MixBuzz500 build/support tHread

[Igor]

Strange. Did you used new ones? BTW. Don't use INA134 or other 0db line receivers.
INA134 etc will be +6 db overall gain versus bypass.

In any case, THAT1246, INA137 or SSM2143 (-6db line receiver) is the right choice.
Check everything twice before installing on PCB! Op-amps, resistors, diodes,
cap's polarity, etc.

Checked with BOM, in case of whatever:
1  THAT1246 /INA137P          IC1 
1  THAT1646 /DRV134P          IC8 

 

[Brizco]

i used new ones... really strange! never happened before: on both audio boards at the same time!

i will try ina137, but have to buy them first

 

[Igor]

Check the key position, both at the socket and PCB.
All these 8-pin line receivers have same pinout. Difference is gain,
speed, maximum output swing and distortion.
Sonically and measurement-wise, THAT1246 and INA137 more or less same.
Maybe, THAT bit cleaner.

 

[dandeurloo]

Has anyone used Ptowns meter yet?  I'm starting to source parts and was wondering about it. 

Also, if I want to use the Crush and Blend option.  Is that something that can be built into the 2 space case or is that an external hook up of some sort?  Not sure how that works.  Sorry if its a stupid question. 

 

[stereokillah]

hi,
don't have digikey or mouser bom, i've ordered almost parts on farnell cause there is farnell code on the igor Bom 
http://twin-x.com/groupdiy/thumbnails.php?album=405and sifam meter but you could use hairball one now http://hairballaudio.com/shop/product_info.php?cPath=25&products_id=61
for the dip, i've ordered all in that here  http://www.profusionplc.com/pro/gex/pcatdtl0 and http://www.profusionplc.com/pro/gex/pcatdtl0?ipartno=THAT1646P08-Ucheaper than farnell and other , same for the vca 2180LB http://www.profusionplc.com/pro/gex/pcatdtl0?ipartno=THAT2180CL08-U

 

[Igor]

Dan, I started to draw another 500 module for C&B option, it is almost there.
But, got the mind to make 1176 on 500/51x format, and stopped on 500C&B for this time.
If there are people interested to add C&B to MixBuzz500, as 3rd slot, it is easy.
BTW, stay tuned for MixBuzz1 (1RU with more options/flexibility).

 

[Igor]

Stereokillah: thanx!
I ordered some meters from Hairball, will post test results here.

 

[dandeurloo]

Igor I would be interesting in both the CnB and the Meters from Hairball.

Also, you have to stop making all these sweet projects.  I can't keep up money or time wise!

 

[Igor]

Hm. Dan, really thanx! I do these projects for my fun first.
Than, some of projects shared here, I hope another people will have same fun!
If there's an interest in C&B addition to MixBuzz500, 1 slot, 500 format, post here.

 

[dandeurloo]

would the CnB be something that could be used with other projects as well or just the mixbuzz?  Either way is cool but would be great if it could be used with any Stereo Comp or whatever.  Is that even possible?

 

[Igor]

It requires some wiring to MixBuzz500. 6 shielded cables in total.
Yes, it should be possible to hook it to other stereo comp...But what is the reason,
if there are other C&B boards which doesn't require 500' edge connector

 

[dandeurloo]

i feel pretty dumb but what is the deal with VCA replacement boards?  Is there a thread somewhere I'm missing?  I think I'm the only guy who hasn't built a GSSL on the forum yet so I'm in the dark about half of this stuff.

It seems to me that I can either use the DBX or build a VCA replacement board.  How do I know what the sonic difference is and is it possible to build the VCA replacement boards and swap them in and out to see what I like the most?

Another question.  Is there any reason to use a better Quad Op-AMp then a standard TL074.  If so are there any simple solutions for that?  I see there is a TLO74/AD713 on the photos (my boards are not here yet).  Is the AD713 a direct upgrade?  Also which one do I want?  I see a huge price difference between them (link below). Also, sonically what can one expect from the upgrade.  If its a direct plug I can just test them out once built easy enough.

(http://il.farnell.com/jsp/search/browse.jsp?N=500004+1004392&Ntk=gensearch_001&Ntt=AD713&Ntx=mode+matchallpartial)


Thanks

 

[stereokillah]

How do I know what the sonic difference is and is it possible to build the VCA replacement boards and swap them in and out to see what I like the most?

you can used the pin socket for DOA like this you can put and leave your vca board as your choice

 

[Igor]

..but what is the deal with VCA replacement boards?  Is there a thread somewhere I'm missing?

Original 4000' deck compressor used DBX202 VCA. There are many mods of 202, please download docs
(link at first page of this thread) and read. This is "homework"
After homework, soldering will go easier, have a fun!

It seems to me that I can either use the DBX or build a VCA replacement board.  How do I know what the sonic difference is and is it possible to build the VCA replacement boards and swap them in and out to see what I like the most?

