khstudio
Well-known member
Also, What about the caps?
Official Forssell Limiter Build thread
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Nele
Well-known member
[quote author="khstudio"]OK,
Lastly,
What type of caps should the .33uf & .68uf cap be :?:
I'm guessing films?[/quote]
Yep...
Don't know about the values..
Cheers,
Corneel
Lastly,
What type of caps should the .33uf & .68uf cap be :?:
I'm guessing films?[/quote]
Yep...
Don't know about the values..
Cheers,
Corneel
khstudio
Well-known member
Thank you :thumb:
I'm very close to firing it up... I hope the a .47uf will work ok in place of the .33.
& a 1uf in place of the .68uf :roll:
It's all I have for now
I'm very close to firing it up... I hope the a .47uf will work ok in place of the .33.
& a 1uf in place of the .68uf :roll:
It's all I have for now
khstudio
Well-known member
Well... after months of reading & preparation I finally fired it up -
And made a BIG mistake
I hooked the Power trannys secondary directly to the V+, V- & 0v (center tap) I can not believe it...I didn't see the OFF BOARD DIODE BRIDGE ANYWHERE in the schematics... not even the PS one. O... it is in one of the parts list but I thought it was for a TOTAL off board PSU...DAMNIT
The only reason I found it was from Franks drawing.
OK, it passes audio & compressors but it sounds distorted when I talk loudly.
It's hooked up to the un-balanced inserts on my console (-10).
When I pull it everything is clear... so it IS the unit.
What could have happened when I hooked up (about 22v AC) to that spot on the board?
The ONLY amps that were loaded were my Yamaha DOA's & the LED Driver IC :sad:
ALL the 2604's weren't loaded yet... so they're good.
And made a BIG mistake
I hooked the Power trannys secondary directly to the V+, V- & 0v (center tap)
I can not believe it...I didn't see the OFF BOARD DIODE BRIDGE ANYWHERE in the schematics... not even the PS one. O... it is in one of the parts list but I thought it was for a TOTAL off board PSU...DAMNIT The only reason I found it was from Franks drawing.
OK, it passes audio & compressors but it sounds distorted when I talk loudly.
It's hooked up to the un-balanced inserts on my console (-10).
When I pull it everything is clear... so it IS the unit.
What could have happened when I hooked up (about 22v AC) to that spot on the board?
The ONLY amps that were loaded were my Yamaha DOA's & the LED Driver IC :sad:
ALL the 2604's weren't loaded yet... so they're good.
khstudio
Well-known member
I found it :grin:
I put a 49.9k in place of a 49.9 ohm (R8)
This is just after the output DOA & just before the SERVO feed.
Now I have enough output GAIN to blow up my studio... & it sounds pretty damn good.
One thing though... The threshold isn't sensitive enough. I have it set to its lowest point (most sensitive) & I would like it to go lower.
Could it be the -10 insert levels???
I put a 49.9k in place of a 49.9 ohm (R8)
This is just after the output DOA & just before the SERVO feed.
Now I have enough output GAIN to blow up my studio... & it sounds pretty damn good.
One thing though... The threshold isn't sensitive enough. I have it set to its lowest point (most sensitive) & I would like it to go lower.
Could it be the -10 insert levels???
babyhead
Well-known member
[quote author="khstudio"]I found it :grin:
I put a 49.9k in place of a 49.9 ohm (R8)
This is just after the output DOA & just before the SERVO feed.
Now I have enough output GAIN to blow up my studio... & it sounds pretty damn good.
[/quote]
I did the same thing and fried a 992 after some trouble shooting...
It exited life like a roman candle.
:green:
I put a 49.9k in place of a 49.9 ohm (R8)
This is just after the output DOA & just before the SERVO feed.
Now I have enough output GAIN to blow up my studio... & it sounds pretty damn good.
[/quote]
I did the same thing and fried a 992 after some trouble shooting...
It exited life like a roman candle.
