MOTM

I hope you are sitting down when you read this (I just got off the floor 
myself):

Vishay has raised the price of the 148/149 pots (the older black ones, newer 
ones are white) from $3.85ea to $12.25 ea.

This is NOT a misprint. They raised the price **THREE F-ING TIMES**. Oh, and a 
16 to 18 week delivery.

So, effective immediately:

a) I am removing all Spectrol pots from the shopping cart.
b) I an cancelling all pending orders for Spectrol *log* pots. I *think* have 
enough to cover pending linear orders. If not, I will have to cancel those, too.

What does this mean long term?

a) I am going to seek a compatible alternative (pcb-wise). However, this is 
*very unlikely*.
b) There is then a decision to make. I can still offer the Spectrol pots, but I 
will have to increase the price of the assembled modules by as much as $75!
c) Or, I can redesign all of the pc boards to accept blue Bourns pots (like on 
the MOTM-800). All that is needed is to replace the 1/4" standoffs with 1/8".

Now, I know the Bourns "feel" is not preferred. but, (and I need to check, like 
TODAY!!), these pots were <$4 the last time I bought them.

I'm just stunned. Comments welcome.

Paul S.

Paul Schreiber wrote:

> Comments welcome.

Alpha 16mm PCB mount. :-)

On Tue, 22 May 2007, Paul Schreiber wrote:

> Vishay has raised the price of the 148/149 pots (the older black ones, newer
> ones are white) from $3.85ea to $12.25 ea.

Hope they now come with super-special anti-microphonic wood knobs.
Wonder if there's a scenario such as with pharmaceuticals where
you could drive down to the border, walk over to Ciudad Juarez,
and pick them up for cheap at an Electronacia or Radio Bodega...

m

--
Monty Brandenberg

On 5/22/07, Paul Schreiber put forth:
>I hope you are sitting down when you read this (I just got off the floor
>myself):
>
>Vishay has raised the price of the 148/149 pots (the older black ones, newer
>ones are white) from $3.85ea to $12.25 ea.

Wow.  Talk about getting the shaft.  Was there any explanation for
this outrageous increase in price??

>What does this mean long term?
>
>a) I am going to seek a compatible alternative (pcb-wise). However, this is
>*very unlikely*.
>b) There is then a decision to make. I can still offer the Spectrol
>pots, but I
>will have to increase the price of the assembled modules by as much as $75!
>c) Or, I can redesign all of the pc boards to accept blue Bourns pots (like on
>the MOTM-800). All that is needed is to replace the 1/4" standoffs with 1/8".

I'm a bit confused here.  Do the Bourns pots fit the holes in the
PCB's originally designed for Spectrol??  If so, unless you have a
massive inventory of 1/4" spacers, using 1/8" spacers to mount the
boards seems fairly trivial.

>Now, I know the Bourns "feel" is not preferred. but, (and I need to
>check, like TODAY!!), these pots were <$4 the last time I bought
>them.

Imho, the Bourns pots feel just fine.  I never had any complaints
about my 800's, which I probably adjust more than anything, or any of
the pots on the left side of 2U modules.

Does Bourns make cermet pots suitable for VCO's??  Also, what is the
difference between Spectrol 148/149 and Spectrol 248/249 pots??  The
dimensions look the same, but as far as I can tell the 248/249 are
less expensive.

> I'm a bit confused here.  Do the Bourns pots fit the holes in the
> PCB's originally designed for Spectrol??

No. All of the pc boards would need to be redone.

> If so, unless you have a massive inventory of 1/4" spacers, using 1/8" spacers 
> to mount the
> boards seems fairly trivial.
>

The MOTM-800 uses 1/8" spacesr.


>>Now, I know the Bourns "feel" is not preferred. but, (and I need to
>>check, like TODAY!!), these pots were <$4 the last time I bought
>>them.
>
> Imho, the Bourns pots feel just fine.  I never had any complaints
> about my 800's, which I probably adjust more than anything, or any of
> the pots on the left side of 2U modules.
>

I think they are OK as well.

> Does Bourns make cermet pots suitable for VCO's??

I don't think so, but what I can do is change the pcb slightly so the voltage 
swing is much less across the pot to minimize the drift. The Coarse/Fine pots 
are ratiometric, which reduces drift anyway.

