#pcbgrinder

[irfrench]

PQ1549 - The Start

Evening,

So, previously I mentioned about a £65 budget EQ... One of the most costly bits is finding a case and sorting the power out.

Well, in the summer one of our offices closed, and being an old acoustics company there were some old electronics bits of 'junk' going wanting.  Naturally these were snaffled up including one old rack case.  It has been in my mind to re-purpose this case so I thought I'd give it the once over:

I knew there was a helpful power connector and fuse, along with 2 pre-drilled jack holes and a power switch so I was confident I could at least use some of this.

On closer inspection though I noticed:

Or more specifically:

Or even more specifically the heat-sink mounted 7815 and 7915 voltage regulators!  

"Does this mean that the psu is already installed and perfectly suited to this EQ project?"

A quick check with a multimeter, and YES. Yes it does mean that!  Sweet, not only has that saved me some cash (£20ish) I also don't have to build that bit! Hurrah! 

So all I had to do was remove the not-needed bits, tidy the wiring to keep the AC wiring as far from the EQ circuit as possible and get it prep'd:

FROM THIS:

TO THIS:

Hopefully now this will be a very willing host to a lovely sounding EQ.  Also, helpfully, the vero boards of the original circuit hosted a number of TL072s.  Those could come in very handy for this circuit!

Total cost so far = £0

x

[irfrench]

169EQ & OA10 - The Final Frontier

Evening.

So the OA10s were done, almost, only a couple of parts needed and they'd be done-done.

Well. It happened. And it is ALL GOOD!  Just for S.A.Gs this is what a discreet op-amp looks like next to a single DIP8 op-amp...

I know which one is smaller, but I also know which one I like the look of more... ANYWAYs - the import thing is the sound right?  True.  These were always meant to go into the 169EQs - assuming I didn't give up a sack them off, sorry - so here they are:

Things to note:

The Gain pot on one of the Mid EQ controls needed to be changed.  It felt really stiff to actuate when I got it, but I figured it'd loosen up with use (and with a control knob added).  It didn't and it was starting to bug me.  I'm pretty sure Colin would have exchanged it but I had mangled the pot-shaft pretty bad when repeatedly actuating it with a pair of pliers...  Sorry.

The knobs between each unit do not match.  This is because I had to drill one off to be able to remove the PCB to install the DOA sockets.  The pots a 4mm(?) where as the knobs are 6mm... I therefore needed a collet to convert a 6mm control knob to fit a 4mm pot...  Combined with the tightness of the pot ended up with me really tightening the grub screw and making a hash of it. Thus I only had 5 of the 6 matching control knobs I needed. Sorry again.

On the first PCB to accept the test DOA there was a small fire... Some evidence of this is still visible on the EQ pcb (right hand pcb - resistors near the bottom edge). Still sorry.

In any case, they were installed and sound really nice, a little bit noisier than the IC, but also a weeee bit warmer and open...  Its subtle but there.

I DID say I'd give an audible comparison... so here it is.

I like them, and now I can use the ICs elsewhere... See what I did there?

I have another project in the offing. I'm going to build an EQ based on the Calrec PQ1549 EQ project as kindly shared by Gyraf.  This time though I am on a STRICT budget of £65 all in... Including rack and labelling. Reckon it's possible?  I think so.  But then I do have huge stash of parts I want to use up...

x

[irfrench]

169EQ - DOA? Part II

"So Ian, how does it sound?"

"Er, well.  The thing is..."

It was going to happen sooner or later.  It don't work! DOH!

If you look closely you can see the burnt out resistor, hence the reason I could smell GCSE electronics labs all of a sudden.

On the flip side it is good to learn from these mistakes...  As yet though I am unsure of the problems as the usual suspects are OK (transistor orientation, solder bridges etc).  Although I have a feeling that I may have used too small a wattage resistor for that 10ohm swine.  I'm going to have to do something I don't like doing and ask for some advice...

In the meantime have a couple of glamour shots:

They do sound ace as they are though and I'll do some sweep measurements (and then explain how I did them!)

X

[irfrench]

169EQ - DOA?

Righty.

So at lunch I had time to whip up an OA10 DOA.

The first problem was how I was going to interface the DOA with the sockets I had bought already:

The holes on the DOA are sized to accept the sockets, as are the EQ PBCs.  I don't want to go down the socket-pin-socket route so I decided it was time to use up some spare solder and fill the holes appropriately:

Now here's a tip:  As the DOAs are REALLY tight on space it is necessary to stand components up.  To get good consistent bends that do not strain the component use the smallest screwdriver you have and bend the component lead over that:

So then it's 'just' a case of cramming a load of components into a tiny, tiny space.

And this is how it mounts.

So there we have it.  One DOA down...

I'll do some listening tests and decide whether its worth dedicating another 3hrs of my life to making DOAs!

