Any one know the Focusrite mic pre topology?
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SSLtech
Well-known member
Lundahl transformer, NE5534, lastly (and very importantly) "pumpkin" toroidal tranny output stage, which is driven by a strongly biased 5534 with a high current class AB follower stage.
Contrast the Focusrite BLue Lundahl tranny/5534 with the V-series OEP type tranny/5534. One rocks, one doesn't.
It's not Rocket science, it's Rock it science!!!
Keith
Contrast the Focusrite BLue Lundahl tranny/5534 with the V-series OEP type tranny/5534. One rocks, one doesn't.
It's not Rocket science, it's Rock it science!!!
Keith
SSLtech
Well-known member
By the way, the green pre is very very different. Transformerless, high-gain discrete low-current high-gain front end... fully differential front half... about as polar opposite to the focusrite as you can get!
Keith
Keith
I think the gain control of the 110 schematic I have seen is a very nice design. 1/2 is a kind of transformer load/volume control between the transformer and 5534. The other half is used to set the gain of the opamp stage.
It looks to be a clever input level vs gain control. I would guess this was done to help prevent clipping and helps with noise.
It looks to be a clever input level vs gain control. I would guess this was done to help prevent clipping and helps with noise.
[quote author="SSLtech"]By the way, the green pre is very very different. Transformerless, high-gain discrete low-current high-gain front end... fully differential front half... about as polar opposite to the focusrite as you can get!
Keith[/quote]
So the front end of the Green pre is basically replacing the transformer in terms of converting a balanced signal and rejecting noise and also making up for the lack of gain you would normally see with a front loaded mic transformer?
And is the discrete hi-current stage following the 5534 in the Green pre similar to the Focusrite design?
Keith[/quote]
So the front end of the Green pre is basically replacing the transformer in terms of converting a balanced signal and rejecting noise and also making up for the lack of gain you would normally see with a front loaded mic transformer?
And is the discrete hi-current stage following the 5534 in the Green pre similar to the Focusrite design?
SSLtech
Well-known member
[quote author="rich"]And is the discrete hi-current stage following the 5534 in the Green pre similar to the Focusrite design?[/quote]
Which high-current stage is this? -I'm not aware of one in the green pre.
Keith
Which high-current stage is this? -I'm not aware of one in the green pre.
Keith
Oops, I was thinking of some circuit designs I've seen at the Jensen website and got them confused.
Any way besides the clever gain setup between the transformer and 5534, the Focusrite sounds like a very common circuit. It's funny for such a simple and "relatively" inexpensive set of components that people go so crazy about the Focusrite stuff. It makes me wonder how much a name and advertising can affect the sound of a preamp.
Any way besides the clever gain setup between the transformer and 5534, the Focusrite sounds like a very common circuit. It's funny for such a simple and "relatively" inexpensive set of components that people go so crazy about the Focusrite stuff. It makes me wonder how much a name and advertising can affect the sound of a preamp.
Flatpicker
Well-known member
[quote author="rich"]...but maybe that's just all you need.[/quote]Yes, a large part of the task is getting a pure, unadulterated signal from the mic properly impedance-coupled into the 5534, minus the phantom power dc voltage.
Kev
Well-known member
A couple of companies did the trafo & 5534 mic pre thing
A bit of step-up and a bit of gain at the 5534 and a bit of gain with the output can make for a good mic-pre. ... Neve IC ... see JLM Audio.
F110 at The Factory
http://www.diyfactory.com/projects/diy110/diy110.htm
The key could be as Keef said :
A bit of step-up and a bit of gain at the 5534 and a bit of gain with the output can make for a good mic-pre. ... Neve IC ... see JLM Audio.
F110 at The Factory
http://www.diyfactory.com/projects/diy110/diy110.htm
The key could be as Keef said :
Yes. That's the part that makes the sound of this unit.
I've build this preamp with an electronically balanced output and with the transformer ("pumpkin") output stage as in the original schematic. The transformer balanced version sounds very different and much better than the electronically balanced one, IMO.
It's not a cheap preamp to build even though it has an inexpensive 553x gain stages. Especially the "pumpkin" tx was very costly.
