Verellen - Meatsmoke Preamp  [traced]

General documentation, gut shot, schematic links, ongoing circuit tracing, deep thoughts ... all about boutique stompboxes.
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zender
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Post by zender »

The title says it all, I'm looking for the schematic to the Verellen Meatsmoke preamp. From what I can see the pedal and rack are the same PCB, with only the parts in different places. I'd like to shoehorn this in a 1u rack case, it seems that Verellen's 2u implementation of this leaves alot of void in the case, and might only be there because of the large transformer. Yes I could buy a used pedal, and convert it, or as Ben to build me a 1u version. Neither option will really help me in understanding what this thing actually does and why it sounds so massive and loose.

Much obliged gents :D
Verellen Meatsmoke preamp gut shot
Verellen Meatsmoke preamp gut shot

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Post by zender »

Nobody has one? :(

Either the pre-amp or the pedal would do

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Post by vigilante397 »

I'm more or less starting this thread as a placeholder/reminder to myself to upload pictures when I get home. I did a search and saw a couple people ask about the Meatsmoke, but the last thread was 2018 so didn't want to necro bump something that old.

I've met tons of awesome musicians online, and one of them recently offered to let me borrow his Meatsmoke preamp so I could trace it in exchange for building him a more pedalboard-friendly clone. He loves the pedal, but the size is just inconvenient for his rig. Looking at the guts it's a complete spaghetti mess, the designer clearly didn't follow what we at my work call "design for manufacturability," the PCB doesn't seem to be designed with quick and easy building in mind.

But anyway it's a single-sided board (plated TH though) and a fairly straightforward trace. I have the preamp section completely traced, just need to do the record out section now. My phone is out of commission so I can't post pics or a schematic until I get home tonight, but here's the general flow of the preamp:

Meatsmoke Block Diagram.JPG
I'll try to get pics and what I have of the schematic uploaded tonight, and I plan to dig back in and trace the record out in a couple days. I'm not going to bother tracing the power section as I'm planning to use a Nixie supply and take a DC input, but this obviously takes line voltage and uses a transformer and a couple bridge rectifiers plus a regulator for the heater supply. I will get some voltages when I finish tracing and have it all back together though.

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Post by vigilante397 »

Okay, sorry it took me forever to get back to this, but here it is. Delicious spaghetti gutshot:

received_433778817996275.jpeg

And for the record since I forgot to mention earlier this is serial #285. I still need to measure voltages and trace the record out. Also the Channel switch is a 4PDT, the fourth pole is to ground the channel LEDs cathode. I don't have a schematic symbol for 4PDT yet so I used 3PDT and left off the LED. Anyway this is what I have so far:

Verellen Meatsmoke Preamp Section.JPG

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Post by Manfred »

What is the value of HV?

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Post by Jarno »

vigilante397 wrote: 02 Sep 2021, 16:52 the designer clearly didn't follow what we at my work call "design for manufacturability," the PCB doesn't seem to be designed with quick and easy building in mind.
Or reliability, oh my god, what a mess....
Loose wires, heavy filmcaps standing up because they do not fit the PCB layout....
Wrong connection and colour coding for the mains wiring.
"It crackles....., but that's ok"

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Post by vigilante397 »

Manfred wrote: 03 Sep 2021, 07:31 What is the value of HV?
I haven't measured it yet, I still have it dissected. I will measure after I finish tracing and get everything connected back together.
Jarno wrote: 03 Sep 2021, 08:22 Or reliability, oh my god, what a mess....
Loose wires, heavy filmcaps standing up because they do not fit the PCB layout....
Wrong connection and colour coding for the mains wiring.
It is pretty atrocious. Also things like the standoffs being attached to the enclosure by hot glue, one of the standoffs was in the wrong place so instead of removing and regluing it he DRILLED A HOLE IN THE PCB, it really feels like an amateur build.

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Post by Bolsyo »

Found some more gutshots of different units on the web:
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meatsmoke2.jpg
meatsmoke3.jpg
meatsmoke1.jpg

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Post by vigilante397 »

Bolsyo wrote: 04 Sep 2021, 08:27 Found some more gutshots of different units on the web:
Yup, I had looked up gutshots before I got this unit so I more or less knew what I was getting into. But man, seeing it in person is a different feeling. Like it looks like a mess, but in person you can physically feel the mess assaulting your eyeballs.

