pacemaker

Re: MixBuzz500 build/support tHread
« Reply #120 on: August 08, 2010, 07:23:01 AM »
ok so no change on the VCA board,
and R33 and 50k trimpot shouldn't be installed,
thanks for your answer stereokillah !
Regards,
francois


Biasrocks

Re: MixBuzz500 build/support tHread
« Reply #121 on: August 08, 2010, 11:01:01 PM »



Looks great Brizco, may I ask where did you source the control knobs?

Mark
http://SharktankPro.com

"I'd rather use an SPX90 than a UA plugin....." Joe Barresi

dbeeson

Re: MixBuzz500 build/support tHread
« Reply #122 on: August 09, 2010, 12:04:39 AM »
Hi Mark,
I've bought these at Sayal electronics... www.sayal.com.  I was there the other day and they have them.  Funny, because I bought the aluminum ones for this build and the black ones for the 169 eq. They are the same as Brizco's.  Too bad you weren't a little closer to the Toronto area.  Closest store to you is Cambridge.  I'm heading there this week and I'll get a part number for you.

Brizco

Re: MixBuzz500 build/support tHread
« Reply #123 on: August 09, 2010, 02:40:44 AM »
Quote

Looks great Brizco, may I ask where did you source the control knobs?

Mark

Bought them at www.musikding.de:
http://www.musikding.de/product_info.php/info/p2546_Knebelknopf-Alu-schwarz.html


AudioGimmer

Re: MixBuzz500 build/support tHread
« Reply #124 on: August 09, 2010, 06:17:44 AM »
AudioGimmer,

for your ratio check your resistor on the controle board

R65,72,73,77,78,79,80,82,85,86,90,91,92,93 if you've got the good value

on my pictures you could see one line with 620k  diode 68k 270k and 510k and the second 620k diod 68k 510k and 270k

perhaps you did a error here.

Stereokillah, all resistors OK, and I checked the diodes, they are good too. Gotta do some work now, but will test again later today.
Thanks.

AG

Biasrocks

Re: MixBuzz500 build/support tHread
« Reply #125 on: August 09, 2010, 09:29:49 AM »
 Closest store to you is Cambridge.  I'm heading there this week and I'll get a part number for you.

That'd be great.

Mark
http://SharktankPro.com

"I'd rather use an SPX90 than a UA plugin....." Joe Barresi

stereokillah

Re: MixBuzz500 build/support tHread
« Reply #126 on: August 09, 2010, 01:51:35 PM »

ok
try to changed the Tl074 by another one to see if something change and perhaps it's your lorlin, you need to put it in first position before making the "stop position"(sorry i' don't know how to translate it); if not you could have some problem

Quote
Stereokillah, all resistors OK, and I checked the diodes, they are good too. Gotta do some work now, but will test again later today.
Thanks.

AG
« Last Edit: August 09, 2010, 02:07:49 PM by stereokillah »
if your neighbour is hunger .. don't give him fish, teach him how fishing ...

AudioGimmer

Re: MixBuzz500 build/support tHread
« Reply #127 on: August 09, 2010, 05:22:28 PM »
OK.
Changed the TL074, checked the stop on the Lorlin switch.
I adjusted the trim on the control board so the onset of compression requires more input and then re-calibrated the sidechain sym.

With a steady test tone input producing say 6-8dB or GR on the 2:1 ratio and selecting different ratios[ and not adjusting the threshold pot] the 2:1 setting still shows more GR than 4:1 which still shows more GR than 10:1

HOWEVER I then decided to measure the actual gain reduction that each ratio setting is actually producing [by setting up a steady GR of 4dB and then measuring the required increase in input level to give 3-4 dB output gain. The results:

2:1  = 2.4:1
4:1  = 3.7:1
10:1 = 6.5:1

So the compressor and the ratio switch seem to be working OK, just that increasing the ratio doesn't automatically increase the amount of gain reduction. [ which is what I was expecting ] The 2:1 and 4:1 ratios are pretty close, the 10:1 is a little gentle

In terms of the rest of the calibration, I get unity gain in/out, the GR meter is pretty accurate [using tones and some good VUs whilst testing the ratios] and the unit sounds gooooood!

Thats enough for tonight, thanks Stereokillah, for your help and useful suggestions.


AG

stereokillah

Re: MixBuzz500 build/support tHread
« Reply #128 on: August 09, 2010, 07:08:50 PM »
right,
in the gssl and mixbuzz, if i've good remenber the trhesold is not at same point for the difeerents ratio cause of the knee, anybody may confirm?

