rotheu

Re: Another Poor Man's Fairchild 660/670
« Reply #20 on: February 02, 2009, 09:50:04 PM »
Quote
Interesting, I have an original 660 manual & schematic, and it has four 6386 in the 1st section, but the 670 schematic shows only 2 there....was this a compromise on the 2 channel unit?

The 670 also has 4 6386s per channel, they just not shown on the schematic.


rotheu

Re: Another Poor Man's Fairchild 660/670
« Reply #21 on: February 02, 2009, 09:52:08 PM »
Quote
Garen,
what hell man, i like your proto, youre crazy

Thanks for the compliment, bro ;)

rotheu

Re: Another Poor Man's Fairchild 660/670
« Reply #22 on: February 03, 2009, 01:06:04 AM »
Just tried increasing the plate voltage for 6BC8s from 100V to 120V (150V is maximum rating for 6BC8) and different values instead of 350 Ohm resistor in the cathode circuitry to see what will change at different currents through the tubes, but liked original configuration the most. End up using 360 Ohm (more common value) and same 100V on the plates. Also, with this values the VU meter shows exact amount of GR in dBs all the way down to 20dB of GR.
« Last Edit: February 03, 2009, 04:51:47 PM by rotheu »

analag

Re: Another Poor Man's Fairchild 660/670
« Reply #23 on: February 03, 2009, 02:21:13 AM »
(2) 12BH7 vs (4) 5687 equals a lot less power to drive your sidechain.
Audio engineering suffers from misinformation, disinformation, and downright lying more than most fields of endeavour.

rotheu

Re: Another Poor Man's Fairchild 660/670
« Reply #24 on: February 03, 2009, 02:27:14 AM »
Quote
(2) 12BH7 vs (4) 5687 equals a lot less power to drive your sidechain.

Wasn't it 6V6 driving the output of the control amp?
Also Edcor XSM series are rated at 2.5W. You think it's ok to drive it with more than 3-4W?
« Last Edit: February 03, 2009, 02:41:32 AM by rotheu »

analag

Re: Another Poor Man's Fairchild 660/670
« Reply #25 on: February 03, 2009, 02:43:23 AM »
I do observe how the sound of the CV amp influences the sound of the compression...with that level of overdrive hitting the 12bh7's, it's got to sound interesing. How about a Middle Class 660/670.
« Last Edit: February 03, 2009, 02:45:50 AM by analag »
Audio engineering suffers from misinformation, disinformation, and downright lying more than most fields of endeavour.

rotheu

Re: Another Poor Man's Fairchild 660/670
« Reply #26 on: February 03, 2009, 03:22:43 AM »
I just changed 1uF cap in the timing network with 100nF. That gives you practically instant attack (no transients pass through) and 5mS(!) release on position 1. This thing is completely crazy! No thumping at all! Low end of course gets distorted, but vocals (also distorted but in much nicer way) are just coming out of the speakers!  This is just to play around, I don't think it's the way to go, but I'm just surprised how stable this refrigerator looking device is at this crazy speeds! Thank you very much, Mr. Narma! ;)
« Last Edit: February 03, 2009, 04:37:10 PM by rotheu »

Viitalahde

Re: Another Poor Man's Fairchild 660/670
« Reply #27 on: February 03, 2009, 03:42:08 AM »
I approve that prototype. Proper work!

I'm going to start with a similar mess later this year. PCC189's in parallel and a gainclone amp driving the sidechain. I want to try out something Rein Narma would've done if he had chip amps in the 50's.

lolo-m

Re: Another Poor Man's Fairchild 660/670
« Reply #28 on: February 03, 2009, 04:23:31 AM »
Quote
Interesting, I have an original 660 manual & schematic, and it has four 6386 in the 1st section, but the 670 schematic shows only 2 there....was this a compromise on the 2 channel unit?

The 670 also has 4 6386s per channel, they just not shown on the schematic.
There's always something to learn... I don't have a 660 schemo and thought 670 had only two 6386 per channel  :-[ ;D :-[
Hard to be a punk... But sometimes you have to...

MartyMart

Re: Another Poor Man's Fairchild 660/670
« Reply #29 on: February 03, 2009, 04:46:57 AM »
Now that's what I call PROPER bread - boarding !!!
Fabulous, what a gorgeous MESS  :-)

MM.
"Success is the ability to go from one failure to another with no loss of enthusiasm"


rotheu

Re: Another Poor Man's Fairchild 660/670
« Reply #30 on: February 04, 2009, 01:36:31 AM »
Ok, some attack times versus 3 different caps in the timing network 1uF, 2.2uF and 4.4uF. The sine wave is 1KHz, so 1 cycle is 1mS. Sine wave starts at the peak so the first cycle is not full but only 75% or 750uS. It seems like the attack time with 1uF cap is somewhere between 0.1 and 0.2 mS. Thats very close to Fairchild 0.2mS with 2uF cap. I don't quiet understand how is it possible with much weaker control amp.

