Pimp my Tannoy Reveal Active

I have a pair of Tannoy Reveal Actives and one of them suddenly started making a "buzzing" noise, kind of like when you have a guitar cable that has lost its ground. It still plays music, but is useless for any kind of critical listening.

I swapped input cables with the other speaker (which works fine) and it does not appear to be a cable problem. I usually use balanced cables with XLR connectors, but also tried balanced 1/4" and it sounds the same. Unbalanced 1/4" was much loader buzzing. With nothing plugged in its pretty quiet.

I run a home made attenuator inline to the monitors, and it does not matter what the setting is, I get the same amount od buzz. (No volume control on these monitors).

I opened it up and did not see anything obvious. I'm not a full tech, but know enough to be dangerous. I checked the power supply and seem to get a steady +/- 28V. I checked connectivity from the input to the circuit and that looks good. The buzz seems to come out both the woofer and tweeter, so I figure its not in the separate power amp chips. On a whim I replaced "IC1" (TL074CN), which seems to be a preamp/summer of some sort but no change, still get the buzz.

I have a decent digital meter but no scope. Any suggestions?

Here are some pics:
http://home.comcast.net/~ps8899/tannoy/tannoy_pcb_top.jpg
http://home.comcast.net/~ps8899/tannoy/tannoy_pcb_back.jpg
http://home.comcast.net/~ps8899/tannoy/tannoy_amp_side.jpg

thanks.
--Peter

If it's common [ like common ground , maybe something shook loose ,
check all grounds ? ] to both hi /lo speaker , tweeter

Perhaps in the crossover dividing network ahead of the amp chips ,
good luck & skill

regards Greg

can you describe the noise. we had a similar problem with some JBL powereed monitors where out of no where we were getting an

ERRRRRRRR

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sound comming out of it. Sounded like a 60HZ

Errrrr

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Doing a visual check, I couldn't find anything wrong and my boss decided to send it to JBL as it is under warrenty. so we sent it back to JBL for an overhaul. In our case at work I am would say a cap went south/bad in the PSU and was not filtering. Check the caps in the PSU... in the meantime I wait for the speaker to return.

It is a speaker so every thing vibrates inside it. Look for the thing with mass and check solder and connections at them.

Redo all the push on connectors.

The solder side looks like some rework was done on it. Some of the solder has grey look.

I would redo all the solder remove it first then resolder. Just reheating a solder connection can make it worse.

The left power supply cap solder connection looks not so good(back side picture). I would redo that one first.

Sounds like a bad connection not a bad part if you still get sound but have hum.

Any luck peter ? let us know

rgards Greg

Seeing as the sound got much louder with the unbalanced cable, could it be possibly a loose/partial connection at the input side?

Maybe even with the xlr combo connector itself, did you check with a ohm meter?

Ok, I'm looking at the circut board and without a diagram it almost looks like pin 3 is connected to pin1/ground through a resistor. If this is so than if there was as open through pin 2 then the speaker would be using the sheild via resistor as part of the signal hence noise and hum. Open circut on pin 3?

Thanks for all the suggestions, folks.

Heres a little more info. I too was suspicious of those combo connectors, as they are a bit finicky, with the XLR contacts just touching the sides of the pins.

I soldered an XLR cable right to the board and I get the same amount of buzzing, but only when loaded (cable plugged into the attenuator). Its not a pure 60 hz type hum, but sounds a little lika a saw tooth or square wave, with a fair amount of high frequency content.

Then I tried disconnecting either pin 2 or pin 3 (leaving the ground and one conductor) and the buzz was maybe 3-5X louder. Each side with the other disconnected seemed to contribute about the same level of noise.

Then I left 2 and 3 connected and removed pin 1 (ground). There was a little more buzz without the ground. When I connected the ground back the buzz was much lower in the tweeter, but about the same in the woofer.

I was able to disconnect the toroid transformer and test the (2) big caps with my meter (Fluke) which has a cap test function. I'm not sure if this is reliable or not, in terms of detecting noise issues.

Any other easy tests before I try to price a replacement module (assuming they sell these things...)? These things are probably 5 years old, I got them used some time back, so no warranty.

thanks,
--Peter

It's difficult to be sure, but it looks to me as if one of the solder connections to the XLR socket has broken away from the pcb track.
If you haven't done it yet, I would suggest re-soldering all the connections on the XLR socket.

Did you redo all the solder like I posted?

You would be suprised How often resoldering can fix solid state guitar amps and other things that vibrate.

I am going to try resoldering everything this weekend.
Will post back with the results...

thanks,
--Peter

A friend of mine had powered monitors with the same symptoms. I replaced the 2 large bypass caps and it was good as new. You can try replacing them with the caps from the good speaker.

Then replace all 4 (the 2 bad ones + the 2 from the good speaker) as you probably won't find the exact same caps, and you may want both speakers to be identical.

I had this problem on mine,

Check the IEC socket where the power lead plugs in. Directly above it (though its still actually part of the connector housing), you will see a small rectangulat area. This part was vibrating on mine. Bit of tape fixed it.

Well, I resoldered all of the connections on the board, and no change

I am thinking that I should try replacing the (2) big filter caps next...

--Peter

I had the same problem with my Reveal Active. Happily it turned out to be easy to fix - the two large electrolytic capacitors were not properly soldered, and simply re-soldering the joints fixed it. Those capacitors have very thick leads on them, and it looks to me like the flow soldering process did not get them hot enough. I imagine there are many Reveal Actives out there which will eventually fail in the same way.

I was unable to access the pics, but a couple of suggestions come to mind.
1) Is the speaker being driven by a balanced output? Because
2) This sounds like it could be a grounding issue.
2a) Are the speakers, attenuator, console, tape, computer all on one circuit? Note I don't mean that your wall sockets are on the same breaker, but that everything is plugged into the SAME wall socket! Wall sockets 10 feet apart can cause ground loops that will make your hair fall out trying to trace them (ask me what I look like now).
2b) If you have balanced driver and speaker, try lifting the shield (pin 1) at the speaker end. (I know people debate this, but EMI will impinge on the shield and if it connects to the input, guess what happens.)
3) By all means, reflow all solder joints. At least it can't hurt. Just some work.
3a) I endorse Handcrafted Tone's suggestion to try swapping caps from the good speaker. In fact, you might keep swapping stuff until you get the same problem in the good speaker. (Keep notes of what was swapped and when. Test after each swap. (More work, but you'll learn a lot that is more valuable than the time you'll spend.))
4) Try to get a schematic of the speaker electronics. If Tannoy can't/won't supply, check online forums, Google, Qwant, etc.
4a) Instead of posting links to pics, post the pics as attachments. That way they'll be part of your post, not off on a cloud, evaporating.
5) Tannoy doesn't say what class the amplifiers are. There was one review I found that mentioned they were MOSFET amps, which could be class AB (likely), class D (maybe), or class A (unlikely). Are they discrete output devices or a module? (I'm thinking modules.) So there are likely to be bypass caps at the module. You'll want to check those.
6) If your meter has a Hz function, try to identify the frequency at the amp output. Is it the mains power line frequency? (50 or 60 Hz.)
7) Finally, try shorting the input lines to each other, then each to ground, then both to ground. Do this with a short cable to the amp input. Is there any change in the noise? (This should have been at the top of the list, but I've done enough editing, so hopefully you'll have read to the end and see it.) Do THIS first!

Thread started in 2007. OP peters not active here for over two years...

AnalogPackrat said:

Thread started in 2007. OP peters not active here for over two years...

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Thanks. Oh well...