Pedal Mule 30 - Prototype build

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RJ Guitars
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Pedal Mule 30 - Prototype build

Post by RJ Guitars »

I decided to attempt again to post this build, based loosely on the Inger amp. For those that might recall the previous thread... I wanted to see if I could draw some attention to this amp and maybe get a few more eyes, ears, and hands on it to evaluate it. That thread took an interesting direction but wasn't going to accomplish what I had hoped for... Then I got busy so this has been on hold for a while.

I have to say that honestly I looked at the available schematics and couldn't convince myself it would be great, but there were a couple of ideas I had that I wanted to explore in the event that the amp wasn't amazing on it's own.

1) This had a lot of potential for being a clean amp that would be extremely pedal friendly since it has minimal gain and the output section of a Trainwreck Rocket (AC-30).

2) I was curious if this might have any potential for use as an acoustic guitar amp... super clean with minimal gain - it's a thought?

I created a schematic that uses all the front panel knobs and switches although I sorta expect things to be a bit different before it's all done. I am going to use a 12BZ7 for V1 because I have a couple here that are very high gain and sound pretty cool... a little more gain would seem welcome for this amp. I'm also using the octal 6SL7 for the PI just to keep the look of the Inger amp intact and also because they are pretty great sounding tubes...

Edcor EM0881 PT 252-0-252 and Heyboer HTS-8093-1 OT (Dynaco 470 variant) and a Heyboer Fender Spec choke.

I'll post up more build photos as time allows...

Edit May 9, 2014 - I updated the schematic to reflect the final "As Built" amplifier. The amp is really sounding great these days and is one that I would definitely keep. It's got a nice sweet and full clean sound and takes pedals wonderfully. It also works extremely well as an acoustic guitar amp. It has exceeded my expectations in all categories.
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Last edited by RJ Guitars on Sun May 10, 2015 3:37 am, edited 2 times in total.
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johnnyreece
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Re: Pedal Mule 30 - Prototype build

Post by johnnyreece »

I'm curious to see how it turns out. It's always fun trying something a little different!
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David Root
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Re: Pedal Mule 30 - Prototype build

Post by David Root »

Bob, you think too much! Seriously, this is interesting. I'm curious, why the two PS 1M bleeders, particularly R29?

12BZ7 is an overlooked tube;two 12AX7s in parallel in the same glass. I used one as a driver in my 100W SSS, works just fine. However I have heard that their life expectancy is not high, not that I have had any trouble.
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ToneMerc
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Re: Pedal Mule 30 - Prototype build

Post by ToneMerc »

RJ, I ran across a NOS 6188 so I will be doing the octal PI as well.

TM
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RJ Guitars
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Re: Pedal Mule 30 - Prototype build

Post by RJ Guitars »

David Root wrote:Bob, you think too much!...
Some might challenge you on that one...
...Seriously, this is interesting. I'm curious, why the two PS 1M bleeders, particularly R29?
I'll have to look again at what I did, but IIRC I intended on one for each side of the standby switch.
...12BZ7 is an overlooked tube;two 12AX7s in parallel in the same glass. I used one as a driver in my 100W SSS, works just fine. However I have heard that their life expectancy is not high, not that I have had any trouble.
I was really amazed at how much sonic impact it made in the V1 position on a Champ circuit I have here... we'll see how this works out for this amp??
ToneMerc wrote:RJ, I ran across a NOS 6188 so I will be doing the octal PI as well.

TM
I had to look that one up and here is what the tube store had to say about the 6188:
The JAN-Philips 6188 tube is a military grade 6SL7 tube. They are also known as a 6SU7 tube. They are and excellent option when tight triode matching is desired, such as for phase inverter in a vintage Ampeg R-12 amplifier.
Sounds like something KF might have learned when working at Ampeg??
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ToneMerc
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Re: Pedal Mule 30 - Prototype build

Post by ToneMerc »

RJ Guitars wrote: I had to look that one up and here is what the tube store had to say about the 6188:
The JAN-Philips 6188 tube is a military grade 6SL7 tube. They are also known as a 6SU7 tube. They are and excellent option when tight triode matching is desired, such as for phase inverter in a vintage Ampeg R-12 amplifier.



NOS 1955 and thanks for the 8093 by the way.

TM
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lumox0013
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sweet

Post by lumox0013 »

Im so glad you started this thread I have been wanting to try the octal pi it might be a while but I will be putting one of these together for sure .thanxx rj you are the mann
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Re: Pedal Mule 30 - Prototype build

Post by Mark »

How is the amp sounding and how does it compare to the Rocket (where possible.)
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Re: Pedal Mule 30 - Prototype build

Post by Tone Lover »

I would think how the 12bz7 is set up it would be a very quiet 1rst stage even paralleled like that. Please tell your thoughts.
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Re: Pedal Mule 30 - Prototype build

Post by Mark »

I'm not sure I see the benefit of the 12BZ7's other than there might be more NOS valves around. I briefly looked at the spec spec sheet and thought the BZ7 should be slightly more robust.

http://www.philbrickarchive.org/12bz7_sylvania.pdf

http://www.drtube.com/datasheets/12ax7-rca1962.pdf
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Richie
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Re: Pedal Mule 30 - Prototype build

Post by Richie »

I've tried many BZ7,and tried to like them,but just my opinion, I never liked them. They all seemed to induce noise/hum or were microphonic, and compared to a 12ax7, well, they didn't.
Plus I think if they did, you'd see everyone running to grab them or talking about them more.
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Re: Pedal Mule 30 - Prototype build

Post by RJ Guitars »

Well I finished my cleanup and have recovered after the Tempe Guitar Show. I got to put faces with several familiar names and was really pleased to connect with the Phoenix area builders.

I am also caught up on all my orders to be shipped out so I can look at this build again... I've started to wire it up. I like to mount the transformers and wire them before I do anything else. Once I have the transformers wired then I'll wire up the heaters and power it up. I verify that I have it all wired up correctly and after I check some voltages I'll put in a set of tubes and make sure all the heaters are happy, then move on.

I want to use this amp in a combo cabinet with a single 12" speaker so I created a reverse image faceplate to make it into a tube hanger amp. It was still wintery cold outside when I put the first brown-hammertone spray coat on the faceplate and then had it laser etched. It looked good until I decided to give it a clearcoat finish over everything just before the sun went down. Next morning I went to fetch it (i paint outside) and the clear coat had melted and or cracked the brown paint and added all sorts of character to the faceplate. I'm not sure if it was because it was still wet when it got real cold or just a bad match... I had the laser etch redone and it now looks very cool. I'll leave it alone!

Hope to keep chugging away at this. Interesting notes on the 12BZ7's... I have high hopes but if it doesn't sound super sweet it's a direct swap to the 12AX7.

enjoy!
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M Fowler
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Re: Pedal Mule 30 - Prototype build

Post by M Fowler »

Sweet looking amp. :)
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Re: Pedal Mule 30 - Prototype build

Post by RJ Guitars »

Thanks Mark!

I did a little more work on it tonight... soldered parts in tonight and tomorrow I'll get some voltages...
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