MOTM

Hi Chris -

533-24-6337-6401 - organic
533-24-6337-8814 = no-clean

http://www.mouser.com/catalog/catalogUSD/639/2148.pdf

Bill and Will

--- In motm@yahoogroups.com, chris walcott <cedubstudio@...> wrote:

>
> hello list.  i am running out of no-clean solder that i've gotten from paul
> over many kits and was wondering what to order.  does anyone have a mouser
> part number?
> 
> thanks!
>

Check out All-Spec too, pretty good prices on Kester! ;-)

24-6337-6401 organic $23.99
http://www.all-spec.com/products/KW33105.html

24-6337-8814 no-clean  $21.62
http://www.all-spec.com/products/KW24540.html


John L Rice

-----Original Message-----
From: motm@yahoogroups.com [mailto:motm@yahoogroups.com] On Behalf Of
wjhall11
Sent: Saturday, August 01, 2009 10:41 AM
To: motm@yahoogroups.com
Subject: [motm] Re: no-clean solder

Hi Chris -

533-24-6337-6401 - organic
533-24-6337-8814 = no-clean

http://www.mouser.com/catalog/catalogUSD/639/2148.pdf

Bill and Will

--- In motm@yahoogroups.com, chris walcott <cedubstudio@...> wrote:
>
> hello list.  i am running out of no-clean solder that i've gotten from
paul
> over many kits and was wondering what to order.  does anyone have a mouser
> part number?
> 
> thanks!
>




------------------------------------

Yahoo! Groups Links

Woah, baby!  You aren't kidding...



--- In motm@yahoogroups.com, "John L Rice" <Drummer@...> wrote:

>
> Check out All-Spec too, pretty good prices on Kester! ;-)
> 
> 24-6337-6401 organic $23.99
> http://www.all-spec.com/products/KW33105.html
> 
> 24-6337-8814 no-clean  $21.62
> http://www.all-spec.com/products/KW24540.html
> 
> 
> John L Rice
> 
> 
> -----Original Message-----
> From: motm@yahoogroups.com [mailto:motm@yahoogroups.com] On Behalf Of
> wjhall11
> Sent: Saturday, August 01, 2009 10:41 AM
> To: motm@yahoogroups.com
> Subject: [motm] Re: no-clean solder
> 
> Hi Chris -
> 
> 533-24-6337-6401 - organic
> 533-24-6337-8814 = no-clean
> 
> http://www.mouser.com/catalog/catalogUSD/639/2148.pdf
> 
> Bill and Will
> 
> --- In motm@yahoogroups.com, chris walcott <cedubstudio@> wrote:
> >
> > hello list.  i am running out of no-clean solder that i've gotten from
> paul
> > over many kits and was wondering what to order.  does anyone have a mouser
> > part number?
> > 
> > thanks!
> >
> 
> 
> 
> 
> ------------------------------------
> 
> Yahoo! Groups Links
>

On 2 aug 2009, at 00:58, Miguel Mendoza wrote:

> Hi group, I'm starting to build a MOTM 300 kit that I was keeping on  
> a shelf and I'm missing the 22K resistor for R49. I'd like to ask if  
> any of you know if I can replace this one by other value and what  
> range or if this is a critical value. I have many other resistors  
> and I would like to finish mounting the oscillator on this weekend...

It's not that critical. Optimally, it should be the same as the input  
resistance seen on the minus input of U4b, but as that is connected to  
a whole bunch of potentiometers, there's not one right value. So my  
guess: anything between 15k and 33k goes. 5% is good enough.

Ben

On 2 aug 2009, at 02:02, Paul Schreiber wrote:

> Bonus: what is the specific *purpose* of this resistor, and ...

Oooh, pick me, pick me! :-) (Although it's been a while...)

The input bias current into the minus input causes a voltage drop  
across the input resistors. This would then be amplified and to  
compensate for this, that resistor is added on plus input to generate  
an equal voltage on the plus input. Net effect should then be zero at  
the output.

> Bonus #2: what "bad effect" results from using it

It is a carbon resistor, with a 200-250 ppm temp coef. The resistors  
on the minus input are much better, so you get temperature drift.

> (but is compensated for later in the design, and what is THAT  
> compensation?)

Bit of a guess here: normally you would only need 3300 ppm tempco to  
compensate the expo converter, but you are using a 3500 ppm tempco  
resistor. Is that the reason?

Ben

According to the Musical Engineer's Handbook (Bernie Hutchins, 1975), 3a 
(10), "The purpose of the resistor is to compensate for the offset due 
to the current that actually flows into the other input."  It is 
important to use in precision DC summing circuits.  The MEH also tells 
how to calculate the value.  I've wondered how important this resistor 
is in an inverting summer.  I don't know the answers to question #2.

