PLAN B analog blog

Maybe this has been covered.
I love the M13, it's jacks are never lonely!
I just wish I had 4 of them or 2 quad-LPG's.

But...
Sometimes I wish that I could get the gate response time to be a 
little bit shorter.  I know about the leaky vactrols and how they're 
all unique, but besides that, is the response time "set" internally? 
Before I go tinkering around and mess things up, is there a way to 
achieve this?

Thanks!

What are you using to gate your model 13's?

Tim


--- In PLAN_B_analog_blog@yahoogroups.com, "jeswa" <j@...> wrote:

>
> Maybe this has been covered.
> I love the M13, it's jacks are never lonely!
> I just wish I had 4 of them or 2 quad-LPG's.
> 
> But...
> Sometimes I wish that I could get the gate response time to be a 
> little bit shorter.  I know about the leaky vactrols and how they're 
> all unique, but besides that, is the response time "set" internally? 
> Before I go tinkering around and mess things up, is there a way to 
> achieve this?
> 
> Thanks!
>

hello jeswa,

vactrols have a fixed decay time, you cannot change it
without changing the vactrol.

best wishes

ingo


--- jeswa <j@schematic.net> schrieb:

> Maybe this has been covered.
> I love the M13, it's jacks are never lonely!
> I just wish I had 4 of them or 2 quad-LPG's.
> 
> But...
> Sometimes I wish that I could get the gate response time to be a 
> little bit shorter.  I know about the leaky vactrols and how they're 
> all unique, but besides that, is the response time "set" internally? 
> Before I go tinkering around and mess things up, is there a way to 
> achieve this?
> 
> Thanks!
> 
> 


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You can alter the decay - the ringing - of the Model 13.  This is due to circuitry I have 
added to cut the bleeding down.  You can't do this with Doepfer LPGs, or Buchla 292's for 
that matter, nor with the Wiard Borg which is very close to the Buchla 292 in design.

Looking at the PCB, you'll first notice it's basically two duplicate circuits (one each for the 
two TG's) with  a slender line of circuitry in the middle (that's the crossfader section).

On each of the TG halves, at the bottom (edge) of their real estate you'll see four pads in a 
line that are ellipically shaped.  In older M13s there are wires soldered to these pads which 
go to the faceplate.  Newer models have a parallel connection via a 12 (and now 14) pin in 
line connector in the center of the board which lies right in front of the corssfader pot's 
backside.  Holding the PCB so that the power connector is on the upper right, to the left of 
those four pads you'll see two others labelled J1.  In older PCBS - those before rev. 2, there 
a standup resistor soldered into J1.  In Rev. 2 and above, another resistor was added 
directly to the left of those two pads - a 470 K ohm resistor. Those resistors, either 
configured as a standup in the J1 pads, or from the added resistor next to them are the 
current limiters that determines how much of the bleed killer is mixed into the the circuit.

J1 was configured as it was because it will allow for a two position jumper block to be 
installed - like the little things that were on the back of SCSI disk drives to set their ID 
number.  Inserting a jumper there puts the bleed killer on maximum.  removing the 
jumper would remove it altogether.  I stopped installing those jumper blocks early on 
because of availability issues with the jumpers.  I was not willing to slow delivery down to 
to a G.D. part that for some reason (still surprised by that) - hard to get.  THey were listed 
in supplier site, but constantly sold out.

The lower that resistance, the less bleed and slightly less ringing or response time to the 
DECAY of the vactrol.  In earlier models I was shipping with a zero ohm resistor in there - 
putting the bleed killer on maximum, which also cut back the decay.  Later I started 
allowing less of that into the circuit, which slightly increased the bleeding, but made the 
ring longer - that's the 470K resistor.

