# NuAD: Ceriatone OTS Mini "Lunchbox" Build



## Randy (Jun 26, 2015)

*New (unassembled) Amp Day*

Got bit by the bug and decided to build a Ceriatone OTS Mini. This is based on their regular OTS (Overtone Special), which is their version of a Dumble Overdrive Special. I haven't dug into it much yet but so far I'm pretty impressed by the quality of the components (though I did enough research that I knew what to expect) and was REALLY impressed by the shipping (2 day express from Malaysia to New York )

I've been in the market for a lunchbox amp for a while, and this seems to fit the sound I'm after. Depending on how this works out, a Son of Yeti build might be in the cards next.

I'm mostly planning on sticking to the original layout, though I've got a couple secret plans in store for the headshell itself.

















Update 11/21/17:
Amp is finished: http://www.sevenstring.org/threads/nad-ceriatone-ots-mini-i-made-this.326377/

The build:


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## Vostre Roy (Jun 26, 2015)

Nice to see you getting into amp building Randy, the more the merrier! I'll follow that build of yours for sure, keep us updated on your progress man!

Although I can't say I has eared an original Dumble amp, I have helped my friend to build his Weber Halle (their take on the Overdrive Special) and its a surprisingly awesome amp, lots of gain on tap and pretty awesome cleans. We've upgraded the OT for an Hammond and tubes for JJs E34L and 12AX7 aswell as the pots, wich were stocks Weber and not the best quality wise.

All and all, its a very nice project and I'm sure you'll find its sound interesting once its built.

Cheers man!


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## Shask (Jun 26, 2015)

Awesome!

I have a JCM800 based amp I built, but blew the power transformer last year. Need to fix that! It was just starting to sound good after modding it a hundred times!


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## HighGain510 (Jun 27, 2015)

Sweet! I've heard good things about his amps but still haven't played them! Curious to hear your thoughts on how she sounds once this one has been built sir!


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## wakjob (Jun 27, 2015)

Nice Randy. Looks like a fun build. I actually played one of those a few years ago...sounded awesome!

Contemplating doing another 5e3 myself. I love that MoJo Tone kit I built. Having another one to be able to run in stereo has me itching to play with the soldering iron again.


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## Zado (Jun 29, 2015)

Huge Nik fan here,I have a Yeti 50w and it's funny how many major bottoms it kicks.If the Son is anything like his father,then you're gonna have some real fun with that too.

Never played an OTS mini btw,but a friend of mine built the large version some years ago,and it's one of the best sounding amps I've ever heard at what it does.Hope to see some clips as soon as it's finished!


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## Randy (Jul 2, 2015)

Shask said:


> Awesome!
> 
> I have a JCM800 based amp I built, but blew the power transformer last year. Need to fix that! It was just starting to sound good after modding it a hundred times!



Nice! I'd love to hear more about it. What platform you started with, what mods you've done, etc.

I've been tinkering with the idea of getting something like a Peavey Windsors and doing a Jose or Snorkler mod on it.



Zado said:


> Huge Nik fan here,I have a Yeti 50w and it's funny how many major bottoms it kicks.If the Son is anything like his father,then you're gonna have some real fun with that too.



If the clips I've heard are any indication, the differences between the full sized Chup/Yeti vs the Son are significantly less than MOST of the lunchbox formatted heads I've heard. The clips on Ceriatone's youtube channel sound like they've got crazy overhead for being 20 watts. 

Anyway, minor update.

Decided I wanted/needed a chassis cradle. This isn't the first amp I've tinkered around with on the inside and it won't likely be the last, so something I could use to conveniently hold the amp and rotate it was in order.

The general design is basically a mix of all the different cradles I've already seen. I 'overbuilt' the design so that I could slide out the sides to accommodate a much larger head. I also deliberately made the cradle wider than the lunchbox chassis so that I could attach something smaller (in this case, metal 'right angle' reinforcements) that'd be easier to work around, since this is a full wiring job as opposed to a simple repair job.

