Dr. Boogey Questions/Observations

[Paul Marossy]

I really love my Dr. Boogey, but I think there is some room for improvement in my case.

1. The main thing is that there is a lot of noise/hiss when I am not playing anything. The tone controls do not have much affect on the amount. But, when I am playing, it sounds awesome! 

2. I have found that what affects the amount of noise/hiss the most is how the 100K trimpots are set. I started out with them set at about 1V higher than 1/2 the supply voltage. If I set them closer to 1/2 the supply voltage, the noise level increases. If I go too high, then it starts to sound less than pleasing, before they cutoff altogether. Is there a consensus as to what drain voltages sound/work best?

3. In my experimentation with my hi/low gain switch, I have found that a 3M resistor in parallel with the 1M gain pot sounds really good (to my ears). That effectively makes it a 750K pot. There seems to be a sweet spot at there... 

4. I have built many really high gain pedals before without needing any shielded wiring. In this case I think it may help since (in a very limited set of circumstances) I can get some oscillation. But, would that help with hiss/noise? It's helped in the past with hum, but I have no idea of its impact on noise/hiss... 

5. Anyone put a wah before the Dr. Boogey? It sounds good, except for some oscillation that can happen at certain frequencies (the higher ones). This might be used to good effect, although it wants to oscillate at its own frequency rather than being something that you can control... 

6. It seems to sound a little "flubby" on the bass when I am using the neck pickup on my Parker Mojo Nitefly. I thought I remembered reading about this in another thread, but I don't remember what the outcome of that was.

Any help or suggestions are most welcome! I just need to get the bugs worked out a little bit more. 

[MartyMart]

I have similar problems Paul, increasing the drain voltage to about 5.5v helped a bit
and seems to offer more "headroom" to the distortion, if that makes sense ?
I have added a couple of 2n2 caps to ground, one just after Q2 and one pre Q4
this seems to also help some, but there's still some very high "hiss" kind of like when
you crank a mixing desk output fader right up, it seems like it's in the 14k and above area !
If you run the gain pot ( mine is a 1M log ) back to about 60%, most of the hiss will go
and the "crunch" seems to be almost as agressive.
I ran a compressor into it, to boost the front end a little, this gave back the "full crunch"
and did NOT increase the high hiss at all 

Just my 2c's worth FWIW  !

MM.

[Bucksears]

FWIW,
I use an MPF102 for Q1 (sometimes Q2) and the rest are J201s. This keeps the gain a bit more manageable. I think I have a 2N5457 in Q2 which I'm going back to a J201.
Also, I removed the 1n cap between the trimmers; I forget why and what this mod is called, but I like the way mine sounds right now.
- Buck

[Paul Marossy]

I have similar problems Paul, increasing the drain voltage to about 5.5v helped a bit
and seems to offer more "headroom" to the distortion, if that makes sense ?
I have added a couple of 2n2 caps to ground, one just after Q2 and one pre Q4
this seems to also help some, but there's still some very high "hiss" kind of like when
you crank a mixing desk output fader right up, it seems like it's in the 14k and above area !
If you run the gain pot ( mine is a 1M log ) back to about 60%, most of the hiss will go
and the "crunch" seems to be almost as agressive.

I think I'm going back to ~5.5V on mine. I used a linear pot for my gain control - I don't know that it makes any difference, though.

I use an MPF102 for Q1 (sometimes Q2) and the rest are J201s. This keeps the gain a bit more manageable.

I remember reading about you using MPF102s in there. I think I'll try one in the Q1 position and see how that fares.

[WGTP]

JFets are frequently faulted for inconsistancy.  Might try different ones of the same type.  I'm thinking that the bias also controls the gain to some extent and more gain equals more noise...

[Paul Marossy]

I'm thinking that the bias also controls the gain to some extent and more gain equals more noise...

Yeah, that stands to reason. 

[RDV]

Are all these problems present when it's run into an EXTREMELY CLEAN amp? I would think anything with that much gain would hiss and oscillate and generally be very unruly running into anything with some gain already present.