If you want to cut back the amount of ringing, increase the value of those resistors.  If you 
want more, increase it or, to get the longest possible ring, remove those parts altogether.  
Just cut them out.  This will make the vacs rings at their maximum.  Unfortunately, it also 
effects the level of vac's inherent bleed.  WIth no resistor in there, the bleed is about 3mv - 
meaning when the gate is fully closed, about 3mv of signal is still allowed through the 
device at it's outputs.  On the other side of the possible variables - a zero ohm (a jumper 
i.e. no resistance), there's only a third of a mv of bleed, but about half the ringing.

Don't shoot me about the bleeding - it's not my fault!  it's the vacs.  Their technology does 
not allow them to close to zero ohms.  At best they will close down to only 80 ohms.  WIth 
the bleed killer set with a zero ohm resistor, the bleed is pretty much inaudible, unless 
you're gating very very harmonically rich signals with pure silence in between events.  With 
the resistor removed (the bleeder then is taken out of the circuit).  the bleeding is a lot 
more prevalent.

Another issue is no two vactrrols have the same amount of bleed.  You will need to tune 
each if you want them to ring the exact same amount.  Again this is due to vactrerol 
technology.  If you look at the Perkin-Elmer spec sheet, you'll see a spec clled DARK 
RESISTANCE AFTER TEN SECONDS.  THe After seconds part was not thrown in there to fill a 
line - it's there because PE felt that was a safe amount of time to assure the vactrol was 
fully closed - meaning some of them will take almost as long.  Again, part of their charm!  
THe ringing get to be more of an issue with the Model 12 vacsa - we actually have to bin 
them before hand to cut it back to the point I think that filtwer sounds best.  THose which 
don't make the mark are used in the M15 crossfader bacuaee bleed is less of an issue - it 
actually makes for smoother crossfading.  The M13 usesa a slightly different vactrol than 
the ones used in the model 12, 15 and 24, but they still don't go down to zero ohms.  No 
vactrols do.

In summary - you can play around with alternatives if you want less (or more) bleeding.  A 
zero ohm cuts the ringing (and bleeding) down to it's maximum.  Removing the part 
altogether is the other side of the scale - maximum ring and bleed.  If you really hate the 
ring there's a little more you can do - either replace the vac with another type - one which 
is by design much faster -or- get a Deopfer LPG.  He used an exteremely fast vac which 
has little or no ringing. If you elect to change the vac in the M13 - make sure it's a dual 
resistant element type.  These are the ones that have three leads onthe resistor side, not 
just two.

I chose the vacs I did because I like the ringing as i feel it's part of the module's 
personality.  They are really dead sounding in comparison without it. 

Hope this helps,

- P

An MFB-Step64 for the moment(an MCV24 on it's way).


--- In PLAN_B_analog_blog@yahoogroups.com, "amthewalrus" 
<bob_aloha@...> wrote:
>
> What are you using to gate your model 13's?
> 
> Tim
> 
> 
> --- In PLAN_B_analog_blog@yahoogroups.com, "jeswa" <j@...> wrote:
> >
> > Maybe this has been covered.
> > I love the M13, it's jacks are never lonely!
> > I just wish I had 4 of them or 2 quad-LPG's.
> > 
> > But...
> > Sometimes I wish that I could get the gate response time to be a 
> > little bit shorter.  I know about the leaky vactrols and how 
they're 
> > all unique, but besides that, is the response time "set" 
internally? 
> > Before I go tinkering around and mess things up, is there a way 
to 

> > achieve this?
> > 
> > Thanks!
> >
>

Wow, thanks for the epic reply, Peter.
After reading I've decided that I wouldn't want to change anything 
about the M13's sound just to get a shorter decay.  Now, If I had a 
bunch of them then I might go tinkering for the sake of variety.





