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Re: Amptweaker - BigRock/TightMetal Pro

PostPosted: 25 Aug 2017, 05:07
by bajaman
Okay - boards arrived and I have built it - worked first time too :D , except for one small mistake on the pcb - I connected the effect output to the main output terminal instead of the footswitch pad. An easy fix though just involves cutting one trace and adding a small link wire. How does it sound - awesome! On my oscilloscope i observed asymmetrical clipping behaviour similar to my Baja Tube drive pedal - very dynamic, touch sensitive and cleans up nicely with the guitar volume pot wound back. I have a few spare boards available - pm me for details - cheers bajaman

Re: Amptweaker - BigRock/TightMetal Pro

PostPosted: 25 Aug 2017, 05:21
by bajaman
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Re: Amptweaker - BigRock/TightMetal Pro

PostPosted: 25 Aug 2017, 18:18
by nexion777
Awesome build Bajaman! That pcb is... ultra-tight! :D

Re: Amptweaker - BigRock/TightMetal Pro

PostPosted: 26 Aug 2017, 10:24
by DimebuGG
I made a single side pcb yesterday with boost function minus loops and LED lights. It's done already but I need to do final touch. Once finalized, I'll post it herre immediately.

Oh BTW, what's the value of BOOST GAIN and BOOST MASTER pots?. And also I see from bajaman's pcb that R56 is 100K and C31 is 220pF. Is this right?.

Re: Amptweaker - BigRock/TightMetal Pro

PostPosted: 27 Aug 2017, 08:32
by DimebuGG
What's the purpose of the second 1M trimmer and 18K resistor in the noise gate section BTW?. If the gate switch is in OFF position, the 4.75K resistor will be in parallel with the 1M trim/18K resistor. That means less than 4.75K in total resistance, right?. Same thing also when the switch is in ON position(500K pot/4.75K in parallel to 1M trim/18K).

Re: Amptweaker - BigRock/TightMetal Pro

PostPosted: 28 Aug 2017, 04:05
by nexion777
DimebuGG wrote:What's the purpose of the second 1M trimmer and 18K resistor in the noise gate section BTW?. If the gate switch is in OFF position, the 4.75K resistor will be in parallel with the 1M trim/18K resistor. That means less than 4.75K in total resistance, right?. Same thing also when the switch is in ON position(500K pot/4.75K in parallel to 1M trim/18K).


I noted the same thing, in fact that arrangement is absent in the vanilla tight metal schematic, maybe something related to the FET actuator? :scratch:

Re: Amptweaker - BigRock/TightMetal Pro

PostPosted: 01 Sep 2017, 17:40
by J0K3RX
DimebuGG wrote:What's the purpose of the second 1M trimmer and 18K resistor in the noise gate section BTW?. If the gate switch is in OFF position, the 4.75K resistor will be in parallel with the 1M trim/18K resistor. That means less than 4.75K in total resistance, right?. Same thing also when the switch is in ON position(500K pot/4.75K in parallel to 1M trim/18K).



On the standard tight rock or tight metal the gain and gate dual gang 500k are always at a fixed level.. The gate tracks the gain at a fixed level and if you are going to use the gate then you really have no control over it. I am guessing that was one of the complaints about it.. The 1M trim pot lets you adjust the gate to gain ratio basically by throwing parallel resistance across the lugs of the gate. So, when the gate is in the On position you can turn up the gain and at the same time have some control over how much gate comes along for the ride.. When the gate is in the On position the 4k75 resistor and 500k gate pot are connected in series to the other side of the diodes and in parallel with the 1M trim which is in series with the 18k resistor... So, when the gate is On you basically have a 504.75k pot in parallel with a 1.018M trimmer which is adjustable. When the gate is Off the 500k gate pot is taken out of the equation and you have only the 4k75 resistor in parallel with 1M trimmer that is in series with the 18k resistor. To keep it simple lets just say that it's a 4k75 resistor in parallel with a 1.018M trimmer. Now, in the Off position it doesn't matter what the trimmer is set to or the fact that it's in series with the 18k resistor making it 1.018M, it's always gonna be 4.75k or at the very least 3.75 if you have the trimmer dialed off.

Re: Amptweaker - BigRock/TightMetal Pro

PostPosted: 03 Sep 2017, 10:29
by DimebuGG
Here you go. Thanks to bajaman for letting me attach his (simplified) schematic.

Re: Amptweaker - BigRock/TightMetal Pro

PostPosted: 03 Sep 2017, 16:52
by J0K3RX
DimebuGG - Dude, you got Madd Skillz!! :twisted:

Re: Amptweaker - BigRock/TightMetal Pro

PostPosted: 05 Sep 2017, 06:24
by J0K3RX
DimebuGG wrote:I made a single side pcb yesterday with boost function minus loops and LED lights. It's done already but I need to do final touch. Once finalized, I'll post it herre immediately.

Oh BTW, what's the value of BOOST GAIN and BOOST MASTER pots?. And also I see from bajaman's pcb that R56 is 100K and C31 is 220pF. Is this right?.


Boost volume and boost gain are both B100k, R56 is 47k and C31 is 560pF.

Re: Amptweaker - BigRock/TightMetal Pro

PostPosted: 15 Sep 2017, 09:30
by DimebuGG
Oh fuck!. I apologize. There's a mistake on that layout. I built it today and was wondering why didn't I get any signal. Only to find out that "Va" is supplied to 3 opamp's pin 8. I'll revise the layout ASAP.

Re: Amptweaker - BigRock/TightMetal Pro

PostPosted: 15 Sep 2017, 15:17
by agung
already built this from dimebug layout..and yeaah, something wrong with this layout. im using flying jumper from 12v out to all pin 8 opamp , and this thing come alive :applause: . thanks to DImebuGG
http://oi65.tinypic.com/1g3kwm.jpg

Re: Amptweaker - BigRock/TightMetal Pro

PostPosted: 15 Sep 2017, 20:42
by DimebuGG
This is how I did with mine. I kinda fucked up the drilling of the two boost control pots. :slap: And also I used slide switch that I took from a dead M-Audio interface( I actually ordered sub mini toggles from Futurlec and still waiting for it to be shipped..poor customer service :evil: ). I did flying jumpers too.. :lol: . I really dig the boost controls in this one, it adds a different character to the sound.