Help Help

[Audio Al]

:( After accumulating all the necessary bit to get my Quad 11 and 57's working , today was the big day to wire it all up

I had seen the quad 11's working
I had seen the 57's working both when demo done at time of purchase

I have seen the Croft 25 basic working last weekend when at Tarzan's towers on his 1200

All cables were made up for me by David MCRU

Connected everything up
http://img.photobucket.com/albums/v240/bigboobs/IMG_2078.jpg

Left speaker Quad
http://img.photobucket.com/albums/v240/bigboobs/IMG_2079.jpg

right speaker quad
http://img.photobucket.com/albums/v240/bigboobs/IMG_2080.jpg


and when putting the right speaker cable in the croft amp I get a massive feedback blast from the right 57 ? even if I just touch the pin on the end of the cable with my finger it does the same :eek:

I have the Croft switched to Phono

I have the 1200 MK11 earth wire connected to the Croft earth post

Both Quad 2's are lighting up fine

left
http://img.photobucket.com/albums/v240/bigboobs/IMG_2081.jpg

right

http://img.photobucket.com/albums/v240/bigboobs/IMG_2083.jpg

If I touch this pin I get the blast

http://img.photobucket.com/albums/v240/bigboobs/IMG_2084.jpg

The other red one I can put in either outlet and all is quiet , put the blue one on any part of any outlet post and the blast happens :scratch::scratch::scratch:

Any ideas please :)

[Barry]

How are the Quad IIs earthed? Are you using the screens of the cables between the Croft pre and the Quads to earth the power amps? What does the "blast" sound like - a loud hum? If so then you have a hum loop.

Make sure the dangling unconnected yellow/green eath wires are not touching the metalwork of the Quad IIs. It would help if the two interconnect leads are loosely twisted together.

What happens if you swap over the red and blue plugs? Does the "blast" change channels? If it does then there is a problem with the Croft, if it does not then the problem is with the 'blue' channel Quad II, and I would suspect the input capacitor has become leaky.

Make sure those bullet-plug phono plugs are pushed fully home.

[Audio Al]

Hi Barry

How are the Quad IIs earthed? The Quad 11's are not earthed as they are only 2 pin plugs Are you using the screens of the cables between the Croft pre and the Quads to earth the power amps? Not sure The cables were made up for me by David What does the "blast" sound like - a loud hum? If so then you have a hum loop. No Its a loud blast not a hum

Make sure the dangling unconnected yellow/green earth wires are not touching the metalwork of the Quad IIs. OK will move them It would help if the two interconnect leads are loosely twisted together.

What happens if you swap over the red and blue plugs? Does the "blast" change channels? No it stays the same If it does then there is a problem with the Croft, if it does not then the problem is with the 'blue' channel Quad II, and I would suspect the input capacitor has become leaky.

Make sure those bullet-plug phono plugs are pushed fully home.

They are well pushed in

[Lodgesound]

Hi Al;

Those amplifiers should seriously be earthed - without a mains earth the casework will possibly have aquired a potential and be causing you a number of problems. You'll probably find that if you touch the amplifiers casework when they are on you get a mild tingle.

Why is the earth wire on the input connection cables not connected? Again this will cause you a number of problems such as you are experiencing.

[synsei]

If you have an amp sitting around with splittable Pre/Power sections then you have the ability to diagnose the component which has the fault Al. Firstly, hook the Croft up to drive the power section of the amp and wire up the speakers. If all is well then it is not the Croft. Next, drive the Quads with the Pre section of your spare amp, hooking the speakers up to the Quads of course. If neither of these options works then the problem is either with the speakers or the IC's. I would suggest trying an alternative pair of speakers as well, just to be on the safe side ;)

[Audio Al]

Had another go at sorting this

I swapped the rca output cables from amp to amp and now 1 57 works so I unplugged the speaker cables from the working 57 and plugged them into the second 57 and that now works , Both speakers are working and it looks like only quad 11

So it looks like one Quad 11 is knackered :(:doh::doh::doh:

or could it be the cable between the rca's and the quad11's :scratch::scratch:

[Lodgesound]

Just had another look at the pics Al.............you must connect that earth wire on the mains cable to one of the screws on the chassis of the amps.

[dantheman91]

You plonker

[Audio Al]

Just had another look at the pics Al.............you must connect that earth wire on the mains cable to one of the screws on the chassis of the amps.

OK

Will do it now and see what happens :)

[Audio Al]

You plonker

Me a plonker :scratch:

Please tell :D

[nat8808]

Is it standard not to have Quad IIs earthed? Seems a little dangerous for a valve amp with hundreds of volts running inside.