--- In PLAN_B_analog_blog@yahoogroups.com, "(i think you can figure 
that out)" <peter@...> wrote:
>
> You can alter the decay - the ringing - of the Model 13.  This is 
due to circuitry I have 
> added to cut the bleeding down.  You can't do this with Doepfer 
LPGs, or Buchla 292's for 
> that matter, nor with the Wiard Borg which is very close to the 
Buchla 292 in design.
> 
> Looking at the PCB, you'll first notice it's basically two 
duplicate circuits (one each for the 
> two TG's) with  a slender line of circuitry in the middle (that's 
the crossfader section).
> 
> On each of the TG halves, at the bottom (edge) of their real estate 
you'll see four pads in a 
> line that are ellipically shaped.  In older M13s there are wires 
soldered to these pads which 
> go to the faceplate.  Newer models have a parallel connection via a 
12 (and now 14) pin in 
> line connector in the center of the board which lies right in front 
of the corssfader pot's 
> backside.  Holding the PCB so that the power connector is on the 
upper right, to the left of 
> those four pads you'll see two others labelled J1.  In older PCBS - 
those before rev. 2, there 
> a standup resistor soldered into J1.  In Rev. 2 and above, another 
resistor was added 
> directly to the left of those two pads - a 470 K ohm resistor. 
Those resistors, either 
> configured as a standup in the J1 pads, or from the added resistor 
next to them are the 
> current limiters that determines how much of the bleed killer is 
mixed into the the circuit.
> 
> J1 was configured as it was because it will allow for a two 
position jumper block to be 
> installed - like the little things that were on the back of SCSI 
disk drives to set their ID 
> number.  Inserting a jumper there puts the bleed killer on 
maximum.  removing the 
> jumper would remove it altogether.  I stopped installing those 
jumper blocks early on 
> because of availability issues with the jumpers.  I was not willing 
to slow delivery down to 
> to a G.D. part that for some reason (still surprised by that) - 
hard to get.  THey were listed 
> in supplier site, but constantly sold out.
> 
> The lower that resistance, the less bleed and slightly less ringing 
or response time to the 
> DECAY of the vactrol.  In earlier models I was shipping with a zero 
ohm resistor in there - 
> putting the bleed killer on maximum, which also cut back the 
decay.  Later I started 
> allowing less of that into the circuit, which slightly increased 
the bleeding, but made the 
> ring longer - that's the 470K resistor.
> 
> If you want to cut back the amount of ringing, increase the value 
of those resistors.  If you 
> want more, increase it or, to get the longest possible ring, remove 
those parts altogether.  
> Just cut them out.  This will make the vacs rings at their 
maximum.  Unfortunately, it also 
> effects the level of vac's inherent bleed.  WIth no resistor in 
there, the bleed is about 3mv - 
> meaning when the gate is fully closed, about 3mv of signal is still 
allowed through the 
> device at it's outputs.  On the other side of the possible 
variables - a zero ohm (a jumper 
> i.e. no resistance), there's only a third of a mv of bleed, but 
about half the ringing.
> 
> Don't shoot me about the bleeding - it's not my fault!  it's the 
vacs.  Their technology does 
> not allow them to close to zero ohms.  At best they will close down 
to only 80 ohms.  WIth 
> the bleed killer set with a zero ohm resistor, the bleed is pretty 
much inaudible, unless 
> you're gating very very harmonically rich signals with pure silence 
in between events.  With 
> the resistor removed (the bleeder then is taken out of the 
circuit).  the bleeding is a lot 
> more prevalent.
> 
> Another issue is no two vactrrols have the same amount of bleed.  
You will need to tune 
> each if you want them to ring the exact same amount.  Again this is 
due to vactrerol 
> technology.  If you look at the Perkin-Elmer spec sheet, you'll see 
a spec clled DARK 
> RESISTANCE AFTER TEN SECONDS.  THe After seconds part was not 
thrown in there to fill a 
> line - it's there because PE felt that was a safe amount of time to 
assure the vactrol was 
> fully closed - meaning some of them will take almost as long.  
Again, part of their charm!  
> THe ringing get to be more of an issue with the Model 12 vacsa - we 
actually have to bin 
> them before hand to cut it back to the point I think that filtwer 
sounds best.  THose which 
> don't make the mark are used in the M15 crossfader bacuaee bleed is 
less of an issue - it 
> actually makes for smoother crossfading.  The M13 usesa a slightly 
different vactrol than 
> the ones used in the model 12, 15 and 24, but they still don't go 
down to zero ohms.  No 
> vactrols do.
> 
> In summary - you can play around with alternatives if you want less 
(or more) bleeding.  A 
> zero ohm cuts the ringing (and bleeding) down to it's maximum.  
Removing the part 
> altogether is the other side of the scale - maximum ring and 
bleed.  If you really hate the 
> ring there's a little more you can do - either replace the vac with 
another type - one which 
> is by design much faster -or- get a Deopfer LPG.  He used an 
exteremely fast vac which 
> has little or no ringing. If you elect to change the vac in the 
M13 - make sure it's a dual 
> resistant element type.  These are the ones that have three leads 
onthe resistor side, not 
> just two.
> 
> I chose the vacs I did because I like the ringing as i feel it's 
part of the module's 
> personality.  They are really dead sounding in comparison without 
it. 

