# My M800 is apparently a bust



## PKRPedals

I can't get this pedal to do right. It sounds pretty good when the chord is struck but there is very little sustain and the notes just sort of fizzle out. I've tried a new set of J201's and still the same thing. I have tweaked till I can't tweak anymore and can't get it to act right. So I guess this one will go on the shelf for awhile.


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## music6000

PKRPedals said:


> I can't get this pedal to do right. It sounds pretty good when the chord is struck but there is very little sustain and the notes just sort of fizzle out. I've tried a new set of J201's and still the same thing. I have tweaked till I can't tweak anymore and can't get it to act right. So I guess this one will go on the shelf for awhile.


My M800 was doing exactly what you describe
 All the Trimmers were adjusted to 4.5v & it was meh, no sustain. 4.75, 5v, 5.25v & 5.5v, Louder with no Gain!
*Old School*, Strummed a Chord each time & tuned each Trimmer by ear til it was at its Fullest.
Did this 3 times as each adjustment effects the other Trimmers.
The Tone Trimmer is actually a Internal Potentiometer.
CCW will yielda a Bigger Brighter Sound, Mine is at 9.00 with 7.00 being Fully CCW
The J201 below it is separate from it & has Fixed Voltage.

*Awesome JCM800 Emulation !!!*


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## PKRPedals

I get what you're saying, but I have done that over and over but just can't get rid of the fizzle out on the notes. It has plenty of gain and volume, just the notes won't ring out like they should. I have went back through and checked components and looked at solder joints but I didn't find anything weird.


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## PKRPedals

UPDATE: Lesson learned
Solder transistors into the socket or they might not make good contact. Anyway, I still need to tweak it but it already sounds way better. Thanks to the help of a really good forum member Music6000.


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## Nostradoomus

Glad you got it going! I find putting a thin layer of solder on the legs (like pre tinning  your wire) can help a lot too.


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## PKRPedals

I did get it going but it’s not great, but that just may be me. It still has the tiniest bit of sputter but is way better than it was. The problem is I built the Thermionic Deluxe and it is amazing so everything else has to sort of measure up to that in my mind. It’s all good though, I’ll keep messing with it until I’m happy or it gets put on the shelf.


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## Nostradoomus

I’ve always like 5457s in J201 circuits...I made a sunn model T preamp that acted much the same as your 800 until I put 5457s in it.


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## PKRPedals

I’ll try that next time I need J201’s. I also read that J112 were a good sub as well. These are soldered I’m so it would be too much trouble to try and change them. I haven’t had too much luck with the JCM style circuits. I built the one from PCB Mania and it wasn’t great either. I also think the trimmers that I have been using aren’t very good. I’m going to order some of the Cermet trimmers next time.


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## Jovi Bon Kenobi

So far I've had a couple builds with j201s. FWIW, they came alive when I used Siliconix branded one's. They had better gains for each application I guess...in the .80mA  to .90mA range. The Fairchild j201s I tested had way lower gain, like around .35mA to .50mA. The difficulty is sourcing Siliconix j201s though.


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## PKRPedals

J201’s in general are hard to find. The ones I used are Fairchild though. I’ve used them in other builds and they are good. It just seems the JCM style circuits don’t turn out good for me.


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## Barry

I built a KOTB (King of the Brits) from GuitarPCB using J201's that sounds awesome, it's a hotrodded JCM circuit


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## PKRPedals

I also built the KOTB and wasn’t impressed with it. I couldn’t seem to get the gain out of it that is is supposed to have. In the video of the KOTB, it has a lot more gain than I could get from mine. Maybe I just suck at building JCM pedals. Haha


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## Barry

Where were you buying your J201's? there are lots of fakes out there


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## PKRPedals

The ones I have now I got from pedalhacker on reverb


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## Barry

I think I bought mine from GuitarPCB when he offered them


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## Barry

I had to build three more KOTB's for friends that wanted them after hearing mine.


