Official Forssell Limiter Build thread
- Thread starter soundguy
- Start date
Help Support GroupDIY Audio Forum:
clintrubber
Well-known member
... question removed ...
khstudio
Well-known member
[quote author="clintrubber"]Hi,
I'm looking for the accompanying schematic of the Tommytones-PCB.
I've been browsing the various Forssell-opto-threads here but couldn't find something like it. I did find sections of the circuit and also several dead links.
Is the PCB-equivalent schematic indeed spread out across various sections (like at http://www.diyfactory.com/projects/forsselllimiter/ffosc.htm which will do fine of course) or is there also a full complete one available ?
Thanks,
Peter[/quote]
mAN i THOUGHT i WAS THE ONLY ONE...
I have 2 boards & I'm about ready to dive in also but I'm a little confussed.
Peter, please post back if you find out anything.
Also, is there a standard way of building these or does everyone pretty much customize to their liking???
Kevin
I'm looking for the accompanying schematic of the Tommytones-PCB.
I've been browsing the various Forssell-opto-threads here but couldn't find something like it. I did find sections of the circuit and also several dead links.
Is the PCB-equivalent schematic indeed spread out across various sections (like at http://www.diyfactory.com/projects/forsselllimiter/ffosc.htm which will do fine of course) or is there also a full complete one available ?
Thanks,
Peter[/quote]
mAN i THOUGHT i WAS THE ONLY ONE...
I have 2 boards & I'm about ready to dive in also but I'm a little confussed.
Peter, please post back if you find out anything.
Also, is there a standard way of building these or does everyone pretty much customize to their liking???
Kevin
Kev
Well-known member
on the subject of dead links and missing info etc
if you have any stuff you think or want tied to this project, I'm happy to add it to what is currently at the above link.
if you have any stuff you think or want tied to this project, I'm happy to add it to what is currently at the above link.
clintrubber
Well-known member
[quote author="khstudio"][quote author="clintrubber"]Hi,
I'm looking for the accompanying schematic of the Tommytones-PCB.
Is the PCB-equivalent schematic indeed spread out across various sections (like at http://www.diyfactory.com/projects/forsselllimiter/ffosc.htm which will do fine of course) or is there also a full complete one available ?
Thanks,
Peter[/quote]
mAN i THOUGHT i WAS THE ONLY ONE...
I have 2 boards & I'm about ready to dive in also but I'm a little confussed.[/quote]
Hmm, would you believe that during my morning shower I was in fact planning to delete my post above ? Since I realized all the info was just there, only in sections. No problem here, I'm used to that kind of representation, I was only a bit lazy I have to admit.
There's also the silkscreening guiding you what to put where.
If you want to have 'one' schematic then you could always copy & paste of course. Given those separate sections being available I can't imagine there's also a full one around (unless someone goes copy&pasting).
Regards,
Peter
I'm looking for the accompanying schematic of the Tommytones-PCB.
Is the PCB-equivalent schematic indeed spread out across various sections (like at http://www.diyfactory.com/projects/forsselllimiter/ffosc.htm which will do fine of course) or is there also a full complete one available ?
Thanks,
Peter[/quote]
mAN i THOUGHT i WAS THE ONLY ONE...
I have 2 boards & I'm about ready to dive in also but I'm a little confussed.[/quote]
Hmm, would you believe that during my morning shower I was in fact planning to delete my post above ? Since I realized all the info was just there, only in sections. No problem here, I'm used to that kind of representation, I was only a bit lazy I have to admit.
There's also the silkscreening guiding you what to put where.
If you want to have 'one' schematic then you could always copy & paste of course. Given those separate sections being available I can't imagine there's also a full one around (unless someone goes copy&pasting).
Regards,
Peter
khstudio
Well-known member
:thumb:
I see what you mean... not a problem just a hair more work.
Does TOMMYTONES have a site :?: I can't find it.
I read that he had one with some more info... mayby like, what's new on the rev. 1-C boards :?:
I really only have a few questions:
Do you NEED a seperate suppply board to run a pair or can you just use ONE of the boards & share?
Has anyone found a good resource for the POTs... they aren't too cheap -
& 2x that for a stereo unit.