Don't have my material since 3 week can't try myself
if your neighbour is hunger .. don't give him fish, teach him how fishing ...

zayance

Re: MixBuzz500 build/support tHread
« Reply #129 on: August 09, 2010, 07:33:51 PM »
My GSSL works the same...


Igor

Re: MixBuzz500 build/support tHread
« Reply #130 on: August 09, 2010, 08:01:46 PM »
Wow!!! Was busy some days, opened this thread, you cool, guys! Nice progress!

Some words about ratio.
I copypasted ratio switch exactly as it was on 4000' deck. This is the way it works,
like gain reduction on 33609 goes "more-right".

Quote
With a steady test tone input producing say 6-8dB or GR on the 2:1 ratio and selecting different ratios[ and not adjusting the threshold pot] the 2:1 setting still shows more GR than 4:1 which still shows more GR than 10:1
Yes, it done by way to keep same amount of compression at different ratios.
For me it seems....strange at least, BUT that's the way it goes in original comp.

Quote
HOWEVER I then decided to measure the actual gain reduction that each ratio setting is actually producing [by setting up a steady GR of 4dB and then measuring the required increase in input level to give 3-4 dB output gain. The results:

2:1  = 2.4:1
4:1  = 3.7:1
10:1 = 6.5:1
Quote
So the compressor and the ratio switch seem to be working OK, just that increasing the ratio doesn't automatically increase the amount of gain reduction. [ which is what I was expecting ] The 2:1 and 4:1 ratios are pretty close, the 10:1 is a little gentle

Pretty close. Try to measure with more gain reduction, or, maybe, check resistors
at ratio switch for Deutch precision :)

Quote
In terms of the rest of the calibration, I get unity gain in/out, the GR meter is pretty accurate [using tones and some good VUs whilst testing the ratios] and the unit sounds gooooood!

This is the best news :)

Quote
Thats enough for tonight, thanks Stereokillah, for your help and useful suggestions.

I want to thank Stereokillah for support too!
http://www.ij-audio.com
(new site hopefully will be up in July)

AudioGimmer

Re: MixBuzz500 build/support tHread
« Reply #131 on: August 10, 2010, 02:56:59 AM »

Quote
So the compressor and the ratio switch seem to be working OK, just that increasing the ratio doesn't automatically increase the amount of gain reduction. [ which is what I was expecting ] The 2:1 and 4:1 ratios are pretty close, the 10:1 is a little gentle

Pretty close. Try to measure with more gain reduction, or, maybe, check resistors
at ratio switch for Deutch precision :)

Hey Igor.
I checked all components going in [and good thing too, there were some mislabelled caps and resistors in my order from Farnells...] so I think resistors are OK. I double checked them when trouble shooting too. I'm not too concerned and actually I'm just going to enjoy using it for a little bit! Strange that the 2 low ratios are a touch high, but that 10:1 is low. If I adjusted R60 I might bring the two lower ratios nearer to spec I suppose.

I might consider swopping the 3352s for OPA 604s on the audio pcbs if they are just drop in replacements.

One last question about RV1 on audio PCBs. I set both my trimmers to 5K1 before I put them in. Is it necessary to adjust them in circuit with tones so that both sidechains are producing exactly the same control signal? What would be the best way to do that?

Great project, Igor

AG

Igor

Re: MixBuzz500 build/support tHread
« Reply #132 on: August 10, 2010, 04:29:12 AM »
Hi AG!
IMHO, everything is fine with your compressor.
To be 100% up-to-specs, try to measure again at 1:10 ratio and maybe change
(decrease) R60 for 10-15%. Simply put something like 470Ohm...3k in parallel to R60.

Here is a lot of info:
http://www.groupdiy.com/index.php?topic=944.0

Do search over the forum, I saw similar question about ratios/threshold.

Quote
I might consider swopping the 3352s for OPA 604s on the audio pcbs if they are just drop in replacements.
OOPS. You mean 5532, right? OPA2604 will be fine there.

Quote
One last question about RV1 on audio PCBs. I set both my trimmers to 5K1 before I put them in. Is it necessary to adjust them in circuit with tones so that both sidechains are producing exactly the same control signal? What would be the best way to do that?

If resistors are 1% and caps are from same batch, no need to care about this,
the tracking should be very close. Just fit 5k1 instead of trimmer and forget.
To be at more than safe point, feed 1Khz, get 10db of compression,
check both channels with and without filters, than,
check with 50Hz and 10kHz for same GR tracking with SC filters.

