My Latest Build

[Paul Marossy]

I just got done with my "English Channel" this morning. I built it per the perfboard layout at ROG.

I just re-used the enclosure I did for my "Blackfire" with a Marshall tone stack, which just didn't excite me much. Anyhow, I just wanted to say that I really like it, and kudos to the ROG team for coming up with this.

[kurtlives]

Nice build Paul.

I also like my EC, very chimey yet has that great "girth" even at low gain settings. Imo it seems like the closet thing to the real amp ROG has released.

Is the mid knob the cut knob now?

[Paul Marossy]

Nice build Paul.

I also like my EC, very chimey yet has that great "girth" even at low gain settings. Imo it seems like the closet thing to the real amp ROG has released.

Is the mid knob the cut knob now?

Thanks. Yep, the mid knob is now the cut knob. And I agree on the tone, it really does sound very good.

[oldrocker]

Nice job Paul.  Did you bread board it before you built or did you just start perfing?  I've been considering building this one but haven't read too many reviews about it until now.  It looks like an interesting amp sim.  Wow, that's alot of knobs!

[Paul Marossy]

Nice job Paul.  Did you bread board it before you built or did you just start perfing?  I've been considering building this one but haven't read too many reviews about it until now.  It looks like an interesting amp sim.  Wow, that's alot of knobs!

Thanks.

I just built it per the perfboard layout at ROG. The hardest part about it was getting everything to fit in there. You can't really see it in the picture, but I had to notch each end of the circuit board for the tips of the cables. The circuit board is held in place by a couple of flat top screws generously super glued to the enclosure.

As far as sound, it really does sound great! I was playing it some more yesterday, and I have to say that it really does bring out all of the nuances in my playing, without it sounding too harsh (I hate harsh!). It's kind of what I've been looking for for a long time but haven't been able to quite find. Until now that is. 

[MikeH]

When I built the EC, I found that I couldn't find a biasing point that worked well for all gain settings.  If I bias it kind of cool, it sounds great with the gain all the way up, but the lower gain settings sound crappy.  If I bias it to get nice low gain tones, the high gain settings are too saturated and squishy/spattery.  Anyone else have this issue?

[Paul Marossy]

When I built the EC, I found that I couldn't find a biasing point that worked well for all gain settings.  If I bias it kind of cool, it sounds great with the gain all the way up, but the lower gain settings sound crappy.  If I bias it to get nice low gain tones, the high gain settings are too saturated and squishy/spattery.  Anyone else have this issue?

I haven't tried with it with all the possible control combos, but the way I set the controls, it sounds great. The only complaint I have is that it does have a slight "fizz" on the decay when play single notes. It almost sounds to me like it's a real low key oscillation happening. I don't quite know how to describe it.

My voltage measurements are slightly different than what is specified at ROG. The source on Q1 & Q2 is in the 0.35-0.36V range instead of around 0.16-0.17V and the source on Q4 measures about 1.8V instead of around 1.6V. I don't know how much of a bearing that has on what I am hearing. I'm going to tweak it a bit more to see what can be done to perfect it.

It sounds like the variability of the J201s is what causes most people grief when they build this particular circuit.

[aziltz]

great looking build paul.  i have a half-built EC built on the OLC PCB.  Waiting on some 1M Pots.  I'm pretty stoked about my enclosure, I got PPP to do a brushed/anodized finish in red, like the faceplates of the newer vox custom classics.

you used J201s?  Have you tried 2n5457s or 2n5458s?  I've had good experiences with them in other FET builds (Fetzer, Omega, etc...)

[Paul Marossy]

great looking build paul.  i have a half-built EC built on the OLC PCB.  Waiting on some 1M Pots.  I'm pretty stoked about my enclosure, I got PPP to do a brushed/anodized finish in red, like the faceplates of the newer vox custom classics.

you used J201s?  Have you tried 2n5457s or 2n5458s?  I've had good experiences with them in other FET builds (Fetzer, Omega, etc...)

Yeah, I used the last of my J201s for this project. I think have some 2N5457s & 2N5458s that I could also try for kicks.

[kurtlives]

When I built the EC, I found that I couldn't find a biasing point that worked well for all gain settings.  If I bias it kind of cool, it sounds great with the gain all the way up, but the lower gain settings sound crappy.  If I bias it to get nice low gain tones, the high gain settings are too saturated and squishy/spattery.  Anyone else have this issue?

