Zvex - Box of Metal  [traced]

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bajaman
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Post by bajaman »

....... more details - the input also feeds one half of a high variable gain stage op amp controlled by the gate potentiometer.
the output of this is fed to a half wave rectifier and also to the other half of the op amp which is usd as a unity gain inverting stage - the latter also is fed into a half wave rectifier and the two rectifier outputs are summed and these drive the led in the vactrol optocoupler (any numbers on it?? or did Zachie buff them off as well!!!) through an NPN bipolar transistor stage. This controls the resistance of the LDR which is effectively in parallel across the output volume potentiometer.
I am not certain - but there appears to be a p type Jfet in series with the signal from the treble wiper. This is normally a very low resitance when no voltage is applied to it's gate - when the noise gate circuit is not activated. When the noise gate circuit is activated the p jfet gate is connected to the junction of the LDR and top of the output master volume control - depending on the level predecided by the setting of the gate control which as mentioned sets the gain of the detector and hence the rectified DC output level which activates the LED section of the optocoupler.
As a result a varying dc voltage is applied to the gate of the p jfet which increases and decreases its drain source resistance accordingly.
There is also a precision virtual earth half rail 8 pin chip too - this is most likely to be a TLE2426 device from Texas Instruments - the previous mentioned dual opa mp is most likely to be a TL072 or similar - not critical, but you could use a higher speed device if you want to.
more later
Cheers
bajaman
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ShortScaleMike
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Post by ShortScaleMike »

Absolutely top-drawer work, Bajaman.

And thanks very much culturejam for posting the pictures.

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bajaman
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Post by bajaman »

Hi Culture jam
What is the distance between the controls please??
inches or millimetres no problem :wink:
thanks - board layout nearly ready :)
cheers
bajaman
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audioguy
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Post by audioguy »

awesome.... I've got a clear bench this weekend. I would love to give it a go!

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Post by culturejam »

bajaman wrote:Hi Culture jam
What is the distance between the controls please??
8mm from the edge of one pot to the edge of the next.

There are no markings of any kind on the opto coupler.

I'm thinking I'd have to desolder the caps to read them properly? I'd rather not have to do that, because I have doubts about my ability to re-solder them properly. :oops:

Would it be possible to measure them in circuit, and then back-calculate the value based on how they are connected to other components?

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Post by DWBH »

culturejam wrote:
bajaman wrote:Hi Culture jam
What is the distance between the controls please??
8mm from the edge of one pot to the edge of the next.

There are no markings of any kind on the opto coupler.

I'm thinking I'd have to desolder the caps to read them properly? I'd rather not have to do that, because I have doubts about my ability to re-solder them properly. :oops:

Would it be possible to measure them in circuit, and then back-calculate the value based on how they are connected to other components?
bajaman wrote:
I do have a capacitance meter function on my DMM, but it's only for leaded components. It's just two little slots that you slide the leads into
Just grab some insulated hookup wire - strip, twist and tin both ends with solder - plug into capacitance slots and use the other two ends and place them against the ends of the smd capacitors ( the cream coloured flat slab things).
bajaman
;)

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bajaman
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Post by bajaman »

Would it be possible to measure them in circuit,
Yes - should be reasonably accurate to do - make sure the pots are all set at half rotation though :wink:
cheers
bajaman
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Post by culturejam »

bajaman wrote:
Would it be possible to measure them in circuit,
Yes - should be reasonably accurate to do - make sure the pots are all set at half rotation though :wink:
cheers
bajaman
I'll see what I can do.

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culturejam
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Post by culturejam »

Okay, here's what I came up with. Let me know if you need anything else, Bajaman.
Attachments
left.jpg
center.jpg
right.jpg

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bajaman
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Post by bajaman »

Thanks culturejam
I have finished my drawings with the component values etc.
I would not consider this an easy to build project - it would be a lot easier to build in a larger box with veroboard or some other through hole component construction.
I would not bother with the gate etc. - far too complicated for very little useability.
Instead use my earlier sketch (now amended with capacitor values and output volume components).
I think that switching some of the SHO stages out may give a more useable function - use a boost control footswitch instead of the gate. More later
cheers
bajaman

members/bajaman/Baja/Vzex/MoxofBetalfirstsketch.jpg
members/bajaman/Baja/Vzex/Moxofbetaltop.png
members/bajaman/Baja/Vzex/Moxofbetalbottom.png
members/bajaman/Baja/Vzex/Moxofbetaloverlay.png

PLEASE do not try to build this smd layout - it is for educational reference only - you will go blind if you try and build it :wink: :D
bajaman
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borislavgajic
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Post by borislavgajic »

:thumbsup :applause:

great job

boris

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mike_a
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Post by mike_a »

bajaman wrote: PLEASE do not try to build this smd layout - it is for educational reference only - you will go blind if you try and build it :wink: :D
bajaman
I can't imagine why anyone would want to clone this horrible sounding unit :?
it's funny to see that is, in fact, another "original" SHO cascaded "design" from the uber-master of cascaded SHO's ... :lol:

Great job on the tracing Bajaman!

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Post by bajaman »

The signal path looks strangely familiar to me - almost peavey 5150 or bogner or mesa dual rectum frier.
Only tubes overload and generate those nice smooth tube harmonics though :wink: - no hissy BS170 is gonna get you there. :lol: Still some folks like them I guess. :roll: Maybe a string of TL072 op amps run into clipping diodes like those backwood D2G guys do - see Briggs Kustom Kretin Drive :wink: Ahhh the Super Hard On - It came to me in a dream :hmmm: :blackeye :lol: :lol: :lol: :lol: :lol: :lol:
I wonder what it would sound like with some of those small Russian pentodes (wired as triodes of course) :wink: - another project for a rainy day - they run nice and cool off 30v dc too :wink: - easily done with a 16v AC power pack supply - (or four 9v batteries :lol: :lol: )
I'm beat - too much Christmas pudding and 27 degree celsius temperatures - too hot to sleep for an old codger like me.
Hope you all had a PEACEFUL Christmas
Peace and Goodwill to all
Do good deeds and do not expect anything in return. You will be surprised when the kharmic wheel turns and repays you for an act of kindness - often when you least expect it.
cheers
bajaman
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Post by moltenmetalburn »

Dont feel bad! :hug: Lets just try to stay on topic! :horsey:
"The Humans Will Never Destroy Us"

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borislavgajic
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Post by borislavgajic »

moltenmetalburn wrote:Dont feel bad! :hug: Lets just try to stay on topic! :horsey:
:thumbsup :thumbsup :thumbsup
Yes ,stay in freestompboxes land ....no religion ,politics...........just electronics,and no bad feelings!

boris

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Post by bajaman »

my apologies Mike a :oops: - I just do not like seeing ANY innocent people killed for whatever reason.
Back to the Mox of betal.
i shall draw the noise gate section soon (unless someone else beats me to it :wink: )
cheers
bajaman
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Post by mike_a »

No hard feelings :thumbsup

Thanks again for your work on the tracing.

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Post by bumblebee »

Nice work bajaman!
I so dislike the modern digital world that I need to use semi-digital effects to emulate the analog world of cassette, VHS, and vinyl.

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Post by Cow4prez »

Okay - so here it is - a 5 stage super hard on with a modified Marshall tone stack.
[smilie=eek2.gif]

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Torchy
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Post by Torchy »

Polite request -

Can we keep the politics out of stompbox threads please ? Its a multinational board and we all have our own views/opinions. Ta :wink:

Thanks for the B-O-M work so far. I'd be interested in the gate element of this too.

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