'Perceive' Contruction Diary

[tiroth]

If you get buzz only when connecting a source, it probably will be pretty easy to sort out.

Do you get buzz with no source connected?

Do you get buzz with no source and no connection from active xover to amp? (You can probably test this simply by shorting the amp input to local ground -- but make sure this doesn't force your xover to drive a dead short)

I find with these kinds of setups you often have to do some experimentation. If your boards do not have seperate power and signal grounds I'd start by bringing power ground from each amp and the xover to star ground, and DO NOT connect signal ground between xover and amps.

You should have exactly one connection to chassis ground. If you have an earth connection it should also be made at one point.

If this doesn't help, then you probably will need to draw an outline of current grounding arrangement to be able to go into more depth.

[5th element]

Interesting, my hifi buzzes but only some of the time. I have narrowed this down to the preamp/active xover. Its only a preamp because of the pot! Anyway I think this has something to do with another appliance somewhere either in our house or next door polluting the mains. Sometimes it buzzes sometimes it doesnt, there is not a lot I can do about this. It may be due to less then perfect grounding in my first PCB design, but Im not sure considering its completely silent when not buzzing.

If you have only run the amps for a short period of time it could be something similar, my buzzing can last for hours at a time and then it will just dissapear. Try running the amps for an few hours or so into the speakers, just on in the background and see if it comes and goes.

My buzzing is high frequency orientated there is no lows in it whatsoever. By high freq I mean around 2000hz or something similar and its not amp oscillation.

[ShinOBIWAN]

Really making some headway now, one cabinet around 80% done(not including finishing):

Also note the filler at the bottom of the bass cabinet, I wasn't paying attention and ended up cutting the driver recess at the wrong end! To top that its was also too big, clearly a case of cut once measure 5 times The automotive filler has done me proud though and rubbing you hand over it reveals a seamless plane, will look fine once its sprayed.















I'm biased of course but I think these look fantastic, better than I could have imagined. Really solid too, knocking on the side reveals negligible vibrations and resonances, the double layer of dedshete panels really did its job here.

[ShinOBIWAN]

EDIT: Resized the pictures as they were distorting the page frame.

Now the electronics:

Here's the amps being tested in pairs with the superb BMM Electronics M2010R1 PSU, this is really well designed supply and I couldn't imagine it being bettered for ripple, aside from using fully regulated. 70u thick 20mm wide PCB tracks, all discrete schottky diodes for the recitifier with RF filter caps, 18 x 4400uf caps with a ten fold RC filter and bleeders for balancing and ripple rejection - nice! Highly recommended.









I'm going to try some of the suggestion from the people here, BMM and Rod Elliot to try and get rid of the hum.

[Noksukau]

Originally posted by ShinOBIWAN
Also note the filler at the bottom of the bass cabinet, I wasn't paying attention and ended up cutting the driver recess at the wrong end!

LOL! Now it's a lucky horse-shoe.

I must say I've never made THAT mistake before, but plenty came close. Just last night I almost made a woofer cut-out that was 18cm too low, simply by adding 20cm rather than 20mm in Excel. It wasn't until I got the compasses out that I thought something looked wrong!

They are looking very nice indeed, I apologise as I haven't read the rest of your thread (will do later), your cabinets have a very 'Tony Gee' look about them (a compliment, angles and big baffles are a pig to build). It's more fun skipping to the end of a thread to see the (near) finished article, then reading how it came into being. Looking forward to updates...

[ShinOBIWAN]

Originally posted by tiroth
If you get buzz only when connecting a source, it probably will be pretty easy to sort out.

Do you get buzz with no source connected?

Do you get buzz with no source and no connection from active xover to amp? (You can probably test this simply by shorting the amp input to local ground -- but make sure this doesn't force your xover to drive a dead short)

I find with these kinds of setups you often have to do some experimentation. If your boards do not have seperate power and signal grounds I'd start by bringing power ground from each amp and the xover to star ground, and DO NOT connect signal ground between xover and amps.

You should have exactly one connection to chassis ground. If you have an earth connection it should also be made at one point.

If this doesn't help, then you probably will need to draw an outline of current grounding arrangement to be able to go into more depth.

Very interesting tiroth,

I hadn't actually thought of disconnecting the inputs - they are soldered so it was considered a hassle However when I did so the speaker are deadly quiet, I have to stick my head right up to the tweeter to hear a very faint background hiss, no hum or buzz.

What do I do to keep this great noise floor but actually have an input signal to the amps?

BTW: I don't have the active XO's in the circuit at the moment and it didn't make a difference whether it was or was not regarding the hum before. It does it with both the RME HDSP9632 soundcard and or the active XO.

Also I'd like to thank Jean Benoist from BMM electronics for creating a DC offset mod for the P101, this isn't his product and nor did he have to spend time analysing and designing this. It allow for an impressive 0.6mV measured across the speaker terminals with no input. It was around ~4-5mV before. I'm sure this has helped with the very nearly silent amps - with no input connected though

He's also suggested a change for Q7 that would help yield better performance - I will certainly check this out to.

[ShinOBIWAN]

Improved the hum issue, though not totally eliminated it to the extent of when there's no input connected.

Still can hear it from around a meter away, faintly that is. Without input its near impossible to hear without sticking your ear right upto the tweeter.

Unfortunately I had to remove the earth which is a dangerous practice and I'd rather find another solution.

Really had a good listen to the P101 and its a remarkable amp for its size and power ratings. Rod did a great job with the design.

Hmm, balanced is so much superior its not even funny.

[ShinOBIWAN]

I'm throwing around idea's for the wiring in the sub box.

Do you think parallel or serial?

Drivers specs are 2 x 8ohm 160w RMS and the amp is a single ESP project 101 rated at 150w into 8ohm and will be powering both drivers.

Parallel looks to be a 4 ohm load with 150w to each driver or serial with 8ohm load and around 75w to each.

Which would you go with?

[ScottG]

Originally posted by ShinOBIWAN
I'm throwing around idea's for the wiring in the sub box.

Do you think parallel or serial?

Drivers specs are 2 x 8ohm 160w RMS and the amp is a single ESP project 101 rated at 150w into 8ohm and will be powering both drivers.

Parallel looks to be a 4 ohm load with 150w to each driver or serial with 8ohm load and around 75w to each.

Which would you go with?

definitly parallel.. voltage amp + 2 drivers in parallel = +6 db; voltage amp + 2 drivers in series = 0 db increase (..+3 db for doubling driver, -3 db for series connection = 0).

btw, its look'in reeeeel good.

[george a]

Hi Sinobiwan

Nice Works.
If your body filler and Mdf are like we have hear in Oz, be careful about difeerent expansion rates for both at joins or filled screw holes etc.

We usually find the mdf shrinks compared to the filler and becomes quite visible even after spraying.....
Cheers


ps: should you consider a groove or "control joint" where the two materials are meeting in the same plane...