Basic Audio - Scarab Deluxe  [traced]

General documentation, gut shot, schematic links, ongoing circuit tracing, deep thoughts ... all about boutique stompboxes.
User avatar
Intripped
Cap Cooler
Information
Posts: 670
Joined: 25 Aug 2009, 01:03
Location: Italy
Has thanked: 985 times
Been thanked: 305 times

Post by Intripped »

...but where is the 5th film cap?
i see in the pics that there are 5 film caps, but this version has 4 only

User avatar
jalmonsalmon
Solder Soldier
Information
Posts: 212
Joined: 14 Sep 2012, 22:49
Has thanked: 97 times
Been thanked: 30 times

Post by jalmonsalmon »

Intripped wrote:...but where is the 5th film cap?
i see in the pics that there are 5 film caps, but this version has 4 only
There is a post earlier where John says to remove C8...
I assume that missing cap has something to do with the Tone since I saw it posted on an earlier schematic :hmmm:

User avatar
rs
Breadboard Brother
Information
Posts: 67
Joined: 01 Dec 2007, 14:40
Has thanked: 95 times
Been thanked: 7 times

Post by rs »

Hey guys is it me or theres a capacitor and a resistor missing?

User avatar
IvIark
Tube Twister
Information
Posts: 2235
Joined: 01 Jan 2008, 23:59
Location: Manchester UK
Has thanked: 562 times
Been thanked: 586 times
Contact:

Post by IvIark »

Well there's definitely one extra cap and resistor in the gut shots. Maybe the resistor is current limiting for the supply or something?
"If anyone is a 'genius' for putting jacks in such a pedal in the only spot where they could physically fit, then I assume I too am a genius for correctly inserting my legs into my pants this morning." - candletears7 - TGP

User avatar
storyboardist
Breadboard Brother
Information
Posts: 104
Joined: 28 Dec 2013, 00:08
Location: Georgia, USA
Has thanked: 85 times
Been thanked: 225 times
Contact:

Post by storyboardist »

My guess is that the tone control is probably more like the Hot Silicon/Mictester Tonebender. If ~arph's guesses on the comoponent values from the first page are right, the 8n2 cap is very close to the other tone control components...

This would be my guess:
Attachments
Scarab Deluxe Schematic 2.jpg

User avatar
storyboardist
Breadboard Brother
Information
Posts: 104
Joined: 28 Dec 2013, 00:08
Location: Georgia, USA
Has thanked: 85 times
Been thanked: 225 times
Contact:

Post by storyboardist »

Found out I made a mistake on my perf layout (thanks to deadmenonly for the heads up and partial verify of the layout), so disregard the layout on page 2. Here's the updated one:

Image

I made another layout reflecting the last schematic I posted with the extra tone control components:

Image
(Just added another row on the right side for the extra resistor and cap)

User avatar
roseblood11
Tube Twister
Information
Posts: 1886
Joined: 23 Aug 2008, 14:21
Has thanked: 366 times
Been thanked: 313 times

Post by roseblood11 »

Nice, but which one is correct now? John? :secret:

User avatar
~arph
Cap Cooler
Information
Posts: 607
Joined: 20 Sep 2007, 10:35
Has thanked: 60 times
Been thanked: 163 times

Post by ~arph »

storyboardist wrote:My guess is that the tone control is probably more like the Hot Silicon/Mictester Tonebender. If ~arph's guesses on the comoponent values from the first page are right, the 8n2 cap is very close to the other tone control components...

This would be my guess:
This one i guess, it also makes more sense. The dubious 10k parallel with the 50k pot is gone too. I guess we just have to build one and find out if it's close.
In the quiet words of the virgin Mary: "Come again?"

User avatar
IvIark
Tube Twister
Information
Posts: 2235
Joined: 01 Jan 2008, 23:59
Location: Manchester UK
Has thanked: 562 times
Been thanked: 586 times
Contact:

Post by IvIark »

Someone verified it with my layout and said it sounds excellent. But it could be excellent and wrong of course.
"If anyone is a 'genius' for putting jacks in such a pedal in the only spot where they could physically fit, then I assume I too am a genius for correctly inserting my legs into my pants this morning." - candletears7 - TGP

User avatar
jalmonsalmon
Solder Soldier
Information
Posts: 212
Joined: 14 Sep 2012, 22:49
Has thanked: 97 times
Been thanked: 30 times

Post by jalmonsalmon »

IvIark wrote:Someone verified it with my layout and said it sounds excellent. But it could be excellent and wrong of course.
I made one with your layout Mark and it sounds excellent indeed :applause: and it can stand up to my Ge Tone Bender too which is excellent! Fired up the 1st time... just need to box her up and call it done :mrgreen:
Attachments
image (2).jpeg

User avatar
roseblood11
Tube Twister
Information
Posts: 1886
Joined: 23 Aug 2008, 14:21
Has thanked: 366 times
Been thanked: 313 times

Post by roseblood11 »

jalmonsalmon wrote:I made one with your layout Mark and it sounds excellent indeed
Sure, but we still don't know, what's correct. There's definitely a fifth capacitor...

