proposed dr. boogey layout -- seeking comments

[MartyMart]

I recognize those caps John 

MM.

[John Lyons]

Yes, Thanks again Marty for sending those. I was babying my dwindling suppy of the ones I got from RDV a while back (1uf box caps)
Sure wish I would have just bought a bunch (more) of those then! The other caps and even the Ge transistors will get used as well marty!!!
Too kind.

Victor
Despite the data sheet specs on FETs they will all sound a little different and at different gains.
Run off groove does have a table of average values in their Fetzer valve article. No noise specs though.


Did I say that I was going to build a FET matcher...?

John

[gaussmarkov]

why not just breadboard the FET matcher?  that's what i do with R.G.'s HFE measurement circuit as well.

[John Lyons]

Yeah, I could breadboard it but may as well commit to it. I'll use it, may as well get it off the bread board to free up space.
Make a little proto box for it....

John

[Victor]

Victor
Despite the data sheet specs on FETs they will all sound a little different and at different gains.
Run off groove does have a table of average values in their Fetzer valve article. No noise specs though.


Did I say that I was going to build a FET matcher...?

John

Hm... and what's gonna be your approach on bulding this? I have some sheets of paper that I did some math envolving Vgs and Idss on Boogey...... let me know if you want some of my impressions.....

[John Lyons]

I was going to build one of mark M's in his gallery. Maybe there was another one in the gallery as well.
I don't know the details. I was just going to match fets for gain etc as some kind of standard to sort gain levels etc for these multi fet builds.

John

[Victor]

Matching FETs is good. Especially for replacing trimpots by resistors. Althought our impressions about drain voltage being equal to half supply voltage are going to a new path (setting to an ears' friendly voltage and it's done, maybe ), I've found some values for Rd of each stage with 9V supply....

for Q1, Q2 and Q4, Rd=22k, Vd=4.4548V and Q3, Rd=33k, Vd=4.875V, with Vgs(off)= -0.9V and Idss= 0.6mA in all J201....   

Next week my pots arrive so I can start my 2º Boogey..... can't wait any longer 

[Nashtir]

I can't see the value of c21 neither in the scheme nor in the part list..which is its value?thanks!

[mojotron]

I can't see the value of c21 neither in the scheme nor in the part list..which is its value?thanks!

If I'm thinking of the same schematic you are, C21 is a coupling cap that blocks DC from preceding effects. I have a bunch of (NP or film) 1uF caps that I use for these kinds of caps, but you can use a .1uF or .01uF film cap. If someone has a different understanding of this let me know, but this is how I would compute the value of caps like C21 for maximum signal coupling:

Assuming R=1M, C=C21, for different values of C21:

1uF,   - the attenuation is -3db at frequency F= 1/(2*Pi*R*C) = 1/(2*Pi*1)=.16Hz
.1uF,  - the attenuation is -3db at frequency F= 1/(2*Pi*R*C) = 1/(2*Pi*.1)=1.6Hz
.01uF - the attenuation is -3db at frequency F= 1/(2*Pi*R*C) = 1/(2*Pi*.01)=16Hz

So at .001uF you are going to hear the lowend start to drop off.

I'm guessing you could use .1uF and not hear any change to the low end - your ears will vary.

[gaussmarkov]

my thought was .1uF but i left it open because the coupling cap is there by request, not because it is necessary.  look at the runoffgroove emu circuits and you will see them without the coupling cap as well.  if anyone wants they can just short the coupling cap connection and leave out the pull down resistor.

all the best, gm

[dschwartz]

hey guys!!
i breadboarded the buffer, and did no mods to the tonestack or the volume pot (1M), it sounds good, but the presence control seemed to stop making any effect..i put the buffer after de vol pot, 0.068uF coupling cap...did i missed something??
Do i have to change the cap and/or pot of the presence control?..

please help!!

[John Lyons]

Sometimes the presence control is not vey noticable.
Try turning down the treble and see if you can hear the presence control doing anything.

The Buffer shouldn't affect the pres pot.

I still have not finished my build with the scaled down tonestack. Just need those pots... I'm broke..

[MuNdrY]

http://www.diystompboxes.com/smfforum/index.php?topic=56188.0

[dschwartz]

ehm... the pot was broken... i have to replace it...

[Pushtone]

I got around to replacing the 100K VOL pot I used in my Buck version to the stock 1M.

The two builds sound the same now. With the 100K pot the sound had a lot more ultra high end hash.
Can't wait for someone to finish a scaled TS version.

I'm still liking the 500k GAIN pot over the 1M. Better low-gain tones.
With the 1M the sound past 12 o'clock is about the same. It gets thicker with low mids like an angry swarm of bees

[audioguy]

It gets thicker with low mids like an angry swarm of bees

With the 1M or the 500k?

[mojotron]

I got around to replacing the 100K VOL pot I used in my Buck version to the stock 1M.

The two builds sound the same now. With the 100K pot the sound had a lot more ultra high end hash.
Can't wait for someone to finish a scaled TS version.

I'm still liking the 500k GAIN pot over the 1M. Better low-gain tones.
With the 1M the sound past 12 o'clock is about the same. It gets thicker with low mids like an angry swarm of bees

With my strat I get some useful tones from 1/2-3/4 on the 1M gain pot - but with a humbucker, ya, about 1/2 on the 1M gain does it for me. I'll try the latest build with the changes and let you guys know what I get.

[Pushtone]

The thickening "like swarm of bees" comes with the 1M GAIN pot from 12 o'clock to max.

I've only tried it with humbuckers. Good point about single coils Mojotron.

[Victor]

I got around to replacing the 100K VOL pot I used in my Buck version to the stock 1M.

The two builds sound the same now. With the 100K pot the sound had a lot more ultra high end hash.
Can't wait for someone to finish a scaled TS version.

I'm still liking the 500k GAIN pot over the 1M. Better low-gain tones.
With the 1M the sound past 12 o'clock is about the same. It gets thicker with low mids like an angry swarm of bees

And how are you biasing all the J201? Half supply's voltage, or just by ear?

[Pushtone]

And how are you biasing all the J201? Half supply's voltage, or just by ear?

All J201's
Q1 biased by ear and set for least noise while still sounding full (not gated). Reads 7.7V
Q2 at 6.5V
Q3-5 at 5.5V and biased with fixed resistors.



Will have some MPF102's to try soon - Thanks SB.