> 
> Hope this helps,
> 
> - P
>

A bit off-topic: Is it normal, that output is much quieter in Amp-mode?

Best regards
Jari Jokinen

I did a test using white noise and no CV: If the Offset pot is at 
full clockwise position and thus the gate fully open, the amplitude 
drops 6dB when switching to Amp-mode. The relative volume drop is 
bigger, if the Offset pot is at more counter clockwise position - In 
most situations (using CV from an envelope for example) the percieved 
volume drop is much bigger than 6dB. Perhaps there is a reason for 
this, but it is somewhat inconvenient in my opinion.

Indeed, this also means, that in Amp-mode there is much less "bleed" 
between notes - both relatively and absolutely.

Best regards
Jari Jokinen  

--- In PLAN_B_analog_blog@yahoogroups.com, "jalmari3" 
<jari.jokinen@...> wrote:
>
> A bit off-topic: Is it normal, that output is much quieter in Amp-
mode?

> 
> Best regards
> Jari Jokinen
>

How many volts is the gate output for EOA on the M10?  

I've been feeding this into the octave switching input on my Blacet VCO (a +2.5 or higher signal will cause the octave to switch) and then sending the logarithmic out of the M10 to a filter.  The result is that when the filter sweep reaches its highest point the VCO jumps up an octave.  Really makes for an enhanced "whuuuPish" sound.  Now I want to send it to other oscillators I have that don't have the same kind of octave switching capability.  It seems like I should just be able to attenuate the EOA until it is exactly one volt.

Bryan

The End of Attack and End of Cycle outputs of the Model 10 are designed to be triggering 
pulses so that other EGs could be linked as an overlap (EOA) or after the completion (EOC) 
of the first event.  To that, to meet Doepfer standards they must be a minimum of 5 volts 
high - that's the spec we had to meet.  They are actually a bit  higher than that - about 6 
volts.   To scale them so they would boast a VCO 1 oct, we'd have to limit it to 1 volt high, 
which would not trigger many of the devices they were designed to stimulate.  

My suggestion in your application would be to route the EOA into a scaled input of the 
VCO - one with an attenuator so you could taper it down to whatever level you wish. That 
would work out fine.

hope this helps,

- P

______________
Peter Grenader
e: peter@ear-group.net
p: 866-755-4468 (818 761-9906)
w: http://www.ear-group.net




--- In PLAN_B_analog_blog@yahoogroups.com, "Bryan E Cornell" <bcor@...> wrote:
>
> How many volts is the gate output for EOA on the M10?  
> 
> I've been feeding this into the octave switching input on my Blacet VCO (a +2.5 or 
higher signal will cause the octave to switch) and then sending the logarithmic out of the 
M10 to a filter.  The result is that when the filter sweep reaches its highest point the VCO 
jumps up an octave.  Really makes for an enhanced "whuuuPish" sound.  Now I want to 
send it to other oscillators I have that don't have the same kind of octave switching 
capability.  It seems like I should just be able to attenuate the EOA until it is exactly one 
volt.

> 
> Bryan
>