Gotta love scheduled publishing.  I'll be doing a rehabilitative walk when you read this.  Probably.

x

[irfrench]

169EQ - Phase (geek-lol?) 2

This will no doubt be a short post.  It's the way I roll pre-midday.

The first unit fired up straight off - and sounds REALLY good - so bolstered by my success I continued on into Stereo-town. Or more accurately dual-mono-town.

Much more happy with the metalwork on this second attempt.  I suppose it should always be like that - but it'd be nice to be ace at something first time around.

I also needed to add the freq. selection switches to the other channel.

It is really simple when the original engineer (Audiox) had the foresight to include additional pads to add freq. select.  Choose your base frequency then add to that base other caps to change the cut-off. SIMPLE.

All I need to do now is wait for the knobs (from Musikding) and add the DOAs...

...tiny little fuerkers.  Don't suppose anyone wants to make them for me for free?  No takers? Thought not.

There looks to be a solution to the DOA mounting conundrum - I'm hoping it works and will be sure to make you even more bored when I tell you ALL ABOUT IT.

On an amusing side note, it turns out a family member has one of these kicking around in the loft gathering dust.

I'm not going to lie, I wanted to rob it.

Hard.

Instead though I decided to try earn some brownie points and help find a copy of the inner 'lid' sheet that had gone missing when he used to gig with it.  Once again the kind, kind people at GroupDIY came to the rescue (thank you Dreams) here.  Even Roland UK didn't have a copy like this!

The internet is a wonderful thing, and the people on it can be even better.

x

[irfrench]

169EQ - The story so far...

So the planning was/is done.  Things needed to arrive - and they did:

This meant that the planning could be put into action.  Now I don't think I've said what I like to have with me before I start a project - but typically it'll be something like this:

On this table is ALMOST everything you'd need to build a pair of 169EQs, obviously you need all the components, PCBs, hardware etc. but I also like to have 3 copies of the following:

BOM

Layout (designations)

Layout (values)

Schematic

Project specific notes

You'd be surprised how many times I have needed more than two copies of a document when building pairs of things.

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I like to begin working on the PCB when I know that everything else has been done so that I can simply assemble and test.  In this case I need to prepare the 500-series support bracket.  The details are available at GroupDIY and other places (I think I have already linked to them in another post) but essentially I took some aluminium sheet cut to the correct dimensions and bend it according to this - wot I dun gon' drawn:

Now as I also 'designed' the front panel for these I have access to the layout file - this made it VERY easy to have a VERY accurate drill guide:

Simply cut out the drill guide using a Manly pair of scissors:

And use the most non-permanent glue you can find. Pritt-stick (OTHER RUBZ GLUES ARE AVAILABLE):

Then drill where you should using the subtle reminders about hole size to stop you screwing up:

It is also a good idea to not have the ENTIRE board shorting out on the support bracket, so drill some holes for the mounting posts/screws:

Butcher it with a drill, some files, a pair of even more Manly scissors and a Dremel and you're good to go:

Next up?  THE PCB! Hurrah I hear you say... As always start with the low profile stuff and build up:

OOoooooooooooooooohhhhhhhh.... PING! Done.

This is such a simple build it is ridiculous. Pretty much anyone could build one of these lovely things. SO SIMPLE!

Things to note.  This as yet does not have a front panel attached, duh.  It also does not have the switchable (mod) High and Low shelf caps added yet - hence the fly leads still waving their leady-leads.

The moment of truth? What I've been fearing all along?  Does the panel fit?

Yis. Yis it doewz.  And It looks real nice-like too. Cool.  Now to test it.  I have to be honest here - I did not expect this to fail.

And it didn't.  PLUS it sounds LOVELY - even with 'just' the NE5534s.  Hopefully the OA10's will make this even more $exy-fied.

I decided these would be really useful for tracking - adding weight and snap to a kick? Easy. Taming the bottom end on guitars and adding mid-range bite? Easy. Adding weight and air to a vocal whilst at the same time reducing that irritating splatty 3.5KHz weirdness? DEFO.

I digress.

How does it look in the RACK?

Like it was meant to be. Even without its knobs on - which I will cover in another post.  It's irritated me, I'll admit.

Anyway.  ONWARDS.  Channel 2 should/will be done soon along with the finishing off of Channel 1.  Heck I may even do freq. response curves.  JOY!?

I'll leave this here also as I'll need it soon enough - at least I'll know where to find it.  This is how the modded caps need to be added in.  No probs.

AUDIOX posted on GroupDIY that I missed that BOTH C4 and C5 need to be switched at the same time for this to work.  LINK

x

[irfrench]

Yeah, but maybe he did what?

Evening,

This will be a quick one...  Fnnar fnnar. 

I really should take some photos of the adapter boards in their final-all-singing-all-dancing-ribbon-cabled-state.  Instead though, here is a photo of the calibration process.

