CJ
Well-known member
:grin:
Name That Engineer
- Thread starter CJ
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:grin:
NewYorkDave
Well-known member
So, you met Mr. Narma, I presume? That looks like it was shot in a hotel lobby. Great picture, by the way.
NewYorkDave
Well-known member
All I had to do was to notice that he's holding a Fairchild schematic.
CJ
Well-known member
Rein sat down with me for a little over three hours and we talked about as much stuff as he could remember pertaining to the 670.
Rein is 82 but looks to be in great shape.
I have to listen to the tape to remember it all, as I was in a semi state of shock the whole time, but a few things I remember, some of it might need further verification:
only about 45 units were ever sold
he assembeled the first ten himself
he designed it in his cellar before coming on board Fairchild
he liscensed it to Fairchild and was to recieve aproximately one hundread dollars per unit, but can't remember if he ever recieved said monies
the prototype was sold to somebody and it looked pretty much like the final units
tube data sheets from an RCA loose leaf tube handbook were used
the reason for designing the 670 was because he felt that there were no compressors out at the time which did the music justice-most were "like using a hammer and chisel, when they should have been like using a scapel"...
the front panel was designed by him
the instruction manual was written by him
one of the reaosns for using the 6386 was the relatively low transconductance which meant less distortion
about four out of five 6386 tubes passed matching tests
he wanted more headroom than most compressors had
he wanted a very low output impedance on the control amp, it is close close to 0.5 ohms
different time constants were used to catch different things- some of the time constant settings have dual values, one for catching a symbol crash, the next for other things
they sold for about five or six hundread dollars back then
they took three to four days to build
they use Weston meters and Allen Bradley pots
transformers were picked according to the turns ratios that he needed
transformer balance was a factor in picking certain brands
relatively little test equipment was used while desinging the 670 , a scope, oscilator, VTVM....
transformer balance was tested by inverting the signals feeding the transformers and looking at the output
the 670 was first intended as a tool for a cutting lathe
the 660 chassis was done by Rein, but someone else layed out the chassis for the stereo version
no regulation was needed on the B+ voltages on the last two control amp stages because of the negative feedback
the negative feedback helped lower the impedance of the control amp
the control amp input resitors form a pad to help isolate the output signal from the control amp input transformer
the tapped ac threshold pot was used so that the control matched up with what the compressor was doing
if he were to design the 670 today, he would use a solid state sidechain (op amp) , solid state regulated power supply, the unit would be smaller...etc ( I tried to talk him out of this!)
the push pull balanced circuit cancels second order distortion
hum from the tube heaters is cancelled by the push-pull circuit
the compressor was designed to be as clean as possible from a circuit standpoint, as can be seen in the audio path
it is fairly simple, an audio amp, a side chain and a power supply (yeah, right!)
he can't recall Les Paul having anything to do with tweaking the circuit
he did help Les Paul with that Ampex eight track prototype, it needed a lot of work as far as distortion, etc, when it first arrived
Rein used to hang out a bit at Rudy VanGelder's studio. He modded about twenty Nuemann U-47's that came through at the time. The mod involved reducing the gain by connecting the pentode as a triode and converting the circuit to a cathode follower in order to match up with the transformer better.
Rein plays piano, played coronet and trumpet in a marching band, loves the sound of a live orchestra and has yet to hear recorded music come anywhere close to the experience of hearing a live orchestra, and thus does not listen to a lot of recorded music.
he was very pleased to learn that a 670 was used in the recording of some Beatles things.
I had been dreaming of doing this interview for about three years, ever since I first saw the 670 schematic, so am very pleased that it came off so well.
Sorry if this was stuff we already knew, but it's good to hear it from the designer.
Thank You Rein!
cj :thumb:
Rein is 82 but looks to be in great shape.
I have to listen to the tape to remember it all, as I was in a semi state of shock the whole time, but a few things I remember, some of it might need further verification:
only about 45 units were ever sold
he assembeled the first ten himself
he designed it in his cellar before coming on board Fairchild
he liscensed it to Fairchild and was to recieve aproximately one hundread dollars per unit, but can't remember if he ever recieved said monies
the prototype was sold to somebody and it looked pretty much like the final units
tube data sheets from an RCA loose leaf tube handbook were used
the reason for designing the 670 was because he felt that there were no compressors out at the time which did the music justice-most were "like using a hammer and chisel, when they should have been like using a scapel"...
the front panel was designed by him
the instruction manual was written by him
one of the reaosns for using the 6386 was the relatively low transconductance which meant less distortion
about four out of five 6386 tubes passed matching tests
he wanted more headroom than most compressors had
he wanted a very low output impedance on the control amp, it is close close to 0.5 ohms
different time constants were used to catch different things- some of the time constant settings have dual values, one for catching a symbol crash, the next for other things
they sold for about five or six hundread dollars back then
they took three to four days to build
they use Weston meters and Allen Bradley pots
transformers were picked according to the turns ratios that he needed
transformer balance was a factor in picking certain brands
relatively little test equipment was used while desinging the 670 , a scope, oscilator, VTVM....
