Official Forssell Limiter Build thread

[soundguy]

what pots has everyone been able to source? The only thing I can find in the right values are alpha pots from mouser, would prefer to find something a little better with an 1/8" shaft if possible.

dave

 

[Greg]

I bought some CTS pots from Digikey with 1/8" shafts for a different project, but I don't remember the values... I remember the selection wasn't too good. Have you tried there?

[EDIT]: What about these from Digikey? The 1/4W... I see the 100k logs and 500k linears.
http://dkc3.digikey.com/PDF/T043/1009.pdf

 

[tk@halmi]

[quote author="soundguy"]what pots has everyone been able to source? The only thing I can find in the right values are alpha pots from mouser, would prefer to find something a little better with an 1/8" shaft if possible.
dave[/quote]

Newark has all the nice Bourns pots including the 5k reg log. :sam:

 

[TomWaterman]

Is anybody thinking about picking some values from the pots and using rotary switches instead?

I was planning on building them with temporary pots and picking some combos that sound good on both program and individual instruments, and then using switches for ratio, attack and release, keeping threshold and make-up gain on pots......

Good idea?

How could one calculate the actual ratios? and measure the attack / release with a scope?

Cheers Tom

 

[tommytones]

The web page is almost up...Kev is fixing some last minute things. A couple of fixes on the parts list. I forgot C2 (33pF) + C3 (.68uF/16v) and C9 + C10 do not exist and have been removed.

As soon as the files are ready I or Kev will post a link.

 

[Kev]

[quote author="tommytones"]The web page is almost up...Kev is fixing some last minute things. .[/quote]
:shock:

... I am ?? :?

KEV - check your emal !!!checkemailcheckemailcheckemailcheckemailcheckemailcheckemail

ooo ? I have some work to do ....

diydiy
happyhappy
...

 

[okgb]

Excuse the ignorant question , but where is the bulk of the
info for the forsell limiter ?

regards Greg

 

[soundguy]

(utfsf)

http://www.groupdiy.com/index.php?topic=374&highlight=forssell

shows the development

parts are here

http://www.groupdiy.com/index.php?topic=2470&highlight=forssell

ad you can get boards here

http://www.groupdiy.com/index.php?topic=2127&highlight=forssell

dave

 

[babyhead]

I think I am really into the stepped ladder attenuator solution for the pots on this project. Do I remember there being a discussion in the original thread about matching the optos and it being difficult? So I guess my design question is this:

How do we make a matched pair?

Looking over the schematic, it seems that the controls would be active for both channels in linked mode...I'm just trying to get a grip!

Can we use DLR-1s for this project? What about 1731s?

That's all for now...putting together my orders...

-

 

[wilebee]

you can use the dlr on the input but not the output it won't drive a load below 3k I think ask fred . I like to know about the opto isolators and there orientation in the board. How are we to tell which end is which ?

Wil Wilebee

 

[wilebee]

you can use the dlr on the input but not the output it won't drive a load below 3k I think ask fred . I like to know about the opto isolators and there orientation in the board. How are we to tell which end is which ?

Wil Wilebee

 

[tommytones]

If you use VTL5C1, it's orientation is the same as the silk screen. Otherwise just look at the data sheet...

 

[wilebee]

so the same direction as the letering of the part # ? Wil

Wilebee

 

[rafafredd]

got my red PCBs today. Thanks, Tommy!

Now I have to find the time to stuff it!

 

[tommytones]

The VTl5c1 should be shaped the same as the screen on the boards. There's a corner notched out...

 

[tommytones]

Okay, here it is. This should help out with files and finding information on this project. Thanks Kev as always!!

DIY Factory Forssell Opto

It's a work in progress but the important stuff should be there.

 

[synthetic]

Just a reminder that you can get your 5532s and OPA2604s for free from TI.com. Mine just arrived.

Tommy - great resource, thanks. So, is anyone passing audio yet? How does this baby sound?

 

[Bear]

Is there any matching/sorting to be done with the vactrols? Wanna know how many to get.

Bear

 

[soundguy]

some more stuff:

-- dont need c33 for the discrete input?

-- is c29 & c30 on the silk equivalent to c27 and c28 on the schem? Im assuming so.

-- What steps do I need to take in order to use an analog meter with these boards, and assuming its possible, what kind of meter will work best (vu or dc)? If an analog meter is not possible, can anyone point me towards an LED array that would work here, Ive never had to look for one of those parts before...

thanks

dave

 

[j.hall]

i grabbed the front panel express design file for the front panel. i didn't see a "make-up gain" knob for either channel.

i read through most of the 26 page original thread and didn't see much about that. is there a make-up gain pot?

if so, is there an updated FPE files floating around that i haven't found yet.