Dual mono Forssell Opto Comp finished..!

[Black Dog]

Here are some pictures of my Forssell opto comp -->

Many thank to Mr. Forsell and everybody else, who contributed to this project.
It was alot of fun and the comp's sounds great..!

Cheers :guinness: :guinness: :guinness:

Lars

 

[Greg]

Very nice work !

Damn impressive !

Enjoy the comp :guinness: .

 

[SonsOfThunder]

Nice job!

Tell us what opamps you used and the story on your I/O iron...!

 

[syn]

Very impressive ! Llike the wireing... yeah, tell us about the iron...

Cheerz

 

[AnalogPackrat]

Very nice--especially all the flying leads. Do tell about the iron...

A P

 

[skipwave]

Nice work! I'm so jealous of you guys close enough to utilize Gyrafs engraving machine.

 

[clintrubber]

Looks very nice indeed !

Yes please, tell about the TXs.

Did you skip the stereo-link on purpose ?

Bye,

Peter

 

[TomWaterman]

Woo!

You got the VU meter working with the forssell - hows that working out, do you get good, accurate deflection?

Nice work!

-Tom

 

[clintrubber]

And what kind of ratio-pot did you end up with ? I'll be going switched, but always nice to know how which pot turns out.

 

[Black Dog]

Thanks a bunch for the compliments, guys..!

[quote author="SonsOfThunder"]Tell us what opamps you used and the story on your I/O iron...![/quote]
I'm using 5534 - and TL072 for the sidechain - everything is running of +/-15V.

Iron is taken from some "Bosch Fehrnsehen" racks made for the Danish National Television in the seventies.
I can't be shure, but I'm guessing Haufe, because the racks contained alot of that as well..

[quote author="skipwave"]I'm so jealous of you guys close enough to utilize Gyrafs engraving machine.[/quote]
Well, Jakob haven't used the Gravograph for ingraving his Gyraf's for years, so he kindly lent it to me, as I promised to put it to good use.
I can only hope, he see's my humble work as being worthy of this legendary machinery..

[quote author="clintrubber"]Did you skip the stereo-link on purpose ?[/quote]
Yes I did :razz:

[quote author="TomWaterman"]You got the VU meter working with the forssell - hows that working out, do you get good, accurate deflection?[/quote]
You bet - I'm just feeding the meter instead of the LM3916 and it tracks fine up until 10dB reduction, at which point I really don't care anyway..

[quote author="clintrubber"]what kind of ratio-pot did you end up with ?[/quote]
5KC - just as the BOM suggests.

Cheers :guinness:

Lars

 

[TomWaterman]

Awesome thanks - do you have any other cicuitry between the sidechain and the meter?

What meter is it - mA?

Cheers Tom

 

[guy_4]

Beautiful job, Black Dog !

Here I recognise two Studer transformers on the inputs, same look as those used on the A80's . Look like Haufe for the outputs.

 

[clintrubber]

[quote author="Black Dog"]
I'm using 5534 - and TL072 for the sidechain - everything is running of +/-15V.[/quote]

Hi Lars,

That's interesting - I actually forgot if the (original higher) supply voltage was the only reason or not that the TL072 couldn't be used & the more expensive opamps were called for. But it might have been the only reason and then yes, why not ?

Wait, if you haven't already you might want to increase the 1k resisitors around U5B. The '72 might not like that, but no idea if you could hear a difference because of it.

Cheers/Skål!

Peter

 

[okgb]

Neat & tidy the care shows , bravo looks great hope it sounds just as good

 

[Black Dog]

Thanks again, for the nice words :grin:

[quote author="TomWaterman"]do you have any other cicuitry between the sidechain and the meter?[/quote]

No I don't - I just feed the meter from pin5, where the LM3916 is supposed to go.

[quote author="TomWaterman"]mA?[/quote]
Yes, they are very simple (and cheap) DC-meters i found at a local surplus store.
I just handdrew a scale and fitted two minature lightbulbs in each of the meters.
Cost me about 3 EUR each :thumb:

[quote author="guy_4"]Here I recognise two Studer transformers on the inputs, same look as those used on the A80's . Look like Haufe for the outputs.[/quote]
Good info, thanks!
I have a few friends with A80's - I will see if they will let me have a look inside to verify.

[quote author="clintrubber"]I actually forgot if the (original higher) supply voltage was the only reason or not that the TL072 couldn't be used & the more expensive opamps were called for. But it might have been the only reason and then yes, why not ?[/quote]
My thought exactly - and they seem to do the job fine, but I haven't tried anything else.

[quote author="clintrubber"]Wait, if you haven't already you might want to increase the 1k resisitors around U5B. The '72 might not like that, but no idea if you could hear a difference because of it.[/quote]
I used 10K's, like you suggested in the Forssell build thread.

Cheers :thumb:

Lars

 

[tommypiper]

Looks great! How many mA are the meters? (I've tried to figure this out from the schems, no luck.) Nice to see a 1U solution.

 

[Black Dog]

[quote author="tommypiper"]How many mA are the meters? [/quote]
1mA FSD :thumb:

Lars

 

[TomWaterman]

Thanks Lars.

How are you liking the sound of this compressor?
I still haven't finished mine - waiting on the BFBlokes from Fabio!

-T

 

[Svart]

I have FF optos with blokes. they need tweaking. make sure your feedback Rs are 10-15k, that is where they are most happy. I am still working on these but I have a level problem in the output section, tends to clip some. more on this later.

 

[Black Dog]

[quote author="TomWaterman"]How are you liking the sound of this compressor?[/quote]

I like it alot. It's not the kind of thingy that makes you pee your pants, because the 5534 stages doesn't have much "sound" to them.
But the addition of iron helped a bit in that department and the compression is very, very nice.

Cheers :guinness:

Lars