Building the WHAT compressor

[smallbutfine]

The vactrols can be ordered internationally via paypal at smallbear electronics, US. Made good experiences with them.
P1, P2 sounds like potentiometer, 10 KA means 10kOhm, linear...
Sorry didn't look at the schems for your other questions...just a quick answer dropping by...

 

[mfdu]

the 10 KA being pots makes sense to me. thanks for that.

so. the build is well underway. all caps resistors and most semiconductors (or at least the dip8 sockets) are in on the main board.

haven't started on the melcor 1731's yet.

DIODE QUERY :
the DS5 > DS8 designated diodes are all listed as 1N4004.

what about the DS1 > DS4 diodes? i presume i'll need them if i'm running the unit off a 15VA toroidal, but cant find the designation.

am i only supposed to run one of the sets of four? ie DS1>DS4, OR DS5>DS8?

CAPACITOR QUERY :
no part listed for the CD1 > CD8. are these supposed to be more 100n caps?


cheers. this is all going towards a more complete BOM which i will post for corrections soon.

chris.

 

[alk509]

[quote author="smallbutfine"]10 KA means 10kOhm, linear...[/quote]

I know there is no standard for pot designations, but in my experience A-law pots have logarithmic tapers... A=log, B=linear and C=reverse log. This is true at least for the Alps pots you can get from Mouser in the US.

So test them before you install them.

Peace,
Al.

 

[JayDee]

Maybe it´s already answered but couldn´t fin any info...

there are some atserix (*) on some of the resisitors, does that have any meaning?

also...

560R has ???? what does that mean ?

Jay

 

[mfdu]

and what value is resistor RR1 ????

 

[mfdu]

built the two boards with OEP trannies, minus vactrol and the melcor op amps (still awaiting bc550's).

put in all items except option jumpers - eight 1N4004 diodes, tl072's and ne5534's

built into a 2RU case from jaycar, with only threshold and make-up controls at present (on huge 50mm knobs).
will add ratio control tonight i think (using 10K log or lin pot = variable compression ratio, correct?)

powers up, rails stable, power led's light up.
will throw some signal at it this afternoon.

chris.

 

[mfdu]

ok

sorry it took a while to get back to you'se.

vactrols and J1 are inplace and the unit is passing signal.
appears to be compressing. but no change to the led to show how much compression.

output and ratio pots definately affecting signal, but input pot does not seem to drive signal into unit any harder.

still have not resolved required value for RR1 resistor.

have not yet played with bias trimpot.

would the pos.adj and neg.adj impact on the "compression metering" led?

so thats where the project stands at present. hopefully fabio will step up to the plate soon.

i have revised the BOM - could somebody host it?

chris.

 

[Bauman]

Ok guys,

still need to write down some info but dayjob stuff hit me hard since my last post, anyway,
here's the RIGHT schematic for the What V2 boards. I believe this will raise more Q's but will clear a lot of doubts also.

http://www.thediypill.phx.com.br/forumfiles/what_sch_rev2.pdf

more to come.

cheers and sorry for being away...

cheers,
Fabio

 

[cannikin]

Thanks Fabio :thumb: :thumb:

 

[AnalogPackrat]

Many thanks, Fabio.

 

[kiira]

Hey,

Could someone characterize the sound of the What? I am building an all in one box with an api312 board (from Fabio), a Pultec eqp-1 with Neve makeup gain and a compressor... was going to do PRRs var-mu but if I use a What I can escape making another power supply. The idea is an all in one box that is kinda optimized for guitar. How would the What fit in do ya think? It would make construction simpler for sure. Opinions wanted.

thanks,

Kiira

 

[pmroz]

'
Kiira,
Didn't see a What meta, so posting links here (some again).
haven't built it yet, but here's some opinions:
http://dt.prohosting.com/hacks/what.html
http://www.groupdiy.com/index.php?topic=6696&postdays=0&postorder=asc&start=30
http://www.geocities.com/m_natsume/what_compressor.html
Some sound files in the links.
Also known as Weak Joe, Joe Weak, Joe Cheap etc.
Seems a mostly-clean unit, so maybe not the kind of compression you'd be after. Maybe good to preserve Pultec tone, but (I hope) not really a hyper-colored effect-type.
Paul

 

[AnalogPackrat]

Hi Kiira,

Sounds like a neat project. Do you plan on using it for recording or live or both? Can you give us some hints about your playing style/tone preferences?