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Post by Jarno »

And to think the original manufacturer could have easily solved everything. Just build a prototype, give the board another spin so components fit, look up the rules for mains wiring and adjust accordingly (not even heatshrink on those connections). Also, determine a good routing for cables, and tie them down (and don't use f*cking hot glue to mount standoffs.....).
Luckily for everybody, he stopped making amps, lets hope no houses have burned down.
"It crackles....., but that's ok"

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Post by vigilante397 »

Jarno wrote: 04 Sep 2021, 19:11 And to think the original manufacturer could have easily solved everything. Just build a prototype, give the board another spin so components fit, look up the rules for mains wiring and adjust accordingly (not even heatshrink on those connections). Also, determine a good routing for cables, and tie them down (and don't use f*cking hot glue to mount standoffs.....).
Luckily for everybody, he stopped making amps, lets hope no houses have burned down.
Another thing that is shocking to me is that this PCB is labeled as v4.2! There have been multiple revisions and this is where it ended up!

I've heard great things about the sound (I opened it up as soon as I got it, still haven't even plugged it in :P), but I definitely am glad there aren't more of these still being made like this.

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Post by vigilante397 »

Okay, I finally got around to finishing the trace of the record out tonight, I'll get the complete circuit posted in the morning. Also I got it all put back together and measured B+ at 301V.

Also, the B+ line on the PCB runs right under a standoff, so if you tighten the nut on that one too tight it will short the high voltage line to ground and release some magic smoke in the power supply. This is version 4.2 of this PCB, I can't even imagine the issues all the previous versions must have had.

I did get around to plugging it in and listening to it, and it does sound quite good, particularly the drive channel, but I'm not sure it's $900 and deal with all the repairability issues good. So build your own PCB of it (I'm not liable if you don't know what you're doing) and make it better.

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Post by Nocentelli »

vigilante397 wrote: 04 Sep 2021, 19:18
Jarno wrote: 04 Sep 2021, 19:11 And to think the original manufacturer could have easily solved everything. Just build a prototype, give the board another spin so components fit, look up the rules for mains wiring and adjust accordingly (not even heatshrink on those connections). Also, determine a good routing for cables, and tie them down (and don't use f*cking hot glue to mount standoffs.....).
Luckily for everybody, he stopped making amps, lets hope no houses have burned down.
I definitely am glad there aren't more of these still being made like this.
sunburnedgoat wrote: 25 Jul 2010, 21:26 This dude makes awesome amplifiers - that is his bread and butter, not pedals. They are affordable, p2p, hand wired monster tube amps. So cut him some slack before breaking out the torches.
modman wrote: Let's hope it's not a hit, because soldering up the same pedal everyday, is a sad life. It's that same ole devilish double bind again...

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Post by Jarno »

We are not breaking out torches at all, there is no excuse for delivering products which are not compliant and safe, even if they are affordable etc.
There are regulations on delivering mains powered devices for a reason, people can die, and houses can burn down if products are not safe.

There's a lot of hubbub about p2p building being better and SMT being inferior but the objective fact is that it is a lot easier to make equipment more reliable and safer by using the bare minimum amount of wiring, and compact components without long wires.
If you do vibration testing on equipment (amps are transported, amps are subjected to vibrations when they are on top of cabinets and are going full tilt) you see that heavier components (in my experience big radial electrolytic capacitors, because I haven't seen axial ones being used in new equipment that I was involved in designing) you can see them wobble left-right, until fatigue causes the leads to break. If these are used they need to be glued down to prevent issues and keep them stable. Ditto with wiring, you can see that doing it's own little dance until they break. Screws also, snapfits are a right pain when servicing, but screws have tendency to work themselves loose and rattle around potentially causing shorts.
"It crackles....., but that's ok"

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Post by Ben N »

Looks like there would be some interactivity between the tonestacks.

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Post by vigilante397 »

This dude makes awesome amplifiers - that is his bread and butter, not pedals. They are affordable, p2p, hand wired monster tube amps. So cut him some slack before breaking out the torches.
The preamp absolutely sounds good, I will give him that. Zero arguments there. I can totally see it carrying over into a full amplifier. I will cut him all the slack in the world on the side of tone.

