Resurrecting Richard kaplan's "Bigger Muff"

[illuminatiNPS]

Just a quick update guys. Traced down the pedal to its current owner, Rich Costey. Yeah I know, major producer. Shot him over an email to see if we can get a picture of the reverse side of the board. Fingers crossed.
Also contacted a few  boutique pedal companies, and the feedback was mostly negative, due to no "full" schematic. That and its probably a copyright thing because they are selling an EHX circuit. No biggie, Its up to us. Without the schematic of the tube stage, we are stuck with propabilities. No harm in solderless breadboard for the circuit and then experimenting with the addition of a tube gain stage from their. This pedal was built on trial and error anyway. In the meantime, I successfully created a patch on my PODHD 500 that nails the sound almost 95% to my ears. Its basically a Chandler Tube driver going in series to a big Muff and adjusting the blends. That is ran into a plexi model with V30 speakers with a parametric EQ post amp. Pretty close and noisy as hell without a noise gate, just like he original. 

[illuminatiNPS]

Hey guys,

   I noticed this topic has gone cold but have some new developments for the possibility of cloning this "Bigger Muff"

1) Listening to the StudioRatHQ interview about the pedal, Richard stated that the pedal has 2 power supplies. After talking with an experienced pedal designer (he cloned a mutron biphase), he thinks the tube section is plugged in, maybe even 250v, and the board is powered by a 9v battery.

2) Also being that the tube gain stage is classified as high gain, its possible the tube gain stage is inserted before the 1st transistor stage. Or even in between the clipping stages. The pedal designer i spoke to beleives the silver cables are carrying audio to and from the tube stage, which maybe means it leaves a transistor stage goes to the tube and back.

3) The pedal designer I spoke to also sparked an interest in this Bigger Muff pedal enough to consider it for a new product. Keep your fingers crossed

4) This isn't the only time a tube Big Muff has been produced. Check out this schematic.



Give me your thoughts fellas. probably gonna start ordering parts. Never soldered anything in my life, but this has me curious enough

[Blitz Krieg]

would the diodes be necessary/desired in that design?

[Gus]

illuminatiNPS

The picture posted shows a dangerous build.  Two wire AC cord no fuse that I can see no power switch no enclosure etc.

Of course it will need two supply voltages as a minimum.  One for the tube heater and one for the tube B+.  The heater could also be used for the BMP supply as well.

The pictures tube stage and BMP build looks crude.  

I would guess it is standard stuff stuck together in an unsafe way

I am surprised a studio would let something like this be used would the insurance cover the studio if there was a fire or someone got shocked?

This is not a 9VDC effect.  The picture looks like the person who built it did not care or maybe did not know how to build a line powered device.

[illuminatiNPS]

Yeah anything exposed would be unsafe. I too wonder if the diodes would be necessary. Kinda of reminds me of the Dual rectifier switch in the back where you can choose between tube or diodes. I wonder what transistor stage he introduced the Tube into.

[anchovie]

Kinda of reminds me of the Dual rectifier switch in the back where you can choose between tube or diodes.

Totally different thing - the rectifiers that many an over-excited metal guitarist has boasted about having two or three of are actually the part of the power supply that converts AC to DC, and the quantity depends on how many watts the amp puts out. They don't provide amplification or clipping, just a change in "feel" for those that notice such things.

My contributions to the guesswork:

From what can be made out of the writing, it does look like one of the switches selected between "Diode" and "ECC???" - I'm assuming the tube hadn't been set up in a "triodes-as-diodes" configuration as Kaplan referred to "high gain". The pair of shielded wires from the tube board look like they end up before and after the first clipper stage (working right to left to end up with the volume control). What if...the switch swapped Q2 for a ECC83-or-whatever dual gain stage - meaning the input of Q3 gets slammed with a >100Vp-p guitar signal that is then diode-clipped on top by the feedback loop?

Remember, this is somthing deemed worthy of the name "Bigger Muff", so it's not going to be a case of just sticking a cathode follower somewhere!

[anchovie]

...though I'm not sure if there's a transistor with the ability to withstand that input swing. Still, my hunch is that the tube had to provide something "more" than a stock Muff does.

[illuminatiNPS]

Kinda of reminds me of the Dual rectifier switch in the back where you can choose between tube or diodes.

