drewtronics sherlock dead or alive ?

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reanimatorstudio

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Is there a way to bring the drewtronics sherlock back alive?
It looks like Drew is not offering them anymore.
Does anyone have the PCB layout or sources for the transformers?
Can you imagine, I'm asking to clone a clone!  :)

I hope these questions are not in conflict with the forum rules.


regards,

Studioreanimator

 
Radiance was so friendly to send me his Drewtronics Sherlock PCB.
Thanx Radiance.
I have scanned the PCB and I did some Photoshop on it, so if anybody is interested I will post it. So you can make your own pcb's and the cloning can continue.
 
I'd love to get that PCB.... I've been wanting to make one of these badboys for awhile.
Thanks!!
 
Instead of just straight cloning, is anyone else interested in re-working the design to be more useful and flexible. Like Standard Audio did for their Level-or:

http://standard-audio.com/home.html

At least read the old threads here, search "levelloc" and "level-loc".
 
skipwave said:
Instead of just straight cloning, is anyone else interested in re-working the design to be more useful and flexible. Like Standard Audio did for their Level-or:

http://standard-audio.com/home.html

Hell ya! A 500 form factor would be a nice feature.

Mark
 
From what I've read, the fixed release time seems like it could use a couple different options.  I just bought a kit off the black market so I haven't gotten it yet, but does anyone know how different the drewtronics schem is from the shure one?  Does anyone HAVE a drewtronics schem?
 
And here's a retraced copper layer.
Note:  I added the top layer to this one and added a jumper so it can be single sided

EDIT: I just realized I hadn't flipped the traces for etching... they're as they should be now
 

Attachments

  • sherlock pcb.jpg
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So im trying to figure out how the distance switch wiring from the instruction booklet matches up to the schematic.  In the written in notes of the drewtronics pdf, it says an sp3t switch.  I can't for the life of me find a sp3t switch diagram or can i picture it in my head based on the diagram in the instructions.  I'm just wondering how each position is switched into the circuit. 

I've drawn out on the schematic how the instructions say to wire up the switch, but what the does the switch connect together?  usually there is one terminal that gets connected to different terminals (lorlin rotary is the best example for me).  so how does this fit in?
 

Attachments

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Sherlock doesn't show the 33k in series with the input before the cap. Isn't it the top leg of the L-pad with the FET as bottom leg?

Taking a closer look at what the distance switch is doing in the Shure schem... Feeding the side chain from a voltage divider or L-pad

1. (18") direct from the line amp with only the 22k shunt to ground - no attenuation
2. (12") L-pad 12k/22k - if I've done the math right -4dB referenced to the voltage entering the pad
3. (6") L-pad 12k/5k6 - about -10dB

Why not just replace this whole mess with a 25k pot labeled "Threshold"?

As far as Release time, you can switch different cap sizes in. The M62 has 1uF instead of the 2uF shown on the M62V. Which brings me to another interesting question: The M62 uses regular silicon diodes for sidechain rectification (not fast enough), and it looks as though we could just change the 1M resistor to a 1M pot and get variable release. In the M62V rectification is via N-P junctions of the TIS93 PNP devices. What happens to those PNP if we lower the resistance at their collectors? The 47k resistors to their Bases are biasing them on, and with the low V+ we won't exceed their Collector-Base Voltage rating if we short the collector?

Or am I missing something crucial, as usual?  ;)
 
i'm a little too tired and not quite hip enough to transistor circuits to understand all that quite yet, but believe me, i'm gonna wake up tomorrow and stare at schematics and read all that again in hopes of figuring this circuit out.  So thanks for that explanation!  It will come in handy to me soon hopefully.  I've figured out the basic function of each block so far (except for the distance switching), but thats about as far as I've gotten...
 
Hi reanimatorstudio,
Thanks for the headsup on the 33k after the input pot!  I can't seem to find it in any of the documentation, can you point me in the right
direction.
Cheers,
Dave
 
To quote myself:

skipwave said:
Sherlock doesn't show the 33k in series with the input before the cap. Isn't it the top leg of the L-pad with the FET as bottom leg?

See original schematic.

http://www.freeinfosociety.com/electronics/schematics/audio/shurem62v.pdf
 
alright, i have a couple more questions about modifying this circuit for a few things.  First of all, is it possible to just use a 24v wall wart psu instead of 9v?  All the transistors look like their Vce rating is 25v or higher for the TIS93.  What are the pros and cons of doing this?  More headroom?  Possibly less of the "character" since there is more headroom?  This would be a super easy mod to do, just buy a different wall wart.  I guess once I get it wired up I can find out.  i just wanted to make sure so I wouldn't blow up the transistors and have to replace them.

Next is a way to link 2 channels to act as a stereo pair.  From my limited knowledge, it would involve summing the inputs to each sidechain into 1 of the sidechains, and then feeding the output of that SC into both Q9s.  Am I on the right track?  Could you just add equal (summing) resistors to both and feed them into Q4 on one board as is?  Or would there have to be a separate summing stage before hand?  Am I right in saying that Q4 is the beginning of the sidechain?  And then could you just hook the output to both of the Q9s straight or would there need to be some resistors or other inbetween?

Also, just an aside, but can someone explain the difference/need for the A+ and B+ voltages on the schematic?
 
I think you misunderstood me.  I was trying to understand what would change if I did use the higher supply voltage.  I'm not trying to make it into a pristine compressor.  I WANT it to be grungy and imperfect.  I'm just asking questions.  I know enough about electronics to make me dangerous, not much more.  I'm trying to change that.  So i overlook or just don't consider the fact that this is operating at mic level except for the aux out.  So thanks for making me aware of the obvious! (no sarcasm intended there, i'm completely serious.  i tend to find the details and miss the obvious)  If I wanted to use it for line level, i'd probably just use the pad on the input since you say it would act differently with the higher supply voltage, and that would require changes that i don't know how to make. 

So, the increased supply voltage seems useless and/or unnecessary.

Still interested in the stereo linking though.  If I used this on a pair of ribbon mics as stereo drum room mics, or stereo acoustic guitar, or stereo anything else, wouldn't you have to have them linked?  Or else the image will shift back and forth because each channel is doing something different.  I don't like that.  That is the only feature that I need to be like nicer compressors.  So am i on the right track with my earlier thoughts? 

I wish I had time to actually try my ideas out, but its my busy time and i've been out of town away from my "lab" from a month ago until february except a few chance weekends.  I'm just organizing my thoughts so that when I do get home, i'm productive as hell!  I'm just hoping someone has tried this before.  I guess I could look into how an 1176 is stereo linked.  They're both fet compressors, so maybe there's insight there.

Any other ideas?
 
I WANT it to be grungy and imperfect.

You don't need to up the psu voltage, it is grungy & imperfect to begin with !

With regards to linking for stereo, in my experience you will have to be pretty careful matching things up.  I built a pair using the same parts in the same places on both, & they don't behave similarly enough to work as stereo, but they do sound grungy & imperfect ! 

 

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