transformer balance was tested by inverting the signals feeding the transformers and looking at the output
the 670 was first intended as a tool for a cutting lathe
the 660 chassis was done by Rein, but someone else layed out the chassis for the stereo version
no regulation was needed on the B+ voltages on the last two control amp stages because of the negative feedback
the negative feedback helped lower the impedance of the control amp
the control amp input resitors form a pad to help isolate the output signal from the control amp input transformer
the tapped ac threshold pot was used so that the control matched up with what the compressor was doing
if he were to design the 670 today, he would use a solid state sidechain (op amp) , solid state regulated power supply, the unit would be smaller...etc ( I tried to talk him out of this!)
the push pull balanced circuit cancels second order distortion
hum from the tube heaters is cancelled by the push-pull circuit
the compressor was designed to be as clean as possible from a circuit standpoint, as can be seen in the audio path
it is fairly simple, an audio amp, a side chain and a power supply (yeah, right!)
he can't recall Les Paul having anything to do with tweaking the circuit
he did help Les Paul with that Ampex eight track prototype, it needed a lot of work as far as distortion, etc, when it first arrived
Rein used to hang out a bit at Rudy VanGelder's studio. He modded about twenty Nuemann U-47's that came through at the time. The mod involved reducing the gain by connecting the pentode as a triode and converting the circuit to a cathode follower in order to match up with the transformer better.
Rein plays piano, played coronet and trumpet in a marching band, loves the sound of a live orchestra and has yet to hear recorded music come anywhere close to the experience of hearing a live orchestra, and thus does not listen to a lot of recorded music.
he was very pleased to learn that a 670 was used in the recording of some Beatles things.
I had been dreaming of doing this interview for about three years, ever since I first saw the 670 schematic, so am very pleased that it came off so well.
Sorry if this was stuff we already knew, but it's good to hear it from the designer.
Thank You Rein!
cj :thumb:
ioaudio
Well-known member
wow! great first hand info! thanks a lot!
Larrchild
Well-known member
Great Job, and Thank You!
CJ
Well-known member
And thank you! I mentioned your 670 to Rein by the way. He was very pleased that someone was still doing his circuit. And he was also amused when I told him that there were software plug-ins, but they did nott do the 670 justice.
And thanks to PRR for that clean schematic. Rein took a copy with him along with some color glossies of the chassis that I had printed.
I will listen to the tape to gleen further details on the 670. There were db levels mentioned from time to time, etc.
Thanks to PRR also for the hint on using a digital voice recorder. Saved interupting the interview to change tapes, batteries, etc. I did take about twenty minutes of video, just enough not to be intrusive. There was no power outlets in the hotel lobby, so everything had to be battery operated. I lucked out with a table large enough to hold the schematic!
And thanks to PRR for that clean schematic. Rein took a copy with him along with some color glossies of the chassis that I had printed.
I will listen to the tape to gleen further details on the 670. There were db levels mentioned from time to time, etc.
Thanks to PRR also for the hint on using a digital voice recorder. Saved interupting the interview to change tapes, batteries, etc. I did take about twenty minutes of video, just enough not to be intrusive. There was no power outlets in the hotel lobby, so everything had to be battery operated. I lucked out with a table large enough to hold the schematic!
Larrchild
Well-known member
If he would have said "Oh those 670's, they go up in price every year" ..That would be expected.
But the fact that he had no idea all these years that these things were so coveted and pricey makes it doubly enjoyable for you to meet with the man and tell him that there is a good chance that somewhere in 2060, a person is going to be using a Fairchild lol. Now That's good engineering!
But the fact that he had no idea all these years that these things were so coveted and pricey makes it doubly enjoyable for you to meet with the man and tell him that there is a good chance that somewhere in 2060, a person is going to be using a Fairchild lol. Now That's good engineering!
CJ
Well-known member
Here he is doing some calculations for me on the ol slap stick!
SonsOfThunder
Well-known member
CJ looks like a kid who just met Mickey Mouse!
Good job, CJ! Thanks for sharing!!
Peace!
Charlie
Good job, CJ! Thanks for sharing!!
Peace!
Charlie
jensenmann
Well-known member
Wow
:thumb: :sam: :thumb: :sam: :thumb: :sam:
Big load of :sam: for CJ (and Mr Narma) for this history lesson.
I can imagine how CJ felt.
When I was 17 I visited my cousine in LA. We went to a girlfriend of her and it turned out that her girlfriends husband was one of the leading rocketscientists of the NASA through the 50s to the 70s! He worked with Werner von Braun! Later in the evening he took me out and showed me some of the sattelites he´s been shooting in the space. Man, I was so impressed, it can´t be described.
Thans, CJ for doing this and sharing!!!!
Jens
:thumb: :sam: :thumb: :sam: :thumb: :sam:
Big load of :sam: for CJ (and Mr Narma) for this history lesson.
I can imagine how CJ felt.
When I was 17 I visited my cousine in LA. We went to a girlfriend of her and it turned out that her girlfriends husband was one of the leading rocketscientists of the NASA through the 50s to the 70s! He worked with Werner von Braun! Later in the evening he took me out and showed me some of the sattelites he´s been shooting in the space. Man, I was so impressed, it can´t be described.
Thans, CJ for doing this and sharing!!!!
Jens
chrissugar
Well-known member
My hat of to you CJ. You are the man. Great job. :thumb:
Hope to read the transcription in the future.
chrissugar
Hope to read the transcription in the future.
chrissugar
VacuumVoodoo
Well-known member
Thanks for sharing this with us. Is there such a thing as "Pro Audio Hall of Fame" ? Mr. Narma should obviously be there.
Thanks, CJ...!
Jakob E.
Jakob E.
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