MixBuzz500 build/support tHread
- Thread starter Igor
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Biasrocks
Well-known member
Brizco said:
Looks great Brizco, may I ask where did you source the control knobs?
Mark
dbeeson
Active member
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.
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
Well-known member
Bought them at www.musikding.de:
http://www.musikding.de/product_info.php/info/p2546_Knebelknopf-Alu-schwarz.html
AudioGimmer
Well-known member
stereokillah said:
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
Well-known member
dbeeson said:
That'd be great.
Mark
stereokillah
Well-known member
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
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
AudioGimmer
Well-known member
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
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
Well-known member
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
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
My GSSL works the same...
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".
For me it seems....strange at least, BUT that's the way it goes in original comp.
Pretty close. Try to measure with more gain reduction, or, maybe, check resistors
at ratio switch for Deutch precision
This is the best news
I want to thank Stereokillah for support too!
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".
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.
Pretty close. Try to measure with more gain reduction, or, maybe, check resistors
at ratio switch for Deutch precision
This is the best news
I want to thank Stereokillah for support too!
AudioGimmer
Well-known member
Igor said:
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
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.
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.
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.
OOPS. You mean 5532, right? OPA2604 will be fine there.
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.
AudioGimmer
Well-known member
Igor said:
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
Well-known member
igor, do you have a frontpanel file to share? corel, fpd, whatever...
i want to customize mine. cheers, alex
i want to customize mine. cheers, alex
Biasrocks
Well-known member
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
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
stereokillah
Well-known member
oh! will be a few concurency
check the spec
http://www.mercenary.com/dramobsid500.html
sorry to disturb your question Biasrocks
check the spec
http://www.mercenary.com/dramobsid500.html
sorry to disturb your question Biasrocks
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
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.
/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
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.
Attachments
ultra-alex
Well-known member
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
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
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