Official Forssell Limiter Build thread

GroupDIY Audio Forum

Help Support GroupDIY Audio Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

soundguy

Well-known member
Joined
Jun 4, 2004
Messages
2,041
Location
NYC, USA
I figured since many of have boards now, instead of sorting through the development thread we could post our build issues here. To start, I have two questions-

What is the best size to use for pin receptacles for the discrete opamp?

There shouldnt be any issues with using a single power transformer to feed two boards in a single box, right?

If anyone has time, can someone post a link to ALL the docs for this project here, would be helpful.

dave
 
I'm using the knurled sockets from Farnell for the JLM unit and I'm 99% sure they are fine for the pins on the Forssell unit.

RS have a silver socket but min order of 20
RS :- 434-712 $0.49

Farnell :- 149-319 knurled gold $0.66aust (I like this one)
Farnell :- 149-318 plain silver $0.50aust (min 20)
Farnell :- 150-501 plain gold $0.70aust


These are listed as 1.0 mm sockets


The JLM power supply or any other supply that suits Project 2 will also suit this project.
 
Don't forget Dave that you must feed dc voltage to the boards. There's no problem with using 1 main psu to feed the individual boards. This is how I'm gonna handle mine.
As for the docs, I'll have to search through the main thread we had going cause I've sorta lost track of who's hosting what. I'm also gonna add a few things like a block diagram to help make use of the various schems and pdf artwork for those who wish to home brew this board.
 
Dave,

Digikey sells these sockets. I use them with the JLM board.
http://www.groupdiy.com/FORUM/viewtopic.php?t=3170&sid=ef7447f064fc85f3c5409be5ee428734

Tamas
 
So I've done the pdf files and the block but need someone to host. Ideally this should be the same person who's hosting the other stuff too.
 
[quote author="Kev"]RS have a silver socket but min order of 20
RS :- 434-712 $0.49

Farnell :- 149-319 knurled gold $0.66aust (I like this one)
Farnell :- 149-318 plain silver $0.50aust (min 20)
Farnell :- 150-501 plain gold $0.70aust

[/quote]

Do you have RS and Farnell part numbers for pins?
 
I'm working on the hosting thing with Kev. I think this will be another addition to the Factory. I'll post back as soon as I have a url for you guys.
 
[quote author="rafafredd"]Do you have RS and Farnell part numbers for pins?[/quote]

err ... :? ... um ... we did this
I'm sure there is another thread here that did list that.

however the pins are short and if you want to load a PCB upside down so you can pot and poor ....
does that make sense ??
... you will need long pins.
I think Joe told us he used brass or copper rod cut to length.
I used some pins from DB to RJ45 adapters.
DB15 and 25 had enough pins to make it worthwhile.
 
[quote author="Kev"]I think Joe told us he used brass or copper rod cut to length.
I used some pins from DB to RJ45 adapters.
DB15 and 25 had enough pins to make it worthwhile.[/quote]

Two nice solutions. :grin:
 
can anyone reccomend the appropriate regulators in the power supply for use with +/- 24 V opamps?

Do I need to increase the voltage ratings of the caps used in the circuit with a +/-24 supply?

what DC voltage does the PS want to see?

thanks

dave
 
Hi Soundguy Dave,

You can use the LM317, 337 pair with no problems as a +/- regulator pair. Without the boards and spec sheets in front of me I'm not sure if the layout was designed for a 7824/7924 fixed reg, or the 317/337 adjustable type. I hope it was set up for the adjustables as they provide better performance (less ripple when the adjust pin is properly bypassed).

You'll want to feed the regulators with about 3-5V more than their output 24V, so +/- 27-29VDC or so. You'll get a little more than this from a full wave recitfied +/-22VAC power transformer.

Cheers,

Kris
 
thanks, I thought the 317 was a fixed reg, nevermind...

Do I need to double the voltage on the caps? Seems like it was tested with +/-15 supply, dont caps want to be more than twice the voltage swing? Should I be sourcing 50v caps with a +/- 24v supply?

dave
 
Hi!

I may be wrong but I thought 35V would be fine for a +-24V design when used as PSU bypass caps, as each rail is treated to a bypass cap individually (?)

Cheers Tom
 
Either way will be fine but I wouldn't go less than 35V. There's plenty of room for individual experimentation and customization.
 
reminder for everyone building this compressor.. check the leg orientation on your 5457 FETs.. I found that the brand that i bought has different leg assignments than what's on the board. I did some research and it seems that there are at least 3 different brands, each with different leg assignments. My gate leg was where the drain hole was...

cheers!
 

Latest posts

Back
Top