Edit: The attack time for 1uF cap is 6 samples, at 44.1KHz that's  0.136 mS.

« Last Edit: February 04, 2009, 07:37:53 AM by rotheu »

rotheu

Re: Another Poor Man's Fairchild 660/670
« Reply #31 on: February 04, 2009, 01:12:13 PM »
Attack times with 100uF and 320uF caps. Same 1KHz sine wave.
100uF ~ 10 mS
320uF ~ 32 mS


lolo-m

Re: Another Poor Man's Fairchild 660/670
« Reply #32 on: February 04, 2009, 01:30:23 PM »
Can you make some tests with a 12K sine wave if you're in 48kHz, or a 10500 Hertz if you're in 44K1 ?
I want to compare some results  ;D
Hard to be a punk... But sometimes you have to...

rotheu

Re: Another Poor Man's Fairchild 660/670
« Reply #33 on: February 04, 2009, 03:48:19 PM »
Can you make some tests with a 12K sine wave if you're in 48kHz, or a 10500 Hertz if you're in 44K1 ?
I want to compare some results  ;D

Tried to record 10500 Hz sine wave ( I'm on 44.1KHz) on the audio track to do the test, but for some reason it's all distorted??? Doesn't look like sine wave, more like saw wave but it's randomly distorted. It didn't go to the compressor, just internal bussing in protools, exactly the way I did it with 1KHz wave. Any ideas?
« Last Edit: February 04, 2009, 03:49:56 PM by rotheu »

[silent:arts]

Re: Another Poor Man's Fairchild 660/670
« Reply #34 on: February 04, 2009, 03:58:04 PM »
Can you make some tests with a 12K sine wave if you're in 48kHz, or a 10500 Hertz if you're in 44K1 ?
I want to compare some results  ;D
wouldn't 11025Hz better compare to 44K1 ?

rotheu

Re: Another Poor Man's Fairchild 660/670
« Reply #35 on: February 04, 2009, 04:10:47 PM »
Quote
wouldn't 11025Hz better compare to 44K1 ?

Tried 11025 Hz, and this one is just a saw or triangle wave but it's symmetric. Still don't understand why? I'm using sine wave in the protools signal generator and everything is internal?

[silent:arts]

Re: Another Poor Man's Fairchild 660/670
« Reply #36 on: February 04, 2009, 04:27:44 PM »
Quote
wouldn't 11025Hz better compare to 44K1 ?
Tried 11025 Hz, and this one is just a saw or triangle wave but it's symmetric. Still don't understand why? I'm using sine wave in the protools signal generator and everything is internal?
normal. how many samples from a 11025 Hz sine wave are there at 44.1kHz ?
draw it up, take a ruler and draw a line from one point to the other.
has nothing to do with Pro Tools btw

lolo-m

Re: Another Poor Man's Fairchild 660/670
« Reply #37 on: February 04, 2009, 04:38:21 PM »
Can you make some tests with a 12K sine wave if you're in 48kHz, or a 10500 Hertz if you're in 44K1 ?
I want to compare some results  ;D
wouldn't 11025Hz better compare to 44K1 ?
Yes 11025Hz of course sorry  ;D

It will look like a triangle in soundforge too, and will look like a pyramid in cubase or nuendo...

A quarter of the sampling frequency allow you to have a regular "something" wave... You can have normalising the signal a full wave... That's why I asked for those frequencies...
« Last Edit: February 04, 2009, 04:43:00 PM by lolo-m »
Hard to be a punk... But sometimes you have to...

rotheu

Re: Another Poor Man's Fairchild 660/670
« Reply #38 on: February 04, 2009, 04:43:20 PM »
Quote
wouldn't 11025Hz better compare to 44K1 ?
Tried 11025 Hz, and this one is just a saw or triangle wave but it's symmetric. Still don't understand why? I'm using sine wave in the protools signal generator and everything is internal?
normal. how many samples from a 11025 Hz sine wave are there at 44.1kHz ?
draw it up, take a ruler and draw a line from one point to the other.
has nothing to do with Pro Tools btw

Ok, understood. Then there is, 11025 Hz

The wave again starts at the peak, so the first cycle is only 75% even though for some reason it looks extended, but we can ignore those 25%. With 1uF cap the second half of the first cycle is already attenuated by at list 63%. That means that the attack time with 1uF cap is ~half cycle of 11025 Hz. That's 0.045mS! Too good to be true. That's  2X faster than Fairchild  ??? :o

« Last Edit: February 04, 2009, 05:27:13 PM by rotheu »

lolo-m

Re: Another Poor Man's Fairchild 660/670
« Reply #39 on: February 04, 2009, 05:24:32 PM »
My knowledge don't allow me to understand why but you've got around 0,2ms of attack time with a 2uF... Really impressive !!!  :o :o :o
Hard to be a punk... But sometimes you have to...


 

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