Behringer VM1 Vintage Time Machine

A forum devoted to mod, tips and suggestions for upgrading and rehousing your VERY CHEAP commercial stompbox to near boutique excellence.
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Dirk_Hendrik
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Post by Dirk_Hendrik »

Look at a real DMM. It's got an amplifier stage in between the BBD's to buffer and provide some makeup gain. That's the road you've got to go.
After that, take out BBD no 2 and connect the input pcb pad with the output pcb pads. Adjust BBD1 for minimal distortion. When done take out BBD1, put BBD2 back, connect bbd1 input pad to output pads and adjust bbd1 for minimal distortion.
Then place BBD1 as well and both BBD's are calibrated individually for minimal distortion.
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Post by Zokk »

Thanks Dirk

well, I see what you mean: that's U2B on my DMM schemo...
I could try a TLO71 here, but I don't know how to implement it on the VM1 board...
I will try to remove the two BBDs before that, inorder to put sockets for them on the pcb (that will help me a lot with the procedure you've described).

I will post results as soon as I can got a new vacuum pump to desolder the ICs ( bad luck: mine has gone yesterday :evil: )

Many thanks again for this trick!

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Post by rasta_maleek »

could any post the diagrams or schematics of the ultimate mods for this pedal.
thanks for all the effort.

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Post by rasta_maleek »

any could tell me how implement the 3dpdt true bypass to the VM-1?
thanks all responses

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Post by rasta_maleek »

rasta_maleek wrote:any could tell me how implement the 3dpdt true bypass to the VM-1?
thanks all responses
true bypass did it, lets do some DMM transformation and look what happend

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Post by Hides-His-Eyes »

If only it were through-hole, you could pretty much just leave the delay chain intact and redo the wrapper

as it stands that's still possible, but you'd need a full trace
Testing, testing, won too fwee

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Post by rasta_maleek »

I did the electrolytic capacitor change that some dude comments up threats and really are a good mods. Now sound very clear delay, before was a little dark, and results a good delay, better vibrato/chorus. Recommended.
Now need someone who tell me how to tunning the BBD to less noise, some teach off the delay masters of freestompboxes, I will acquire a oscilloscope the next month.

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Post by rasta_maleek »

im wonder if would be very dificult to change the opamps to tl072 to eliminate the backgruond noise.Are smd opamps sensible to the heat?

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Post by Hides-His-Eyes »

The op-amps are probably pretty low on the noise stakes
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Post by rasta_maleek »

Hides-His-Eyes wrote:The op-amps are probably pretty low on the noise stakes
i think that is a mod on the memory man, soo maybe reduce the backgound noise, with the preamp at 12 oclock and the mix at o, you can hear a lot of noise, try it.

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Post by rasta_maleek »

i try it in a marshall(jcm i think) fx loop and WoW, this pedal sound amazing, i put in the first IC a LM833, the only IC that i find on the electronics store. A great improvement. I wonder what will happen if change all the capacitors and resistors to DMM schematics reference.

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Post by rasta_maleek »

some video of my modifications playing vm-1 with other pedals.


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Post by Dirk_Hendrik »

Mr Malleek,

Since you've made DMM from a VM1 a personal goal some hints;

The way the BBD's are driven is different. MN3102 vs 4047. This is the least of concern. A clock is a clock.

With reference with the original DMM:
There's a make up gain stage between BBD1 and BBD 2 in a DMM. This will help you with the noise problem as well as lessen BBD distortion. A piggyback PCB might be a suggestion.

There's a huge difference between DMM and VM1 component values in the pre and post BBD filtering. That would be my 2nd focus of improvement when tuning a VM1 to dmm specs (as much as possible).

If you do not have a copy of a DMM schem (in a readable form) drop me a PM with an email adress and I'll mail it to you. Cannot upload here since there's still sad entities lurking here who think that doing that will immediaty cause EHX to go bankrupt.
Sorry. Plain out of planes.

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Post by rasta_maleek »

Dirk_Hendrik wrote:Mr Malleek,

Since you've made DMM from a VM1 a personal goal some hints;

The way the BBD's are driven is different. MN3102 vs 4047. This is the least of concern. A clock is a clock.

With reference with the original DMM:
There's a make up gain stage between BBD1 and BBD 2 in a DMM. This will help you with the noise problem as well as lessen BBD distortion. A piggyback PCB might be a suggestion.

There's a huge difference between DMM and VM1 component values in the pre and post BBD filtering. That would be my 2nd focus of improvement when tuning a VM1 to dmm specs (as much as possible).

If you do not have a copy of a DMM schem (in a readable form) drop me a PM with an email adress and I'll mail it to you. Cannot upload here since there's still sad entities lurking here who think that doing that will immediaty cause EHX to go bankrupt.
thanks for reply Mr. Hendrik
i notice the diferences that you say between the two circuits, but i don,t know if the schematic traced by the other guy is verified or not.
the mods that i did were about the input/output IC, i changed for a LM833, and the filtering of the dry/mixed signal, electrolitical caps before the mix pot, and the speed pot caps of the chorus and vibrato.
when the schematic will be finish, maybe i will do the mods.
And thanks for the support, i will send my mail for the schem.
cheers.
Ivan.