« Last Edit: August 10, 2010, 04:31:12 AM by Igor »
http://www.ij-audio.com
(new site hopefully will be up in July)

AudioGimmer

Re: MixBuzz500 build/support tHread
« Reply #133 on: August 10, 2010, 05:11:28 AM »

Quote
I might consider swopping the 3352s for OPA 604s on the audio pcbs if they are just drop in replacements.
OOPS. You mean 5532, right? OPA2604 will be fine there.

Yes of course, 5532! I'm a terrible typist ???

I'll check the sidechains as you suggest, just for thoroughness, but really I'm just going to start using the Mixbuzz. Maybe next time I put an order in with Farnell I'll get some OPAs to try out. [I suspect that could be soon, seeing that your 51x 1176I is progressing nicely  ;) ]

I had read the thread on ratios, I'll have another read through.

Cheers

AG

ultra-alex

Re: MixBuzz500 build/support tHread
« Reply #134 on: August 13, 2010, 06:12:22 AM »
igor, do you have a frontpanel file to share? corel, fpd, whatever...
i want to customize mine. cheers, alex

Biasrocks

Re: MixBuzz500 build/support tHread
« Reply #135 on: August 14, 2010, 10:29:11 PM »
I'm using an original black can dbx 202 vca in my build.

Gain Control Constant: -6mv/db
Gain Control Input R: 197R +/- 2%

In the THAT corp application note for this VCA

http://www.thatcorp.com/datashts/dn127.pdf (pg 2)

they are showing 100K RIN and 100K ROUT values.

Should I set R6/R3 to 100K and R100 to 197R?

The RSYM resistor appears to be 1M as well.

Any guidance would be appreciated.

Mark
http://SharktankPro.com

"I'd rather use an SPX90 than a UA plugin....." Joe Barresi

stereokillah

Re: MixBuzz500 build/support tHread
« Reply #136 on: August 15, 2010, 07:39:46 AM »
oh! will be a few concurency


check the spec
http://www.mercenary.com/dramobsid500.html

sorry to disturb your question Biasrocks
if your neighbour is hunger .. don't give him fish, teach him how fishing ...

Igor

Re: MixBuzz500 build/support tHread
« Reply #137 on: August 15, 2010, 07:59:51 AM »
Front panel.cdr: mailing within some minutes

/hehe. saw the post about competitors, was posted at same time;
IIRC Ob*dian 500 comp exists about a year, TXIO...OK, nice!
/back to VCA's

Quote
I'm using an original black can dbx 202 vca in my build.

Gain Control Constant: -6mv/db
Gain Control Input R: 197R +/- 2%

Oh.... OK :)
JFET opamp should be used, like OPA2604.
/100k Rin/Rout arevery high impedances, to avoid dc offsets/thumps.
R2, R6, R4, R3, C1, SYM trimpot: see drawing C.

Here is the math how to recalculate VCA resistors.
If there's mistake in my calculations, I don't pretend to be final instance:)

According to drawing A, 50mV/db on 832 OHM for "original" as well 202x VCA.
So, 50/832=0.06 - current in microampreres to cause 1db drop; the current is same on
series connected resistors; than, we take whole chain resistance
and divide it to current to find "total" voltage:
(100+909+832)*0.06=110.46 mv
this is the voltage causing 1db of gain reduction at pin7 of IC7B
(actual sidechain control voltage to cause 1db of gain reduction).

Was really surprized btw why this question wasn't answered before :)

See drawing B.
We represent VCA control port with 197 Ohm resistor (in case of 202 black) going to ground.
r60 still 100 Ohm, R100 is our X, the rest is school math.
(197/6)=((100+X+197)/110.46)
Please don't ask if this about 3k31 and is this correct. I did not tried :)
But, should work.
« Last Edit: August 15, 2010, 08:06:26 AM by Igor »
http://www.ij-audio.com
(new site hopefully will be up in July)

ultra-alex

Re: MixBuzz500 build/support tHread
« Reply #138 on: August 15, 2010, 08:34:01 AM »
okay, once again. if using a 202 black can, THEN...
R6 100k, R3 100k, R2 1M = R100 3k33, use OPA2604 instead of NE5532, change C1 to 10p and the SYM trim to 100k!
did i interpret your last post and attached drawings right?  ;D
thanks, alex
« Last Edit: August 15, 2010, 08:39:35 AM by ultra-alex »

Igor

Re: MixBuzz500 build/support tHread
« Reply #139 on: August 15, 2010, 08:42:44 AM »
Seems right, but why do you going to use black 202? :)
http://www.ij-audio.com
(new site hopefully will be up in July)


 

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