:green:
khstudio
Well-known member
I feel like the "Lone DIY Ranger" on this one.
Still have a few unanswered questions on last page... Please help me out yo
:green:
Still have a few unanswered questions on last page... Please help me out yo
:green:
khstudio
Well-known member
OK,
My phase is flipping too... like others have said.
Also, even with a +4 input my threshold needs to be all the way down.
FRED said with a +4 input it "should" reach the threshold point at 2:00 on the dial :?
Mine isn't.
Where should I look?
My phase is flipping too... like others have said.
Also, even with a +4 input my threshold needs to be all the way down.
FRED said with a +4 input it "should" reach the threshold point at 2:00 on the dial :?
Mine isn't.
Where should I look?
khstudio
Well-known member
Things are going well. :green:
#1
I had a 604k instead of 604 ohm in the side chain... Ordered wrong part.
Then the threshold was TOO sensitive.
#2
Had to flip the threshold (100kA) pot... now it is smooth (the threshold)
Goes from low to high (left to right) instead of backing into the threshold (Normal)
#3
Ran some sweeps & it "looks" flat, but when in use I feel I'm loosing a little "AIR & SUBs"
My Output DOA is NOT a JFET. I was thinking about adding the JFET stage only, in front of my output amp.
FRED suggested a JFET after the Opto because of loading.
#4
The attack & release are VERY sensitive & just about useless because of it.
Are you guys sure they are LIN. & not LOG Taper :?:
#5 PHASE:
I left the output alone but had to swap PINS 2 & 3 on the input.
FIXED!
#1
I had a 604k instead of 604 ohm in the side chain... Ordered wrong part.
Then the threshold was TOO sensitive.
#2
Had to flip the threshold (100kA) pot... now it is smooth (the threshold)
Goes from low to high (left to right) instead of backing into the threshold (Normal)
#3
Ran some sweeps & it "looks" flat, but when in use I feel I'm loosing a little "AIR & SUBs"
My Output DOA is NOT a JFET. I was thinking about adding the JFET stage only, in front of my output amp.
FRED suggested a JFET after the Opto because of loading.
#4
The attack & release are VERY sensitive & just about useless because of it.
Are you guys sure they are LIN. & not LOG Taper :?:
#5 PHASE:
I left the output alone but had to swap PINS 2 & 3 on the input.
FIXED!
khstudio
Well-known member
:?
clintrubber
Well-known member
[quote author="khstudio"]#5 PHASE:
I left the output alone but had to swap PINS 2 & 3 on the input.
FIXED![/quote]
You wrote that in bold on purpose, not ? :wink: :twisted:
I left the output alone but had to swap PINS 2 & 3 on the input.
FIXED![/quote]
You wrote that in bold on purpose, not ? :wink: :twisted:
Greg
Well-known member
hey Kevin:
I have some of Fred's JFET opamps.
I'd be willing to mail one to you if you'd send it back when your finished. Just for comparison purposes. I plan to use it in my Forssell's when I get around to them.
I have some of Fred's JFET opamps.
I'd be willing to mail one to you if you'd send it back when your finished. Just for comparison purposes. I plan to use it in my Forssell's when I get around to them.
khstudio
Well-known member
Peter,
Yes. I figured I'd share everything I'm encountering with this project to help others out. I'm not sure if it's OK to short pins 1 & 3(neg input on DOA) but it seems to work fine & I don't hear a sound difference either way :idea: ??
Greg,
That would be cool BUT before we do that... I'm just getting ready to try & add the JFET stage ONLY in front of my Yamaha DOA output amp.
Is there any way you guys could look at the schematics to see if I need to change anything when doing this?
If you look at the 2 output schematics -
I'm going to cut the trace that splits the signal to the DOA section.
I'll let the signal go thru the JFET section, then go from R37 into
EITHER:
RV1- 10KA (just like the IC output) into my DOA + in
OR
A 100KA (wiper out into my DOA + in)
What do you guys think?