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Post by JiM »

Dirk_Hendrik wrote:There's a make up gain stage between BBD1 and BBD 2 in a DMM. This will help you with the noise problem as well as lessen BBD distortion. A piggyback PCB might be a suggestion.

There's a huge difference between DMM and VM1 component values in the pre and post BBD filtering. That would be my 2nd focus of improvement when tuning a VM1 to dmm specs (as much as possible).
Thanks Dirk !
The pads of C20 would be a convenient in/out point for a recovery gain piggyback board, as it's through-hole. Or maybe IC4A could be made useful ?
When comparing in detail the schematics of the DMM and VM1, there are indeed a lot of small differences, and some not so small in pre/de-emphasis networks. The preamp is also permanently engaged in the DMM.
The schematic i have uses MN3005, thus negative power. Is there a factory schem with MN3205 ?
rasta_maleek wrote:i notice the diferences that you say between the two circuits, but i don,t know if the schematic traced by the other guy is verified or not.
the mods that i did were about the input/output IC, i changed for a LM833, and the filtering of the dry/mixed signal, electrolitical caps before the mix pot, and the speed pot caps of the chorus and vibrato.
when the schematic will be finish, maybe i will do the mods.
I'm "the other guy", i guess. And i eventually managed to get the schematic verified, thanks to FSB member AndyPederson (who seems a bit too shy to chime in here).
Enjoy, and tell me if you want the source file.
Attachments
Vintage Time Machine, verified !
Vintage Time Machine, verified !
I only give negative feedback.

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Post by rasta_maleek »

JiM wrote:
Dirk_Hendrik wrote:There's a make up gain stage between BBD1 and BBD 2 in a DMM. This will help you with the noise problem as well as lessen BBD distortion. A piggyback PCB might be a suggestion.

There's a huge difference between DMM and VM1 component values in the pre and post BBD filtering. That would be my 2nd focus of improvement when tuning a VM1 to dmm specs (as much as possible).
Thanks Dirk !
The pads of C20 would be a convenient in/out point for a recovery gain piggyback board, as it's through-hole. Or maybe IC4A could be made useful ?
When comparing in detail the schematics of the DMM and VM1, there are indeed a lot of small differences, and some not so small in pre/de-emphasis networks. The preamp is also permanently engaged in the DMM.
The schematic i have uses MN3005, thus negative power. Is there a factory schem with MN3205 ?
rasta_maleek wrote:i notice the diferences that you say between the two circuits, but i don,t know if the schematic traced by the other guy is verified or not.
the mods that i did were about the input/output IC, i changed for a LM833, and the filtering of the dry/mixed signal, electrolitical caps before the mix pot, and the speed pot caps of the chorus and vibrato.
when the schematic will be finish, maybe i will do the mods.
I'm "the other guy", i guess. And i eventually managed to get the schematic verified, thanks to FSB member AndyPederson (who seems a bit too shy to chime in here).
Enjoy, and tell me if you want the source file.

thanks a lot Jim.
let do a methamophosis

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Post by airfrankenstein »

Hi, hope this hasn't been dealt with already elsewhere. How would one go about wiring a jack to control the delay level with an expression pedal ?

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Post by TheDams »

Hi,

I am very interested in implementing a true bypass on a VM1, and I have read that some people did it... is it possible to have a tutorial for this mod ?
I'm starting to be interested in the DIY (I've built and rehoused some pedals...)

Thanks a lot !

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Post by JiM »

airfrankenstein wrote:How would one go about wiring a jack to control the delay level with an expression pedal ?
Do you mean the "MIX" pot ?
I would try and wire an isolated, switching stereo jack in series with the 3 lugs of the pot. When the expression pedal is plugged in, this would remove the original pot from the circuit, and replace it with the one in the pedal. Two problems that may arise are 1) the absence of ground reference (use a plastic pedal) and 2) possible differences in pot value and taper (althrough 10k log is common in expression pedals).
TheDams wrote:I am very interested in implementing a true bypass on a VM1, and I have read that some people did it... is it possible to have a tutorial for this mod ?
Hmm, any True Bypass schematic will do, either with a 3PDT, the stock DPDT (and no indicator LED), or the Millenium Bypass.
There is no need to deal with stereo outputs, as the other output is "direct out", e.g. a permanent true-bypass already ...
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Post by el-folie »

@Jim and Dirk Hendrik:

Hi, it´s my first post here and my head is spinning. I spent the whole night above Jim´s VM-1 schematic and the MN3005 DMM schematic. I´m waiting for my own VM-1 right now - just ordered it. I´d like to contribute an idea about the gain trim stage that´s preventing the original DMM from collecting too much noise between the two bbds. Attached is a first idea about how to implement that on the VM-1. I know it won´t be correct yet or maybe even totally wrong but maybe with your help we can do it. Please let us know what you think about the circuit additions within the red line. I did this in windows paint so ;-) ...

Regards
el-folie
gain trim circuit - not verified
gain trim circuit - not verified

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