Analogman - King of Tone  [traced]

General documentation, gut shot, schematic links, ongoing circuit tracing, deep thoughts ... all about boutique stompboxes.
User avatar
modman
a d m i n
Information
Posts: 4890
Joined: 19 Jun 2007, 16:57
Has thanked: 4394 times
Been thanked: 2131 times

Post by modman »

I moved some discussion on reverse log tapered pots to a separate thread.

thanks
Please, support freestompboxes.org on Patreon for just 1 pcb per year! Or donate directly through PayPal

User avatar
Torchy
Information

Post by Torchy »

Mods to the GGG Bluesbreaker board to KOT specs.

GGGBluesbreakerKOTMod.png

User avatar
guiltyspark
Solder Soldier
Information
Posts: 202
Joined: 18 Aug 2007, 05:24
Has thanked: 3 times
Been thanked: 39 times

Post by guiltyspark »

Nice work, thanks Torchy!

Guiltyspark

User avatar
guiltyspark
Solder Soldier
Information
Posts: 202
Joined: 18 Aug 2007, 05:24
Has thanked: 3 times
Been thanked: 39 times

Post by guiltyspark »

One question: according to the schem, the KOT has a 10k and a .1uf between the 2 gain stages, whereas the GGG Blues Breaker has 2).22 and 2) 4.7k (C6,C7 and R7,R8). These need to be changed too, no? Looks like the 47pf in the feedback loop of the GGG needs to be 100pf as well.

Guiltyspark

User avatar
Torchy
Information

Post by Torchy »

The mods above say to jumper (ie short out) C6 and R7 pads. That leaves R8 and C7 in the signal path a la KOT. You can change R8 to a 10k ( sounded the same to me), and the mods say change C7 to a 100nF. If you can hear the difference between a 47pF and a 100pF in an OD feedback loop then your ears are bionic. :D

FWIW I modded my GGG board to *full* KOT spec. The treble boost trimpot was useless, the extra output dc block cap did nothing to the sound. The interstage cap to 100nF was good, I left the resistor at 4k7. The R2 & R3 change was good. Adding the dip sitches and extra clipping diodes was the significant change. I tried the modded BB with two vintage AC30's, Marshall JTM, Mig50, and a Peavey Classic 50 (4x10 cab) with USA Strat, SG and Les Paul. I took back out the trimpot, the extra output cap and the stupid stupid stupid CC resistors. My bestest friend now has a killer OD and I'm building another.

User avatar
guiltyspark
Solder Soldier
Information
Posts: 202
Joined: 18 Aug 2007, 05:24
Has thanked: 3 times
Been thanked: 39 times

Post by guiltyspark »

Thanks again for your contribution, looks like I should have looked at your mods more closely before posting. :oops: I have a GGG board, I'm going to try it out. I got some cool 1s1588 diodes, might try them for the 2nd set of clippers.

Guiltyspark

User avatar
Torchy
Information

Post by Torchy »

No problem :D

Please reload the image as I got a trace cut slightly out - you need to break the track between the 6k8 and the 220k/pin5 connection, the old cut left it connected to pin 5 :oops: .

I've checked the image against my modded board and looks fine.

User avatar
guiltyspark
Solder Soldier
Information
Posts: 202
Joined: 18 Aug 2007, 05:24
Has thanked: 3 times
Been thanked: 39 times

Post by guiltyspark »

analogguru wrote:
selectortone wrote:I read through the whole thread but didn't see anything - just wondering - why the two 1uF caps in parallel on the output?
Nobody knows this.....
... but what do you expect else from the "King of Solder-Jockeys" than: "cause they dont know what they are doing" ?

Normally you can place a smaller (approx 1/10th of the value) film capacitor in parallel to the electrolytic to improve the high-end frequency response.

So it would make sense if there would be a 47n or 100n in parallel to the electrolytic or if he would ommit the electrolytic completely since the film capacitor is big enough...

analogguru
Back to the dual 1uf caps, technically this equals 2 uf total capacitance on the output, correct? The original BB has a single .1 cap. AG, what do you recommend for this cap? a single 1uf film? Torchy mentioned adding the 2nd 1uf had no audible effect.

Guiltyspark

User avatar
analogguru
Old Solderhand
Information
Posts: 3238
Joined: 26 Jun 2007, 13:58
Been thanked: 124 times
Contact:

Post by analogguru »

Back to the dual 1uf caps, technically this equals 2 uf total capacitance on the output, correct?
correct....
The original BB has a single .1 cap.
true....
As long as the following stage has more than 47k input impedance the 0,1 µF cap is big enough...
AG, what do you recommend for this cap? a single 1uf film?
yes....
Torchy mentioned adding the 2nd 1uf had no audible effect.
no wonder..... I doubt that the next following stage he used had only 2k input impedance....

analogguru
There´s a sucker born every minute - and too many of them end up in the bootweak pedal biz.