But I will not excuse the build quality. There is no way that is okay. Someone that makes awesome amplifiers should 100% know better. I'm not just getting after it for being messy, it's unreliable (three of his wires-dangling-on-a-floating-component broke while I was gently working on it), it's unsafe (WHO RUNS A HIGH VOLTAGE LINE RIGHT OVER A STANDOFF CONNECTED TO CHASSIS GROUND???), and as a former technician I would refuse to work on this. In fact the friend I'm borrowing it from is a semi-professional musician, and his tech DID straight up say that if it ever stops working he isn't touching it.

I'll say it again, I really like the circuit, it's a really great sounding preamp. But in my opinion that built quality is unacceptable in a commercial product.
Jarno wrote: 09 Sep 2021, 08:54 There's a lot of hubbub about p2p building being better and SMT being inferior but the objective fact is that it is a lot easier to make equipment more reliable and safer by using the bare minimum amount of wiring, and compact components without long wires.
100% this. I've switched over 100% of my builds to SMD, I use board mounted pots, I use footswitch PCBs that connect to the main board with headers so there are no dangling wires. I haven't taken the plunge to board-mounted jacks yet, but those are the only wires on my builds. The number of builds that need to come back to me for repair has dropped dramatically, and zero of my customers have been zapped by high voltage. Also from a production standpoint, once an enclosure has been finished and a board has been populated, I can completely finish a pedal in 10-15 minutes. I can't even imagine how long it takes to run all of these wires.

/endrant

On a lighter note I'm firing up Altium now and I'll get the rest of the schematic put in. I'll see if I can get around to a PCB layout today, but it will obviously be SMD (see above). Shooting for 1590XX, I'll be using a 9-12VDC input and a nixie supply for high voltage, because that's my jam. I have the beginnings of a PCB order that's been waiting for the Meatsmoke and one other reverse engineering project (Effectrode Mercury Fuzz, in case anyone wants to see that one too) so I'm hoping to get the order in this weekend.

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Post by vigilante397 »

Ben N wrote: 09 Sep 2021, 10:13 Looks like there would be some interactivity between the tonestacks.
Agreed, I thought the way that was designed was a little odd. I'm sure if a 5PDT (or relays) had been available he would have used the extra pole to switch between the two so the unused tone stack is removed from the circuit.

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Post by vigilante397 »

Alright, final schematic. I left out the power supply, because frankly if you don't already know how to build a high-voltage supply then you shouldn't be learning it from me, you should do a lot of reading so you don't kill yourself. The original runs at 300V, I'll probably run around 240V so I can use 250V caps. Also the op-amp runs on a 25V supply; Verellen uses a fat resistor divider to get close then uses a 25V zener to keep it at 25V. I'm using an LM2733 to boost from the 9-12V input up to 24V, close enough for me.

Let me know if anything looks off, I'm not perfect and welcome any corrections, and I still have the unit so I can go back and double check anything that looks weird.

Verellen Meatsmoke.png

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Post by ppluis0 »

Hi vigilante,

To avoid have mains wires inside a tube pedal, the best option (IMHO) is to employ something similar to this diagram:

Image

The subsection drawing inside a dashed lines must be a 12v wallwart with enough capacity to feed all the heaters and the internal transformer also be of a smaller size than the one seen in your photograps.

Cheers,
Jose

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Post by vigilante397 »

ppluis0 wrote: 09 Sep 2021, 17:05 Hi vigilante,

To avoid have mains wires inside a tube pedal, the best option (IMHO) is to employ something similar to this diagram:

Image

The subsection drawing inside a dashed lines must be a 12v wallwart with enough capacity to feed all the heaters and the internal transformer also be of a smaller size than the one seen in your photograps.

Cheers,
Jose
Thanks for sharing Jose, that's definitely a way to do it. When I do tube pedals I take a 9VDC input and step it up to high voltage with a "nixie style" SMPS. Much smaller and less expensive than a transformer, and makes the end result much more pedalboard friendly.

I'm finishing up my layout for the Meatsmoke now, I'll post pics when it's done. A couple things I added: jumper option to bypass LM2733 to run opamp at 9V instead of 24V, in case the LM2733 layout is noisy I still want to be able to test the record out, and jumper option to bypass the MOSFET output buffer so I can try going straight out from the last tube section.

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