I think it's the unusual design of the output stage that makes this unit sound as it sounds. It could be interesting to try out the output with discrete amps and see if it makes a big difference.
-Okko
[quote author="omeiko"]
Yes. That's the part that makes the sound of this unit.
I've build this preamp with an electronically balanced output and with the transformer ("pumpkin") output stage as in the original schematic. The transformer balanced version sounds very different and much better than the electronically balanced one, IMO.
It's not a cheap preamp to build even though it has an inexpensive 553x gain stages. Especially the "pumpkin" tx was very costly.
-Okko[/quote]
I was always under the impression that a well designed output transformer has the least amount to do with the sound, actually I heard that from the owner of Jensen transformers, and a couple other highly respected fellas. Is that pumpkin toroidal transformer causing some musical distortion, meaning it's not very neutral?
I've previously built several 990 preamps, a couple with output transformers and a couple with, and to my ears the sound was extremely close, maybe just a tiny bit warmer with the output transformers.
Also does anyone know which particular input and output transformer Focusrite used, and was the toroidal output transformer used on the red series or the top of line blue series?
Jensen transformers
Yes. That's the part that makes the sound of this unit.
I've build this preamp with an electronically balanced output and with the transformer ("pumpkin") output stage as in the original schematic. The transformer balanced version sounds very different and much better than the electronically balanced one, IMO.
It's not a cheap preamp to build even though it has an inexpensive 553x gain stages. Especially the "pumpkin" tx was very costly.
-Okko[/quote]
I was always under the impression that a well designed output transformer has the least amount to do with the sound, actually I heard that from the owner of Jensen transformers, and a couple other highly respected fellas. Is that pumpkin toroidal transformer causing some musical distortion, meaning it's not very neutral?
I've previously built several 990 preamps, a couple with output transformers and a couple with, and to my ears the sound was extremely close, maybe just a tiny bit warmer with the output transformers.
Also does anyone know which particular input and output transformer Focusrite used, and was the toroidal output transformer used on the red series or the top of line blue series?
Jensen transformers
Well the pumpkin certainly has some tone but I don't know if that's distortion or something related to the tertiary feedback topology. It's not only the transformer but the whole driver stage that contributes to the sound.
I've done some experiments with different op-amps and output transformers when I was prototyping a preamp project and what I learned was that it's very hard to predict how something is going to sound like. Sometimes a tx that sucked with a certain op-amp worked great with another op-amp and vice versa. The pumpkin has more tone than for example a lundahl LL5402. So the op-tx does affect the sound but how much it depends on the situation and application.
BTW the pumkin tx can?t be used without a proper connection of the tertiary winding. I don?t know why but it distorts weirdly when it?s left open.
-Okko
I've done some experiments with different op-amps and output transformers when I was prototyping a preamp project and what I learned was that it's very hard to predict how something is going to sound like. Sometimes a tx that sucked with a certain op-amp worked great with another op-amp and vice versa. The pumpkin has more tone than for example a lundahl LL5402. So the op-tx does affect the sound but how much it depends on the situation and application.
BTW the pumkin tx can?t be used without a proper connection of the tertiary winding. I don?t know why but it distorts weirdly when it?s left open.
-Okko
Send me one of dem pumpkins!
:razz:
:razz:
Tekay
Well-known member
I bought some moduls with pumpkin outputs from here!
http://www.allprogear.com/misc.html
If you buy more than one you'll probably get a better price! There'a also 8 concentric ELMA 2 pol / 3 pos in there complete with knobs! + some 1034 IC's
http://www.allprogear.com/misc.html
If you buy more than one you'll probably get a better price! There'a also 8 concentric ELMA 2 pol / 3 pos in there complete with knobs! + some 1034 IC's
Samuel Groner
Well-known member
BTW, if someone has nicely drawn info on the red or blue colored Foc-stuff, drop me a PM, please!
Samuel
Samuel
SSLtech
Well-known member
Platinum = cynical attempt to sell using the Focusrite name.
You have to understand the history of the company.
The original ISA Blue series were designed by Rupert, who listens to what stuff sounds like. 5534s are excellent op amps. I know you'll read otherwise, but consider the source: many of these people saying so are sheep rather than engineers.