User avatar
roseblood11
Tube Twister
Information
Posts: 1886
Joined: 23 Aug 2008, 14:21
Has thanked: 366 times
Been thanked: 313 times

Post by roseblood11 »

What we still don't know is, if John selects the transistors for a certain hfe...

-----------------

As I want to try both variations of the tone control, I added a switch to IvIarks layout:

Image

User avatar
jalmonsalmon
Solder Soldier
Information
Posts: 212
Joined: 14 Sep 2012, 22:49
Has thanked: 97 times
Been thanked: 30 times

Post by jalmonsalmon »

roseblood11 wrote:What we still don't know is, if John selects the transistors for a certain hfe...

-----------------

As I want to try both variations of the tone control, I added a switch to IvIarks layout:

[ Image ]
Sweetness... I need to order up some 2N5088s, imo I would select the lowest gain transistors out of a nice batch, and maybe try out some others with higher gains. I will try out this layout in a few days.
Thanks for the added tone control on this layout! :lol:

User avatar
HEAD
Resistor Ronker
Information
Posts: 442
Joined: 16 Dec 2008, 00:13
Location: Leipzig, Germany
Has thanked: 24 times
Been thanked: 49 times

Post by HEAD »

roseblood11 wrote:What we still don't know is, if John selects the transistors for a certain hfe...
Any high gain tranny will do it. I prefer BC550 though... very low noise. Some 47pF caps across the collector-emittor-path of Q2 and Q3 will let it sound even smoother! A James tone controll fits also very nice. A did a build with mictester powser supply filter instead of the 47µF cap and an additional bjt output buffer after the volume pot. Near perfect to my ears! ;-)
Attachments
IMG_20140514_143325.jpg
IMG_20140514_143238.jpg

User avatar
roseblood11
Tube Twister
Information
Posts: 1886
Joined: 23 Aug 2008, 14:21
Has thanked: 366 times
Been thanked: 313 times

Post by roseblood11 »

Nice one, Helge!
Looks like the bigger brother of a "hot silicon" you posted a few years ago, if I remember that right?!

- the extra smoothing cap connects collector and base ... I hope ;-)
- the trimmer is the collector resistor for Q3?
- you are talking about this power conditioner? viewtopic.php?t=14410&p=164328
What's the voltage drop here? I read that R.G. talked about a much higher drop than you actually measured?

User avatar
HEAD
Resistor Ronker
Information
Posts: 442
Joined: 16 Dec 2008, 00:13
Location: Leipzig, Germany
Has thanked: 24 times
Been thanked: 49 times

Post by HEAD »

roseblood11 wrote:Nice one, Helge!
Looks like the bigger brother of a "hot silicon" you posted a few years ago, if I remember that right?!

- the extra smoothing cap connects collector and base ... I hope ;-)
- the trimmer is the collector resistor for Q3?
- you are talking about this power conditioner? viewtopic.php?t=14410&p=164328
What's the voltage drop here? I read that R.G. talked about a much higher drop than you actually measured?
Thx! I build several versions of this basic circuit. Nearly every peer guitarist plays now one build by me. :D
To answer your questions:
- Yes.
- No. In this case it's a 100k trim pot replacing the 47k feedback-r between q2 and q3. Gives you a better control over the max available gain and compression.
- Yes. For the voltage drop I didn't care because it had no audible effect to my ears. But as far as I remember it was ~0.4V since I always use a 1N5817 schottky diode.

User avatar
kinski
Resistor Ronker
Information
Posts: 293
Joined: 01 Oct 2009, 05:57
Location: Brooklyn, NY
Has thanked: 10 times
Been thanked: 4 times

Post by kinski »

roseblood11 wrote:What we still don't know is, if John selects the transistors for a certain hfe...

-----------------

As I want to try both variations of the tone control, I added a switch to IvIarks layout:

[ Image ]
Hey roseblood11, did you ever build your vero with the tone switch? If so, can you hear much of a difference between the two? Any thoughts?

User avatar
roseblood11
Tube Twister
Information
Posts: 1886
Joined: 23 Aug 2008, 14:21
Has thanked: 366 times
Been thanked: 313 times

Post by roseblood11 »

Has anyone built the version with the tone switch? I never tried it...

User avatar
roseblood11
Tube Twister
Information
Posts: 1886
Joined: 23 Aug 2008, 14:21
Has thanked: 366 times
Been thanked: 313 times

Post by roseblood11 »

Has anyone tried to bypass the first transistor, similar to the Fender Bender? Would be great to get a sound similar to a Fuzz Face out of this circuit...

User avatar
Cub
Cap Cooler
Information
Posts: 458
Joined: 29 Aug 2011, 07:14
Location: The Netherlands
Has thanked: 102 times
Been thanked: 118 times

Post by Cub »

Found this on the blog of drdFX Stompboxes. A nice post and a link to a project PDF with a PCB layout for a 1590A ! There's also one for 125B enclosures, though the contributors to this thread already got you covered for that.
http://drdfx.hu/en/ankh/
I wish I were a chestnut tree, nourished by the sun.
With twigs and leaves and branches and conkers by the ton.

Post Reply