> Also, what is the difference between Spectrol 148/149 and Spectrol 248/249 
> pots??  The
> dimensions look the same, but as far as I can tell the 248/249 are less 
> expensive.
>

24x are all plastic. I tried those on the original MOTM modules. Awful!!!

Paul S.

What about the Alco knob? I would have to check the height and bushing 
diameter/length (I'll bet the thread on the bushing is metric).

Paul S.

----- Original Message ----- 
From: "Jay" <synthbaron@...>
To: "Paul Schreiber" <synth1@...>
Cc: "MOTM litserv" <motm@yahoogroups.com>

Sent: Tuesday, May 22, 2007 3:42 PM
Subject: Re: [motm] **IMPORTANT** Massive price hike on pots


> Paul Schreiber wrote:
>
>> Comments welcome.
>
> Alpha 16mm PCB mount. :-)
>
>
>
> Yahoo! Groups Links
>
>
>
>

>Now, I know the Bourns "feel" is not preferred. but, (and I need to check, 
>like
>TODAY!!), these pots were <$4 the last time I bought them.
>
>I'm just stunned. Comments welcome.

I for one love the feel of those blue Bourns pots.
I know it's not much comfort, because you have to redesign.
But I always thought the Bourns are quite superior to the Spectrols.

JH.




Yahoo! Groups Links

On 2007-05-22 14:58 -0500, Paul Schreiber wrote:

> Vishay has raised the price of the 148/149 pots (the older black
> ones, newer ones are white) from $3.85ea to $12.25 ea.
> 
> This is NOT a misprint. They raised the price **THREE F-ING
> TIMES**. Oh, and a 16 to 18 week delivery.

If the Spectrol pots are now indeed made by Sfernice... Well
Sfernice have never been cheap.

Still, it's stunning. I wonder what the commercial logic is behind
this move.

-- 
Andr\ufffd Majorel <URL:http://www.teaser.fr/~amajorel/>
Do not use this account for regular correspondence.
See the URL above for contact information.

Hi
...have you tried 248 Spectrols? In the UK 148's are 3x the price of 248's,
at 7.50 UK Pounds. I would never dream of using 148's in a synthesizer, and
even 248's are becoming over priced along with those lovely Bourns 91A.
Although I still use 248's over 91A because of the better feel and resistor
accuracy. Maybe MOTM format can be the high price/high quality Bourns 91A
flavour, and the FracRac format is Alpha 16mm.
 
Regards
Rob
www.emulatorarchive.com
    

 


I hope you are sitting down when you read this (I just got off the floor 
myself):

Vishay has raised the price of the 148/149 pots (the older black ones, newer

ones are white) from $3.85ea to $12.25 ea.

This is NOT a misprint. They raised the price **THREE F-ING TIMES**. Oh, and
a 
16 to 18 week delivery.

So, effective immediately:

a) I am removing all Spectrol pots from the shopping cart.
b) I an cancelling all pending orders for Spectrol *log* pots. I *think*
have 
enough to cover pending linear orders. If not, I will have to cancel those,
too.

What does this mean long term?

a) I am going to seek a compatible alternative (pcb-wise). However, this is 
*very unlikely*.
b) There is then a decision to make. I can still offer the Spectrol pots,
but I 
will have to increase the price of the assembled modules by as much as $75!
c) Or, I can redesign all of the pc boards to accept blue Bourns pots (like
on 
the MOTM-800). All that is needed is to replace the 1/4" standoffs with
1/8".

Now, I know the Bourns "feel" is not preferred. but, (and I need to check,
like 
TODAY!!), these pots were <$4 the last time I bought them.

I'm just stunned. Comments welcome.

Paul S.

On 22 May 2007, at 21:58, Paul Schreiber wrote:

> Vishay has raised the price of the 148/149 pots (the older black  
> ones, newer
> ones are white) from $3.85ea to $12.25 ea.
>
> This is NOT a misprint. They raised the price **THREE F-ING  
> TIMES**. Oh, and a
> 16 to 18 week delivery.

I'd take that as an insult and never use them again. Did that with  
Maxim when they tripled the price/delivery time of a LED driver (7219  
I believe) on one of our designs a couple of years ago.

Don't any of their distributors have stock at reasonable prices to  
help you in the short term?

Paul, what will the impact of this be on the pre-MOTM2.0 kit orders?