Potentiometers:
500K Lin $11.28 2 $22.56 Newark 03F7522 Clarostat 308NPC500K
100K Log $6.60 1 $6.60 Mouser 652-91A1A-B24-D20 Bourn 91A1A-B24-D20
5K Rev. Log $8.15 1 $8.15 Newark 90B4116 Bourn 91A1A-B24-T13
2k Trimmer $2.20 1 $2.20 Mouser 652-3296W-1-202 Bourn 3296W-1-202
500R trimmer $2.20 1 $2.20 Mouser 652-3296W-1-501 Bourn 3296W-1-501
Thanks,
Kevin
I see what you mean... not a problem just a hair more work.
Does TOMMYTONES have a site :?: I can't find it.
I read that he had one with some more info... mayby like, what's new on the rev. 1-C boards :?:
I really only have a few questions:
Do you NEED a seperate suppply board to run a pair or can you just use ONE of the boards & share?
Has anyone found a good resource for the POTs... they aren't too cheap -
& 2x that for a stereo unit.
Potentiometers:
500K Lin $11.28 2 $22.56 Newark 03F7522 Clarostat 308NPC500K
100K Log $6.60 1 $6.60 Mouser 652-91A1A-B24-D20 Bourn 91A1A-B24-D20
5K Rev. Log $8.15 1 $8.15 Newark 90B4116 Bourn 91A1A-B24-T13
2k Trimmer $2.20 1 $2.20 Mouser 652-3296W-1-202 Bourn 3296W-1-202
500R trimmer $2.20 1 $2.20 Mouser 652-3296W-1-501 Bourn 3296W-1-501
Thanks,
Kevin
Kev
Well-known member
[quote author="khstudio"]Does TOMMYTONES have a site :?: I can't find it.[/quote]I don't think so
but I haven't communicated with ToM for a while
basically the stuff is at the Factory
but others do have more/different info on their sites and in threads
if someones wants to check it out I can add stuff to the Factory page but no time right now to analyse it all
but I haven't communicated with ToM for a while
basically the stuff is at the Factory
but others do have more/different info on their sites and in threads
if someones wants to check it out I can add stuff to the Factory page but no time right now to analyse it all
tommytones
Well-known member
All the info for this project is at Kev's site (follow the link above). There's not 1 file which contains all of the information...not yet anyhow. If someone wants to do that, go right ahead. Look at the parts list...it shows each section broken down.
Rev1c boards which come from Gustav have some changes from the the red boards others are building. The 5534 output stage has been changed to accomodate for the make-up gain pot and other changes which need to be mod'ed on the red boards. These changes can be seen here. Kev please load this to the main project page. I also removed a couple of stabilizing caps as they were redundant. That's it.
As for the 5534 output circuit, if you read back you'll see I measured some loss in the low freq's. I made some changes to R33 around the fet and now the bandwidth is quite acceptable. My notes say it was changed to 1K from 10K. Probably right but my notes are a bit sketchy and I haven't looked at my boards to verify. Not to mention this happened a long time ago. Try it out and take some measurements.
As for calibration, I'm sure I wrote up something for this but I can't find it. Whatever the case, there not much to know. You have to set yourself up and take some measurements. Futz with it until you get output close to the metering...that's about how I did it. I only managed to meter 12db reduction accurately...past this meant inaccuracy metering small reduction. If I'm gonna squash signal past 12db I don't really need to see it so this works out fine for me.
Rev1c boards which come from Gustav have some changes from the the red boards others are building. The 5534 output stage has been changed to accomodate for the make-up gain pot and other changes which need to be mod'ed on the red boards. These changes can be seen here. Kev please load this to the main project page. I also removed a couple of stabilizing caps as they were redundant. That's it.
As for the 5534 output circuit, if you read back you'll see I measured some loss in the low freq's. I made some changes to R33 around the fet and now the bandwidth is quite acceptable. My notes say it was changed to 1K from 10K. Probably right but my notes are a bit sketchy and I haven't looked at my boards to verify. Not to mention this happened a long time ago. Try it out and take some measurements.