O, Thank you :thumb:
Yes. I figured I'd share everything I'm encountering with this project to help others out. I'm not sure if it's OK to short pins 1 & 3(neg input on DOA) but it seems to work fine & I don't hear a sound difference either way :idea: ??
Greg,
That would be cool BUT before we do that... I'm just getting ready to try & add the JFET stage ONLY in front of my Yamaha DOA output amp.
Is there any way you guys could look at the schematics to see if I need to change anything when doing this?
If you look at the 2 output schematics -
I'm going to cut the trace that splits the signal to the DOA section.
I'll let the signal go thru the JFET section, then go from R37 into
EITHER:
RV1- 10KA (just like the IC output) into my DOA + in
OR
A 100KA (wiper out into my DOA + in)
What do you guys think?
O, Thank you :thumb:
khstudio
Well-known member
[quote author="FredForssell"]Hey everyone,
The value of the series R working against the minimum on resistance of the LDR determines the maximum amount of gain reduction. I use VTL5C1 optos because a) they have 500 ohm on resistance, and b) because they have as fast an attack time as any opto I have seen (rate at about 1.5 ms).
The value of the series R that I use is 10k which gives a max gain reduction of 20 or about -26 dB. When the cell is completely turned off, I do not want the input impedance of the gain make-up/buffer amp to cause a signal drop across the series R, so I want the input impedance of the buffer amp to be at least 10x the value of the series R... in my example that means 100k. If you can live with some drop across the series R you can make the buffer input impedance smaller.
All of this brings up another point in choosing an opamp for your gain make-up/buffer amp. When the cell is off, the source impedance (seen from the input of the buffer looking back into the series R) is at least the value of the series R, or in this example at least 10k. So I'd recommend using a opamp with a JFET input stage, like our (gee, surprise) JFET-992/993 opamps, or any good low noise IC opamp with a JFET input stage.
[/quote]
What does he mean by "When the cell is completely turned off"?
I know what loading sounds like (like on a FUZZ FACE guitar pedal)
I don't think this would be THAT extreme but I feel like I'm hearing something... especially when compressing.
That's why I'm focusing on Fred's comment above & JFET/loading.
The only other BS I'd like to take care of is the ATTACK & RELEASE control... you can hardly turn them without being drastic. :roll:
I think a LOG taper would better suit, maybe. It would be nice if other builders of this thing could chime in. :green:
The value of the series R working against the minimum on resistance of the LDR determines the maximum amount of gain reduction. I use VTL5C1 optos because a) they have 500 ohm on resistance, and b) because they have as fast an attack time as any opto I have seen (rate at about 1.5 ms).
The value of the series R that I use is 10k which gives a max gain reduction of 20 or about -26 dB. When the cell is completely turned off, I do not want the input impedance of the gain make-up/buffer amp to cause a signal drop across the series R, so I want the input impedance of the buffer amp to be at least 10x the value of the series R... in my example that means 100k. If you can live with some drop across the series R you can make the buffer input impedance smaller.
All of this brings up another point in choosing an opamp for your gain make-up/buffer amp. When the cell is off, the source impedance (seen from the input of the buffer looking back into the series R) is at least the value of the series R, or in this example at least 10k. So I'd recommend using a opamp with a JFET input stage, like our (gee, surprise) JFET-992/993 opamps, or any good low noise IC opamp with a JFET input stage.
[/quote]
What does he mean by "When the cell is completely turned off"?
I know what loading sounds like (like on a FUZZ FACE guitar pedal)
I don't think this would be THAT extreme but I feel like I'm hearing something... especially when compressing.
That's why I'm focusing on Fred's comment above & JFET/loading.
The only other BS I'd like to take care of is the ATTACK & RELEASE control... you can hardly turn them without being drastic. :roll:
I think a LOG taper would better suit, maybe. It would be nice if other builders of this thing could chime in. :green:
khstudio
Well-known member
While I'm asking a shit load of questions...