Ben

I bought some 100K Spectrol 249 cermet pots from Mouser, #594-249-7104.  
These have metal shafts and plastic bushings.  They can be used on the 
new Oakley boards.  Similar pots I have bought from Oakley were the 248 
series with plastic shafts.  Mouser carries the 249 cermet in 1/4-inch 
shaft size.  But for some reason, they offer the 248 series only with 
1/8-inch shaft.  I would expect the 248/249 series to have a price hike, 
too.  Still, they would be less expensive than 148/149.

Richard Brewster
http://www.pugix.com

>> Also, what is the difference between Spectrol 148/149 and Spectrol 248/249 
>> pots??  The
>> dimensions look the same, but as far as I can tell the 248/249 are less 
>> expensive.
>>
>>     
>
> 24x are all plastic. I tried those on the original MOTM modules. Awful!!!
>
> Paul S.
>

Paul,

Mouser is still listing the non-ROHS part 594-148-1102 at $5.18 qty 100. So am I reading this right and does this mean there is some relief over here vs. Europe? Should we be stocking up if this is true?

Greg

(getting tired of "stocking-up")

>-----Original Message-----
>From: Paul Schreiber [mailto:synth1@...]
>Sent: Tuesday, May 22, 2007 03:58 PM
>To: 'MOTM litserv'
>Subject: [motm] **IMPORTANT** Massive price hike on pots
>
>;I hope you are sitting down when you read this (I just got off the floor
>myself):
>
>Vishay has raised the price of the 148/149 pots (the older black ones, newer
>ones are white) from $3.85ea to $12.25 ea.
>
>This is NOT a misprint. They raised the price **THREE F-ING TIMES**. Oh, and a
>16 to 18 week delivery.
>
>So, effective immediately:
>
>a) I am removing all Spectrol pots from the shopping cart.
>b) I an cancelling all pending orders for Spectrol *log* pots. I *think* have
>enough to cover pending linear orders. If not, I will have to cancel those, too.
>
>What does this mean long term?
>
>a) I am going to seek a compatible alternative (pcb-wise). However, this is
>*very unlikely*.
>b) There is then a decision to make. I can still offer the Spectrol pots, but I
>will have to increase the price of the assembled modules by as much as $75!
>c) Or, I can redesign all of the pc boards to accept blue Bourns pots (like on
>the MOTM-800). All that is needed is to replace the 1/4" standoffs with 1/8".
>
>Now, I know the Bourns "feel" is not preferred. but, (and I need to check, like
>TODAY!!), these pots were <$4 the last time I bought them.
>
>I'm just stunned. Comments welcome.
>
>Paul S.
>
>
>
>
>Yahoo! Groups Links
>
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On 5/22/07, Paul Schreiber put forth:
>  > I'm a bit confused here.  Do the Bourns pots fit the holes in the
>  > PCB's originally designed for Spectrol??
>
>No. All of the pc boards would need to be redone.

Yikes.  That is a PITA.  Maybe it would be better to use Bourns lug
pots and change the board brackets, or use 248 pots, or find some
other solution, rather than have all the boards redone??

While I don't know anything about CAD/CAM, changing the design seems
like it would be fairly simple.  However, as I see it, the problem
isn't trying to figure out how to move a few holes around, it's that
you would have to pay for all new boards, and would be stuck with the
old boards.  That sounds like an expensive proposition you would want
to avoid.

You asked for comments, so I'm just throwing ideas out there.  I'm
not trying to tell you how to run your business.

>  > Does Bourns make cermet pots suitable for VCO's??
>
>I don't think so, but what I can do is change the pcb slightly so the voltage
>swing is much less across the pot to minimize the drift. The Coarse/Fine pots
>are ratiometric, which reduces drift anyway.
>
>24x are all plastic. I tried those on the original MOTM modules. Awful!!!

According to Richard Brewster, the 249 cermet pots have metal shafts.
So maybe they aren't so bad??  Regardless, the MOTM-300 is the
flagship of the line, so I would be extremely hesitant in reducing
its durability or performance in any way.  Perhaps it's one case
where using 149 pots would be worth it, even if you make less profit
on that one module.

[mega-snip]
>I'm just stunned. Comments welcome.
>
>Paul S.

That's some way to treat a customer. :-/

Such are the pitfalls of board-mounted pots.

Given this situation, Paul, would you design things differently if 
you were starting over? Say, use a daughterboard for the front panel 
components? Not sure how useful that would be, though.

