Highway 89 prototyped

[cbriere]

Someone has tried this one from DougH?
I prototyped it and found some discreapencies,
I know this circuit is kept confidencial.
Can we discuss,  Doug?
cbriere

[cbriere]

Is there interest in this design?

I found not much search results on this design,
i think it should have more interest as this is one
is one of the best i have tried since a long time.
It cleans up really well, from long sustain no harsh
down to overdrive with simple guitar volume turning down.

[syndromet]

This is one of the effects on my list of "things to build". I hear only good things about it. But first I need to get my parts. Ordered them a month ago, and they still haven't arrived....

[Doug_H]

Can we discuss,  Doug?
cbriere

I only ask that people don't post the schematic, since I used an idea from an amp design for which the designer has asked not be posted. Other than that, discuss away...

Doug

[MartyMart]

cbriere, it's a fine sounding overdrive, I made one about a year ago and it gets used a lot !
Cuts through very well and has a good clean tone.
What's your question ?

Marty.

[cbriere]

Ok,  questions/comments time.

Q/:
C3 =0.68uF, what the use of this cap?
i think is way too high value for this cap?
I first test with this value on my prototype but found that it affects the biaising
of the first stage transistor.
So at low Gain adjustement the sound is harsh and a look with my oscilloscope showed
that the clipping was on one side of the signal only. That's because this 0.68uF
is causing the Collector voltage to raise.
I removed it , and found clipping to remain consistant for the range of GAIN position.
May want to put back with a smaller value so it reduce the gain of the
high frequencies, at lower GAIN setting.

Q/:
How do you explain the tone change when turning down guitar volume.
It goes from full , BigMuff type of sound at max (volume at 8-10)
down to thinner treble booster type (volume from 0 to 7) ?

cbriere

[Paul Marossy]

I like mine, too. 

[Doug_H]

Christian, check you email. I sent you a response to that question yesterday.

In a nutshell, the .68u is a "scaled" bright cap. You can remove it completely or tweak it if you don't like it. I don't like the way the gain control works at all and am going to revisit that at some point and either try to improve it or just remove it completely. FWIW I don't think you really need a gain control in this circuit. It's not a high gain monster to begin with and I think there is enough tonal variation available with the treble, bass, and your guitar volume controls. I figure that, with the gain control dimed, if I can get it completely clean with a twist of my guitar volume knob, what do I need a gain control for on the pedal? Plus the guitar vol knob is much more handy.

Doug

[MartyMart]

I used a .1uf for C3, then a slightly altered BM tonestack, then back at R8, so I guess mine is
a little different !
As far as turning gtr vol down, I have not noticed that problem, but it occurs on a number
of circuits .... it does have a kind of BMTB circuit at the front though ! ( see schem notes )

MM.

[cbriere]

Doug, did not receive your answer yet, slow server...

Mine has ALOT of gain,
i could not get it to clean,
or guit volume must be at 0.5 
I probably fell on really high gains 5089's....
will try other parts to see effect on the gain.

[Doug_H]

You've probably miswired something. The 2n5089 hfe variations will not make that dramatic of a difference.

Try removing RGAIN and replacing with a fixed 10k resistor. Remove C3 and connect C4 to the collector of Q1. If that doesn't fix it, triple-check your tone control connections.

Doug

[cbriere]

I'm still tuning this one on my bench, 
I am looking for ,  1-Good lead tone at Guit vol Maxed,,   2- Good overdrive when lowering guit vol. (all with a strat ,3 single coils)
witch i think this circuit does well at the beginnning.
but not 100% satisfied with it, i would say 90%...

tweaking is related to:

1) Playing with it at different volume/GAIN settings and changing guitars, some settings does not clean well lowering guit volume.
    but most of the time it's good.

2) C3 value???   has this caps will have an effect only at lower GAIN setting (at max. GAIN it is shorted)
    and it's effect will be to lower stage gain of the high frequencies. What value to put? i will have to play with
    different value and hear it's effect. Maybe endup with no cap?

cbriere