MOTM

Hi,

I'm working on the Ken Stone Power delay and Tube VCA projects for my MOTM system.

Trying to find the correct parts is driving me insane.  Does anyone have the correct part #'s 
for mouser, digikey, or whatever for these projects?

Thanks,

Dave

PS also posted this on the ken stone board.

On 5/2/07, earthtodylan2000 put forth:
>Hi,
>
>I'm working on the Ken Stone Power delay and Tube VCA projects for
>my MOTM system.

So what are you using for a panel??  :)

If you are buying it from Front Panel Express, perhaps we should try
to get a bunch of orders together so we can avoid duplicating set-up
charges, and get a volume discount.

>Trying to find the correct parts is driving me insane.  Does anyone
>have the correct part #'s for mouser, digikey, or whatever for these
>projects?

Well, the parts for both those projects seem rather common.  In fact,
except for the tubes, I might not have to order any parts to build
the Tube VCA.  When I get the boards, I'll see if the caps and
trimmers I have fit (Bourns trimmers and those poly caps in the
little yellow boxes don't have much wiggle room with their tiny
leads).

Always use caps with an appropriate voltage rating, eg. 50-100V.  For
the three capacitors in the signal path, I would use poly caps with
radial leads.  Polyester, aka Mylar, caps are inexpensive and space
efficient but their dielectric absorption is terrible.  So I would go
with either polycarbonate or polypropylene (tantalum caps are polar,
and polystyrene caps are large, expensive, and generally overkill).
For the bypass caps, please see Richard's last post on the CGS list.

The Tube VCA uses an op-amp which can swing to its negative rail (a
TL072 can't do that).  Although not singular in that ability, the
LM358 specified by CGS is both inexpensive and widely available:

http://www.mouser.com/search/Refine.aspx?Ne=1447464+254016&Ntt=*LM358*&Msb=0&Mkw=LM358&N=1323038

Just make sure that you order IC's in DIP packages!!

Also, while I'm typing, I'm thinking of using bullet connectors for
the tube.  That way I can replace the tube without soldering the PCB.


Looking at the Power Delay, it uses a 741, which is an antique, but
afaik, you can still buy them.  Although, you should be able to
replace it with a modern op-amp with the same pinout.  The switching
transistor also seems pretty generic:

http://www.mouser.com/search/refine.aspx?Ntt=512-BC338


Sorry, I have no idea which relay would fit.

>...
>Looking at the Power Delay, it uses a 741, which is an antique, but
>afaik, you can still buy them.  Although, you should be able to
>replace it with a modern op-amp with the same pinout. ...

LM741s are readily available (and still in production, as far as I 
know). Note that the 741 is internally compensated, I think with 30 
pF. Many op amps require external compensation. This isn't at all 
hard to deal with, but you must deal with it.

Also, I've read that some circuits require the relatively low slew 
rate of the 741. I.e., using a high slew rate op amp in place of a 
741 can occasionally result is performance issues.
--
john


-- 
No virus found in this outgoing message.
Checked by AVG Free Edition. 
Version: 7.5.467 / Virus Database: 269.6.2/784 - Release Date: 5/1/2007 2:57 PM

>Hi,
>
>I'm working on the Ken Stone Power delay and Tube VCA projects for 
>my MOTM system.
>
>Trying to find the correct parts is driving me insane.  Does anyone 
>have the correct part #'s
>for mouser, digikey, or whatever for these projects?

I will have a Mouser list for the power delay board in a couple of 
weeks. I've ordered parts, but I won't know if they're correct until 
I get them in my grubby little hands.