Secretefx - Secret-1 STD overdrive  [traced]

General documentation, gut shot, schematic links, ongoing circuit tracing, deep thoughts ... all about boutique stompboxes.
User avatar
YuGi
Degoop Doctor
Information
Posts: 164
Joined: 01 Nov 2009, 19:22
Has thanked: 1 time
Been thanked: 26 times

Post by YuGi »

Hi all, I dissected the secret-1 pedal. The work is already on the italian forum http://www.fennecelectronics.it, http://www.fennecelectronics.it/smf/ind ... ic=11684.0
The soul of this hobby is sharing informations, so.. my two cents to the community :mrgreen:
pedale_esterno.jpg
pedale_esterno.jpg (57.84 KiB) Viewed 4360 times
As you can see, lot of degooping work :slap:
pedale_interno.jpg
pedale_interno.jpg (70.9 KiB) Viewed 4360 times
pedale_interno_front.jpg
pedale_interno_front.jpg (56.09 KiB) Viewed 4360 times
Last edited by YuGi on 09 Feb 2014, 16:56, edited 1 time in total.

User avatar
YuGi
Degoop Doctor
Information
Posts: 164
Joined: 01 Nov 2009, 19:22
Has thanked: 1 time
Been thanked: 26 times

Post by YuGi »

I removed and measured all components. This is the "naked" PCB :D
PCB_top_bottom.jpg
And finally the schematics :applause:
Secret-1_Schematics.jpg
What you think about? On the other forum we are discussing about in and out buffers.. is not strange that biasing? :scratch:

User avatar
IvIark
Tube Twister
Information
Posts: 2235
Joined: 01 Jan 2008, 23:59
Location: Manchester UK
Has thanked: 600 times
Been thanked: 608 times
Contact:

Post by IvIark »

Thanks for this :applause:
What are the transistors?
"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
YuGi
Degoop Doctor
Information
Posts: 164
Joined: 01 Nov 2009, 19:22
Has thanked: 1 time
Been thanked: 26 times

Post by YuGi »

IvIark wrote:Thanks for this :applause:
What are the transistors?
All components values are scraped! Then i can only say BJT NPN, hFE around 200.

User avatar
IvIark
Tube Twister
Information
Posts: 2235
Joined: 01 Jan 2008, 23:59
Location: Manchester UK
Has thanked: 600 times
Been thanked: 608 times
Contact:

Post by IvIark »

Great, thanks
"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
AAntonio
Breadboard Brother
Information
Posts: 83
Joined: 15 Jan 2009, 11:40
Has thanked: 21 times
Been thanked: 15 times

Post by AAntonio »

Great!!!!! :applause:

User avatar
okgb
Diode Debunker
Information
Posts: 777
Joined: 16 Mar 2010, 03:58
Has thanked: 199 times
Been thanked: 30 times

Post by okgb »

Nice work , seems to be nothing special is that considered active tone control ?
and funny that those huge caps are even silk screened on the pcb .

User avatar
Nocentelli
Tube Twister
Information
Posts: 2162
Joined: 09 Apr 2009, 07:06
Location: Leeds, UK
Has thanked: 981 times
Been thanked: 842 times

Post by Nocentelli »

YuGi wrote:What you think about? On the other forum we are discussing about in and out buffers.. is not strange that biasing? :scratch:
+1
It looks like it's missing a 1M to ground from the base of both BJTs. That would make sense.
vanessa wrote: 20 Aug 2007, 17:51 You can't arrest someone for reverse engineering something.

User avatar
IvIark
Tube Twister
Information
Posts: 2235
Joined: 01 Jan 2008, 23:59
Location: Manchester UK
Has thanked: 600 times
Been thanked: 608 times
Contact:

Post by IvIark »

In the Tubescreamer and similar the base resistor goes to VCC/2
"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
YuGi
Degoop Doctor
Information
Posts: 164
Joined: 01 Nov 2009, 19:22
Has thanked: 1 time
Been thanked: 26 times

Post by YuGi »

Nocentelli wrote:
YuGi wrote:What you think about? On the other forum we are discussing about in and out buffers.. is not strange that biasing? :scratch:
+1
It looks like it's missing a 1M to ground from the base of both BJTs. That would make sense.
The schematics is absolutely correct (I have the PCB on my desktop..).
I simulated the buffers with LTspice and the headroom is better then a classic bjt buffer (bias with 1M to v/2 and 10K emitter resistor). Why?! :scratch:

