Forssell Opto Compressor
- Thread starter sismofyt
- Start date
Help Support GroupDIY Audio Forum:
Hi!
I haven't read the whole thread (I'm to lazy I guess), so maybe someone has already mentioned what I'm posting, and in that case I appologize.
When I look at the schematic: http://www.forsselltech.com/SideChain.PDF
One thing stikes me as a little odd....
Is the attack and release time really separatly controllable? The release time is controlled by C1, VR2 and R6. But the release time is also affected by the discharge of C2 through VR3 and R5, meaning that if you adjust the attack time you also change the release time (at least for short release times). Have I got this wrong, or is the affect of this so minimal that it can be ignored?
I'm working on a schematic that will fix this, and add some compensation for the unlinearities in the vactrols as well, if anyone is interested I can post it when it's done.
I haven't read the whole thread (I'm to lazy I guess), so maybe someone has already mentioned what I'm posting, and in that case I appologize.
When I look at the schematic: http://www.forsselltech.com/SideChain.PDF
One thing stikes me as a little odd....
Is the attack and release time really separatly controllable? The release time is controlled by C1, VR2 and R6. But the release time is also affected by the discharge of C2 through VR3 and R5, meaning that if you adjust the attack time you also change the release time (at least for short release times). Have I got this wrong, or is the affect of this so minimal that it can be ignored?
I'm working on a schematic that will fix this, and add some compensation for the unlinearities in the vactrols as well, if anyone is interested I can post it when it's done.
chrissugar
Well-known member
[quote author="Gubbe"]Hi!
Is the attack and release time really separatly controllable? The release time is controlled by C1, VR2 and R6. But the release time is also affected by the discharge of C2 through VR3 and R5, meaning that if you adjust the attack time you also change the release time (at least for short release times).
[/quote]
The attack and release times are separately controllable.
C2 VR3 and R5 do not affect the release time because they are separated by U3 which is a buffer (OPA604). The buffer being a jfet input opamp will not draw any current, so it will not discharge the release circuit. This is the idea to use a buffer. To have the same voltage at the input of the attack circuit, but without the disadvantage of interacting between the attack and release circuits.
chrissugar
Is the attack and release time really separatly controllable? The release time is controlled by C1, VR2 and R6. But the release time is also affected by the discharge of C2 through VR3 and R5, meaning that if you adjust the attack time you also change the release time (at least for short release times).
[/quote]
The attack and release times are separately controllable.
C2 VR3 and R5 do not affect the release time because they are separated by U3 which is a buffer (OPA604). The buffer being a jfet input opamp will not draw any current, so it will not discharge the release circuit. This is the idea to use a buffer. To have the same voltage at the input of the attack circuit, but without the disadvantage of interacting between the attack and release circuits.
chrissugar
just.sounds
Active member
After i finish my g7 ventures I think I'll dive into the ff opto.
I hope to hear some experiences with it from you. How are the units performing? I would like to know how fast they can be and if you all like the sound quality of them. Thanks in advance
Greetings
I hope to hear some experiences with it from you. How are the units performing? I would like to know how fast they can be and if you all like the sound quality of them. Thanks in advance
Greetings
chrissugar
Well-known member
This is an excellent compressor, very transparent. You can have 20dB of gain reduction without any trace of distortion It's speed is limited by the VTL5C1 to 1milisecond, which is the fastest optocoupler available for audio.
The big advantage is that you can use any make up gain circuit you want, tube, jfet, bipolar.
I built it last year only on protoboard and it is great. Now I'm working on eight channels with optional tube or jfet make up gain.
Highly recomended.
chrissugar
The big advantage is that you can use any make up gain circuit you want, tube, jfet, bipolar.
I built it last year only on protoboard and it is great. Now I'm working on eight channels with optional tube or jfet make up gain.
Highly recomended.
chrissugar
just.sounds
Active member
Welll that sounds promising!
I hope to start asap. thanks for the reply Greetings
I hope to start asap. thanks for the reply Greetings
khstudio
Well-known member
I finally started this comp & will be ONLY using it UN-Balanced.
