abechap024
Well-known member
Thanks Stuart,
Confirming Payment.
Confirming Payment.
[BUILD] DBX 160VU
- Thread starter abechap024
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abechap024
Well-known member
Espen Payment Confirmed.
Thanks!
AC
Thanks!
AC
Great projet, it will be fun. Payment for 1 PCB sent
Thanks, Alberto
Thanks, Alberto
haima
Well-known member
payment sent! thanks abe
abechap024
Well-known member
Confirming payment for Haima and Manuel.
Thank you!
Thank you!
abechap024
Well-known member
Check first post for update.
Thanks!
AC
Thanks!
AC
tommypiper
Well-known member
Hi, I'm interested. Thanks for the project. 
But your links are not working. :'( Would like to see the schem and such... and the layout of your board too.
But your links are not working. :'( Would like to see the schem and such... and the layout of your board too.abechap024
Well-known member
Hey,
Thanks tommypiper I've put up so many different versions of the schematic its hard to keep up with them all sometimes I did order a few extra PCBs for anyone that might want to jump on board when they arrive. I'm just hoping there are no MIZTAKES!!!
oh and links on first post should now work
AC
Thanks tommypiper I've put up so many different versions of the schematic its hard to keep up with them all sometimes
I did order a few extra PCBs for anyone that might want to jump on board when they arrive. I'm just hoping there are no MIZTAKES!!!oh and links on first post should now work
AC
tommypiper
Well-known member
Thanks, where is the DBX 200 footprint?
abechap024
Well-known member
They are there, look for the small rectangles. but they are filled with optional parts if one doesnt already have a dbx 200 vca/rms they can build one on board
cheers
AC
cheers
AC
SSLtech
Well-known member
I'd just take a moment to point out that -while the spirit of DIY is a highly commendable thing, it's worth making sure that everybody understands that the DISCRETE VCA option is a VERY difficult thing to get right.
dbx had to individually measure and hand-select transistors across a variety of temperatures, and then thermally-couple the devices together as closely as possible, which ultimately proved to be the single greatest limit to VCA performance, particularly in terms of (particularly unpleasant) distortion.
I'd expect anyone who tried to hand-roll their own VCAs to end up with an inferior result, in terms of performance. THD and temperature drift would likely be compromised.
While I'm not saying that this isn't a great idea, to allow people to try and build their own VCAs, the advantages of monolithic devices are just out of this world... and I'd have used something like a MAT-04 in a VCA, instead of four individual devices.
I'd prefer people to understand up front that -if decent performance is a priority- it's almost certainly better NOT to attempt a discrete build of the VCA section.
However, if you're cool with that, and the idea of building the whole thing from scratch is more important than decent distortion performance, by all means have at it.
By the way, the distortion is NOT 'cool' distortion; it's the type of distortion which gave VCAs such a bad name all those years ago. -It's why dbx had to spend so much time and money building specialized test-and-match setup, which the vast majority of DIY-ers simply wouldn't ever be able to recreate.
Just a caveat which I think should be clearly added; and not anything which should detract from a noble effort.
Keith
dbx had to individually measure and hand-select transistors across a variety of temperatures, and then thermally-couple the devices together as closely as possible, which ultimately proved to be the single greatest limit to VCA performance, particularly in terms of (particularly unpleasant) distortion.
I'd expect anyone who tried to hand-roll their own VCAs to end up with an inferior result, in terms of performance. THD and temperature drift would likely be compromised.
While I'm not saying that this isn't a great idea, to allow people to try and build their own VCAs, the advantages of monolithic devices are just out of this world... and I'd have used something like a MAT-04 in a VCA, instead of four individual devices.
I'd prefer people to understand up front that -if decent performance is a priority- it's almost certainly better NOT to attempt a discrete build of the VCA section.
However, if you're cool with that, and the idea of building the whole thing from scratch is more important than decent distortion performance, by all means have at it.
By the way, the distortion is NOT 'cool' distortion; it's the type of distortion which gave VCAs such a bad name all those years ago. -It's why dbx had to spend so much time and money building specialized test-and-match setup, which the vast majority of DIY-ers simply wouldn't ever be able to recreate.
Just a caveat which I think should be clearly added; and not anything which should detract from a noble effort.
Keith
haima
Well-known member
you are right keith - but perhaps we can use the THAT 300 series matched arrays to circumvent some of those issues... obviously not with this pcb revision - unless we use some kind of adapter/floating wires...
abechap024
Well-known member
Hey all. Got them today! Pleasantly surprised with the quality of the PCB. Shipping them all out tomorrow. I have 3 extra if anyone wants to pay 35$ a piece for one or two or three. Thanks again for everyone who participated! This place rocks
AC
Thanks Keith,
that is something I've been wondering about...and all those "select" resistors in the VCA. I for one wouldn't even know were to start on how and why to select the right resistors. Though if someone could spread some light on that I am eager to learn(does it have to do with the bias for the transistors??). The Discrete VCA is definitely not for everyone. Luckily with the help of many people on the forum we have added a THAT 2180 vca option. But I would like to start gathering any information on how and why to select the components inside the VCA. Should be a good learning experience if nothing else
Thanks all
AC
AC
SSLtech said:
Thanks Keith,
that is something I've been wondering about...and all those "select" resistors in the VCA. I for one wouldn't even know were to start on how and why to select the right resistors. Though if someone could spread some light on that I am eager to learn(does it have to do with the bias for the transistors??). The Discrete VCA is definitely not for everyone. Luckily with the help of many people on the forum we have added a THAT 2180 vca option. But I would like to start gathering any information on how and why to select the components inside the VCA. Should be a good learning experience if nothing else
Thanks all
AC
abechap024
Well-known member
ALL PCBS sent out today. Thanks to all those here who participated, now time for the fun stuff!
AC
AC
haima
Well-known member
thanks for all your work AC - hopefully we don't have TOO much "fun"....
it'll be interesting to see how the hard it is to get that discrete VCA right ;D
good thing we have a few options
it'll be interesting to see how the hard it is to get that discrete VCA right ;D
good thing we have a few options
abechap024
Well-known member
Yes. Sooner than later. Very soon hopefully.
Abe
Abe
haima
Well-known member
Has anyone built a 100% functional unit?
damnyankee
Well-known member
I'm wrapping up soldering the last few components on the board.
I have a few questions:
On the BOM, R11, R13, R15, R67, R106 are "trim" resistors and C10 is supposed to be a trim/timing cap...but there's no values listed. Thus, these components have not been installed on the board. Can anyone help as to what values these components are supposed be?
Thanks in advance!
DY
I have a few questions:
On the BOM, R11, R13, R15, R67, R106 are "trim" resistors and C10 is supposed to be a trim/timing cap...but there's no values listed. Thus, these components have not been installed on the board. Can anyone help as to what values these components are supposed be?
Thanks in advance!
DY
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