Roger Arrick's approach is interesting. For those who haven't seen a 
"dotcom" module, the pots (24mm Alpha) are fitted with 3-conductor 
pigtails terminated with small MTA connectors 
(http://www.synthesizers.com/technical.html). PCBs have the 
complimentary MTA connectors on them. This makes it really easy to 
mount and replace pots (which will *need* to be done, some would say, 
since the pots are not sealed on S.com modules). There is the extra 
expense of fitting the pots with pigtails and connectors, but you 
avoid flying wires between the front panel and the PC board. The net 
result: panel-mounted components without soldering any wires to circuit boards.

I'm not suggesting that Paul adopt Roger's approach. More like I'm 
wondering what the MOTM community thinks of it.

Naturally, there's no perfect or best solution -- you just need to 
pick the set of trade-offs that works for you. Cost / convenience / 
reliability / non-obsolescence / etc...
--
john


-- 
No virus found in this outgoing message.
Checked by AVG Free Edition. 
Version: 7.5.467 / Virus Database: 269.7.6/815 - Release Date: 5/22/2007 3:49 PM

On Wed, 23 May 2007, John Mahoney wrote:

> I'm not suggesting that Paul adopt Roger's approach. More like I'm
> wondering what the MOTM community thinks of it.

To use the ever-popular automotive analogy, it's like a modern
BMW versus a Series LandRover.  The former tries to be a
perfect artifact but repair is expensive and difficult, the
latter has frequent issues but is trivial to repair.  And
oddly, while the BMW has stranded me the LR tries to but always
manages to come home.  (And some would say the modern LR
manages to combine the worst of both worlds...)

m

--
Monty Brandenberg

I have generally tried to buy these potentiometers for all my 
projects.  My last AM4075 module used the new Vishay white RoHS 
version which had gone up in price.  I looked to see if I should buy 
any more to have on hand on my most recent Mouser order and saw some 
$12.45 prices!  I decided then that I probably couldn't afford these 
any more.

As a user, I couldn't tell you from the front of the modules which 
were Vishay/Spectrol/Sfernice or Bournes.  The Bournes seem to have 
gone up in price also.  I'm more interested in long-term reliability 
than price.

If the PCB issue is the mounting height, I would think that perhaps 
changing the spacer along with using a Stooge-type bracket might be 
easier/better than changing the PCB layout if the dimensions work out.

I have used plastic bushing potentiometers without any problems 
although I am very careful.  I would think discontinuing kits would 
alleviate any issues with damaging plastic bushings.

Now the reason for the post.  In looking at potentiometers, I see 
Mouser carries the Vishay 9MM multigang P9A series.  I have always 
used the Piher 16 mm carbon for my dual potentiometers.  Does anyone 
have any experience with these?  They don't have many values but the 
dual 50K would have been useful for a couple of projects.

Dave

On 2007-05-24 16:34 -0000, djbrow54 wrote:

> Now the reason for the post.  In looking at potentiometers, I see 
> Mouser carries the Vishay 9MM multigang P9A series.  I have always 
> used the Piher 16 mm carbon for my dual potentiometers.  Does anyone 
> have any experience with these?  They don't have many values but the 
> dual 50K would have been useful for a couple of projects.

The recent sealed carbon Pihers don't feel very nice. Can't tell
you how long they last.

Piher pots are well known here and have a long history of being
cheap crap that becomes scratchy after ten rotations. They might
have improved but I wouldn't buy a hundred just to find out.

I have an 80's Rocktron EQ3 on the bench with seven pots, four of
which are scratchy and three of which are not Pihers...

-- 
Andr\ufffd Majorel <URL:http://www.teaser.fr/~amajorel/>
Do not use this account for regular correspondence.
See the URL above for contact information.

I was wondering about the difference between the Bourns and Spectrol
pots and why the MOTM-800, which uses Bourns, would need different
spacers.  What had confused me was that the Bourns pots I had been
using for diy are a different size that those used for the 800.

The Bourns 50K linear pots I have been using for diy are labeled
"51AADC20A18 50K MEXICO H9114X" (which I purchased surplus for $2
each).  They have metal bushings and metal shafts.  The only issue I
have with them is that the shafts are a bit short, but they still
work.  My point is that they have 1/2" bodies just like the Spectrol
148.  The Bourns pots for the 800 have 5/8" bodies.  So I'm
wondering, are 1/2" Bourns pots a possible replacement for 148 pots
on MOTM PCB's and does Bourns make 1/2" log pots??

