Pedal Mule 20 - Prototype build

[dorrisant]

Great job on the project Gary... Pictures look just fine too me. Glad to see another build post.

I think I'm gonna do this circuit with all octals. Thanks for sharing!

[RJ Guitars]

Tony, those 6SL7's sound really good but i did find that they also have an inclination to Hum. I think I'll use a DC heater supply if I mess with them again.

[DocJames]

Looks fantastic Gary. With my renovations coming to an end, I think I'm going to start sourcing parts for this build. The real question is 20 watts or 30 watts??

[RJ Guitars]

... The real question is 20 watts or 30 watts??

Answer = Both

[dorrisant]

Hey guys,

What are your voltages on the preamp tubes? Power tubes too if you have them...

[BLT]

Seeing what the PT was for this build, I'd be very interested in how the voltages turned out. I have an old MusicMaster Bass amp chassis I'd like to convert into something else.

[RJ Guitars]

Seeing what the PT was for this build, I'd be very interested in how the voltages turned out. I have an old MusicMaster Bass amp chassis I'd like to convert into something else.

I haven't heard from Gary for a while. I think he found that life down in Georgia allows him to go outdoors a lot more since he moved out of the frozen north... not sure if he is building amps these days or not. I do expect he has been doing some fishing though.

Anyway, I wired up the PS board before I sent this out to him. This amp was intended to make use of an oddball power tranny and a handful of other parts I had sitting idle on the shelves for a while. It is an Edcor 125-0-125 @ 125mA PT and if you look at the PS board you'll see I used a full wave bridge rectifier to try and get a little more juice out of it. Should be something like 250 x 1.4 = 350 volts. Gary has posted some voltages on his schematics and you can see what kind of actual numbers he got from that.

I really liked the sound of the Pedal 30 (Think Songwriter 30) but as with most of my amps it was just too loud and I couldn't get the good stuff until the volume was cranking. So I came up with this idea for a 20 watt version with a pair of 6V6GT output tubes running at a lower voltage. I didn't have time to put it together but Gary was looking for an amp project and volunteered to build it so I sent it off to him to finish.

No reason you couldn't build this using your Music Master tranny set. Yours will probably be more powerful but it should sound good and will really take pedals nicely.

hope this helps,

rj

[BLT]

I forgot how a Blues Jr. does a Full Wave bridge. I'm now thinking of a good use for 6GK6s in this circuit. Am I right in thinking that Full wave SS rectified AC is times .71 instead of 1.4 with the bridge?

[RJ Guitars]

My bad - I think you've got that right...

http://www.trans-tronic.co.uk/rectifier ... calculate=

If my strategy woulda worked then I would need to patent it in addition to writing some new laws of physics

Now I have to go back and look at that tranny and see what voltages it really has on the secondaries in order to get the voltages out that Gary reported??

Loss of memory can really be painful if not downright embarrassing sometimes!

[BLT]

Put a Pedal Mule with 6GK6s that I'm calling Pedal Bomb, in an old Musicmaster Bass Amp chassis.

[RJ Guitars]

BLT - I really like the way you did that. Fits in there nicely and looks like a great recycle of the old amp. I am not familiar with those output tubes - how does she sound?

[BLT]

I wasn't either, but they kept popping up in EL84 discussions. They pinout
differently, but sonically very similar. 6GK6s also are less expensive.
The data sheets are almost identical to EL84s.
I guess I'll have to build an EL84 version to see what's different about
the 2 tubes.

[gktamps]

That's an interesting tube - thanks for posting that. I haven't found them to be much if any cheaper than EL84s or Russian equivalents in my brief online search. In fact, some of the prices are ridiculous - $100/tube? Wonder if the buzz in the diy audiophile community has pushed prices upward.

[BLT]

The $100 a tube I haven't seen, but you have to wonder what they're
smokin'. I pulled my first pair off "The Bay," a pair of not NOS Motorolas
for $15. I didn't see anything that scares me price-wise like NOS
Tungsram or Amperex EL84s have in the past. So I took the plunge
and felt like it was worth a try.

Oh, I should probably add up front (it's on the voltage chart), that I used
the old PT from the Musicmaster, a stock Blues Jr. OT, and the choke is
a 158L.

[BLT]

Here's a before and after of the Musicmaster Bass amp and the new amp.