Black Box Buffer  [schematic]

All about modern commercial stompbox circuits from Electro Harmonix over MXR, Boss and Ibanez into the nineties.
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Mbas974
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Post by Mbas974 »

Hi this is a buffer box from Italian brand.
Really good quality assembled pedal.

Buffer circuit nothing really new.

What surprise me is the IC2 of TL072 used for LED purpose.
I do not think audio will benefit of this use of the other half IC, can someone explain it ?

a double check to schematic is welcome also !
Attachments
Buffer - BlackBox.jpg
BBB - DOWN.jpg
BBB - DOWN.jpg (22.53 KiB) Viewed 3561 times
BBB-UP.jpg

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Post by mictester »

The second half of the TL072 is being used as a battery condition monitor. If the battery voltage falls below a certain point, the LED won't light.
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Post by alexradium »

Mbas974 wrote:Hi this is a buffer box from Italian brand.
Really good quality assembled pedal.

Buffer circuit nothing really new.

What surprise me is the IC2 of TL072 used for LED purpose.
I do not think audio will benefit of this use of the other half IC, can someone explain it ?

a double check to schematic is welcome also !
i would say that most buffers are made with a very low output impedance,this one instead is more similar to the guitar out with volume on 10,which seems more accurate tonally (not so bright) and its both good if you plug into a pedalboard or directly to the amp's input.
But in the end it all depends on cables length and so on.

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Post by Intripped »

I think there are some minor errors with that schematic,
On the PCB I can clearly see two 2.2M resistors (1M in the schem?), and 1 capacitor is missing: there are 7caps on the PCB and 6 in the schematic.

Mbas, can you post some other pics with caps values please?

Also, in this pic the opamp seems different

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Post by tube-exorcist »

Intripped wrote:I think there are some minor errors with that schematic,
On the PCB I can clearly see two 2.2M resistors (1M in the schem?), and 1 capacitor is missing: there are 7caps on the PCB and 6 in the schematic.

Mbas, can you post some other pics with caps values please?

Also, in this pic the opamp seems different
BTW can you verify what is written on the smaller diode ? It is not an 1N4148 - instead it is a zener-diode, probably a C5V1.
IMHO the ouput resistors are 100 Ohm in series and 47k pull down.
and the second 1N4001 is not connected to ground instead one is for the battery the second for the DC-IN jack.
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Post by tube-exorcist »

Mbas974 wrote:pls moderator cancel previuos one.

this is the final schematic.
Not really.... R6 + R7 are 2M2
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Post by Intripped »

Op-amp in the pic from effectsdatabase is probably an Analog Devices OP275

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Post by Mbas974 »

last one
discards all the previous, better moderator remove these to clean the topics (i can't).

..in this stomp IC is TL072, as clearly stated from the picture.
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Buffer - BlackBox.jpg

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Post by Intripped »

Yes, the IC in your pics is clearly a TL072, I was referring to that unit at effects-database only, but now we know that there are at least 2 versions of this pedal.

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Post by Bernardduur »

Here is the schematic of my unit
Masotti - Black box.JPG
Mods: Please change the name of the thread to Masotti - Black box
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Post by snofla1900 »

Hi ,


What voltage did you use to power the buffer : 9 volts or more ?

Tia, Alf ( Netherlands)

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Post by Manfred »

I made a board clone according the PCB shot and the schematic drawn by Bernardduur.
BlackBoxBufferLayout.JPG
BlackBoxBufferComponents.pdf
(12.66 KiB) Downloaded 133 times
BlackBoxBufferPCB.pdf
(18.24 KiB) Downloaded 124 times
BlackBoxBufferPCBmirrored.pdf
(18.2 KiB) Downloaded 125 times

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