User avatar
guiltyspark
Solder Soldier
Information
Posts: 202
Joined: 18 Aug 2007, 05:24
Has thanked: 3 times
Been thanked: 39 times

Post by guiltyspark »

Thanks AG, 1uf it is. Hopefully the removal of the mojo electrolytic/film cap combination will not affect the tone of my build too much! :lol:

Guiltyspark

User avatar
guiltyspark
Solder Soldier
Information
Posts: 202
Joined: 18 Aug 2007, 05:24
Has thanked: 3 times
Been thanked: 39 times

Post by guiltyspark »

I built one of these using Torchy's GGG layout and the MA2c856.. diodes from Digikey. I used a 1uf film cap on the output, left the 1st set of diodes always on and switched the 2nd set. Didn't put in the treble boost trim. My build sounds good but isn't real loud, you really have to crank the volume. I used the same value/taper pots as in the provided KOT schem. Anyone else have this problem? I tried a RC4580 and then a JRC4558, I liked the 4558 better. I lent my real KOT to a buddy, I have to get it back and compare-

Guiltyspark

User avatar
tlpruitt
Information
Posts: 23
Joined: 30 Oct 2007, 17:56
Has thanked: 1 time
Been thanked: 1 time

Post by tlpruitt »

guiltyspark wrote:I built one of these using Torchy's GGG layout and the MA2c856.. diodes from Digikey. I used a 1uf film cap on the output, left the 1st set of diodes always on and switched the 2nd set. Didn't put in the treble boost trim. My build sounds good but isn't real loud, you really have to crank the volume. I used the same value/taper pots as in the provided KOT schem. Anyone else have this problem? I tried a RC4580 and then a JRC4558, I liked the 4558 better. I lent my real KOT to a buddy, I have to get it back and compare-

Guiltyspark
I used a 100KB pot for the volume control and that seems to work well for me. I can get just above unity at around 11:00-12:00 with the 100KB instead of around 3:00 with a 100KA pot.

If you used 100KB for the drive pot you will still need to crank the drive. I have a 100KB drive pot in mine and I run it between 3:00 and wide open. Some use a 100K Rev Audio pot to improve the drive knob's sensitivity.

I have tried a bunch of opamps in mine and at the moment I am digging a TL072 like the stock Bluesbreaker uses. I have a bunch of other ODs with 4558 opamps in them so for me this circuit with a TL072 gives me some variety.

-Tim

User avatar
The Rotagilla
Diode Debunker
Information
Posts: 744
Joined: 20 Aug 2007, 18:24
Has thanked: 7 times
Been thanked: 61 times

Post by The Rotagilla »

tlpruitt wrote:I used a 100KB pot for the volume control and that seems to work well for me. I can get just above unity at around 11:00-12:00 with the 100KB instead of around 3:00 with a 100KA pot.
+1
The television will not be revolutionized.

User avatar
guiltyspark
Solder Soldier
Information
Posts: 202
Joined: 18 Aug 2007, 05:24
Has thanked: 3 times
Been thanked: 39 times

Post by guiltyspark »

Thanks guys, think I'll try that. My builds pot tapers are the opposite of that, audio on the volume and linear on the gain.

If anyone wants to get fancy w/diodes, I mentioned the ones in a post above that came from digikey. These have a reverse voltage of around .72v and are amber with a yellow stripe and are very small. I used these for the 1st set of 4 clippers. For the 2nd set, I used 1S1588's from effectsconnection.com. These are bigger, also with a yellow stripe. Small bear also carries 1s1588's, but they don't look as cool as the effectsconnection diodes. Note that the MA diodes are about 50 cents each and the 1s1's about 30-50 cents each, compared to about 1 cent for 1n914's.

Guiltyspark

User avatar
tlpruitt
Information
Posts: 23
Joined: 30 Oct 2007, 17:56
Has thanked: 1 time
Been thanked: 1 time

Post by tlpruitt »

guiltyspark wrote:Thanks guys, think I'll try that. My builds pot tapers are the opposite of that, audio on the volume and linear on the gain.

Not exactly the opposite...try linear taper for both volume and gain. Or linear for volume and reverse audio for gain.

-Tim

User avatar
guiltyspark
Solder Soldier
Information
Posts: 202
Joined: 18 Aug 2007, 05:24
Has thanked: 3 times
Been thanked: 39 times

Post by guiltyspark »

Ok, now I have linear pots for both vol and gain. The linear definitely works better for the volume. I noticed Deaj used a 250k RA on his build. Does the larger pot increase the gain or just give a smoother transition?

Guiltyspark

User avatar
JHS
Cap Cooler
Information
Posts: 483
Joined: 14 Jul 2007, 11:20
Been thanked: 5 times

Post by JHS »

Larger output vol-pot = less bass and lower mids and more treble.

JHS

User avatar
analogguru
Old Solderhand
Information
Posts: 3238
Joined: 26 Jun 2007, 13:58
Been thanked: 124 times
Contact:

Post by analogguru »

Larger output vol-pot = less bass and lower mids and more treble.

JHS
:hmmm: And what is the technical background for this claim ? :hmmm:

analogguru
There´s a sucker born every minute - and too many of them end up in the bootweak pedal biz.

User avatar
guiltyspark
Solder Soldier
Information
Posts: 202
Joined: 18 Aug 2007, 05:24
Has thanked: 3 times
Been thanked: 39 times

Post by guiltyspark »

analogguru wrote:
Larger output vol-pot = less bass and lower mids and more treble.

JHS
:hmmm: And what is the technical background for this claim ? :hmmm:

analogguru
I'm curious about this too, please fill us in, JHS.

My clone is growing on me, this seems to be a good circuit. Anyone else think it needs a little more gain?

Guiltyspark

User avatar
Barcode
Diode Debunker
Information
Posts: 820
Joined: 27 Sep 2007, 17:03
Has thanked: 14 times
Been thanked: 32 times

Post by Barcode »

guiltyspark wrote:
analogguru wrote:
Larger output vol-pot = less bass and lower mids and more treble.

My clone is growing on me, this seems to be a good circuit. Anyone else think it needs a little more gain?

Guiltyspark
Depends on the setup. It has all the gain i need when i am playing through my tele with a hot rail in the bridge and a texas special in the middle.

Post Reply