Richard Brewster
http://pugix.com


Paul Schreiber wrote:
>
>
> Correct, not critical, 15K to 33K will work, 5% ok.
>  
> Bonus: what is the specific *purpose* of this resistor, and ...
> Bonus #2: what "bad effect" results from using it (but is compensated 
> for later in the design, and what is THAT compensation?)
>  
> Paul S.
>  
>
>     ----- Original Message -----
>     *From:* Miguel Mendoza <mailto:miguel@...>
>     *To:* motm@yahoogroups.com <mailto:motm@yahoogroups.com>
>     *Sent:* Saturday, August 01, 2009 5:58 PM
>     *Subject:* [motm] Missing resistor
>
>     Hi group, I'm starting to build a MOTM 300 kit that I was keeping
>     on a shelf and I'm missing the 22K resistor for R49. I'd like to
>     ask if any of you know if I can replace this one by other value
>     and what range or if this is a critical value. I have many
>     other resistors and I would like to finish mounting the oscillator
>     on this weekend...
>      
>     Thanks!
>      
>     Miguel.
>      
>      
>
>
>
> 
>
>
> __________ Information from ESET NOD32 Antivirus, version of virus 
> signature database 4297 (20090801) __________
>
> The message was checked by ESET NOD32 Antivirus.
>
> http://www.eset.com



__________ Information from ESET NOD32 Antivirus, version of virus signature database 4297 (20090801) __________

The message was checked by ESET NOD32 Antivirus.

http://www.eset.com

> 
> The input bias current into the minus input causes a voltage drop  
> across the input resistors. This would then be amplified and to  
> compensate for this, that resistor is added on plus input to generate  
> an equal voltage on the plus input. Net effect should then be zero at  
> the output.
> 

This is correct but only half the answer. Keep going.............

>> Bonus #2: what "bad effect" results from using it
> 
> It is a carbon resistor, with a 200-250 ppm temp coef. The resistors  
> on the minus input are much better, so you get temperature drift.
> 
>> (but is compensated for later in the design, and what is THAT  
>> compensation?)
> 
> Bit of a guess here: normally you would only need 3300 ppm tempco to  
> compensate the expo converter, but you are using a 3500 ppm tempco  
> resistor. Is that the reason?

No, but a good guess :)

Paul S.

> According to the Musical Engineer's Handbook (Bernie Hutchins, 1975), 3a 
> (10), "The purpose of the resistor is to compensate for the offset due to 
> the current that actually flows into the other input."  It is important to 
> use in precision DC summing circuits.

This is sort of a "hand waving" answer you write on a test when you forgot 
the real answer :)


> The MEH also tells  how to calculate the value.

Well that part is correct.

>  I've wondered how important this resistor  is in an inverting summer.

Application dependent.

 I don't know the answers to question #2.
>

It's a toughie :)

Paul S.

My guess is that it's probably a relict from a circuit that used an opamp with higher input bias current.
The MXL1014 would probably just work as well with the + input tied directly to GND.

Bad effect? *Theoretically* that resistor increases noise, and EMI receptivity, if not bypassed with a cap. But certainly not here 
in this application, summing large controll voltages, so I can't really think of any bad effect!

JH.

>Correct, not critical, 15K to 33K will work, 5% ok.
>
>Bonus: what is the specific *purpose* of this resistor, and ...
>Bonus #2: what "bad effect" results from using it (but is compensated for later in the design, and what is THAT compensation?)

I vaguely recall discussion of audio mixer circuitry where the reason to
omit the resistor was that it adds noise. If that's right, I guess here you
make the tradeoff that less offset is more important than less noise. It
looks like for example the audio input mixer on the 440 filter does not have
a resistor on the + input.

What would compensate for it... I would guess the fact that the oscillator
core is basically integrating the noise and acts like an LPF?

			...Craig

-----Original Message-----
From: motm@yahoogroups.com [mailto:motm@yahoogroups.com] On Behalf Of Paul
Schreiber
Sent: Saturday, August 01, 2009 8:39 PM
To: Richard Brewster
Cc: motm@yahoogroups.com
Subject: Re: [motm] Missing resistor

> According to the Musical Engineer's Handbook (Bernie Hutchins, 1975), 3a 
> (10), "The purpose of the resistor is to compensate for the offset due to 
> the current that actually flows into the other input."  It is important to

> use in precision DC summing circuits.

This is sort of a "hand waving" answer you write on a test when you forgot 
the real answer :)


> The MEH also tells  how to calculate the value.

Well that part is correct.

>  I've wondered how important this resistor  is in an inverting summer.

Application dependent.

 I don't know the answers to question #2.
>

It's a toughie :)

Paul S.



------------------------------------

Yahoo! Groups Links