Building the WHAT compressor

I figured there were enough of us WHAT builders out there in Lurkland to warrant a new thread. I'm currently collecting parts for a pair of Fabio's hopped up versions with transformer coupling and discrete op amps. I'm going with the Lundahl LL1540 inputs and CineMag outputs (either CMOB-2H or 2L). Given all the extras that Fabio included on the PCBs, I can't resist having all the options.

One thing I would like to add is metering. It would be really nice to have switchable meters (in, out, or GR), but given the rectified sidechain I'm guessing this is non-trivial (if I'm wrong, please advise!). So, I'm assuming I'll have to do something like the GSSL and use an ammeter for GR. Anyone else in the same boat?

Analog Packrat

The yellow compression indicator LED could be replaced with a vactrol, giving way to the implementation of a metering circuit much like it is done in the Forssell compressor.

Thanks Tamas. I haven't been following the Forssell Limiter thread (too many things on the list already). I'll pop over there and have a look at the schemo. I have a bunch of vactrols and even more bare CdS cells, so it should be easy to prototype something.

Cheers!

Or take a look at the LA-4A: http://www.waltzingbear.com/Schematics/Urei/LA_4A.htm

hey good stuff with starting this one up - just in time. i'm expecting my two fabio boards any day now.

so what mods are available?
and whats this about metering? i thought there was facility for running a meter already?

chris.

Michael K -- Thanks for the pointer on the LA4A metering. That's a possibility, too.

mfdu -- It looks like Fabio has laid out his boards for maximum flexibilty. You can build the thing many different ways--from simple two knob (compression, gain) original WHAT to full blown five knob (threshold, ratio, attack, release, makeup gain) "Weak Joe." He also has pads for a switch to bypass the sidechain prefilter and a pad for stereo linking (which I assume is just a summing node for the two sidechain signals).

Of course you get your choice of input and output iron (or none) and discrete or IC op amps in the signal path. That's all I've found--anyone see other goodies?

As for metering there is just an LED paralleled with the vactrol LED for a rough indication of what's going on. Hence my questions.

Analog Packrat

I was kinda hoping someone would start this thread!!
I haven't got my board yet, but it will be nice when i get it as a reference.
I'd like to hear more about what people are doing with their boards, since there are so many options.
Pictures would be sweet also!! :green:
Ryan

Keep this thread alive here!!

So i'm looking at the BOM (Please bear with the newbiness):
http://www.thediypill.phx.com.br/forumfiles/whatopto_bom_rev2.htm
and the schem
http://www.thediypill.phx.com.br/forumfiles/whatopto_sch_rev2.pdf

I'm gonna start placing an order, can anyone help me to fill in the blank spots on this.
The diodes DS1 through DS4: do these need to be any certain kind? (bottom center of schem)

JI1, JI2, JI3 - what are these, i don't recognise the symbols - (bottom left of schem)

and is U1 through U7 - are these amplifiers?

Any help is appreciated
Ryan :sam:

Ryan,

I don't have the pcb or payout handy, but I believe the JIx are just jumper locations. It looks like Fabio has allowed for maximum flexibility with the Lundahl input trafo. You could set it up with series windings, parallel windings, or put in some switching for selecting the primary winding configuration.

U1, U6, and U7 are single op-amps which are in the audio path and can be discrete or IC (5534). The others are in the sidechain and are all duals (hence the A and B suffixes on the schemo). I plan to use TL072 or TL082 for these since I have a bunch.

The bridge diodes (DS1-4) can be 1n4004 types. I'm using UF4004 which are inexpensive fast rectifiers which may or may not reduce PS noise. They don't cost much more than standard 1n4004 parts. Check Digikey.

Analog Packrat

Thanks for the info!

Are the TL072 & TL082 for dual or single? It is unclear there.
Also is it common to use multiple opamps? Or is this the kind of thing you choose which one you want to use? Because 3 descrete opamps is gonna be pricey, right?

Thanks again

No problem. I hope Fabio will chime in with some detail on the LL1540 primary side options. The TL0xy series is one of the few places where the naming convention is consistent and useful. There are several versions (x) of the family with different optimizations. The 6 series is low power, for instance. "y" is the number of devices and can be 1, 2, or 4. So a TL072 is a dual part in the 7 version. I can't remember what the differences are between the 7 and 8.

If you get some discrete op amp pcbs (order some from Fabio), they are relatively cheap to build. Maybe $2-3 in parts plus the pcb. I plan to mount the DIP sockets and do testing with IC op amps in the signal path to start with and then plug in some Melcor 1731s (pcbs from Fabio). You can decide which way to build it. I would imagine that NE5534 (single IC op amp) parts would sound OK in the signal path and be the easiest to start with. You can always upgrade to discretes later if you use sockets for U1, U6, and U7.

Analog Packrat

just got my boards today.

they look great.

but with all those options, it's going to take a bit of time sitting down with it to understand what it's all on about.

and what are those six small boards that came with the two main boards?

i've grabbed pretty much every bit of info i can find on the build, but it just isn't as nicely prepped as the ssl or 1176 projects.

hell, i can rebuild a chrysler 273 V8, i can do this.

chris.

It also looks good on Veroboard - greetings from Czechoslovakia..............oooooooooooooops Czech Republic!!!!
Stephen

Sheesh, what next. Burnley drops in fronm Chile?
:thumb:

[quote author="mfdu"]
and what are those six small boards that came with the two main boards?

i've grabbed pretty much every bit of info i can find on the build, but it just isn't as nicely prepped as the ssl or 1176 projects.

hell, i can rebuild a chrysler 273 V8, i can do this.

chris.[/quote]

Chris,
Those are Melcor 1731 discrete op amp pcbs. Search the forum for Melcor and 1731 and you'll find all kinds of info on them. Fabio's stuff is more heavy duty DIY and less kit-like. Even so, I think its great bang for the buck and plan to buy some of his A*P*I and N*e*v*e boards sometime soon. It's really cool that there are so many guys on this forum making pcbs--plenty of options. If you can read a schemo and trace the layout, you should be good to go!

:guinness:
A P

Hey guys,

I will try to help in any way I can, probably putting down some guide or instructions. Just need a weekend to get togheter after some hard work and will get back here.

:guinness:
Fabio

pedro came in and told me :

those small boards are opamp`s(1731-2520).
to connect those boards to the main board,you need a male pin that it is soldered in the small board,and female socket`s,that you solder in the main board.
i`ll give you the part number for those.
both from mill-max(manuf)
socket:0344-2-19-01-34-27-10-0
mouser p/n:575-034420

pin`s:3102-2-00-21-00-00-08-0
mouser p/n:575-310220

Click to expand...

makes sense. been looking at the fabio what comp+zulu image, to get an idea of the build.

doesn't look as challenging this morning as it did last night.



chris.

Can't wait to get this, and i'm pleased to hear he is including the opamp boards!!

This should test my newbie DIY skills, but i'm up for a challenge.
Ryan

[quote author="louder"]those small boards are opamp`s(1731-2520).[/quote]

Can you tell me what the name of the third opamp is?
I am gonna do a digi-key order here and don't wanna leave anything out!

Hopefully those boards safely get our of brazil this time.

ehem, i think you didn't get the point. The boards are prepared for the option to get either ic or discretes...but normally stay with one type of opamps (3x melcor 1731 or 3x a*p*i 25.20 or 3x opa637 or 3x AD797 or whatever) to maintain a sonical character...
BTW if you search for discrete opamps you will probably find alot more types to choose from...a quite interesting field...
You will get 3x melcor with it i think (at least i got), as a goody :grin: . (No way to buy this one anymore anywhere i think...)
got it?