You are here

D.I.Y. amp

Customising, building or repairing your own gear? Need help with acoustic treatment or soundproofing? Ask away…

Re: D.I.Y. amp

Postby James Perrett » Fri Jun 15, 2018 8:07 pm

Folderol wrote:I still haven't run it at full power.

I keep meaning to suggest that you bring it over here sometime and we can compare it with my Hypex powered 405 and a standard 405 through the Tannoys.
User avatar
James Perrett
Moderator
Posts: 9224
Joined: Mon Sep 10, 2001 12:00 am
Location: The wilds of Hampshire
JRP Music - Audio Mastering and Restoration. JRP Music Facebook Page

Re: D.I.Y. amp

Postby Folderol » Fri Jun 15, 2018 8:32 pm

No, :(
The problem is I would have to completely dismantle the existing scruffy panel to make a template, rending the amp unusable. The spacings for the controls look pretty equal but are not quite the same. This was necessary to fit everything in.

Aha! I've just had an idea :bouncy:

I need to take photos absolutely square on. We know the dimensions of the panel itself so everything can be worked out to scale from those :lol:

This would mean only one removal and replace... Wooo!
User avatar
Folderol
Jedi Poster
Posts: 10577
Joined: Sat Nov 15, 2008 1:00 am
Location: The Mudway Towns, UK
Yes. I am that Linux nut.
Onwards and... err... sideways!

Re: D.I.Y. amp

Postby blinddrew » Fri Jun 15, 2018 9:26 pm

I would make you have a ruler against the front of the amp* as well, otherwise you could be led astray by distortion from the lens.

Or on the desk in front of it would work as well, basically as long as it distorts with the fascia.
User avatar
blinddrew
Jedi Poster
Posts: 10201
Joined: Sun Jul 05, 2015 12:00 am
Location: York
Ignore the post count, I have no idea what I'm doing...

Re: D.I.Y. amp

Postby Wonks » Fri Jun 15, 2018 10:46 pm

Preferably taken with a large telephoto lens from a long way away to minimise the distortion.
User avatar
Wonks
Jedi Poster
Posts: 10885
Joined: Thu May 29, 2003 12:00 am
Location: Reading, UK
Correcting mistakes on the internet since 1853

Re: D.I.Y. amp

Postby Folderol » Fri Jun 15, 2018 11:22 pm

Well I had a go at this.

I had my camera on maximum zoom, and about 6ft away from the panel with the camera directly in line and resting on a table. The image pretty much filled the view.

On pulling the image into an editor, the only thing I had to do was rotate it about 2 degrees. The grid is showing it pretty square, with just the top edge very slightly concave. X/Y proportions seem spot on.

I've cropped the image and loaded it into Inkscape so I can annotate it, and if Sahib is still around here I'll ask if he's interested.
User avatar
Folderol
Jedi Poster
Posts: 10577
Joined: Sat Nov 15, 2008 1:00 am
Location: The Mudway Towns, UK
Yes. I am that Linux nut.
Onwards and... err... sideways!

Re: D.I.Y. amp

Postby Jumpeyspyder » Fri Jun 15, 2018 11:36 pm

If you get stuck, give me a call, Not done anything like this before but..

I can call in a few favours at work and get access to;

a/ UV printer (can print on anything flat; glass aluminium, slate, concrete, wood..)
b/ lasercutter

That amp deserves a great panel!!
User avatar
Jumpeyspyder
Frequent Poster
Posts: 1152
Joined: Fri Jan 20, 2006 1:00 am
Location: Yorkshire

Re: D.I.Y. amp

Postby blinddrew » Sat Jun 16, 2018 9:50 am

If it were me, i might try making a wooden panel.
User avatar
blinddrew
Jedi Poster
Posts: 10201
Joined: Sun Jul 05, 2015 12:00 am
Location: York
Ignore the post count, I have no idea what I'm doing...

Re: D.I.Y. amp

Postby Folderol » Sat Jun 16, 2018 10:34 am

@jumpey
Thanks. I may call on you depending on 'stuff'.

@BD
That really would not work. Lots of controls quite tightly packed, and it would look totally out of place with everything else being either black or copper coloured metal.

I have actually come up with an even cunning-er plan.

Rescale the image down to exactly 1:2 then create an overlay in inkscape with accurate position info, that can be printed on A4 paper, but also keep the image for reference.
User avatar
Folderol
Jedi Poster
Posts: 10577
Joined: Sat Nov 15, 2008 1:00 am
Location: The Mudway Towns, UK
Yes. I am that Linux nut.
Onwards and... err... sideways!

Re: D.I.Y. amp

Postby Folderol » Wed Mar 06, 2019 8:42 pm

Hmmm. Amazing how much dust has accumulated in this room.
{brush}
{brush}
{brush}{brush}{brush}{brush}
{brush}
{COUGH}{brush}
{brush}

That's better.