What's your opinions on SERVOs?
Besides the JFET thing or these older Yamaha DOA's being a "slower" type of amp... I'm wondering if I'm hearing (or even liking) the Servo?
Like I said, I'm hearing some roll-off in the "Air & Subs".
No it's not from over compressing.
Just to note: my feedback cap is 47pf (like Yamaha used with these amps on the PM2000)
What's your opinions on SERVOs?
Besides the JFET thing or these older Yamaha DOA's being a "slower" type of amp... I'm wondering if I'm hearing (or even liking) the Servo?
Like I said, I'm hearing some roll-off in the "Air & Subs".
No it's not from over compressing.
Just to note: my feedback cap is 47pf (like Yamaha used with these amps on the PM2000)
khstudio
Well-known member
Hey guys...
I just had an EXCELLENT conversation with Fred... what a cool dude. :green:
He hasn't been around here for a long time and didn't know about a lot of the developments... like the input & output buffers, etc...
#1
The threshold is wired WRONG on the PCB & should go from left to right (low=no compression, to high) 100KA is correct. This is easy to fix when wiring & NOT PCB mounting.
#2
He did NOT like the idea of the input buffer amp (unless needed for differential input) he likes it Un-Balanced directly to the 4.99k for a cleaner signal path. (which I will be trying)
If this does end up sounding better it will make this project even cheaper!
#3
I told him about the added circuits & he had a few recommendations:
R11 @ 1k gives about 20dB Gain
Fred said it might be better @ around 3k for about 10dB Gain
Also, He mentioned that R6 @ 100k may be too high & told me to try 10k.
The last thing he said (when I asked him about his JFET-990-3)
"Once you try it you'll NEVER look back" Fred
I just may have to get them :roll:
He recommended that I DON"T add the JFET "Stage" in front of my Yamaha DOA... so that's out.
I just had an EXCELLENT conversation with Fred... what a cool dude. :green:
He hasn't been around here for a long time and didn't know about a lot of the developments... like the input & output buffers, etc...
#1
The threshold is wired WRONG on the PCB & should go from left to right (low=no compression, to high) 100KA is correct. This is easy to fix when wiring & NOT PCB mounting.
#2
He did NOT like the idea of the input buffer amp (unless needed for differential input) he likes it Un-Balanced directly to the 4.99k for a cleaner signal path. (which I will be trying)
If this does end up sounding better it will make this project even cheaper!
#3
I told him about the added circuits & he had a few recommendations:
R11 @ 1k gives about 20dB Gain
Fred said it might be better @ around 3k for about 10dB Gain
Also, He mentioned that R6 @ 100k may be too high & told me to try 10k.
The last thing he said (when I asked him about his JFET-990-3)
"Once you try it you'll NEVER look back" Fred
I just may have to get them :roll:
He recommended that I DON"T add the JFET "Stage" in front of my Yamaha DOA... so that's out.
Svart
Well-known member
damn I just got around to reading all this and it seems you have it all figured out!
Hmm, never thought about just leaving out the input buffers.. gonna have to try that myself!
I still haven't gotten around to fooling with the output buffer circuit again. using a CFB, I'm going to need to just sit down and figure out the right combination for everything.
Hmm, never thought about just leaving out the input buffers.. gonna have to try that myself!
I still haven't gotten around to fooling with the output buffer circuit again. using a CFB, I'm going to need to just sit down and figure out the right combination for everything.
khstudio
Well-known member
Even thought "Soundguy" Dave could be a real ass sometimes (to me at least) I respect his opinions. He had said the amps have a LOT to do with the sound. Not only do I agree, this is what Fred said... the sidechain is made to be transparent as possible. So keep it simple!!!
I THINK what I'm hearing is the Yamaha DOA.
I just listened without the input buffer & it does sound a little better (for me - unbalanced)
I'm about to try the 10k in place of the 100k (R6) (My output control)
Am I right in saying that without the input buffer (for differential input) I could just use an input transformer :?: Just curious.
