideas?

Thanks,
Rob

[Structo]

I don't see why you couldn't try it.
May want to test it before drilling holes in the chassis.

One of the tricks to the OD gain stages in the ODS amps is that when the OD is off, that tube is grounded and shut off.

Holy buckets!

I just looked up the EF86 tube, it has a MU of 5,000?!!!

Uh, maybe it isn't a good idea, because the OD "channel" on the ODS amps is just a cascaded gain stage (four gain stages), so not sure how you would do that unless you shut off the EF86 and added a tube so the four stages of overdrive are preserved.
Just thinking out loud really....

[dave g]

It's absolutely possible. Just drive the 2-stage OD section with the EF86 preamp. You will have to use an OD input trimmer or control to pad the signal enough, but it should work fine.

[wicker]

Or 2 clean stages that drives EF86, not common, but possible. There are many variations, whatever you want.

[exocet]

Definitely worth driving the EF86 from another gain stage to experience the very characteristic harmonic content imparted by that tube. Nothing Dumble about it...a whole lot of fun though.

[phsyconoodler]

Better to use a 5879 pentode.No microphonics to worry about.

[10thTx]

Just drive the 2-stage OD section with the EF86 preamp

OR ........... you can use a Dumble type preamp into a 5879 OD (or EF86).

This is my favorite amp.

With respect, 10thtx

[rsalinger]

Better to use a 5879 pentode.No microphonics to worry about.

I'm not very familiar with 5879 pentodes. How similiar are they to EF86's?
Currently, I'm using EF 806 tubes in my Stangray Clone and Ceriatone DC-30... with excelent results.

How do the two tubes compare? I understand that the 5879 requires a pin change, when used as a EF86 replacement?

Rob

[rsalinger]

When they say that there are a lot of knowledgable, well-informed and helpful induviduals here, they aren't kidding...

It's absolutely possible. Just drive the 2-stage OD section with the EF86 preamp. You will have to use an OD input trimmer or control to pad the signal enough, but it should work fine.

Hmm... so, I can basically 'lift' the relay and OD section (including V2) from the ODS schematic and install it pre-PI in my amp?

My current PT is a Canadian made Cin-Tran 3428. What are the transformer requirements to power the ODS overdrive circuit?

Or 2 clean stages that drives EF86, not common, but possible. There are many variations, whatever you want.

Definitely worth driving the EF86 from another gain stage to experience the very characteristic harmonic content imparted by that tube. Nothing Dumble about it...a whole lot of fun though.

From my understanding, this is what goes on, under the hood of the Dr.Z RxES. Can anyone confirm that?

So many questions... so little time.

Thanks,
Rob

[Luthierwnc]

I was going to throw up the T-lite link but its author beat me to it. Very worthwhile project! Skip

[rsalinger]

I was going to throw up the T-lite link but its author beat me to it. Very worthwhile project! Skip

Hmmm... I am unfamiliar with the T-Lite. Could someone fill me in?

Thanks,
Rob

[Luthierwnc]

The schematic is above. Do a search for "5879" on the Hoffmanamps.com forum and you'll get the layout and details. There are a number of other variations (and predecessors). Thumbs up for the site.

If you are interested in more experimental amp designs, it is definitely worth a look. Skip

[10thTx]

You can find some information here if you have the free ExpressSCH program:

http://www.el34world.com/Forum/index.php?board=12.0

There is a very poor quality recording with mediocre playing that shows some of the tone here (T-Lite 5879 OD):

http://www.soundclick.com/bands/default ... tent=music

Unfortunately, the VVR had to be turned down to get it to record at a reasonable level and that eliminated much of the "blooming". It doesn't sound like a D amp, it has more chime to it.

With respect, 10thtx