As for calibration, I'm sure I wrote up something for this but I can't find it. Whatever the case, there not much to know. You have to set yourself up and take some measurements. Futz with it until you get output close to the metering...that's about how I did it. I only managed to meter 12db reduction accurately...past this meant inaccuracy metering small reduction. If I'm gonna squash signal past 12db I don't really need to see it so this works out fine for me.
tommytones
Well-known member
and no, I don't have a web-site...yet :green:
khstudio
Well-known member
Thanks Tom :thumb:
I'm on it.
I'm on it.
Kev
Well-known member
thanks ToM
that jpg is a changes so I guess it doesn't replace ... just adds to your stuff on the page
I'll add it to the bottom of the list with a short err
??
" The 5534 output stage has been changed to accomodate for the make-up gain pot and other changes which need to be mod'ed on the red boards. " ... or .... something ?
[EDIT] update done jpg added
Tom
let me know if I say something out of turn
I try to answer on behalf of people and lately i seem to be putting my foot in it
IF the calibration stuff turns up ... yell !!
it's all good
:thumb:
OH !!!
and big thanks to Fred Forssell himself
go visit him and say hello
... I think he may have an EQ on the way soon
that jpg is a changes so I guess it doesn't replace ... just adds to your stuff on the page
I'll add it to the bottom of the list with a short err
??
" The 5534 output stage has been changed to accomodate for the make-up gain pot and other changes which need to be mod'ed on the red boards. " ... or .... something ?
[EDIT] update done jpg added
Tom
let me know if I say something out of turn
I try to answer on behalf of people and lately i seem to be putting my foot in it
IF the calibration stuff turns up ... yell !!
it's all good
:thumb:
OH !!!
and big thanks to Fred Forssell himself
go visit him and say hello
... I think he may have an EQ on the way soon
TomWaterman
Well-known member
Alright guys, just wondering if the VU meter circuit here is all good to use for GR?
http://www.diyfactory.com/projects/forsselllimiter/helsing_vu.jpg
I've just re-read thru the whole thread and some guys said it works, others not. Soundguy hasn't been around for a while - if you're about Dave did you ever get the VUs rocking? Hitchhiker you said it works fine - is that still the case?
Cheers Tom
http://www.diyfactory.com/projects/forsselllimiter/helsing_vu.jpg
I've just re-read thru the whole thread and some guys said it works, others not. Soundguy hasn't been around for a while - if you're about Dave did you ever get the VUs rocking? Hitchhiker you said it works fine - is that still the case?
Cheers Tom
clintrubber
Well-known member
Hi,
While stuffing the (mirrored) boards some things caught my eye:
#1
On the rev1C-PCBs there's the added provision for connecting the
make-up gainpot for the JFET+5534-output buffer.
C38 (33pF) is in // with R42 (10k), so not in // with R42+100k-pot.
I'm not sure if this was done on purpose to avoid the changing BW
when gain is changed, but we may want to correct this.
Putting the cap across both resistors will still give a BW of 44kHz
at max gain.
If this sounds too low then you could decrease C38. Or of course do the
gain by means of making R38 variable, as also mentioned before (& increase C37).
#2
People considering using TL072 in the sidechain i.s.o. the more
expensive OPA2604 will want to increase R24,25 since the '072 won't be happy
with such low impedance levels.
Don't know why they were chosen this low BTW; the OPA2604 can handle this,
but making them both larger would still work as well I expect and it will
'strain' the opamps U5A,B less.
#3
In the more useless department we could toy around with the MODE-pin of
the LM3916.
I was thinking about a meaningful use for the dot/bar-selection but haven't
settled on anything yet.
The application-circuit op page 20 of the '3916 datasheet is fun,
using dot-mode but automatically changing to bar when full GR is reached
(for a nice emphasis that you're using a lot of GR, or just nice to have
now Xmas is coming up).
The 'best' I could think of so far is to have 'bar' when the unit is
active and 'dot' when bypassed (provision needs to be made that the
sidechain keeps working but doesn't drive the signal-attenuator any longer). This will show you the amount of GR you're going to get when enabling the compressor. You could of course still add a separate green/red LED or something for bypass-status.