It looks as though all of these pots, the 5/8" Bourns, the 1/2"
Bourns, and the 1/2" Spectrol all have the same lead spacing.  I can
see how the MOTM-800 5/8" body Bourns pots would place the PCB at a
different height so different spacers would be needed, but I don't
understand why they wouldn't fit in MOTM PCB's designed for Spectrol
148/149.

Could someone please explain this??


On 5/22/07, Paul Schreiber put forth:

>  > I'm a bit confused here.  Do the Bourns pots fit the holes in the
>  > PCB's originally designed for Spectrol??
>
>No. All of the pc boards would need to be redone.

OK,

So I've read here and on some other lists about people moving certain
modules on or off various power rails to isolate them from noise, etc. Is
there anywhere I can find some good, comprehensive, guidelines for the what,
why, how and when to do this?

For example, one recommendation I read is to isolate all CVAs from 'dirty'
modules. Another is to isolate all modules with digital circuitry. And
another person wrote about LEDs causing problems.

I'm just looking for "best practices" here. I understand that in the end,
every system can have it's own quirks. But high-level rules of thumb would
be helpful.

Thanks,
Greg

a) Those pots you bought are 16 *years* old :)

b) Log would be a custom order anyway (all of the 1M logs on the '800 are 
custom).

c) Let's hope the 248J Spectrols will be OK.

d) 91A Bourns pots have 2 "issues"

#1: the distance from the center of the shaft to the pcb (when mounted) is 1/8" 
more than Spectrol. Hence, the MOTM-800 uses 1/8" spacers and all the other 
modules use 1/4" spacers.

#2: the diameter of the leads on the 91A Bourns are larger diameter than 
Spectrol.

If the 248J turns out not to work, then I will investigate the 51A from Bourns.

Paul S.

----- Original Message ----- 

From: "Mark" <yahoogroups@...>
To: <motm@yahoogroups.com>
Sent: Saturday, May 26, 2007 9:31 AM
Subject: [motm] Bourns and Spectrol differences??


>
> I was wondering about the difference between the Bourns and Spectrol
> pots and why the MOTM-800, which uses Bourns, would need different
> spacers.  What had confused me was that the Bourns pots I had been
> using for diy are a different size that those used for the 800.
>
> The Bourns 50K linear pots I have been using for diy are labeled
> "51AADC20A18 50K MEXICO H9114X" (which I purchased surplus for $2
> each).  They have metal bushings and metal shafts.  The only issue I
> have with them is that the shafts are a bit short, but they still
> work.  My point is that they have 1/2" bodies just like the Spectrol
> 148.  The Bourns pots for the 800 have 5/8" bodies.  So I'm
> wondering, are 1/2" Bourns pots a possible replacement for 148 pots
> on MOTM PCB's and does Bourns make 1/2" log pots??
>
> It looks as though all of these pots, the 5/8" Bourns, the 1/2"
> Bourns, and the 1/2" Spectrol all have the same lead spacing.  I can
> see how the MOTM-800 5/8" body Bourns pots would place the PCB at a
> different height so different spacers would be needed, but I don't
> understand why they wouldn't fit in MOTM PCB's designed for Spectrol
> 148/149.
>
> Could someone please explain this??
>
>
> On 5/22/07, Paul Schreiber put forth:
>>  > I'm a bit confused here.  Do the Bourns pots fit the holes in the
>>  > PCB's originally designed for Spectrol??
>>
>>No. All of the pc boards would need to be redone.
>
>
>
> Yahoo! Groups Links
>
>
>
>

On 5/26/07, Paul Schreiber put forth:
>a) Those pots you bought are 16 *years* old :)

d00d, that's vintage sound!! ;)

Seriously, I don't think it will matter.  I have pots on gear that
have been in use for four times as many years that work fine.  Afaik,
electrolytic caps are the only components that age.

>b) Log would be a custom order anyway (all of the 1M logs on the '800 are
>custom).
>
>c) Let's hope the 248J Spectrols will be OK.
>
>d) 91A Bourns pots have 2 "issues"
>
>#1: the distance from the center of the shaft to the pcb (when
>mounted) is 1/8"
>more than Spectrol. Hence, the MOTM-800 uses 1/8" spacers and all the other
>modules use 1/4" spacers.
>
>#2: the diameter of the leads on the 91A Bourns are larger diameter than
>Spectrol.
>
>If the 248J turns out not to work, then I will investigate the 51A
>from Bourns.

