MOTM

Hi

Sorry if this question has been brought up before, but I´ve been
searching the list for a while and can´t find a clear answer. The
thing is that my newly build MOTM-101 SH has quite a low output;
around 100mV on the white noise out (Trimmer TP1 at max measured
with my Wellemann DVM891)and this gives a maximum SH output (with
noise as internal S/H source) on around .7 - .9 Volts. (with "Level"
at max setting) According to the manual I should get higher levels,
but here it says that the first OP-AMP after the noise diodes has a
gain of 100, as I se it its only 10 - 100k (R4) / 10k (R3). Could
I just reduce R3 (to 3,3K or something) or should I check a 4.th
time if everything is rigth, maybe check-measure resitors? I would
like a bit more out of the S/H to modulate filters.
Apart from that, as a new MOTM user I can only say I´m a fan. Fan of
the sound, fan of the quality.
Which brings me to the next question. Mounting in 19" racks is nice
and easy but I can quickly se this sytem grow, wich means high racks
or broad cabinets (dot. com style)What do you guys prefer - broad or
high?
Or maybe the system goes so big its gotta be both. But then I´ll be
broke.

greetings from Denmark

Gregory

Hi Gregory,

Welcome to the MOTM world! As far as your gain, something is indeed
out of whack, since you should have more gain than that on the output.

Did you check resistors with a multimeter? Sometimes it's easy to
misread a color band.

As far as cabinets, I've written a little treatise on the subject:
http://www.hotrodmotm.com/cab.htm

Moe
http://www.hotrodmotm.com

--- In motm@yahoogroups.com, "gregorykjar" <greg@i...> wrote:
>
> Hi
>
> Sorry if this question has been brought up before, but I´ve been
> searching the list for a while and can´t find a clear answer. The
> thing is that my newly build MOTM-101 SH has quite a low output;
> around 100mV on the white noise out (Trimmer TP1 at max measured
> with my Wellemann DVM891)and this gives a maximum SH output (with
> noise as internal S/H source) on around .7 - .9 Volts. (with "Level"
> at max setting) According to the manual I should get higher levels,
> but here it says that the first OP-AMP after the noise diodes has a
> gain of 100, as I se it its only 10 - 100k (R4) / 10k (R3). Could
> I just reduce R3 (to 3,3K or something) or should I check a 4.th
> time if everything is rigth, maybe check-measure resitors? I would
> like a bit more out of the S/H to modulate filters.
> Apart from that, as a new MOTM user I can only say I´m a fan. Fan of
> the sound, fan of the quality.
> Which brings me to the next question. Mounting in 19" racks is nice
> and easy but I can quickly se this sytem grow, wich means high racks
> or broad cabinets (dot. com style)What do you guys prefer - broad or
> high?
> Or maybe the system goes so big its gotta be both. But then I´ll be
> broke.
>
> greetings from Denmark
>
> Gregory
>

Thanks alot. Nice site you´ve done, very informative with lots of
good thoughts.
Great thing the internet, when I half a year ago started considering
going real modular - after several years with loads of soft synths -
I thought that Doepfer where the only supplier. Luckily I made a
google search for "modular synthesizer" and ended up with the first
MOTM-modules and so far I havent been dissapointed. A lot of soft
synth programming (especially Reaktor) had grown a wish for knobs,
and a midi controller didn´t do it so now I´m beginning to twiddle
real knobs and its great. And if you go for hardware you should go
for top quality not quantity. In another studio Í´m working in we
bougth a George Massenburg mic preamp last year. Thats 1 - one -
channel strip with a pricetag of a car! And its worth every penny!
Doepfer (I have a "Regelwerk" and its much fun an a good tool for a
lot of things) is probably good for some but I´d rather have fewer
modules with higher quality. And not that software is dead neither,
you should hear an analog drone modulated through a good (software)
vocoder. You can really hear that the "base" sound is thick.

Sorry about all the words they just came out.

greetings form Denmark

Gregory

--- In motm@yahoogroups.com, "mate_stubb" <mate_stubb@y...> wrote:
>
> Hi Gregory,
>
> Welcome to the MOTM world! As far as your gain, something is indeed
> out of whack, since you should have more gain than that on the
output.
>
> Did you check resistors with a multimeter? Sometimes it's easy to
> misread a color band.
>
> As far as cabinets, I've written a little treatise on the subject:
> http://www.hotrodmotm.com/cab.htm
>
> Moe
> http://www.hotrodmotm.com
>
> --- In motm@yahoogroups.com, "gregorykjar" <greg@i...> wrote:
> >
> > Hi
> >
> > Sorry if this question has been brought up before, but I´ve been
> > searching the list for a while and can´t find a clear answer.
The
> > thing is that my newly build MOTM-101 SH has quite a low output;
> > around 100mV on the white noise out (Trimmer TP1 at max measured
> > with my Wellemann DVM891)and this gives a maximum SH output
(with
> > noise as internal S/H source) on around .7 - .9 Volts.
(with "Level"
> > at max setting) According to the manual I should get higher
levels,
> > but here it says that the first OP-AMP after the noise diodes
has a
> > gain of 100, as I se it its only 10 - 100k (R4) / 10k (R3).
Could
> > I just reduce R3 (to 3,3K or something) or should I check a 4.th
> > time if everything is rigth, maybe check-measure resitors? I
would
> > like a bit more out of the S/H to modulate filters.
> > Apart from that, as a new MOTM user I can only say I´m a fan.
Fan of
> > the sound, fan of the quality.
> > Which brings me to the next question. Mounting in 19" racks is
nice
> > and easy but I can quickly se this sytem grow, wich means high
racks
> > or broad cabinets (dot. com style)What do you guys prefer -
broad or
> > high?
> > Or maybe the system goes so big its gotta be both. But then I´ll
be
> > broke.
> >
> > greetings from Denmark
> >
> > Gregory
> >
>

a) you can't measure the White Noise output with a DVM. For one, the noise
bandwidth is like 250Khz, and your DVM goes to 500Hz if you are lucky. Second,
by definition white noise has an *average value of zero volts*. In fact, 1
'figure of merit' of just how "white" the white noise is, is to measure it with
an *averaging* (not RMS) meter. The closer to zero, the 'better the noise' :)

b) the S/H uses *pink noise* internally, through the switched jack. If you did
not wire the switching jack correctly, this would explain it.

c) do you have approx 8V pk-pk of Pink Noise at the Pink Out jack? If not, then
there is an error with the Pink Noise filter.

Paul S.

Thanks Paul, I´ll check everything again tonigth.

Gregory

--- In motm@yahoogroups.com, "Paul Schreiber" <synth1@a...> wrote:
>
> a) you can't measure the White Noise output with a DVM. For one,
the noise
> bandwidth is like 250Khz, and your DVM goes to 500Hz if you are
lucky. Second,
> by definition white noise has an *average value of zero volts*. In
fact, 1
> 'figure of merit' of just how "white" the white noise is, is to
measure it with
> an *averaging* (not RMS) meter. The closer to zero, the 'better
the noise' :)
>
> b) the S/H uses *pink noise* internally, through the switched
jack. If you did
> not wire the switching jack correctly, this would explain it.
>
> c) do you have approx 8V pk-pk of Pink Noise at the Pink Out jack?
If not, then
> there is an error with the Pink Noise filter.
>
> Paul S.
>