User avatar
Cub
Resistor Ronker
Information
Posts: 427
Joined: 29 Aug 2011, 07:14
Location: The Netherlands
Has thanked: 78 times
Been thanked: 88 times

Post by Cub »

I don't remember where, but I saw a demo if it in front of a number of Big Muff pedals and it was a really nice sounding combination.
Thanks for sharing, YuGi ! :thumbsup
I wish I were a chestnut tree, nourished by the sun.
With twigs and leaves and branches and conkers by the ton.

User avatar
smanq
Information
Posts: 14
Joined: 05 Sep 2007, 14:47
Has thanked: 1 time
Been thanked: 2 times

Post by smanq »

It's possible to bias a buffer in this way, but it's definitely the worse one, simply because it's higlhy hfe and temperature related.
A classic 2 resistors partition from supply and ground it's more stable and it permits to use a wide range of transistors (wide range of hfe), without any relevant difference in bias point. It will sound the same... or better (more dinamic, because you can adjust the bias point by design, not trying some different BJTs)!

If we connect the 1M resistor to V/2 like in a classic tube screamer, we've less trouble (less voltage difference across the resistor) and it will bias at good point.
If a circuit works fine from some decades, why we need to change it? :D

User avatar
pamaz
Breadboard Brother
Information
Posts: 74
Joined: 14 Jan 2008, 19:55
Location: Italy
Has thanked: 33 times
Been thanked: 10 times

Post by pamaz »

hey smanq, its' exactly what I've written yesterday in the italian forum. We share the same thought.

User avatar
Cannibal
Breadboard Brother
Information
Posts: 76
Joined: 24 Jul 2010, 12:53
Location: Milan, Italy
Has thanked: 30 times
Been thanked: 15 times

Post by Cannibal »

Aside from the buffers, is R5 just a positive feedback resistor? Also the frist opamp max gain is around 500x, so this thing should have a massive amount of distortion going on, instead is just a medium gain overdrive. Am i missing something?
Seiche wrote:there's a difference between being drugged (I don't think it was only booze) and retarded.

User avatar
IvIark
Tube Twister
Information
Posts: 2235
Joined: 01 Jan 2008, 23:59
Location: Manchester UK
Has thanked: 600 times
Been thanked: 608 times
Contact:

Post by IvIark »

Here's the vero:
"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
YuGi
Degoop Doctor
Information
Posts: 164
Joined: 01 Nov 2009, 19:22
Has thanked: 1 time
Been thanked: 26 times

Post by YuGi »

Cannibal wrote:Aside from the buffers, is R5 just a positive feedback resistor? Also the frist opamp max gain is around 500x, so this thing should have a massive amount of distortion going on, instead is just a medium gain overdrive. Am i missing something?
The inverting opamp mixes dry and wet so the resulting wave is smootly distorted.

User avatar
Nick123
Information
Posts: 29
Joined: 02 Jul 2007, 09:13
Has thanked: 7 times
Been thanked: 9 times

Post by Nick123 »

Schematic shows that the Gretsch Controfuzz could have been the source of the inspiration.

User avatar
Mbas974
Resistor Ronker
Information
Posts: 280
Joined: 29 Aug 2011, 12:13
Has thanked: 36 times
Been thanked: 39 times

Post by Mbas974 »

Please note that IL072 JRC4558 will works but in the original unit the chip is too silent...
we do not know exactly what it is but an OPA will be better choice

User avatar
Agent86
Information
Posts: 12
Joined: 22 Dec 2008, 13:37
Been thanked: 13 times

Post by Agent86 »

is similars to Boss OD-1

User avatar
IvIark
Tube Twister
Information
Posts: 2235
Joined: 01 Jan 2008, 23:59
Location: Manchester UK
Has thanked: 600 times
Been thanked: 608 times
Contact:

Post by IvIark »

Someone pointed out an error in the layout, the link to pin 2 should be going to pin 3, but I can't edit the post above so here is the updated layout.
Secret efx - Secret-1 Standard - FIXED.png
"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

Post Reply