OK :)  Thank you for explaining that, and I hope it all works out.

On 5/26/07, Greg James put forth:
>So I've read here and on some other lists about people moving certain
>modules on or off various power rails to isolate them from noise, etc. Is
>there anywhere I can find some good, comprehensive, guidelines for the what,
>why, how and when to do this?
>
>For example, one recommendation I read is to isolate all CVAs from 'dirty'
>modules. Another is to isolate all modules with digital circuitry. And
>another person wrote about LEDs causing problems.

What's a CVA??

>I'm just looking for "best practices" here. I understand that in the end,
>every system can have it's own quirks. But high-level rules of thumb would
>be helpful.

Well, I would say that moving modules around to isolate them from
power supply noise is very much fine tuning.  Each module has its own
power supply filtering, and in some cases the distribution boards
have their own power supply filtering.  In addition, many modules use
local voltage regulators which provide a massive amount of ripple
rejection.  The MOTM VCO's have voltage regulators which provide
immunity to small changes in supply voltage.  The MOTM-120 has its
own regulator for its digital circuitry.  So unless you are
experiencing problems, there shouldn't be any need to move modules
around.

Imho, putting all of the "dirty" modules on one stem is going to have
a cumulative effect.  I think it would be better to add more
filtering to the modules that are making noise, thereby solving the
problem at its source, rather than trying to arrange them with your
other modules in such a way that will reduce the effect that noise
has.

I am at the point where I should consider buying a another power
supply for my modular.  At the this point in time, I don't have any
modules that require 5V, nor are there any MOTM modules currently
available that I am considering that require 5V (I already have a
MIDI-to-CV converter).  I'm wondering if I should get a triple supply
that provides 5V or another supply that only provides -15/15+??

Is there any disadvantage in adding a separate 5V supply at a later
time??   Further, since it isn't used to power the signal path,
is there a disadvantage in using a 5V switching supply??  They are
much less expensive than 5V linear supplies.


Also, while I'm typing, does anyone know why the Blacet modules use
such a massive amount of bypass capacitance??  The MiniWave and
TimeMachine have ~270uF and ~320uF respectively, using two 100uF caps
and a bunch of 10uF caps, with very few smaller caps.  Does anyone
know why that is??

Mark, why don't you hustle over to the MOTM catalog website and pick up 
that last MOTM-950 kit, especially if you plan to order the MOTM-730 VC 
Pulse Divider that will probably be the next MOTM module released in 
standard format -- don't quote me ;)

One disadvantage of adding a separate +5V supply is wiring it up.  If 
you're cool with that, it is an option.  But stay away from the 
switching supplies!  You don't want that noise near your modular.  All 
my supplies are Power One.  These are reasonably priced and available 
from Digikey.

Why did John Blacet use large, multiple, electrolytic caps for 
decoupling?  One reason could be that Blacet the modules have a lot of 
chips on them and different sections of circuit that need to be 
isolated.  Sometimes it is better to over-engineer.  Too much decoupling 
is generally better than not enough.  Some drawbacks of using big caps:  
takes up extra space; is a tad more costly; and of course the problem 
with power supply startup.

-Richard Brewster
http://www.pugix.com

Mark wrote:

> I am at the point where I should consider buying a another power
> supply for my modular.  At the this point in time, I don't have any
> modules that require 5V, nor are there any MOTM modules currently
> available that I am considering that require 5V (I already have a
> MIDI-to-CV converter).  I'm wondering if I should get a triple supply
> that provides 5V or another supply that only provides -15/15+??
>
> Is there any disadvantage in adding a separate 5V supply at a later
> time??   Further, since it isn't used to power the signal path,
> is there a disadvantage in using a 5V switching supply??  They are
> much less expensive than 5V linear supplies.
>
>
> Also, while I'm typing, does anyone know why the Blacet modules use
> such a massive amount of bypass capacitance??  The MiniWave and
> TimeMachine have ~270uF and ~320uF respectively, using two 100uF caps
> and a bunch of 10uF caps, with very few smaller caps.  Does anyone
> know why that is??
>
>
>
>  
> Yahoo! Groups Links
>
>
>
>
>

I would estimate that 70% of all new MOTM modules going forward will require 
+5V.