For ....s and giggles, the process involved.

Sketch on the back of a piece of mail (dimensions are approximate and did change a little by the time it was finalized)






Some free time on the weekend, so fed the design into Sketchup.






Final product made out of barn siding. The uprights were left rough deliberately on the outside, all surfaces that needed to rest securely on anything else were planed smooth. I may eventually to more 'finishing' type work on it (erasing pencil marks, hiding screws, etc.) but for now, it's all about function and, well, it functions.


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## Zado (Jul 2, 2015)

^Me likes dat! Following with tons of interest!


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## Vostre Roy (Jul 3, 2015)




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## Shask (Jul 6, 2015)

Randy said:


> Nice! I'd love to hear more about it. What platform you started with, what mods you've done, etc.
> 
> I've been tinkering with the idea of getting something like a Peavey Windsors and doing a Jose or Snorkler mod on it.



It started out as part of a Weber kit I got in a trade in pieces. I replaced a lot of things with Metro parts, and kind of Frankenstein merged the 2 designs together. First it was a typical 4 input Plexi. As a high gain guy, that got boring quick, so I rewired it into a 2203 JCM800. That sounded pretty good, but my vision was always to have something that could sound like Fear Factory's Demanufacture mixed with something like Anthrax's Among the Living with a little bit of Slayer's tone. I really didn't care about having a ton of switches and stuff, I just wanted that tone straight in.

This spanned out several years. I would tweak on something, then play it for a month or 2 and then blow a tube. It would sit for a year, then I would get the itch to mess with it, so then I would fix it up and play with modding it for a few weeks, then something else would happen, and it would sit for a year, etc.... it was never my main amp, just something fun to play with.

I have went mostly digital (Axe-FX) so it sat for a long time, but I started messing with it again last winter. I actually upgraded several parts I had ordered years ago, and tweaked out the mods and finally got it to where I felt like it was done. I was messing with trying to put a noise gate in it, and something happened and the power transformer fried itself. Again it sits. I need to get a new power transformer and bring it back to life again. It was starting to sound pretty good!

I have modded it so many times. Constantly tweaking the gain stages and EQ. It is almost a curse to build amps because as soon as you think it is done, you start thinking about that last capacitor and wondering what happens if you lower it  Basically, now it is a stock 2203 JCM800 with a depth control, and an extra gain stage before the stock amp to bring it up to modern levels of gain. I found that as I made extreme EQ changes I could get it to sound good for some particular sound, but at the same time taking away that classic Marshall tone. After modding and modding, I decided that keeping it close to the standard JCM800 specs sounded best for most situations. For example, I could change the slope resistor and make it sound all scooped and heavy, but then it couldn't really do any other tone than that. For awhile it had so much gain I had to keep the gain on like 2  Any more than that and it was super fuzzed out and thick with no definition. My goal was to have the right amount of gain with the knob at 8, because I like the effect of the treble cap on the gain knob. Finding the right level of gain was always the thing I struggled with the most. I think I finally clipped a pot in there, turned it to where I wanted it, and then measured it and replaced with resistors.

I could go on and on about this, but I am sure you dont want to read a novel, lol. It is a lot of fun to build an amp. I have always thought about building another, but it just seems like "why" when you can buy so many different amps for pretty cheap. I could build a Recto or something, but it would be cheaper to just buy one. I have heard Windsors are hard to mod. It might be worth it if you got a broken one, gutted it, and put a hand-wired board in there. Replace all the guts and only reuse the enclosure.