Ooo pretty.  And after the calibration process...  Lady and gentlemen - I present in line embeded YouTube links (uuhhh ohhh,  Happy learned to put.)

OK, not quite the exciting party of joy I'd hoped but it proves it works, and I now think I can embed links.  Cool.  Ish.

What else, well, fundamentally I have little/no money at the moment as I'm having some work done on the house next month and need to get everything in order before that begins.  Beans on toast isn't sooo bad.  Quite nice occasionally.

Anyway.  I thought I'd do the DIY-gear equivalent of admin and finish up/tidy some loose ends.  For a while I've had parts for some reamps (see previous posts - I had too) that I've just had breadboarded.  Well, I decided to start the ball rolling.

Look familiar?  Good.  I want to have them protected and portable and rack mountable if I see fit so I've gone for some cool little cases off eBay.

No prizes for guessing the country of origin.

They should squeeze in there quite nicely, and at only 38mm tall they will be able to sit in/on a rack shelf.  Cool.

So what have I got in the pipeline?

Finish the 2nd GIX-51x preamp - this would be SO useful to have done already, but alas, Loft Conversion

I've been looking at interfacings for external units, I've pretty much got all bases covered with the reamp and DIs - but I realised I don't have a reverb driver circuit...  Rod Elliot (that site is SO useful) has a project which can be adapted for Spring Reverb duties, in all honesty it would be a piece of cake to create my own version of his circuit (he shares so much info) but I want to do something to support his site, so I'll probably end up purchasing his project.  Nats I'll show the results here.  In the meantime it turns out that the SRPP DI I built a while ago is also capable of driving a reverb tank, unfortunately the tanks I have here are not ideal on the impedance front for the SRPP (nats I tried it out though) - sounds GREAT on vocals and sounds POO on drums!

Er, what else?

Oh yeah, I'm redoing some face plates using Razorlab again,  The staff are ace there.  I think they'll all be black with white lettering.  I think I'm going to redo the Pultec/s800 panel, do the Nite EQ3D panel, and whilst there do a panel or two for prospective projects... Such as the reverb driver and the 'dirty' compressor based on the Siemens U274a limiter.

In an amusing twist I have been looking at the Studer 169EQ (PCB GRINDER sell a 51x board), an SSL 4000 or 9000 preamp or two (PCB GRINDER again) and most amusingly I think, once I have the funds, I'll build a couple of mics - U67, C12/ELA M251 and possibly a U47fet.  I'll see how it goes.

One last thing... A while ago I read about some mods to a pair of SDCs I bought - turns out that these are a great candidate to turn into something akin to a pair of Neumann KM84s.  Cool.  All I need to do is crank up the ol' Dremel, swap a few caps and hope the Cardinals choose wisely in their Conclave.

Bedways.

x

[irfrench]

LA4-51x: You seem to misunderstand us.

Hi.

Before anything else I want to say that yesterday we lost a really good friend to the family, a true gentleman.  

You will be missed Stan.

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It's been one of those days today.  I've kept myself busy by tidying the whole house and engrossing myself in small repetitive jobs.  Still, it has been productive and the house now smells like it wants the occupants to be here...

Righty.

The LA4. Last time it got to this point:

Lets carry on:

The boards arrived from PCB Grinder.  The boards are REALLY well made.

But needed to be prepared:

See that it's too big? Not if I can help it.

For some reason I LOVE this photo. So simple yet explains loads.  Here you can see that power supply section is completely separate from the audio section.  This makes it REALLY easy to remove.  Drawing the line gives a good target for the saw, and holding the board up to the light clearly shows that the cut will not break any PCB tracks.

For my records, this is how far into the board the cut was made.

One last cut.

Test fit.

To make sure there is enough clearance over the 18-pin connector I'm using a 5mm spacer.

First I wanted to make sure the VU meter was powered properly.  That way if I connect this up and the power doesn't like something - I know its not the VU.

Populate the board.

Test fit to check clearances.

All fine.  Now for the 'fun' bit.  having completed this I can tell you that this is a REAL PITA to wire up.  I've made more guitar pedals than I care to remember, some of which were absolute pigs to wire up, but none NONE were even in the same league as this.

A REAL test.

All off-board wiring done before fitting.  Patience, experience and perseverance turned this:

Into this:

It fired up first time, and sounds wicked.  I need to calibrate it (which I cannot do until I can finish building that extension-thingy) to get it to behave EXACTLY as it should, but at the moment it compresses/limits and sounds great when doing so.  Can't ask for more than that!

Glamour Puss:

Very happy with how it turned out.

VERY HAPPY.

I think for the other LA4 build I'll try and present it in a more palatable fashion and try to include bits of information that are really useful to have in context.

Werd.  Innit.

x