FWIW.... and chime in when somebody has other more fancy suggestions.
Regards,
Peter
While stuffing the (mirrored) boards some things caught my eye:
#1
On the rev1C-PCBs there's the added provision for connecting the
make-up gainpot for the JFET+5534-output buffer.
C38 (33pF) is in // with R42 (10k), so not in // with R42+100k-pot.
I'm not sure if this was done on purpose to avoid the changing BW
when gain is changed, but we may want to correct this.
Putting the cap across both resistors will still give a BW of 44kHz
at max gain.
If this sounds too low then you could decrease C38. Or of course do the
gain by means of making R38 variable, as also mentioned before (& increase C37).
#2
People considering using TL072 in the sidechain i.s.o. the more
expensive OPA2604 will want to increase R24,25 since the '072 won't be happy
with such low impedance levels.
Don't know why they were chosen this low BTW; the OPA2604 can handle this,
but making them both larger would still work as well I expect and it will
'strain' the opamps U5A,B less.
#3
In the more useless department we could toy around with the MODE-pin of
the LM3916.
I was thinking about a meaningful use for the dot/bar-selection but haven't
settled on anything yet.
The application-circuit op page 20 of the '3916 datasheet is fun,
using dot-mode but automatically changing to bar when full GR is reached
(for a nice emphasis that you're using a lot of GR, or just nice to have
now Xmas is coming up).
The 'best' I could think of so far is to have 'bar' when the unit is
active and 'dot' when bypassed (provision needs to be made that the
sidechain keeps working but doesn't drive the signal-attenuator any longer). This will show you the amount of GR you're going to get when enabling the compressor. You could of course still add a separate green/red LED or something for bypass-status.
FWIW.... and chime in when somebody has other more fancy suggestions.
Regards,
Peter
clintrubber
Well-known member
Here we go again w.r.t. parallel compression:
I've had a look at the JFET & 5534 output-stage and
it'll be easy to add one of those 'blend'-pots, as also
often discussed for the G-SSL etc etc.
Having a separate blend-circuit that can be used for any box
is still a good appraoch, but adding it here integral to the
box is easy, so why not add it right away?
But first of course the question whether that would make sense,
opto-comp with parallel-compression.
For an application for say elec-bass it'd be nice to keep the
attack, but as I understand optos are not that fast so you keep
that anyway, correct ?
So what are the impressions of people that have worked with this
circuit (or other opto-comps) ? Does parallel compression make sense with an opto-comp ?
Thanks,
Peter
I've had a look at the JFET & 5534 output-stage and
it'll be easy to add one of those 'blend'-pots, as also
often discussed for the G-SSL etc etc.
Having a separate blend-circuit that can be used for any box
is still a good appraoch, but adding it here integral to the
box is easy, so why not add it right away?
But first of course the question whether that would make sense,
opto-comp with parallel-compression.
For an application for say elec-bass it'd be nice to keep the
attack, but as I understand optos are not that fast so you keep
that anyway, correct ?
So what are the impressions of people that have worked with this
circuit (or other opto-comps) ? Does parallel compression make sense with an opto-comp ?
Thanks,
Peter
khstudio
Well-known member
Correct. I wouldn't even think about parallel-compression with my LA-2A on bass... opto does what it does you know.
I can't say I've ever tried it either but I wouldn't think 2 strong attacts would be good except for an effect.
But if it's easy enough to add without bothering the circuit, why not?
Peter,
Please post back when you get yours done. I'm excited to hear what your opinion is & what direction you took.
Kevin
clintrubber
Well-known member
[quote author="khstudio"]I wouldn't even think about parallel-compression with my LA-2A on bass... opto does what it does you know.[/quote]
Hi Kevin,
Oops, here Keith says exactly that (not):
I'm not saying you are, and I don't even touch the subject of what's good or bad, but when I see most basses are fed through a LA2A then it doesn't tell me yet whether that would work for me.
So indeed, while at it why not add the blend-thing?
It's just the usual thing of preventing to add too many gizmo's & whistles to a project. If done well it'll make it great with endless possibilities but when will it be finished ?
:wink:
For me though, thinking about adapting/expanding/simplifying/overkilling circuits & blocks is often the most fun part of a project.