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## Randy (Jul 8, 2015)

Shask said:


> It started out as part of a Weber kit I got in a trade in pieces. I replaced a lot of things with Metro parts, and kind of Frankenstein merged the 2 designs together. First it was a typical 4 input Plexi. As a high gain guy, that got boring quick, so I rewired it into a 2203 JCM800. That sounded pretty good, but my vision was always to have something that could sound like Fear Factory's Demanufacture mixed with something like Anthrax's Among the Living with a little bit of Slayer's tone. I really didn't care about having a ton of switches and stuff, I just wanted that tone straight in.
> 
> This spanned out several years. I would tweak on something, then play it for a month or 2 and then blow a tube. It would sit for a year, then I would get the itch to mess with it, so then I would fix it up and play with modding it for a few weeks, then something else would happen, and it would sit for a year, etc.... it was never my main amp, just something fun to play with.
> 
> ...



Great info! Don't be worried about typing too much, I love geeking out over this stuff  I might need to pick your brain on a few things in the future.

I hadn't heard that about the Windsor before. I had that in mind because I know FJA offer a lot of their Marshall 'high gain' mods on them at or below the price on some of their amps, but that might be a little 'smoke and mirrors'? I'll see if I can find a gut-shot... if it looks too rough, I'll see about a decent Plexi or JCM clone and work my way up from there.

Sorry for bumping with no new info or pics.

As an update, I took all the stuff out of their packaging, did an inventory check versus the item list (matched up near perfectly, sans the rating on one Slo Blo fuse) and organized everything into small plastic bins. I'll probably post a picture of that tomorrow-ish?

Anyway, that out of the way, the amp is all ready to be assembled. I cleared off the bench in my woodshop, vacuumed and got it all ready for this project. I've got my GoPro mounted overhead, so I'm planning on doing probably a time lapse of the build. That will mostly contain the actual assembly of boards, populating the chassis and wiring; then I'll probably make a separate thread for the headshell project (since, spoiler, it's going to be wood so it'll probably fit into 'luthier' subforum better).


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## Randy (Jul 9, 2015)

As promised, a small update.

Like I mentioned earlier, I opted to sort all the baggies into labelled bins. With them sorted this way, I can basically go through the layout from Ceriatone's website, pick the item from the bin and place it in the board.

Quick shot of the workbench, ready to go:






A few pictures of the bins. I bought two cheap-y kinda bins from Harbor Freight. I ended up needing more, so I tried Walmart and the Plano fishing lure organizers were actually similarly priced and MUCH nicer (more secure latches, better fitment, etc.).

Please forgive my chicken scratch handwriting. The masking tape kept swallowing up the ink from my pen, so I'm probably going to use my labelmaker or something next time around to make it more legible.











Like I mentioned before, I'm videoing this to make a time lapse video of the process.

The camera I'm using is a GoPro Hero3, which is awesome and all but the time lapse function is a bit of a PITA. It saves every frame as a JPG at full resolution (my first test clip was 11megapixels per frame ), but you can reduce the image size to 5 megapixels, which makes the file size at least manageable. After that, I just bulk resized all the images in Apple Preview, then you load them into GoPro Studio and it's pretty straightforward to assemble them. I might touch on all that more in depth when I finish the video.

Here's a shot of the recording rig. The mount is from a kit I bought on ebay for ~$25 that came with a crapload of stuff (selfie stick, chest mount, head mount, etc). I've used this mount on my car before and it's crazy sturdy, so it seemed up for the task.






A preview shot of what the view looks like from it. I had to do a lot of tweaking to make sure it gets all of the bench (and preferably little of my beer belly ) The test footage has an annoying amount of that 'rolling' effect from the fluorescent lights that I'm HOPING to eliminate in post processing.


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## Randy (Nov 19, 2015)

Quick update and hoping for some advice...

So, I got this assembled a few weeks ago. I had a little while I had to tweak some electrical gremlins but eventually it came to life and it sounds great. HOWEVER, there a re a couple issues before I'd consider it 100%... I posted on the ceriatone looking for some advice and that place is a ghost town, so I'll defer some of my questions to you guys instead.

Copy pasta

_Now that I've gotten most of the worst operational gremlins out of the way, there's one nagging issue I have yet to settle.

