Synth-DIY Yahoo! Groups Archives

Thread

arp 4075

2008-05-15 by adaaxs

I just got an analog metro 4075 board (a lot of us probably have). Are there enough of us to
get a panel or will I end up housing it in a oops panel.

It has 5 matched pairs of 2n5087, do I have an alternative to measuring a bag of these
things, I don't really know how to do it properly.

Should I use a 1 or 2k tempco Precision has no 1k87 in stock.

Re: [ModularSynthPanels] arp 4075

2008-05-15 by loopcycle

i would be really happy to see a 1U panel for the 4075.

i have no idea where to source a 1k87 tempco, so i was thinking i'd just use a
regular (1% metal film) 1k87. 1v/O tracking will be lost when the filter
self-oscillates.

according to the docs: "the filter works perfectly well without hand matching
the transistors."

--- adaaxs <wonggster@...> wrote:

> I just got an analog metro 4075 board (a lot of us probably have). Are there
> enough of us to
> get a panel or will I end up housing it in a oops panel.
>
> It has 5 matched pairs of 2n5087, do I have an alternative to measuring a
> bag of these
> things, I don't really know how to do it properly.
>
> Should I use a 1 or 2k tempco Precision has no 1k87 in stock.
>
>

Re: [ModularSynthPanels] arp 4075

2008-05-15 by Ti_

I know Dave Brown has a page with a link to an Front Panel Express file of a 1u face.
He's built some kind of summing amp into it so it can accept 3 inputs. If a few more people want one we could save a few $s if we buy 5 or more.
currently it looks like the prices are:
1->5=$55.53
5->9=$49.98
10->19=$44.42
20->29=$38.87
Luckily I got the tempco when I bought my board from another list member a while back. My big problem will be matching the transistors....
~Tim

--- On Thu, 5/15/08, loopcycle <loopcycle@...> wrote:
From: loopcycle <loopcycle@...>
Subject: Re: [ModularSynthPanels] arp 4075
To: ModularSynthPanels@yahoogroups.com
Date: Thursday, May 15, 2008, 12:08 PM

i would be really happy to see a 1U panel for the 4075.

i have no idea where to source a 1k87 tempco, so i was thinking i'd just use a
regular (1% metal film) 1k87. 1v/O tracking will be lost when the filter
self-oscillates.

according to the docs: "the filter works perfectly well without hand matching
the transistors. "

--- adaaxs <wonggster@gmail. com> wrote:

> I just got an analog metro 4075 board (a lot of us probably have). Are there
> enough of us to
> get a panel or will I end up housing it in a oops panel.
>
> It has 5 matched pairs of 2n5087, do I have an alternative to measuring a
> bag of these
> things, I don't really know how to do it properly.
>
> Should I use a 1 or 2k tempco Precision has no 1k87 in stock.
>
>

Re: [ModularSynthPanels] arp 4075

2008-05-16 by JAMES GALLANT

As far as matching transistors go, you should be able to sub either an SSM2220 or a 2SA798 for each matched pair. Granted, it will take some creative mounting to get either of these to fit since the SSM2220 in 8 pin DIP and SOIC-8 styles and the 2SA798 is a 5 pin SIP. I'll be going with the 2SA798's since I already have a bunch of these.

For the 1K87 tempco, I did a little quick math (good old ohms law) and you should probably be able to get away with using a 2K tempco and compensate for that by increasing the value of R13 to 209.625K. I plan on doing a 3-series-resistor-kluge using the stated 196K followed by a 13K and ending with a 626 ohm resistor. On paper that's only an ohm off. Tracking and trim errors should be able to be trimmed out with the existing pots.

Oh, and I'd probably be up for one of those front panels too.

James

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

From: Ti_

To: ModularSynthPanels@yahoogroups.com

Sent: Thursday, May 15, 2008 10:20 AM

Subject: Re: [ModularSynthPanels] arp 4075

I know Dave Brown has a page with a link to an Front Panel Express file of a 1u face.
He's built some kind of summing amp into it so it can accept 3 inputs. If a few more people want one we could save a few $s if we buy 5 or more.
currently it looks like the prices are:
1->5=$55.53
5->9=$49.98
10->19=$44.42
20->29=$38.87
Luckily I got the tempco when I bought my board from another list member a while back. My big problem will be matching the transistors. ...
~Tim

--- On Thu, 5/15/08, loopcycle <loopcycle@yahoo. com> wrote:

From: loopcycle <loopcycle@yahoo. com>
Subject: Re: [ModularSynthPanels ] arp 4075
To: ModularSynthPanels@ yahoogroups. com
Date: Thursday, May 15, 2008, 12:08 PM

i would be really happy to see a 1U panel for the 4075.

i have no idea where to source a 1k87 tempco, so i was thinking i'd just use a
regular (1% metal film) 1k87. 1v/O tracking will be lost when the filter
self-oscillates.

according to the docs: "the filter works perfectly well without hand matching
the transistors. "

--- adaaxs <wonggster@gmail. com> wrote:

> I just got an analog metro 4075 board (a lot of us probably have). Are there
> enough of us to
> get a panel or will I end up housing it in a oops panel.
>
> It has 5 matched pairs of 2n5087, do I have an alternative to measuring a
> bag of these
> things, I don't really know how to do it properly.
>
> Should I use a 1 or 2k tempco Precision has no 1k87 in stock.
>
>