Try 50K or 75K drain trimmers. It's easier to dial in the perfect bias point that way I find. Experimenting to fnd the right FETs also helps I find.

A good "mod" with these FET circuits is to bias your FETs up. Measure the resistance on the trimmer then replace it with a fixed resistor. It really helps kill noise.

[Paul Marossy]

Try 50K or 75K drain trimmers. It's easier to dial in the perfect bias point that way I find. Experimenting to fnd the right FETs also helps I find.

A good "mod" with these FET circuits is to bias your FETs up. Measure the resistance on the trimmer then replace it with a fixed resistor. It really helps kill noise.

Yeah, I've found that the 100K trimpots are a bit difficult to dial in exactly. On all of mine, just the slightest movement can change it by 1/2 a volt. It takes a very light touch to dial those in exactly. I think a 50K pot would be a lot easier to deal with.

[CynicalMan]

Try 50K or 75K drain trimmers. It's easier to dial in the perfect bias point that way I find. Experimenting to fnd the right FETs also helps I find.

A good "mod" with these FET circuits is to bias your FETs up. Measure the resistance on the trimmer then replace it with a fixed resistor. It really helps kill noise.

Yeah, I've found that the 100K trimpots are a bit difficult to dial in exactly. On all of mine, just the slightest movement can change it by 1/2 a volt. It takes a very light touch to dial those in exactly. I think a 50K pot would be a lot easier to deal with.

Maybe I just have weird FETs, but I normally use 20k trimpots.

[Paul Marossy]

Whatever the case, I just added a trimpot to the source of Q4 and kept adjusting them both until I got 4.5V on the drain and 1.6V on the source. It didn't take too long to do.

That seems to minimize the fizz on the decay of the notes as much as possible.

[Paul Marossy]

OK, so now I have a problem that I just discovered since I have been playing it a little louder. 

When I have volume up close to all the way and I turn the master volume up a little past 10 o-clock, I get a pretty noticeable buzz. It's made worse when you turn the treble and cut controls up. If I try to use my wah pedal, it basically starts to oscillate immediately.

I checked the regulated power supply on my pedal board and even added one more filter cap to it. That did help a little bit, but I'm not sure why I have this problem. I do have the wah pedal in front of it, so it's probably amplfying the hum picked up by the inductor.

The only thing I can think of is that the (3) 22uF caps I substituted with 33uF caps might have something to do with it. I'm thinking that perhaps that increased the gain too much and it's just amplifying the heck out of a tiny amount of hum present in the system. It does have quite a lot of gain available, which I take it is not the norm after reading what other people have said about their builds.

Any second opinions on that maybe being the problem?

[CynicalMan]

OK, so now I have a problem that I just discovered since I have been playing it a little louder. 

When I have volume up close to all the way and I turn the master volume up a little past 10 o-clock, I get a pretty noticeable buzz. It's made worse when you turn the treble and cut controls up. If I try to use my wah pedal, it basically starts to oscillate immediately.

I checked the regulated power supply on my pedal board and even added one more filter cap to it. That did help a little bit, but I'm not sure why I have this problem. I do have the wah pedal in front of it, so it's probably amplfying the hum picked up by the inductor.

The only thing I can think of is that the (3) 22uF caps I substituted with 33uF caps might have something to do with it. I'm thinking that perhaps that increased the gain too much and it's just amplifying the heck out of a tiny amount of hum present in the system. It does have quite a lot of gain available, which I take it is not the norm after reading what other people have said about their builds.

Any second opinions on that maybe being the problem?

According to the ROG fetzer valve article, that cap increases the gain by 6dB but also acts like a low pass filter. 1/(2*pi*1500*0.000022) = 4.82Hz and 1/(2*pi*1500*0.000033) = 3.22Hz so there shouldn't be much audible difference between the two.

[Paul Marossy]

Yeah, but increasing the size of the bypass caps also increases the gain. If it's increased by about 6dB at each FET that has a bypass cap (total of 3), then that's 18dB or so of gain in total. 12dB of that would be occuring in the first two stages.

Maybe that's enough to push things over the edge?

EDIT: I played it again this morning and now it sounds pretty quiet. I think it must have been the location in my house where I was doing the testing yesterday. There is a lot of wall warts in the general vicinity and I think that must have been a factor. Anyhow, now I am a happy camper again. It sounds very good with my DiMarzio FRED on the bridge.