And yes, the VC Divider is the next module to be released, and it will need +5V 
(along with +-15V).

And so will the Cloud Generator (I about 6 weeks I will have exciting CG news).

Paul S.

On 5/28/07, Richard Brewster put forth:
>Mark, why don't you hustle over to the MOTM catalog website and pick up
>that last MOTM-950 kit,

Oh, I don't use power supply modules -- they take up way too much
valuable panel space.  Also, the MOTM-950 provides only 400mA of
-15/15+, and it costs way more than putting a similar supply in a
separate box, which I would have to do anyway, to get more -15/15+
current.

>One disadvantage of adding a separate +5V supply is wiring it up.  If
>you're cool with that, it is an option.

I already have the MOTM triple-power distribution board, so
wiring it up shouldn't be that difficult.

>But stay away from the switching supplies!  You don't want that
>noise near your modular.  All my supplies are Power One.  These are
>reasonably priced and available from Digikey.

If it is only used for the digital circuitry, does the noise make a
difference??  The reason I ask, is that switching 5V supplies are a
fraction of the price of linear supplies.

>Why did John Blacet use large, multiple, electrolytic caps for
>decoupling?  One reason could be that Blacet the modules have a lot of
>chips on them and different sections of circuit that need to be
>isolated.  Sometimes it is better to over-engineer.  Too much decoupling
>is generally better than not enough.  Some drawbacks of using big caps:
>takes up extra space; is a tad more costly; and of course the problem
>with power supply startup.

That's true -- many of the sub-circuits on both of those modules
could be rather noisy.  Although it doesn't explain the lack of
smaller (.iuF) caps on the linear IC's or address the issue of noise
at high frequencies.  Anyway, I'm considering replacing the two 100uF
caps at the power input with smaller values.  I'm thinking that there
shouldn't be that much ripple at the inputs and that the aggregate of
all the 10uF should provide enough of a local current reservoir.
Also, the 100uF caps that came with the Blacet kits are only 16V, and
I wonder if that should be a cause for concern.

On May 28, 2007, at 10:56 AM, Mark wrote:

>
> Oh, I don't use power supply modules -- they take up way too much
> valuable panel space. Also, the MOTM-950 provides only 400mA of
> -15/15+, and it costs way more than putting a similar supply in a
> separate box, which I would have to do anyway, to get more -15/15+
> current.
>

If you are buying your own supplies: I bought a pair of Condor triple- 
output
supplies a couple of years ago.  They turned out to be huge, and  
rather difficult
to place physically.  For my next block, I'll buy a dual output  
supply for the +/- 15,
and a separate smaller one for the +5.

Does anyone have any thoughts on using twisted pair cable when there
is no adjacent ground connection on the PCB??  For example, most
third-party PCB's do not have ground connections near the jumper
connections for CV inputs and outputs.  However, they usually have a
method of connecting the shields of all the jacks to ground.  So if
the panel end is tied to ground, is there an advantage in using
twisted pair cable when connecting a CV's to the PCB even when the
ground wire is not connected at the PCB??

Also, as a general rule, should unused high-impedance inputs be
connected to ground using switched jacks??  Some of the MOTM
instructions say to do this, while others don't.

A signal wire combined with a ground wire in a twisted pair won't make much
difference as far as signal quality goes.  The twist just helps with
cable/wire management.

MOTM tends to ground through switched jacks highly sensitive or precision
unattenuated CVs such as 1V/octave inputs.  It is overkill for anything
else.  As far as I can tell, you may not even notice a difference if you
don't ground the precision inputs.

John Loffink
The Microtonal Synthesis Web Site
http://www.microtonal-synthesis.com
The Wavemakers Synthesizer Web Site
http://www.wavemakers-synth.com

> -----Original Message-----
> From: motm@yahoogroups.com [mailto:motm@yahoogroups.com] On Behalf Of Mark
> Sent: Saturday, June 02, 2007 9:51 AM
> To: motm@yahoogroups.com
> Subject: [motm] floating twisted pair cable on one end??
> 
> 
> Does anyone have any thoughts on using twisted pair cable when there
> is no adjacent ground connection on the PCB??  For example, most
> third-party PCB's do not have ground connections near the jumper
> connections for CV inputs and outputs.  However, they usually have a
> method of connecting the shields of all the jacks to ground.  So if
> the panel end is tied to ground, is there an advantage in using
> twisted pair cable when connecting a CV's to the PCB even when the
> ground wire is not connected at the PCB??
> 
> Also, as a general rule, should unused high-impedance inputs be
> connected to ground using switched jacks??  Some of the MOTM
> instructions say to do this, while others don't.
> 
>

