Sherlock Level-Loc Clone Troubleshooting

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If you have a two-chanel level-loc/sherlock, try running them in series with the feedback resistors in each chanel disconnected = jaw dropping distortion.
I installed switches that do this in my sherlock clone. :cool:

~ Charlie
 
damn it. i got my sherlock back yesterday, yay, so i went just now to make an mp3 of its compression sound and damn it if it's not compressing anymore. it's now behaving the same way mattias' is, acts like an overdrive w no compression. i hooked it up same as i always have and no squishy. i don't even know where to begin. great..

one thing i did notice. the jameco 9vdc adapter it came with is putting out 14.5 vdc, not 9, so i hooked it up to a 9v battery. same result. could that extra voltage have hurt something?
 
so i replaced q6 and q7 (tis93) with some 2n4403's from a local shop and i'm back up and running. i'm beginning to think that mattias' prob could be related to not getting the input signal sufficiently below the very low threshold level. i was reminded again how low the threshold really is while testing mine just now. btw, drew sent me a schematic. if anybody needs it just send a pm. also, glad to email an mp3 of a sherlock'd drum loop to anyone interested.
 
My Sherlock is up and running, and I've got a low level coming out (yes, I'm running it into a pre!), but otherwise it's working the way I expect. EXCEPT that when it compresses it adds a distinct BUZZ to the audio - sounds almost like a fret buzz on a high E string on the guitar. I wrote Drew and send an MP3 file and here's what he wrote back:


" install the power filter mod - just a lowpass filter on the power
line using 3 100-ohm resistors and 2 470 or 680uF capacitors!

Some people have experienced this, some not, it's a strange
phenomenon, hopefully this will fix it.

Also make sure you're not hitting it too hard, it has a very low
threshold :)"

Unfortunately, this "power filter mod" doesn't make much sense to a newbie like myself. I'm posting it here incase anyone else is having the same problem. And I'm hoping someone could clarify what he means :cool:

This is only on the XLR out. I haven't tried the aux out. Hopefully I'll get around to it tonight.
 
This unit is capable of squashing signals down to a very low level. The distance switch changes the threshold. I find that the last (or first depending on how you look at it) switch position to be unusable for reasons that you are describing.
 
[quote author="ebartlet"]This unit is capable of squashing signals down to a very low level. The distance switch changes the threshold. I find that the last (or first depending on how you look at it) switch position to be unusable for reasons that you are describing.[/quote]

So that's just how the unit is supposed to be?? Is there a way to clean up the buzz on that setting?
 
[quote author="radiance"]Does spmeone know where to find the scheme of the Sherlock?
I emailed Drew but got no response...[/quote]

I have it somewhere, give me a day or two and I'll send it to you...
 
I realize this thread is very old but I would love to see this schematic. I did a schematic in express SCH and then did some boards in express PCB and built one and it works correct (I think :) however in bypass mode the unit is louder with the output transformer engaged, however with the unit engaged the output transformer lowers and distorts the signal. What am I missing?
 
Yeah, I am pluging a mic into it and then plugging into a mic pre but what is confusing me is why the output drops when I engage the output transformer when the unit is not bypased. It bumps it up when in bypass but bumps it down when engaged. :?
 
If I hear you correctly, you mean change when switching between transformer and transformerless output? If so, that's because the transformer turns ratio steps the signal down in level, in the process of achieving lower output impedance. Is that what you mean?
 
you mean change when switching between transformer and transformerless output? If so, that's because the transformer turns ratio steps the signal down in level, in the process of achieving lower output impedance. Is that what you mean?
Yes, but when the unit (the circuit not the transformers) is bypassed - engaging the output transformer bumps the signal level up. When I engage the circuit, engaging the output transformer lowers the signal and adds distortion. I don't understand why that would be.
 
I think both are effects of loading, and under different circumstances. I may still not have a clear grasp, since your description isn't fully spelled out.

Your output is feeding a mic pre? I'm assuming that from what I'm reading. And assuming lo-Z input position.

In bypas, we are switching an entirely passive signal through transformers, or not.

In bypass, with lo-Z input and hi-Z output, you are stepping up impedance with the input transformer and then trying to dump it into a lo-Z input again (your preamp). So you probably have mismatch loading losses, as your mic is now seeing a very low load impedance reflected from the preamp. Conversely, the preamp is being driven by an impedance that has been stepped up out of the expected range.

Switch to bypass with lo-Z input and lo-Z output, the transformers are then doing reciprocal step up/down and you have correct match for the preamp again, and only transformer insertion loss rather than mismatch loading loss. Probably an actual gain change of -1-3 db over plugging straight into your pre.

Unit active, all sounds normal. hi-Z on output is probably recommended load, and not actual, and can still drive your preamp. lo-Z puts transformer in path, which steps down level.
 
thank you very much sir! That makes complete sense.
I believe I have a problem with this unit and I think I have narrowed it down to the 2 PNP transistors Q6 and Q7. For some reason I have 0VDC on the collector of these transistors. I have tried different trannys and triple checked my pinouts (TIS93's) I also tried some 2N3906's. This is resulting in 0VDC on the gate of Q9- (FET 2N5458). I have 1M to ground on the collectors and the 2uf cap (which I havent pulled and checked yet) and then it goes thru the 1M resistor to the gate of the FET. When I first plug in the power I see 9VDC on the collectors and it quickly drops to 5V or so and then slowly drops to 0V. Any ideas?
http://www.freeinfosociety.com/electronics/schematics/audio/shurem62v.pdf
schematic is on the last page.
 
I think I got it. It appears that the "sherlock" reversed these two transistors and so I tried that (swapped emitter and collector) and now I have voltages that look more correct - I now have 1.9vdc on the gate of the FET. Is it ppossible that Q6 and Q7 are drawn backwards on the schematic?
 
sorry to resurrect an old thread, but i have a few questions (i'm somewhat new to DIY):

i would like to get better switches for my Sherlock. does anyone know what kind of switches i need? SPST? 3PDT? i really like the flat lever type. are mountain switches any good?

also, where can i get another set of similar xfmrs? i have a friend who can clone PCBs so i'm thinking of doing two channels. buss compression rules.

can i power both channels with the one included wallwart supply? wouldn't that split the voltage in half or is there a way around this?

thanks.

(p.s. a schematic would be great!)
 
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