DBX202C should have its own character. I believe it should. But, never tried

The rest of 202's is pretty same : pre-THAT era VCA's with almost same pinout llike 2181/2151,
paralleled in eights or quartets. More or less distortion, more or less CV breakthrough,
this or that values for input/feedback resistors, sometimes, different control port impedances.

Maybe there are other discrete versions. AFAIK, 200 wasn't used in 4000 series compressors.
I don't pretend to be last instance for this info in any case
If somebody have more info to share, wellcome!!!

Replacement board: more or less DBX202R, IIRC.
Using 8 of THAT2181A VCA's is true overkill; have no any benefit IMHO
neither distortion nor headroom-wise.
However, quartet sounds really good. Very clean, but adds tiny bit of second harmonic if bit
misadjusted. For all guys who love "more sound", one 2181C is the option.
Explained some posts ago.

Another question.  Is there any reason to use a better Quad Op-AMp then a standard TL074.  If so are there any simple solutions for that?  I see there is a TLO74/AD713 on the photos (my boards are not here yet).  Is the AD713 a direct upgrade?  Also which one do I want?  I see a huge price difference between them (link below). Also, sonically what can one expect from the upgrade.  If its a direct plug I can just test them out once built easy enough.

No, really, 074 is not in audio. It doesn't matter at all.
Why I used AD713, because I have some tens left, bought about 100 from surplus store for $2.
It is really cheaper for me than buy TL074 at electronics store for $1.25
But, AD713 opamp is fast and have very good DC characteristics (low offset).
If you can get them for cheap, use in every possible compressor's etc control circuit.

Audio op-amp is IC11. NE5532, OPA2604 is good choice.
OPA275 will not be the best here as it has relatively high offset and should work with low impedances
to reach its performance curves.

My last opamp affair was LME49710. Really, cool.
In MixBuzz500 we need dual op-amp.
Maybe, worthy to try LM4562.
One thing. OPA2604 has excellent DC performance (low offset) and very fast.
IMHO, this is excellent choice.

 

[dandeurloo]

Igor and killah, thanks.  This info has been helpful.  I have read everything I think I can except the 200 page thread about the GSSL comp.  Just trying to make sure I have things straight.

Thanks again and Igor let us know what you find about the Hairball meter. 


If any one else has and comments on sonics of different VCA's and what not i would love to know your thoughts as best as audio can be described.

A side note:

A friend of mine say "talking about audio is like dancing about art"  It makes no sense.  So, I understand it may be hard to describe the sonics of the vca's.

 

[dbeeson]

Igor, I'm stoked to hear you're building the 1176 in 500 format.  I was about to spring for an Action, but I think I'll wait for this.  I got the hairball meter a couple of days ago.  Looks cool!  The range on the meter is not quite as wide as the Sifam, but I have no problems with that at less than half the cost.

 

[dandeurloo]

Audio op-amp is IC11. NE5532, OPA2604 is good choice.
OPA275 will not be the best here as it has relatively high offset and should work with low impedances
to reach its performance curves.

Is OPA2604 a good upgrade for IC9 on the VCA Replacement board as well?

 

[Igor]

OPA2604 is dual op-amp. Single op-amp needed for VCA replacement board.
To drive the control port of VCA, requirements are: low noise and low output impedance,
as well as good DC performance. I think OPA604 will work fine at "homebrewed 202",
i.e. VCA replacement board. In original 202* VCA's, NE5534/NE5532 were used
to drive control ports of 8-pin IC VCA's.
I used NE5534, it worked fine.

/BTW.

A friend of mine say "talking about audio is like dancing about art"  It makes no sense.  So, I understand it may be hard to describe the sonics of the vca's.

Absolutely agree. In bad Hebrew-to-English translation, local proverb says:
These words from your mouth to God's ear

 

[Igor]

In case of whatever, link for power supply bypass capacitors (220uF):
http://il.farnell.com/panasonic/eca1ehg221/capacitor-220uf-25v/dp/9692835
http://il.farnell.com/panasonic/eeufc1e221/capacitor-220uf-25v/dp/9692142
http://il.farnell.com/panasonic/eca1ehg221/capacitor-220uf-25v/dp/9692835

 

[AudioGimmer]

The soldering is coming on slowly [not enough free time and a few missing/wrong items delivered from my parts orders ???]

Couple of questions
1. Power for the small board with time constants/ratio etc. Does this come from the 3 points at the top of either audio PCB just above the sym trim pot?
2. My relays have coil resistance of 360 ohm each. So the resistors R98 and R87 should be 60 Ohm right?
I couldn't get any .5watt 60R so I ordered some 60R4 0.6 watt. Now this is going to sound dumb, but they look physically small, like the rest of the 1/4 watt resistors. I guess as their resistance is low they aren't are physically big as say the .5watt 2K resistor in R89.
Does that sound reasonable or are these not right?

BTW, thanks Igor, the PCBs are excellent to work with.


AG