I'll sure post what I've come up with :thumb:
Bye,
Peter
Hi Kevin,
Oops, here Keith says exactly that (not):
But just as an example of course.
Problem is that I suspect I'm not after the 'usual' kind of bass sound.
I'm not saying you are, and I don't even touch the subject of what's good or bad, but when I see most basses are fed through a LA2A then it doesn't tell me yet whether that would work for me.
So indeed, while at it why not add the blend-thing?
It's just the usual thing of preventing to add too many gizmo's & whistles to a project. If done well it'll make it great with endless possibilities but when will it be finished ?
:wink: For me though, thinking about adapting/expanding/simplifying/overkilling circuits & blocks is often the most fun part of a project.
I'll sure post what I've come up with :thumb:
Sounds intriguing for someone like me who knows 'opto' so far only from a plugin-emulation :wink: Could you tell a bit more 'what' is does ? (as far as possible)
Bye,
Peter
khstudio
Well-known member
I feel that opto type compression (at least the La-2A & possibly like my Avalon 747 OPTO - which uses a Vactrol too) are very musical. They seem to wrap around the sound & while controlling it, they seem to maintain a lot of character & life... and attack.
Different animals indeed.
Opto, FET, VCA.
Kevin
clintrubber
Well-known member
Thanks Keven for adding.
A while back I've been lusting after one of those Apex opto-pedals but guess that the ff-opto will be a more than nice alternative to say the least. First opto, we'll see what it'll do for me.
Bye,
Peter
A while back I've been lusting after one of those Apex opto-pedals but guess that the ff-opto will be a more than nice alternative to say the least. First opto, we'll see what it'll do for me.
Bye,
Peter
dustbro
Well-known member
Is it possible to use the sidechain schematic and a Sifam AL-29WF from the G1176 project instead of the LED for compression?
Anyone know of a similar meter to the sifam that would also work in this application?
thanks
Dan
Anyone know of a similar meter to the sifam that would also work in this application?
thanks
Dan
Lowfreq
Well-known member
Ok, it's late here, and my brain is fried. :twisted:
I've been working on my forssell board, with the DOA input and output,(i'm using JLM 99v's) and I've run into something odd that I haven't seen anyone mention round here so far.
When I use an input DOA, it works almost like a gate, only letting through louder peak signals before cutting down to silence. Sounds like a gate or a bad connection (I'm guessing bad connection)
Yet when I take the input DOA out, the compressor passes signal. :shock: :?
Am I missing something here? Can it run without the discreet input? (there are no parts from the IC curcuit installed at all)
None of my preamps pass signal when I take the opamp out, so why would this one? And why does it not like it when it does have an input DOA?
I'll double check all my values tomorrow when I'm not so sleepy, and do some signal tracing, but this is confusing the crap outta me. Voltages are all good.
I thought I grounded it correctly too, but It buzzes when linked up to a preamp, yet the comp and pre are quiet on their own. I double checked the pre just in case, and it's near silent....................
Aaaarrrrggghhh, I need to go to sleep and try again tomorrow. But any suggestions would be awesome :green:
I've been working on my forssell board, with the DOA input and output,(i'm using JLM 99v's) and I've run into something odd that I haven't seen anyone mention round here so far.
When I use an input DOA, it works almost like a gate, only letting through louder peak signals before cutting down to silence. Sounds like a gate or a bad connection (I'm guessing bad connection)
Yet when I take the input DOA out, the compressor passes signal. :shock: :?
Am I missing something here? Can it run without the discreet input? (there are no parts from the IC curcuit installed at all)
None of my preamps pass signal when I take the opamp out, so why would this one? And why does it not like it when it does have an input DOA?
I'll double check all my values tomorrow when I'm not so sleepy, and do some signal tracing, but this is confusing the crap outta me. Voltages are all good.
I thought I grounded it correctly too, but It buzzes when linked up to a preamp, yet the comp and pre are quiet on their own. I double checked the pre just in case, and it's near silent....................
Aaaarrrrggghhh, I need to go to sleep and try again tomorrow. But any suggestions would be awesome :green:
Similar threads