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## PKRPedals

That’s where I got the ones that I used in my KOTB. Actually the KOTB was the first pedal I built because that what I was looking, that hot rod Marshall sound.


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## PKRPedals

pretty much everything I’ve built has turned out great except for the Marshall style pedals. I’ve built quite a few of the Guitar PCB circuits and they all turned out good except for the KOTB and the Plexi Plus, neither one of those really wowed me.


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## Barry

Maybe I've just got the wrong Marshall tone in my head


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## PKRPedals

No it’s probably me just expecting a miracle


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## PKRPedals

I just pulled out my KOTB and I guess it sounds pretty good. I just wasn’t remembering I guess. The gain control doesn’t do a whole lot. I can tell a slight difference when turning it but not much increased gain. Is that what you’ve found with it?


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## Barry

That gain control is for warming up vintage pickups, with modern higher output pickups it won't do much from what I read in the build documents


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## griff10672

Jovi Bon Kenobi said:


> So far I've had a couple builds with j201s. FWIW, they came alive when I used Siliconix branded one's. They had better gains for each application I guess...in the .80mA  to .90mA range. The Fairchild j201s I tested had way lower gain, like around .35mA to .50mA. The difficulty is sourcing Siliconix j201s though.


Interesting ...... I used Siliconix J201's in my M800's as well .... got them from Smallbear I think ... they have the white dots on top ... they sound amazing ...


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## PKRPedals

My M800 has been put on the shelf. I'm still not getting it. I think I've tweaked it as much as it can be tweaked and to be honest, it just doesn't sound great. The gain control is pretty much useless when trying to turn down the gain. I pretty much have to have the gain wide open for it to sound half way decent. It still has that sort of fizzle out on some of the notes. It does have more sustain but not what you would think it should have. I guess this one is just a bad build. I'm sure everyone has had one from time to time. Maybe I'm just expecting too much.


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## griff10672

PKRPedals said:


> My M800 has been put on the shelf. I'm still not getting it. I think I've tweaked it as much as it can be tweaked and to be honest, it just doesn't sound great. The gain control is pretty much useless when trying to turn down the gain. I pretty much have to have the gain wide open for it to sound half way decent. It still has that sort of fizzle out on some of the notes. It does have more sustain but not what you would think it should have. I guess this one is just a bad build. I'm sure everyone has had one from time to time. Maybe I'm just expecting too much.


really sounds like you got some " reject " J201's  ..... 
the more I research obsolete chips and transistors ...... the more I see " beware of fakes and rejects " 
I've read that a lot of obsolete components out there for sale are also " factory rejects "  that work ... but were scrapped for some kind of quality issue ..
but who knows ...... I try whenever possible to get the obsolete parts from Smallbear ..... have never had a problem with anything from there


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## PKRPedals

I may try and get some from smallbear and give it one more shot. These J201’s came from pedalhacker so I assumed they were legit. I’ve tried 2 different sets in it also


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## griff10672

PKRPedals said:


> I may try and get some from smallbear and give it one more shot. These J201’s came from pedalhacker so I assumed they were legit. I’ve tried 2 different sets in it also


hmmmmm I've never heard of Pedalhacker ... have to check them out


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## PKRPedals

He was selling Fairchild J201’s on reverb until he ran out. I’ve used them in a few other pedals and they seem to work great


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## griff10672

PKRPedals said:


> He was selling Fairchild J201’s on reverb until he ran out. I’ve used them in a few other pedals and they seem to work great


sucks when a pedal doesn't work ... or worse ... works half ass .... drives me crazy actually .....

I rechecked Smallbear for more Siliconix after I did my build last weekend..... was already sold out


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## PKRPedals

This is actually my first one that hasn’t done as it should or as it is expected. Every other one has turned good.