Ideally, you would like to see each signal to a panel jack have a ground 
point on the board, which connects straight out to the jack ground.  
Most (if not all) MOTM modules are wired like this.  However, there is 
an advantage in twisting a grounded wire with signal wire, even if it's 
grounded at one end only.  You will get some shielding effect.  (If 
grounding to a panel jack, make sure that some other wire returns the 
jack ground to the board.  You might buss all the jack grounds together 
and run one ground wire from near the power connector on the board.)   I 
try to find a ground point on the board for each signal wire, even if 
it's not right next to the signal connection.  Multiple ground wires can 
share a single ground point with a little creative wiring, too.  Loop 
one around the other and solder, leaving a single wire to insert into 
the ground hole.

Someone may comment on ground loops, which can cause unwanted 
oscillations.  A ground loop is formed when there are multiple ground 
paths for a signal to follow.  I have never encountered a problem that 
turned out to be caused by a ground loop, that I know of.

As to using the normal lug to ground inputs, it depends on the circuit.  
Any input that terminates at an op amp summing node can be grounded.  
But if going into a comparator (like the MOTM-120 inputs) or to a 
passive mixer network (MOTM-490 inputs), then you do not want to ground 
the input when it is unused.

Richard Brewster
http://www.pugix.com

Mark wrote:

> Does anyone have any thoughts on using twisted pair cable when there
> is no adjacent ground connection on the PCB??  For example, most
> third-party PCB's do not have ground connections near the jumper
> connections for CV inputs and outputs.  However, they usually have a
> method of connecting the shields of all the jacks to ground.  So if
> the panel end is tied to ground, is there an advantage in using
> twisted pair cable when connecting a CV's to the PCB even when the
> ground wire is not connected at the PCB??
>
> Also, as a general rule, should unused high-impedance inputs be
> connected to ground using switched jacks??  Some of the MOTM
> instructions say to do this, while others don't.
>
>

>MOTM tends to ground through switched jacks highly sensitive or precision
>unattenuated CVs such as 1V/octave inputs.  It is overkill for anything
>else.  As far as I can tell, you may not even notice a difference if you
>don't ground the precision inputs.

Ever since I attended this EMC workshop at Langer in Dresden
(http://www.langer-emv.de/index.html for the German-speaking), I have a bad 
feeling when I see dangling wires.
It may be no problem in most environments, but it's an antenna, and radio 
frequencies can be demodulated by opamp input circuits, and you _might_ want 
to use your modular system near to a strong RF source some day.

JH.

Does anyone know the part number for the little plastic dust cover
for the AMP MTA156 4-position feed-thru connector for 18AWG wire??
The Digikey part number for the connector is A31374-ND, but I can't
seem to find the dust cover.  The dust cover for the closed-end
connectors does not fit.  This would be for a connector one might use
to power a daughterboard added to an MOTM module -- the wires go in
one side and continue out the other.

Thanks :)

Try a Mouser 571-6406434

Dave

--- In motm@yahoogroups.com, Mark <yahoogroups@...> wrote:
>
> 
> Does anyone know the part number for the little plastic dust cover
> for the AMP MTA156 4-position feed-thru connector for 18AWG wire??
> The Digikey part number for the connector is A31374-ND, but I can't
> seem to find the dust cover.  The dust cover for the closed-end
> connectors does not fit.  This would be for a connector one might 
use

> to power a daughterboard added to an MOTM module -- the wires go in
> one side and continue out the other.
> 
> Thanks :)
>

How much current can the  Lumex LED's used in MOTM (eg. SSI-LXH387ID)
handle safely??  It looks like they list a maximum If (which I'm
assuming means current(forward)) of 30mA.  That sounds about 2-3
times more than I would have guessed.  Another way of asking the same
question, how much current to the single-color LED's used in MOTM
generally draw??  They are sufficiently visible, and increasing LED
brightness unnecesarily would increase the load on the power supply.

8-12ma is sufficient. Unless you want a flashlight :)

BTW: If you like LEDs in your MOTM, just wait a few months and
I'll have something....errr....intersting to show you.

Paul S.