RDV

[Paul Marossy]

Are all these problems present when it's run into an EXTREMELY CLEAN amp? I would think anything with that much gain would hiss and oscillate and generally be very unruly running into anything with some gain already present.

I know what you're getting at, but all of the aforementioned items is with headphones on, with the pedal feeding my old Zoom 9030 effects unit with only some delay/reverb. I haven't even tried it with an amplifier yet - the thought of it scares me at this point. 

[Paul Marossy]

OK, I messed around with it some more tonight. I tried an MPF102 for Q1 and brought up all of the drain voltages about 1V. The noise is quite a bit less now, and is what I would call acceptable. The bass sounds more articulate now, too. Still a little flubby with the neck pickup, but it's a lot better. Some more testing to do with my wah, but I am much happier with it now. I sure am glad that I use sockets for these FET circuits all the time now, it makes life much easier!  I love the sounds this thing'll get ya.

[Bucksears]

Paul,
Cool. With all J201's, it has almost too much gain.(or maybe my pickups are too hot) I started with Q1 swapping in a (lower gain) MPF102, then did the same with Q2, but it had a bit less gain by that point.
I adjusted one of the grounding wires and was surprised at how less noisy this thing actually is.
To quote the old Metal Zone ad from the early 90's "it turns my Super Reverb RI into sonic flamethrower". I'll never buy another MT-2 again.
(Yes, transistor sockets are our friends.)

- Buck

[Paul Marossy]

it turns my Super Reverb RI into sonic flamethrower

Hah! That's good, I never heard that one! 

Thanks for all the help. 

[mydementia]

Buck,
When you say you 'adjusted one of the grounding wires' did you replace it...or simply move it away from its previous position?  If it's the latter, I'm surprised.  I didn't think DC circuits would create interference this way...the power is not alternating...  I'm very interested in this thread because the Dr. Boogey is next on my bench...starting Saturday morning...

Mike

[Paul Marossy]

One other thing: I'm going to have to go with a grounded circuit input true bypass on this baby, because it is oscillating when in bypass and that is somehow finding its way into the bypassed signal as a very high pitched whining noise. It's faint, but there. Actually, this is very similar to what was happening on my Shaka Tube before I switched over to the grounded circuit input scheme. I would definitely suggest doing a grounded circuit input true bypass on this one. 

[Bucksears]

Mike,
I had the (-) voltage from the DC jack running to the ring of the input jack. I ran that to ground and it sounded a little better, to my ears, rather. I think I'm going to do the grounded input jack on a lot of my distortion units to cut down on noise. (I'm assuming that would help)
- Buck

[mydementia]

Hmm...I've been running the DC Jack ground to all my boards, then all other grounds from there...I guess I already got that one.

Paul - what's 'grounded circuit input true bypass'?  Purty P2P picture?  Link?  Have you plugged this beast into an amp yet? 

Marty - any oscillating noise on bypass for you build?

Mike

[Paul Marossy]

Paul - what's 'grounded circuit input true bypass'?

It's a true bypass scheme where the circuit input gets grounded when the switch is in bypass mode. This should make it more clear: http://www.diyguitarist.com/PDF_Files/GCI-TrueBypass.pdf

EDIT: Oh, I forgot. No I haven't plugged it into my amp yet, but I have time put aside tomorrow afternoon for doing so. 

[mydementia]

Thanks for the clarification Paul - I hadn't seen that technique (Grounded Circuit Input True Bypass) before...just been using #2 for all my builds. 

I'm very interested to hear/read how it works with the rest of your rig.  I find that testing in headphones (usually using my ruby amp) is not as telling for noise as plugging it into my tube amp (Peavey XXX).  Let the noise begin! (...good and bad, I suppose!)

Good luck tomorrow!  I hope to build and fire mine up Saturday...
Mike

[Paul Marossy]

You're welcome mydementia. Good luck! BTW, I have all of my FET drains set at about 60% of the supply voltage. I think it sounds pretty good there and it also seems to be the best setting for the least amount of noise.  An MPF102 in the Q1 slot really helps, too.