Totally different thing - the rectifiers that many an over-excited metal guitarist has boasted about having two or three of are actually the part of the power supply that converts AC to DC, and the quantity depends on how many watts the amp puts out. They don't provide amplification or clipping, just a change in "feel" for those that notice such things.

My contributions to the guesswork:

From what can be made out of the writing, it does look like one of the switches selected between "Diode" and "ECC???" - I'm assuming the tube hadn't been set up in a "triodes-as-diodes" configuration as Kaplan referred to "high gain". The pair of shielded wires from the tube board look like they end up before and after the first clipper stage (working right to left to end up with the volume control). What if...the switch swapped Q2 for a ECC83-or-whatever dual gain stage - meaning the input of Q3 gets slammed with a >100Vp-p guitar signal that is then diode-clipped on top by the feedback loop?

Remember, this is somthing deemed worthy of the name "Bigger Muff", so it's not going to be a case of just sticking a cathode follower somewhere!

I agree that the red switch is a Diode/ECC switch. Also if you look at the "Bigger Muff" pic, you can see the same 2 diodes above Q3. I think they match the diodes in other pic I posted.  The 2 diodes that are supposed to be above Q2 maybe be hidden by a disc capacitor in the pic. So if the diodes are visible above Q3, then your 2nd dual gain stage theory would be correct, but that would also mean the switch is a "tube on/off" switch and not a "diode/tube swap" switch.  Also if this is a 250v tube gain stage, he must
have stepped down the voltage at the heater and then sent power to the board via the red wire. Here is a trace of the 76' BMP so you can see where he may have introduced the tube gain stage. Its ver 2 on the right:



If this is a dual gain stage at Q3, how would that be any different than running lets say a tube overdrive pedal in series into a big muff??? Ive done it and it sounds alot like Roots Bloody Roots. Anchovie, do you live in the states??

 

[anchovie]

I'm in the UK.

Looking at the photo again, I'm now not convinced that it says DIODE above the switch. There's a blob above the ECC8?? though that could be a +. Your experiment with the POD is promising, so I think we should certainly give consideration to the idea of the tube acting as a switchable boost before a regular Big Muff. It won't be a Tube Driver though, as that's a hybrid design with low plate voltage and an opamp providing most of the gain. But however it's set up, there's not so much voltage swing that it destroys Q1 of the Muff.

The transformer markings include PREM - Prem Magnetics is a manufacturer, but the numbers on the transformer look nothing like the product codes they currently use. I'm taking a real guess here - in the 0102024 code the 024 denotes 24V. I don't believe that's a proper tube amp transformer, it looks salvaged from something else, and if the 24V is two 12V secondaries in series then you've got your 12VAC heater voltage right there and 24VAC to rectify into DC for a starved-plate tube booster.

[illuminatiNPS]

Anchovie,
Taking your advice I modified the patch and used a dual rectifier pre(high gain tube), into a big muff and it sounds more accurate once te IR EQ curve is added. I am currently trying to bid this project to some boutique pedal builders. Basically asking for a big muff witha high gain tube boost in the q3 section, or even the ability to switch between tube and transistor. Let's see who has the balls.to take it on. Everyone has there price I guess

[slacker]

I can't believe no one has mentioned the word Valvecaster yet in this thread, that is all 

[anchovie]

That's because I don't believe it's a 12AU7 - 12AX7/ECC83 would have been seen as the go-to choice for anything intended for metal bands.

That's not to say that you wouldn't get a decent approximation by putting a Valvecaster in front of a Muff, and it's certainly worth trying in order to get rid of the need for the chunky transformer.

IlluminatiNPS: Your experiments are indicating that tube-before-Muff gives good results. My gut feeling, given the lashed-together look of the unit, is that this may well be all it is rather than a tube/transistor-swapping switch.

[illuminatiNPS]

That's because I don't believe it's a 12AU7 - 12AX7/ECC83 would have been seen as the go-to choice for anything intended for metal bands.

That's not to say that you wouldn't get a decent approximation by putting a Valvecaster in front of a Muff, and it's certainly worth trying in order to get rid of the need for the chunky transformer.

IlluminatiNPS: Your experiments are indicating that tube-before-Muff gives good results. My gut feeling, given the lashed-together look of the unit, is that this may well be all it is rather than a tube/transistor-swapping switch.