Now, about this long running saga...
Although the amp seems to have been behaving perfectly as far as I can tell, the business of that asymmetry at the point of limiting has continued to bug me.

On my last day at work, my bench was clear so I quickly knocked up a rat's nest of a fully symmetrical possible replacement for the 'middle' stage. This is where I think the problem is coming from. The test looked extremely promising.

Now, as I'm expecting to continue to mess about with electronics stuff for fun (and friends) I decided to get accounts set up with both RS and Farnell. I then ordered a few transistors, caps and a stripboard - just to make sure the accounts were set up you understand :tongue:

Also, over the last couple of months I've been pootling about with my drawing package and now have a full scale copy of the exact positions of where all the controls are supposed to be. Originally I had thought of making an overlay of some sort matching the current positions, but now my thinking is that it would be simpler to just make a completely new panel.

The drilling and cutting I can do myself, but I would have the get it etched elsewhere. My idea here is to get a black anodised panel so the etching will reveal the bright aluminium underneath.

So, once more, watch this space :bouncy:
User avatar
Folderol
Jedi Poster
Posts: 10577
Joined: Sat Nov 15, 2008 1:00 am
Location: The Mudway Towns, UK
Yes. I am that Linux nut.
Onwards and... err... sideways!

Re: D.I.Y. amp

Postby Wonks » Wed Mar 06, 2019 8:54 pm

So the whole idea was to show us your etchings all along! :D
User avatar
Wonks
Jedi Poster
Posts: 10885
Joined: Thu May 29, 2003 12:00 am
Location: Reading, UK
Correcting mistakes on the internet since 1853

Re: D.I.Y. amp

Postby blinddrew » Wed Mar 06, 2019 9:49 pm

I was wondering if you'd got the panel sorted on this yet!
User avatar
blinddrew
Jedi Poster
Posts: 10201
Joined: Sun Jul 05, 2015 12:00 am
Location: York
Ignore the post count, I have no idea what I'm doing...

Re: D.I.Y. amp

Postby Folderol » Sat Mar 09, 2019 9:26 pm

I was wondering if you'd got the panel sorted on this yet!

Well I've thought about it quite a bit :tongue:

Anyway, moving on, there is progress!

I've built up the replacement for the dodgy part of the amp onto a proper piece of stripboard with nice new components, and sort-of faked it driving the output stage. Stability is excellent. No nasties when hit with sharp edged square waves, nor with slowly ramping triangles. From cold (where the offset has been zeroed) there's no more than 1mV drift after about half an hour. When a sine wave input is run massively into overload (to almost a square wave) the offset shift is less than 2mV.

I'll do a few more tests to see if I can make it hiccup, then if all is OK I'll unhook one of the existing sections of the amp and try this in its place . I'll probably use the sub amp as if it all goes tits-up that's the one I don't currently use anyway.

Once I'm more confident I'll post drawings and pix.
User avatar
Folderol
Jedi Poster
Posts: 10577
Joined: Sat Nov 15, 2008 1:00 am
Location: The Mudway Towns, UK
Yes. I am that Linux nut.
Onwards and... err... sideways!

Re: D.I.Y. amp

Postby Folderol » Tue Mar 12, 2019 12:56 pm

Well today with the decks cleared, and after extensive testing of the new module on its pcb I carefully connected it up to the sub amp, checked all connections multiple times and switched on.

... I've just put an order in to RS for 28 quids worth of power transistors :madas:
User avatar
Folderol
Jedi Poster
Posts: 10577
Joined: Sat Nov 15, 2008 1:00 am
Location: The Mudway Towns, UK
Yes. I am that Linux nut.
Onwards and... err... sideways!

Re: D.I.Y. amp

Postby Wonks » Tue Mar 12, 2019 1:04 pm

Should have doubled it to save on the postage for the next lot. :D
User avatar
Wonks
Jedi Poster
Posts: 10885
Joined: Thu May 29, 2003 12:00 am
Location: Reading, UK
Correcting mistakes on the internet since 1853

Re: D.I.Y. amp

Postby Folderol » Tue Mar 12, 2019 4:08 pm

What makes you think I didn't?

Found one silly mistake that could have caused quite serious overheating, but not the instant explosive destruction :(

I'd carefully wound the bias preset to the extreme end... the wrong one.

Checked the new module, and that is still fine {phew}.

When the transistors arrive, I'll hook them up directly to the module and feed from my test (current limited) PSU to see if there's something else I missed, although I can't think of anything.
User avatar
Folderol
Jedi Poster
Posts: 10577
Joined: Sat Nov 15, 2008 1:00 am
Location: The Mudway Towns, UK
Yes. I am that Linux nut.
Onwards and... err... sideways!

PreviousNext