Do I still need the trannys or can I just add coupling caps to the in & output? (unless they're already there
)
If so - what value would be good here???
470-1000uf / 25v or so ???
Also, I'm using 2 boards - do I need to load BOTH Power Supply sections or can I just load ONE & jumper it to the other board?
I'm using Gustavs boards.
Thanks
Do I still need the trannys or can I just add coupling caps to the in & output? (unless they're already there
)If so - what value would be good here???
470-1000uf / 25v or so ???
Also, I'm using 2 boards - do I need to load BOTH Power Supply sections or can I just load ONE & jumper it to the other board?
I'm using Gustavs boards.
Thanks
kazper
Well-known member
Didn't know it needed transformers..?
I guess I need to do more research on this one.
There is some documents floating around that has the board layout for both sides if you want to do a home etch.
Kevin
I guess I need to do more research on this one.
There is some documents floating around that has the board layout for both sides if you want to do a home etch.
Kevin
khstudio
Well-known member
Anyone? :sad:
Nele
Well-known member
You could use just one power-supply, but I prefer using an external one with trim-pots for better voltage adjustment
cheers,
corneel
cheers,
corneel
Nele
Well-known member
there's already a 100uF cap on the 5534-output so that should be enough. Maybe you could use the same value for the discrete version...
Don't know if you need some extra impedance-correction.. doesn't look like it.. Think the output is 600 Ohm.
Don't know if you need some extra impedance-correction.. doesn't look like it.. Think the output is 600 Ohm.
kazper
Well-known member
Does it need a transformer only if you use the NE5534's? it looks like a spec of 600:600 isolation.
There is a option on the JH990 to use a JT-11-BM on the output of the 990's
Fred's site has a update but his 990 stuff is not up yet on the new site.
I'm sure a good 600 ohm 1:1, even edcore's should work.
There is a option on the JH990 to use a JT-11-BM on the output of the 990's
Fred's site has a update but his 990 stuff is not up yet on the new site.
I'm sure a good 600 ohm 1:1, even edcore's should work.
khstudio
Well-known member
[quote author="kazper"]Does it need a transformer only if you use the NE5534's? it looks like a spec of 600:600 isolation.
There is a option on the JH990 to use a JT-11-BM on the output of the 990's
Fred's site has a update but his 990 stuff is not up yet on the new site.
I'm sure a good 600 ohm 1:1, even edcore's should work.[/quote]
There are a LOT of options...
I will be using this on UN-BALANCED 10K INSERTS... No need for a balanced circuit OR Balancing TX... unless I want the "COLOR" of the TX.
Nele, Thanks man.
I have 2604's & some left over YAMAHA 80200 discrete Block... I may use the Yamaha's for the "make-up" gain.
Also, I'd like to run it all off of 24v but don't want to waist my 2404's for the metering... not sure how to get around this yet.
thanks again
:thumb:
If anyone has any NEW INFO or PICS - Please post. :green:
There is a option on the JH990 to use a JT-11-BM on the output of the 990's
Fred's site has a update but his 990 stuff is not up yet on the new site.
I'm sure a good 600 ohm 1:1, even edcore's should work.[/quote]
There are a LOT of options...
I will be using this on UN-BALANCED 10K INSERTS... No need for a balanced circuit OR Balancing TX... unless I want the "COLOR" of the TX.
Nele, Thanks man.
I have 2604's & some left over YAMAHA 80200 discrete Block... I may use the Yamaha's for the "make-up" gain.
Also, I'd like to run it all off of 24v but don't want to waist my 2404's for the metering... not sure how to get around this yet.
thanks again
:thumb:
If anyone has any NEW INFO or PICS - Please post. :green:
khstudio
Well-known member
OK, I'm confused.
I read that Fred said that the LED's needed 24v connected to them... if I use 5534's for the in & out I have to run @ lower voltages so how does that work?
Also, as long as I'm using 5534's @ the lower voltage... is there any benifit to using the 2604's in the sidechain? I could see the benifit @ 24v & the discretes.