Focusrite went broke after Rupert was beseiged and plagued by people begging him to make consoles. Despite £1,500,000 (about $3,000,000 at the time) in orders, the company cash flow was so inadequately set up for large-frame manufature that it crashed. Phil Dudderidge (of Soundcraft) saw an opportunity and bought in, keeping the name alive. Rupert was gone, but the existing designs were now Focusrite's property (and therefore Phil could use them)
The Red series was an attempt to make basically the same stuff, but with some cost savings. Many boards inside red equipment that I've worked on have had alternative parts placings for blue and red, so the same motehr board can be used, but perhaps with some transformers skipped here and there, or some cheaper pots or something.
The Green series was the cynical attempt to sell based on the good name of Focusrite, founded by Rupert's early work. It's totally transformerless from everything I've ever seen, the cases are cheap castings, the knobs are cheap mouldings. The gear sounds like utter crap and doesn't deserve to bear the same name.
The Platinum is actually branded as the "entry-level" Focusrite gear. I saw one once. It made me shiver just to be in the same room as it. I never looked inside it, but I felt utter certainty that if it really was a step down from the greens, I wanted no part of it.
My platinum experience is therefore insufficient to give an opinion, but the Focusrite history lesson should put the product lines into better perspective.
Rich, I get the distinct impression from your postings that you're influenced more by what you think something should sound like rather than actually listening to it... I don't mean this as a criticism, but it sounds like your friend summed the original design up nicely: a transformer, a 5534 and a high gain stage (the transformer was omitted from his summary)
If it's simple, it might just sould like gold. That's how it frequently was for tubes, after all!
Keith
You have to understand the history of the company.
The original ISA Blue series were designed by Rupert, who listens to what stuff sounds like. 5534s are excellent op amps. I know you'll read otherwise, but consider the source: many of these people saying so are sheep rather than engineers.
Focusrite went broke after Rupert was beseiged and plagued by people begging him to make consoles. Despite £1,500,000 (about $3,000,000 at the time) in orders, the company cash flow was so inadequately set up for large-frame manufature that it crashed. Phil Dudderidge (of Soundcraft) saw an opportunity and bought in, keeping the name alive. Rupert was gone, but the existing designs were now Focusrite's property (and therefore Phil could use them)
The Red series was an attempt to make basically the same stuff, but with some cost savings. Many boards inside red equipment that I've worked on have had alternative parts placings for blue and red, so the same motehr board can be used, but perhaps with some transformers skipped here and there, or some cheaper pots or something.
The Green series was the cynical attempt to sell based on the good name of Focusrite, founded by Rupert's early work. It's totally transformerless from everything I've ever seen, the cases are cheap castings, the knobs are cheap mouldings. The gear sounds like utter crap and doesn't deserve to bear the same name.
The Platinum is actually branded as the "entry-level" Focusrite gear. I saw one once. It made me shiver just to be in the same room as it. I never looked inside it, but I felt utter certainty that if it really was a step down from the greens, I wanted no part of it.
My platinum experience is therefore insufficient to give an opinion, but the Focusrite history lesson should put the product lines into better perspective.
Rich, I get the distinct impression from your postings that you're influenced more by what you think something should sound like rather than actually listening to it... I don't mean this as a criticism, but it sounds like your friend summed the original design up nicely: a transformer, a 5534 and a high gain stage (the transformer was omitted from his summary)
If it's simple, it might just sould like gold. That's how it frequently was for tubes, after all!
Keith
G
Guest
Guest
[quote author="SSLtech"]Focusrite went broke after Rupert was beseiged and plagued by people begging him to make consoles. Despite £1,500,000 (about $3,000,000 at the time) in orders, the company cash flow was so inadequately set up for large-frame manufature that it crashed. Phil Dudderidge (of Soundcraft) saw an opportunity and bought in, keeping the name alive. Rupert was gone, but the existing designs were now Focusrite's property (and therefore Phil could use them)
Keith[/quote]
Interesting Keith...
Reminds me why Audient use their business model.. (Make to Order and... then farming ALL the work out to sub contractors... no in house assembly)
Keith[/quote]
Interesting Keith...
Reminds me why Audient use their business model.. (Make to Order and... then farming ALL the work out to sub contractors... no in house assembly)
