#169eq

[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]

OA10 - All's well that ends well?

Evening,

Following the euphoria of not having another project just sitting on the 'never gonna do it cos ur 2 lazee' pile - I decided to crack on and get the other OA10s done.  One small hitch - I only bought the right number of parts, not expecting to be a royal munch, so I'm short of a BC327 and BC337.

Who cares right? Plough on bruvva.

I decided to do these en masse rather than one at a time and it flew by... Note to self... Anyway, I needed a better way to mount the DOA pins and being a HUGE fan of blue/white-tac I decided upon this method:

Lay the PCB flat on a thick wodge(?) of tac and stab the pins through the mounts until flush with the board, making sure they go through straight.

Use a pair of pliers (or sommat).

Then solder the joy right in.

So then it was 'just' a case of populating the boards:

Resistors added:

Then the semi-conductors; some of the diodes need to be installed in series-pairs...  I like to bind them like this and seal the deal with a bit of solder:

Progress made, now add the remaining transistors:

Finally add the compensation cap and resistor (needed for low gain circuits apparently) underneath and you've got a family:

Ahh, so sweet. AND cool!!! I love the idea of DOAs (now they seem to work!), I'm not sure why but I hope I'll be able to hear the reasons too when I get these cranked!  Speaking of which...

Ace!  Looks good, but does it smell and make fire when I switch it on?

Nope!  Hurrah!  Not got time to have a proper listen but I'll be sure to bore you with my findings.

Some notes for my (your?) reference re: this build.

Nice one.

X

[irfrench]

169EQ & OA10 - UPDATE!

Evening,

So I've had a busy and humbling day today, firstly AUDIOX (the fine gent behind sharing the OA10 and 169EQ project) posted on the GroupDIY pointing out a mistake I had made, secondly another fine gent (iprovlek) shared his finding that a couple of transistors needed reversing...

First things first - the point of this blog has changed over time, but the single continuous theme has been about me learning, and sooner or later making mistakes.  One of the many reasons I love the GroupDIY forum is that it is so welcoming of people like me, and the mistakes I make.

Anyway, in order to have the High shelf switchable in the 169EQ you need to change both C4 and C5 at the same time. SO. The switch should have been wired like this:

Now that is done, the High-shelf response looks like this:

A more useful separation between slopes for sure.  I'm still not 100% that this is correct though, but it is definitely 'better' than before.

Secondly, I'm going to be honest - given the size of the PCB and the fact that I had a working alternative I honestly wasn't sure I'd get around to troubleshooting the OA10s. I apologise.

Then today iprovlek posted that he'd had success flipping the BC327 and BC337 transistors around... Now I KNOW that I'd checked the other transistor pinouts but couldn't remember if I had for these... It turns out that I had not.  Lesson learned.

So 'all' I had to do was remove the incorrect components without ruining the PCB and 'good' components and replace the incorrectly placed ones nice and neat-like:

So this is what it looked like, and this is what caused the GCSE electronics smell:

Caramelised resistor. Nom nom? Lets get this done:

I've deliberately left the 'new' components high in case this did not fix the issue.  Turns out it DID fix it.  Here is the OA10 installed:

I'm going to do another OA10 and then compare this EQ with the other one.  I'll try and generate some samples for comparison - not gonna promise owt though, those things are really hard to make interesting.

So there it is... Two lessons (re)learned!

Now I can sleep at night.

x

[irfrench]

169EQ - POST

Still not really had time and/or got anywhere with the mystery OA10 bullhickey... Shoody, shoddy, shoddy.

Anyway I said I'd do some EQ sweeps so here they are:

Dunno if you can see them, make them bigger or even care for them! I'll probs post these on the GroupDIY 169 project page anyway... It was really so I could find out a way of measuring EQ sweeps for the PC.  A long while ago I read this post by Ben Lindell - LINKY - where he explains how to measure sweeps using a MAC.

I don't have a MAC.

I have a PC.

And I wanted to measure SWEEPZ MAN!

Thinking about a bit I remembered using Room EQ Wizard:

Which is a free bit of EXCELLENT software developed and very kindly shared on the Home Theatre Shack forum.  Honestly - this is a really REALLY good bit of software that could quite easily have been charged for.

Anyway, recently they added ASIO driver support - obvs helpful for someone who uses ASIO drivers...  The whole process is quite simple once it is set up and you get to actually SEE what your beloved new EQs are doing.

Short and sweet(?) post.

I've got a good one coming up though... Honest.

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.

-------------------------------------------------------------------------------------------

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