I do have some OPA134's, 627's & 637's (I have to check but I think at least 2 of them are singles & MAY be able to replace the 5534's & run @ 24v)
I read that Fred said that the LED's needed 24v connected to them... if I use 5534's for the in & out I have to run @ lower voltages so how does that work?
Also, as long as I'm using 5534's @ the lower voltage... is there any benifit to using the 2604's in the sidechain? I could see the benifit @ 24v & the discretes.
I do have some OPA134's, 627's & 637's (I have to check but I think at least 2 of them are singles & MAY be able to replace the 5534's & run @ 24v)
hitchhiker
Well-known member
I have two mono units running on 18v but I opted for a vu meter. It adjusts to 0 vu without a problem . The circuit is linked in this thread, 1st page I think and elsewhere.
Just be sure to notice it connects to the opposite polarity voltage than the led circuit so you have to be creative with the pcb. a small cut IIRC and one leg of the meter LDR is moved. I drilled a hole in my pcb for this leg but you could just run wire jumpers to where you get the correct rail voltage .(I can't remember if it's + or - v)
The VU circuits are not as quick and accurate but good enough for some folks.
cheers,
Lance
Just be sure to notice it connects to the opposite polarity voltage than the led circuit so you have to be creative with the pcb. a small cut IIRC and one leg of the meter LDR is moved. I drilled a hole in my pcb for this leg but you could just run wire jumpers to where you get the correct rail voltage .(I can't remember if it's + or - v)
The VU circuits are not as quick and accurate but good enough for some folks.
cheers,
Lance
Nele
Well-known member
The LED's are driven by the LM3916 which runs on 3V to 25V so there shouldn't be a problem with 18V.
At least I don't think it will influence the meter. The only thing you might have to adjust is the resistor that regulates the current going to the LED's, I think R18..
I am in the process of building a stereo discreet version and I've already built a 5534 version. To be honest I have no idea if there's any benefit in using OPA2604's.. They should be better than NE5534's but there's an op-amp comparison on the net somewhere (mentioned here a while ago) where specs-wise the 5534 wins hands-down.
Just use 18V and compare the 5534 and 2604 and go with what sounds best.
Cheers,
Corneel
At least I don't think it will influence the meter. The only thing you might have to adjust is the resistor that regulates the current going to the LED's, I think R18..
I am in the process of building a stereo discreet version and I've already built a 5534 version. To be honest I have no idea if there's any benefit in using OPA2604's.. They should be better than NE5534's but there's an op-amp comparison on the net somewhere (mentioned here a while ago) where specs-wise the 5534 wins hands-down.
Just use 18V and compare the 5534 and 2604 and go with what sounds best.
Cheers,
Corneel
khstudio
Well-known member
Thanks for helping :thumb:
I've been reading thru the BIG "Official" thread & have found some answers to these questions.
NOTE:
the 2604 is a DUAL IC
the 5534 a Single
I'm not really comparing THESE IC's... i'm looking at the whole picture when it comes to the voltage of the IC's & what I read about the LED's. I basically have several parts in stock... just have to decide what to go with.
BTW - I'm using the TOMMYTONES Rev 1C Boards.
I've been reading thru the BIG "Official" thread & have found some answers to these questions.
NOTE:
the 2604 is a DUAL IC
the 5534 a Single
I'm not really comparing THESE IC's... i'm looking at the whole picture when it comes to the voltage of the IC's & what I read about the LED's. I basically have several parts in stock... just have to decide what to go with.
BTW - I'm using the TOMMYTONES Rev 1C Boards.
khstudio
Well-known member
I realize this is the Original Design thread & my questions should be in the OFFICIAL THREAD:
http://www.groupdiy.com/index.php?topic=16016
http://www.groupdiy.com/index.php?topic=16016
jtompkinsmd
New member
- Joined
- Apr 25, 2013
- Messages
- 3
mnats said:
I know this is a resurrection, but I wonder if mnats or anyone else has a working link to his revision boards? I am interested in etching this and giving it a go, but the links in that post are broken.