The impedance selector, when set to 4 ohms, works just fine (although it's a mismatch with my speakers, so a little think... hence the issue and hence this thread) but neither 8ohm or 16ohm setting works. Both just send out white noise at full volume, the 8ohm setting fairly loud, and the 16ohm BLISTERING loud... both totally ignore changes to any volume knob on the amp... they just blast full volume and they transmit NO guitar signal at all.

The main part of it that confuses me is the fact that obviously all three settings are originating from the same place and being sent to the same jack, so I'm having a hard time understanding why I'd be getting a varied response from each? I thought I might've wired the selector switch wrong, so I desoldered everything, rotated it to the next group of pins and got the same result.

One thing I noticed was the fact there's a line that runs from the board to just one pin on the impedance selector switch... which just so happens to be the only one that's working for me, the 4 ohm pin. Being the type to do my due diligence, I looked at some other Ceriatone layouts and noticed that same lead wire is attached to different pins of the selector on different amps. There's some degree of continuity between all the secondary wires on the OT, so the design makes sense to me logically but I'm not sure why I'm getting the result I am? Real head scratcher.

Anyway, any advice would be a big help. For reference, here's the area in question... you can see what I'm talking about re: the green lead into the 4ohm pin.






White noise might not be the best description because it's not so much electrical buzzing noise or hissing, it actually sounds like a solid test tone being sent through the amp at FULL volume... it sounds like all the knobs on the amp turned up all the way but it's sort of 'musical' in that you're actually hearing amp tone, not just electrical buzzing._​
Then I posted a follow-up this morning:

_Quick update, incase I'm not the only person reading this thread.

As I was messing around with this today, tried a few experiments and made a couple observations.

My cabinet is 8ohms. If you're following from the first post, the 4ohm position is the only one working, and it's also the one that the green lead from the PCB is wired to. I decided to wire the green lead to the 8ohm lug, and I was able to get guitar to come out of that, the 4ohm AND the 16ohm but all of it was accompanied by LOTS of noise and that same "everything turned up all the way" sound I was getting before. Since I went from "no guitar signal" on two lugs, to "guitar signal through all of them" by soldering it a different impedance setting, does that implicate the rotary switch itself?

Two other observations:

I decided to try running the effects loop 'send' to a different amp to check and see if that was working correctly and to see if the preamp was in full working order.

When I plugged the external amp into 'send', I was getting sound out of both the second amplifier AND the speaker connected to the OTS. That's obviously not right.

When I plugged the external amp into 'return', I was getting signal just through the second amplifier, and it responded to knob adjustments just like it should, with no extra noise.

So is there some potential the impedance selector is originating from something wrong with either the jack(s) or somewhere in the connection between them and the power tube section?_​


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## zilla (Nov 19, 2015)

have you verified the grounds on the other impedance positions on the switch and the power section?


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## Randy (Nov 19, 2015)

As far as I can tell, the impedance selector doesn't have a ground but the secondaries on the OT are "16ohm 8ohm 4ohm and 0ohms" and the 0ohm (black) acts as the ground, which runs to the ground terminal on the output jack. Since there's continuity between all the secondaries, I'm led to assume that's how they reach 'ground'. I suspected an issue there at one point, so I checked and I am getting continuity between the 4/8/16 lugs and the chassis. 

To be honest with you, that's what the wiring diagram shows but the ground system on all the rear jacks never made a whole lotta sense to me in the first place.

Regarding the grounding for the sockets themselves, that's a good point... I'll look all that over more when I get home.

For reference, here's the layout from Ceriatone:






Unfortunately, it doesn't show the signal path. The full-sized OTS does, however, and it's near identical (sans a few values). 






And incase I didn't overload anybody with information, here's the schematic:


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## zilla (Nov 19, 2015)

the FX loop jacks are grounded to the speaker output jacks, which look like they're grounded to the chasis as well as the bias pot and power tubes. i'd double check those grounds to make sure that they're continuous and no cold solder joints are present.