I THINK what I'm hearing is the Yamaha DOA.
I just listened without the input buffer & it does sound a little better (for me - unbalanced)
I'm about to try the 10k in place of the 100k (R6) (My output control)
Am I right in saying that without the input buffer (for differential input) I could just use an input transformer :?: Just curious.
khstudio
Well-known member
OK,
I removed The input buffer amp & went straight into the 4.99k unbalanced... Sounds & works great... probably cleaner & better to my ears.
I changed the 1k to GND on the DOA output amp to 3.3k to lower gain, works great/Better.
Also, changed the 100k (on DOA schematic) to 10k, works great/Better.
NOTE: This is where my gain control is - instead of a resistor. (Wiper to input) Fred said a 10k would be better here. I asked him about the impedence & loading & he said not to worry about it. He also said the 100k was a little high & could roll off some high end. I liked the change better.
This thing is kickin & sound great + the compression is nice & smooth.
You guys could save yourself some time & money & remove the input amp all together. I don't see why you couldn't run an input tranny (for Balaced input) directly to the 4.99k too (Unless you are going Balanced & don't want to use a tranny).
Just wanted to add :idea: :idea: :idea:
The second half of the 2604 (used for the SERVO) is UN-USED!!!
I was talking with JC (Joel) tonite & he mentioned trying to use that section for the output buffer/amp. (it's a JFET & Runs on 24v & is already there)
I'm shocked no one thought of this before :shock:
I will be trying it on my second board to compare.
Sitting back & looking at this whole thing, it's very simple & should probably be kept that way. It just took a lot of research.
I'm sharing everything I'm going thru so others don't have to go thru this much BS.
I hope someone finds it useful.
I hate when all the info is scattered... it make a fairly easy project a PATA.
I removed The input buffer amp & went straight into the 4.99k unbalanced... Sounds & works great... probably cleaner & better to my ears.
I changed the 1k to GND on the DOA output amp to 3.3k to lower gain, works great/Better.
Also, changed the 100k (on DOA schematic) to 10k, works great/Better.
NOTE: This is where my gain control is - instead of a resistor. (Wiper to input) Fred said a 10k would be better here. I asked him about the impedence & loading & he said not to worry about it. He also said the 100k was a little high & could roll off some high end. I liked the change better.
This thing is kickin & sound great + the compression is nice & smooth.
You guys could save yourself some time & money & remove the input amp all together. I don't see why you couldn't run an input tranny (for Balaced input) directly to the 4.99k too (Unless you are going Balanced & don't want to use a tranny).
Just wanted to add :idea: :idea: :idea:
The second half of the 2604 (used for the SERVO) is UN-USED!!!
I was talking with JC (Joel) tonite & he mentioned trying to use that section for the output buffer/amp. (it's a JFET & Runs on 24v & is already there)
I'm shocked no one thought of this before :shock:
I will be trying it on my second board to compare.
Sitting back & looking at this whole thing, it's very simple & should probably be kept that way. It just took a lot of research.
I'm sharing everything I'm going thru so others don't have to go thru this much BS.
I hope someone finds it useful.
I hate when all the info is scattered... it make a fairly easy project a PATA.
Greg
Well-known member
[quote author="khstudio"]I'm sharing everything I'm going thru so others don't have to go thru this much BS.[/quote]
It's not BS, it's called circuit design. Ultimately the time and effort you've spent will make your compressor that much more special and unique.
I have Forssell JFET-992 and Millenia MM-99 opamps, both with JFET inputs. Let me know if you're interested in trying them. For what's it's worth, the Forssell opamps sound great!
It's not BS, it's called circuit design. Ultimately the time and effort you've spent will make your compressor that much more special and unique.
I have Forssell JFET-992 and Millenia MM-99 opamps, both with JFET inputs. Let me know if you're interested in trying them. For what's it's worth, the Forssell opamps sound great!