Just to add to what Paul just said about the multiple flavors of WHAT...Fabio has a board which has some nice options. You can build it as the original What with few controls or as a full-up Weak Joe/Joe Cheap style unit. Fabio also has a couple of other niceties on-board. One is a bypass switch for the sidechain filter and the other is the built in power supply (just feed it ~18VAC). Fabio's version will take 8-pin dip single op-amps OR discrete op-amps in the three audio path positions. And finally, he has the option to use input and output iron. Perhaps you'd want to skip the input iron and just feed it from yout pultec makeup stage. The output iron gives some more flexibility for flavoring.

Analog Packrat

p.s. I've got two of Fabio's boards and am ready to start building when I can find some time...

 

[kiira]

Hi Paul, Hi AP

Thanks for the links and info. Hmmmm, for guitar stuff I was kinda wanting something that was not so transparent that I could push and get some dirt out of. I really like Fabio's ideas on the board though, I would get one from him when they are available. I guess I would go with PRRs vari-mu still though. I would use the What in a box more centered on vocals maybe. It's a lot more bother having to mix a tube compressor with stuff requiring 24/15 volts but oh well.

I got the idea because people know about my front end gear and I get asked to other people's digital studios to help track. It would be cool to have one box I could grab that would do a lot of work, maybe even two with all modules very different and totally patchable. I'd like to use it live too in my rig... or feed it from a Pod.

edited to add: yanno I used the search function but it really has never worked too well like I can't seem to get it to search for a phrase properly like "what compressor" - it defaults to looking for "what" AND "compressor" no matter what I do. :sad: :? unless I'm just totally dense.

thanks again!

Kiira

 

[pmroz]

.
Doesn't the Pultec require HV? Maybe you could somehow use 1 PS for PRR Varimu/Pultec.
Whoops... edit... sorry, just saw 'Neve makeup gain'.

 

[kiira]

[quote author="pmroz"].
Doesn't the Pultec require HV? Maybe you could somehow use 1 PS for PRR Varimu/Pultec.
Whoops... edit... sorry, just saw 'Neve makeup gain'.[/quote]

Yeah. :grin: I stilll messsed up though because the api312 board needs 15-18 v. and the Neve out board needs 24. :? gah!

Kiira

 

[HappyTom]

Hi guys!

What up with all the * on the pcb?
And what is CD1-8? I can't find them in the shemo.

HT

 

[mfdu]

oh dear

we still haven't heard from fabio have we?

cd 1-8 - smoothing caps, 1nF i think? gotta check my notes.

fabio - heeeeelp!

my dual what? sounds great, but the compression light just dont do nothing, and it doesn't seem to compress at all - just ad gain. heaps of gain. soooo much gain, so little compression.

but it sounds great, and i still been using it, along with one of FUM's ribbon mics - mmmmm.

all those *'s on the PCB - they suck. we need to know what are options and what are essential. J1 i need, but what am i missing?

but thank you for a challenging board which has so many options. just document them for us.

but thank you, again.

chris.

 

[pmroz]

.
mfdu, it's cool, if family health is involved then DIY of course is second. If it was me (no insurance) I'd be working double and triple shifts to pay hospital bills.

I have the boards but haven't stuffed them yet. But looking at the Rev2 schemo:
http://www.thediypill.phx.com.br/forumfiles/what_sch_rev2.pdf

"C10 is a jumper if using att/rel controls. Do not mount the other * parts if using those controls"
* parts in this section are *C10, *R15, *R16, *D5. With me?

*R25 parallels ratio pot. Note says "Don't mount R25 if using ratio pot."

CC and CC1 on schemo bottom left are separate compensation caps for different TF1 options. If you used OEP or Jensen, use RC, RL, and CC. If Lundahl, use RL1, RL2, RC1 and CC1. Don't install them all.

I don't get the jumpers...trafo input impedance options? You can see them bottom left next to the Lundahl...

C1 looks to be blocking cap for unbalanced in. Goes to R1 > OP1, bypassing trafos.

Most of the answers are on the schematic... you can see which caps are bypass, their different values, etc. Also a parts list link back somewhere. And for more details, the circuit is still close to the original and variations, and those have webpages to better explain.

What options have you used? Curious as to how I should set them up.
Paul

 

[mfdu]

hiya paul

i went the OEP input, and i reckon i certainly missed a couple of points. mainly the "don't install" items for the input trannies.

where did you get that info you quoted? i think i may have missed a good source of info.

i have a much improved BOM which i need someone to host for me. all i really need (apart from those "don't install" items) are . . .

R1 - what value? i am running it (as i said) without. incomplete.

i didn't mean to flame fabio - i'm sure he'll forgive me.

all the best to you and yours.

chris.