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Old 17th October 2010, 08:14 PM
steveecrane steveecrane is offline
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Location: Staffordshire
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Question K5881 Power Amp Clicking In BOTH Channels

Hello all,

I built this amp a while back - about a couple of months after it was first released, to be honest - and, save for around a year when I had a couple of Audio Innovations S1000s on loan, it's been in near constant use ever since.

I've replaced the valves twice since I've had it (both pre- AND power-stages) with identical valves to those specified in the original Mk1 design, and have been more than happy with it!

However, this afternoon I noticed a mild and regular 'clicking' in both channels (around 2-5Hz) present behind the music. Interestingly, when I disconnected the source (an AI pre-amp) by removing the 2 phono connectors at the back of the power amp itself, the clicking actually got LOUDER; this was a pity as I half-expected it to disappear altogether!

So, any ideas what it might be?

Cheers,

Steve.
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  #2  
Old 17th October 2010, 11:21 PM
John Caswell John Caswell is offline
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Join Date: Dec 2005
Location: Wokingham, Berkshire
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Default Re: K5881 Power Amp Clicking In BOTH Channels

Hi Steve,
This does sound like our old friend static discharge due to the tx cores/covers not being earthed. Try running a wire from both the the Optx covers and the power tx covers to chassis earth. It has probably occurred due to the ravages of time with slight corrosion setting in, thereby insulating/isolating the txs from chassis.
Not serious or dangerous but b****y annoying.

John
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Old 18th October 2010, 02:38 AM
Diamond Geezer Diamond Geezer is offline
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Join Date: Apr 2008
Location: Havant, Hampshire, UK
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Default Re: K5881 Power Amp Clicking In BOTH Channels

Quote:
Originally Posted by steveecrane View Post
Hello all,

I built this amp a while back - about a couple of months after it was first released, to be honest - and, save for around a year when I had a couple of Audio Innovations S1000s on loan, it's been in near constant use ever since.

I've replaced the valves twice since I've had it (both pre- AND power-stages) with identical valves to those specified in the original Mk1 design, and have been more than happy with it!

However, this afternoon I noticed a mild and regular 'clicking' in both channels (around 2-5Hz) present behind the music. Interestingly, when I disconnected the source (an AI pre-amp) by removing the 2 phono connectors at the back of the power amp itself, the clicking actually got LOUDER; this was a pity as I half-expected it to disappear altogether!

So, any ideas what it might be?

Cheers,

Steve.
Hi Steve.

This may sound like a silly question, but have you recently installed either a wi-fi modem, or a DECT 'phone?

I have a WAD K5881 Mk2 connected to QUAD 57's and three years ago, had similar problems. At the time, I had just installed a Linksys 54G wi-fi modem and shortly thereafter, a DECT phone I was evaluating for Phillips. I started getting similar problems and it was only after I removed the DECT phone at the end of the fortnight's test period, that the loud ticking stopped, but I was left with a very quiet buzz, which I hadn't had previously.

Realising at that point, that the phone had been causing the loud clicking, I decided to switch off the wi-fi modem and lo, the clicking stopped. As I had been having problems getting the modem to accept all three of my computers at the same time - which I had failed to do, no matter what I did - I decided to remove it and return to my cabled system and all was well. No more buzzes; clicks, or hum from my Hi-Fi.

I hope this helps you resolve your problem, but if not, maybe someone else can offer you appropriate advice.

As for your Mk1, if you should be interested in upgrading it to Mk2 standards, I have all the info you need, as recently supplied to two other members of this forum.

Cheers

Russ
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  #4  
Old 18th October 2010, 03:00 AM
steveecrane steveecrane is offline
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Join Date: Oct 2010
Location: Staffordshire
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Thumbs up Re: K5881 Power Amp Clicking In BOTH Channels

Russ / John,

I will take a look at both 'solutions' over the next couple of days and let you know.

I have had wi-fi (and these DECT phones) for many, MANY years (multiple variants of the Linksys WRT54xx) and this version has been installed for at least 2 of these!

As to the possibility of static from the Tx covers, this could be a possibility, given the fact that I did not utilise these amps for a while and they were stored in various (cold) places (though no damp, thankfully).

Finally, as regards the v2 'upgrade':

i) What's the difference (in sound terms)?
ii) Why do it (other than it improves the sound)?
iii) What's actually involved?
iv) Where can I acquire any required parts?
v) What's the cost?
vi) Any downsides - concerns, issues, risks, et al?

I suppose the final question is "Are there any other worthwhile 'upgrades' or tweaks to perform first" (or subsequently, for that matter!)? I have to be honest and feel the only thing that would seriously improve my set-up is if I had 2 K5881s to bi-amp with, as I had with the S1000s! :p

(As an aside: These power amps were only 'retired' as one of the 4 wire-wound resistors decided to get somewhat hot, and melt/burn the PCB!!! I think this may be a cathode resistor blowing as a consequence of a failing EL34 valve. Should've replaced them with 5881s as many folks suggest, e.g. http://www.borderpatrol.net/aiind.htm!).

Ah well, live and learn!

Thanks again for all your (rapid) feedback - greatly appreciated!

Cheers,

Steve.
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