I agree totally. The only two questions I would have is 1) does the voltage going to the tube section effect gain. I ask because if it's buildable, then is a transformer necessary,. The transformer makes me think it's a preamp more then a "gain stage". 2) do you think there would be a difference in tone whether it is introduced in q1(vol) or q3(clipping).

[BuGG]

I've been kicking around the idea of building this circuit for a couple months now...

The tone "switch" at the top of the board is actually a pot with the knob missing.

The tube stage is a typical high gain 12AX7 triode stage, similar to the one pictured here.


The power transformer on the right is supplying the B+, you will definitely need high voltage for this circuit to operate properly.      This is not a beginners first build!  
It should be possible to use a nixie power supply or charge pump circuit to produce enough high voltage to safely run from a 9 or 12VDC supply.

You could substitute the triode stage for a valvecaster or fetzer valve, but where's the fun in that? 

You've sparked my interest in this project again....    Stay tuned, I'll report back shortly.    

[illuminatiNPS]

I've been kicking around the idea of building this circuit for a couple months now...

The tone "switch" at the top of the board is actually a pot with the knob missing.

The tube stage is a typical high gain 12AX7 triode stage, similar to the one pictured here.


The power transformer on the right is supplying the B+, you will definitely need high voltage for this circuit to operate properly.      This is not a beginners first build!   
It should be possible to use a nixie power supply or charge pump circuit to produce enough high voltage to safely run from a 9 or 12VDC supply.



You could substitute the triode stage for a valvecaster or fetzer valve, but where's the fun in that? 

You've sparked my interest in this project again....    Stay tuned, I'll report back shortly.     

Bugg,

Thanks for joining the talk. Yes the tone knob is definitly a pot and the board is most likely a Rams Head BMP layout.
There are still a couple of mysteries though. The purpose of the red switch, and where does he introduce the tube gain stage. A few of us think at the q3 transistor clipping stage, this way it become a dual gain stage. Not a beginners build, and I am the detective in this whole thread. I've spoken to Richard and Ross Robinson before to get bits and pieces of info. There is one other person who has been in front of the pedal that may still be of help as well.


Bugg, do you live in the states?? If so we should swap numbers and if you want to take this on, I will
Help with parts cost.

[Gus]

Anything more information on where the tube stage is?

If the tube gain stage is before the BMP you could use a transistor gain stage instead and run it from 9VDC.  9VDC is safer.
If a 12ax7 was used you need to think aboout the Rp and how it adds to the input resistor of the BMP and gain of the first stage of the BMP

[illuminatiNPS]

Gus,

   No concrete info on where the tube gain stage "actually" goes. Ross robinson has confirmed though that the red switch is to switch from "regular muff" to "overblown". It has feed back even when a guitar is not plugged in. Which makes sense because a lot of the sepulture tones sounds like the notes are on the verge of feedback when they are played.

 

[Gus]

The layout could be helping with getting feedback, long wires etc. built on a wood board.

It could be a simple tube stage before the muff.  Something like reply 21 first tube stage with a cathode bypass cap something like 22uf. 

I am still thinking the brown resistor on the perf board at a small angle could be dropping 12VDC to about 9VDC.

A good link for you http://www.aikenamps.com/index.php/designing-common-cathode-triode-amplifiers

An issue is the low input resistance of a BMP it is the about the 27K to 39K series input resistor you see on BMP schematics this loads the stage before and reduces the gain

So maybe both triodes are used in a 12a_7 or maybe  plate out to cathode follower

You could try a fet input opamp set to a gain of 10 with a 1meg input resistance before a BMP as a test, this might sound better.

I did sim a nice BJT stage to use before a BMP

[Gus]

Can anyone tell the directions of the electros and what number the transistor are?
The electro direction will help figure out the powering
is this a NPN or PNP build
could this be PNP being powered by +9VDC

[illuminatiNPS]

I got in touch with PREM, the transformer manufacturer and  they said the Prem8732 means it was built in the 32nd week of 1987. After clean up the pic a bit and looking at the resisotrs along the bottom, it looks like the 430k in Q1 is missing. Also the solid colored white resistors are matching as oh, value resistors.

A closer look at the writing under the red switch makes me think it says : ECCFaT.  The Mallory Electro looks like it says 650k. The Black one above just says CC. The birds nest of wires near Q2 seem to be the wires of the Q2 diodes. the more I look at the tube gain stage, the more I think it was just pulled from an amp and stuck on the plywood.

Still waiting on possible back of board pics. Fingers crossed