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## Vostre Roy (Nov 19, 2015)

Two other things to look at:

The OT primaries (blue and brown wires) might have to be inverted if you haven't tried it already. Just switch the blue and brown wire on the pins 3 of the power tubes.

Since you mentionned the "green wires that goes from the pcb to the 4ohms lug" and by changing it from a lug to another, there's a change, I'd begin to suspect an issue with the negative feedback loop if my first suggestion doesn't solve it. Make sure that the green wire goes to the 4k7 resistor and that the resistor is wired to the presence pot, as illustrated

Cheers!


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## beneharris (Nov 19, 2015)

zilla said:


> the FX loop jacks are grounded to the speaker output jacks, which look like they're grounded to the chasis as well as the bias pot and power tubes. i'd double check those grounds to make sure that they're continuous and no cold solder joints are present.



I'd second that cold solder joint. Whenever I'm debugging a pedal I've built, 90% of the time its not a mismatched component its a cold joint.


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## vick1000 (Nov 20, 2015)

Did you check continuity of the impenace switch? I would also check what's coming off the OT.


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## Randy (Nov 23, 2015)

*IT'S ALIVE!*

Full credit to all you guys that contributed. I tried a combination of most of what was listed in this thread... I can't say for certain which corrected it but the steps I took were:


Checked all jacks for loose and cold solder joints. A couple were questionable, so I warmed the joints and added an extra dab to all connections.
Checked all the connections on the power tube sockets and found one or two questionable point, which I also warmed up and added an extra dab of solder to.
De and re soldered all ground connections involving the power tubes, output jacks and the effects loop.
Reversed the 'brown' and 'blue' primary wires to the OT

After that, I powered it up and 1.) all impedance positions were working 2.) the effects loop was working, fully 3.) while there was no excessive hum before, there was even less now.

I was hoping to get a clip of this thing in action, but my cellphone mic just sounds like noise. I'll try to remember to bring my Zoom recorder with me tomorrow, so I can get a quick clip of the slops.

As far as the next step. I've got a nice piece of Peruvian Walnut I'm planning on using for a headshell, and I picked up a dado stack to assemble it using 'box joints'. 

Anyway, thanks again everybody! I honestly was so deflated the first couple times I powered the amp up and was having all those issues... I sat on it for a few weeks and was pretty seriously considering shelving it and getting something pre-assembled, but all the advice gave me the inspiration to give it another shot and paid off. You guys are the best!


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## Vostre Roy (Nov 24, 2015)

Congrats Randy! Always cool to see a project goes from "parts laying around" to "lets jam with that mofo"!

I'm currently debating about my next amp project and a 100w Overtone Special really looks tempting, I'm interested at hearing some clip of yours, I've saw a couple of youtube videos but the more the merrier!


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## zilla (Nov 24, 2015)

Randy said:


> *IT'S ALIVE!*


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## ElRay (Nov 24, 2015)

Randy said:


> *IT'S ALIVE!*



OK. Now I can make jokes about Randy having two trannies in his shop with a webcam, w/o fears of sprayed coffee shorting something out and electrocuting him.

Ray


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## Randy (Nov 24, 2015)

Vostre Roy said:


> I'm currently debating about my next amp project and a 100w Overtone Special really looks tempting, I'm interested at hearing some clip of yours, I've saw a couple of youtube videos but the more the merrier!



Initial assessment so far... I bought this amp because I wanted clean volume with some break-up on the top end (the kinda sound Robben Ford's known for, and kind of a signature Dumble ODS sound). My experience is a _*little*_ different than what I was anticipating, although I'd say I can still achieve what I'm after.

Channels:

The clean, completely 'un-boosted' channel is probably the most sensitive to EQ adjustments, stays clean most of the way up as you increase volume but it's pretty flat sounding and lacking in volume. Potentially might be the best setting if you want all your tone to come from your pedals.