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## PKRPedals

I ordered another M800 today. I’m gonna give it another run. Maybe the first one was just not going to work. I am going to use 2N5457’s this time, ordered from smallbear. I’m also going to use Cermet trimmers as opposed to the ones I have now. Hoping for a homerun this time


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## griff10672

PKRPedals said:


> I ordered another M800 today. I’m gonna give it another run. Maybe the first one was just not going to work. I am going to use 2N5457’s this time, ordered from smallbear. I’m also going to use Cermet trimmers as opposed to the ones I have now. Hoping for a homerun this time


interested in hearing how it turns out


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## Chuck D. Bones

J201s have very low Idss and that translates to low gain and cold bias.  Spec for J201 is 0.2mA to 1.0mA.  I have to believe that by now all of the good ones have been cherry-picked and the ones still on the market are the runts of the litter.  Or fakes.
Here's an easy way to test JFETs:
Short the Source & Gate together and connect them to the minus side of a 9V battery or pedal power supply.  Connect a 1K resistor from the Drain to the positive side of the battery or power supply.  Measure the voltage across the 1K resistor.  Whatever you get in volts, that's Idss in mA.  If Idss is less than 0.5mA (0.5V on the DMM), then you probably don't want to use it.  If you get 9V across the resistor, then Idss is greater than 9mA.  Won't happen with a J201.  For P-channel JFETs, reverse the battery.
By comparison, Idss is 1 to 5mA for 2N5457, 5mA minimum for J112, 4 to 20mA for PF5102 and 5 to 30mA for MPF4393 or PN4393.
I have built a few pedals using MPF4393s and they all work great.  I built one pedal using J201s (Corduroy) and it works great.  Small Bear sold me some good J201s, but now they're out of stock.


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## PKRPedals

I've got a tester coming tomorrow so hopefully that will shed some light on what I have. I used these same J201's in the Corduroy that I built and it sounds great. I'm looking forward to getting the next M800 built and see if maybe there is a difference.


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## Chad11491

Just finished mine and i got rid of most of the fizzing out by turning the gain all the way up. Turning the guitar volume down and lightly picking the strings and adjusting each trimmer to where i thought it sounded best. Those settings seemed to really exaggerate it “choking” out which helped in adjusting it.  It sounds pretty good now. I think spending more time with the trimmers could probably get it 100%


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## Chuck D. Bones

Can you do us a favor and once you have it dialed in to your liking, measure the drain voltages on Q1, Q2, Q3, Q5 & Q6 and report them here?  Might make it easier for the next guy to dial it in, at least get a good starting point.


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## PKRPedals

I absolutely will. I’ll be starting over on a new board and going on vacation at the end of the week so it may be a bit. I got a tester today and tested my J201’s. They appear to be good, they are reading around .5mA and 366mV or is that low. I have some 2N5458’s that are reading 1.5mA and 1.6V. Would the 5458’s work. I’ve got some 5457’s on the way, they may be better.


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## PKRPedals

Got the second M800 built. I used 2N5457's instead of J201's. It sounds a little better than the first one but still not great. The notes still sputter off instead of ringing through. I measured every component that went into it. I bought new pots for it and it still doesn't sound really good like others have reported. If anybody wants to take a look at it and see if it can be good, I will send it out. As for now it is on the shelf.


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## PKRPedals

Update: I had a little time to go back to this one. I soldered up some SMD J201's and installed them. I set the drain at 4.5 and there it is. Sounds good now. Still have a little tweaking I want to do but it's there, I just want to see if I can get it better. I guess I can chunk those other J201's and just go with SMD from now on. Thanks everybody that replied.


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## music6000

You will be surprised how much that internal Tone Trimmer has on the Final Sound also, Mine is at around 9.00 O'clock!


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## PKRPedals

Yeah I have mine set at about 9 also. I tweaked on this thing several times and ended up back at 4.5 on each 201. That’s where it seems to sound the best. Also I put my EQD Plumes in front of it and it really sounds good like that. It’s kind of like a Marshall, it sounds better with a tube screamer in front.


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## music6000

Have you tried Cranking the MIDS on your M800, that's what a Tube Screamer is famous for, Its Mid Hump!


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## PKRPedals

I put the plumes in front to bump the gain and it does that nicely.


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