The 'Preamp Boost' (green button on the pedal) channel is probably the closest to the sound I had in mind when I purchased the amp. There's a very significant volume increase, some overall increase in brightness and earlier (but still late) break-up. This would be my first choice if you're looking to do clean/crunchy blues, especially with an OD of some kind.

The 'Overdrive" (red button) setting was the biggest surprise. Breaks up VERY early and gets really gainy as the volume goes up. I wouldn't say like, modern high-gain but definitely like a classic, cranked OD channel. The OD Trim knob and Ratio obviously have an effect on the gain level, but also a more noticeable effect on the sustain. The rest of the knobs have a significantly diminished effect on the EQ, in my observation.

Knobs and Switches


As I said, it's the clean channel is MOST receptive to EQ tweaks, which means the Rock/Jazz and mid-boost switches are very effective on that setting. There's still some effectiveness on the 'Boost' channel but significantly less on the 'OD' channel.
[*]The 'Jazz' setting has a very mellow 'flat wound string' sounding effect, like you've got you tone rolled off; the 'Rock' setting has a lot more sparkle to it and chimey-ness... it's got some rock influence but it sounds a little bit twangier to me. There's a noticeable increase in gain if you have the switch on 'Rock' once you get into higher volumes.
[*]With the 'Mid-Boost', once again, the 'off' position has a really flat, muted kind of sound. With the boost engaged, it mostly does exactly as it says.. a mid bump, mostly in the 'high mids'. Personally, I'd consider this almost more of a 'mid cut when it's off' rather than a 'mid boost' when it's engaged; because it sounds a little too dead for most things when it's switched off. YMMV​
The 'Bright' switch (volume knob, pull-out)does as described, although it's not as 'sparkly' as I'd have expected... gives it more of a Marshall-y crunch.


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## Drew (Nov 24, 2015)

Hey, this is an awesome project, Randy. Definitely record some clips, and post up over at MG when you do, as well, so I don't miss it!  

How much soldering experience had you had prior to tackling this? Your stories about "white noise at full blast" have me thinking this isn't a good "condo in the middle of the city" project, but I'd be curious to try something like this one day...


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## Randy (Nov 24, 2015)

Oh yeah, I was going to cross-post that review on MG and forgot. I'm definitely going to get some clips put together, and I'll just copy-pasta along with that when I get around to it.

Re:soldering experience - I've made, modded and repaired a few pedals before this, and I've diagnosed and repaired a few amps and pieces of rack gear. Never anything on this scale, but definitely a bit of soldering small points on printed boards. The biggest challenge was working inside the amp after it started to get populated with wires. In total, the soldering job itself wasn't that bad between having a clean, hot iron and super clean contacts that took solder on the first try (most of the time )

The max volume on a project this size is definitely loud when you've got it powered up and you're not expecting that to happen, but it's still at MOST at or below 'band practice' volume... so it's not something you'd wanna be debugging at 2am but for a Saturday or Sunday afternoon type project, it's nothing too unsettling plus you can kill it with the 'standby' switch pretty quickly.

Another option would be to use an attenuator to make sure you're never above a certain volume no matter what, or a load-box into some kind of oscilloscope (I've got a freeware one on my laptop and on my phone) that'll at least tell you that you've got signal without having to actually power up a speaker; then just hook-up a speaker when you're positive you're not getting any funny stuff or you know your neighbors aren't home.


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## Drew (Dec 1, 2015)

Cool, good to know.  Always wanted to try a pedal, at least, so maybe I'll start there.


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## loganflynn294 (Dec 1, 2015)

Very nice! I'm in the middle of a Chupacabra 100 build myself. Nik really is a great guy, the components and shipping were waaay above expectations.


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## bredniol (May 28, 2016)

Hello everyone,

can someone provide a voltage chart for this amp?


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