AND you're plugging the speakers in and out whilst the amps are on? Sounds like a recipe for blowing up power amps if you're not careful (not sure how that effects those with output transformers.. burnt out transformers if you short the speaker leads?).

Always connect everything first, then turn on the pre, then turn on each power amp (and quickly off again if you have the hum).

Back to the problem, does sound like an earth loop (feedback is only when you have a mic picking up the sound of the speaker which plays the sound from the mic, and on and on). Same would happen if you touched the end of a guitar cable and the amp was on, a loud hum and that would be expected...


Try plugging everything into the same socket via a multi-way. I've had earth loops from having amps plugged in in different sockets before. Perhaps the croft and the good quad are plugged in to one socket and the bad one in another? Then again, perhaps if the Quads aren't earthed, this shouldn't make any difference?

Hang on , just realised, you're using 57s which also have power. My guess is the problem lies between the bad amp and the bad 57. Some kind of earth loop going on there at FULL power. Could be simple or could be hidden within the connections like a stray strand of wire bridging something. You could experiment with plugging them using differnt sockets too.

[Firebottle]

With the working Quad II try both your interconnects, that way you'll know they are both OK.
Cheers

[nat8808]

Me a plonker :scratch:

Please tell :D

My quess would be not having the Quad II's earth's connected but I'd have hoped the previous owner would have explained that to you. Can't expect to just know these things..

[Barry]

Al, did you get a mild electrical shock when you touched the pin of the blue phono plug? If that is what you meant by a "blast", then it sounds like the input capacitor of the respective Quad amp has become leaky and needs to be replaced.

By the way, as nat8808 has pointed out, you should never unplug the speaker leads with valve power amps whilst they are powered up.

[nat8808]

What does the "blast" sound like - a loud hum? If so then you have a hum loop. No Its a loud blast not a hum



A blast of full volume mains hum is still a blast. I'm sure you don't want to have it going on too long to analyse whether it sounds like very loud hum though.

You should hear mains hum on a mega-watt PA for half a second! Certainly a massive blast that stops everyone in their tracks!

[Audio Al]

Al, did you get a mild electrical shock when you touched the pin of the blue phono plug? If that is what you meant by a "blast", then it sounds like the input capacitor of the respective Quad amp has become leaky and needs to be replaced.

By the way, as nat8808 has pointed out, you should never unplug the speaker leads with valve power amps whilst they are powered up.

No the blast was audible not a electric shock , I switched the Croft to mute before unplugging the bananas / speaker cables

[hifi_dave]

Assuming the Burnes plugs are wired correctly, the Quad IIs will get their earth via the incon to the Croft pre.

Do not power up the Quad IIs without the incon and the pre on.

Adding more earths might produce 'hum'.

Touching the inner pin with everything powered up is NOT a good idea and will produce a very loud 'hum/buzz'.

I would suggest you plug everything up completely before turning on - pre first and wait for it to switch on before powering up the Quad IIs. Finally, switch on the ESLs.

Do not unplug anything when powered up.

[Audio Al]

With the working Quad II try both your interconnects, that way you'll know they are both OK.
Cheers


I did this , firstly connected one way I got a massive audible blast from the right hand 57

Swapped the plugs from amp to amp then I had audio from the right hand speaker and no blast , but nothing from the left hand quad

Thats when I swapped the speaker cables from the working 57 to the other 57 then that one worked

I am going to have a look inside the 6 pin connecter plug and see if they are wired the same :scratch:

[Audio Al]

OK

I have used my Bosch meter set the ohms

And I have continuity on 2 pins on each end of the interconnects so it looks like the cable is OK

The same 2 pins on each connector into the Quad 11's / RCA connect into the croft

Time to get the quad 11 looked at

I cant think of anything else that could cause this :scratch:

[Barry]

No the blast was audible not a electric shock , I switched the Croft to mute before unplugging the bananas / speaker cables

At the risk of belabouring the point, is the "blast" a very loud hum? If it is then there is an earth loop problem.

Switching the Croft to 'mute' in insufficient. The Quads themselves must be switched off when changing cables. Valve power amps must always terminated, so the output transformer is loaded.

[Audio Al]

is the "blast" a very loud hum?

Maybe I don't know the difference between a loud audible blast and a loud hum :scratch:, it makes me jump

[Barry]

Maybe I don't know the difference between a loud audible blast and a loud hum :scratch:, it makes me jump

Is it high in pitch or low? Does it sound like a whistle, a buzz or a hum?

[Audio Al]

Looking at the rear of the croft , it has

OUT

Line out

I have the interconnects plugged in the OUT

is this correct or am I a plonker :scratch:

[Audio Al]

Is it high in pitch or low? Does it sound like a whistle, a buzz or a hum?


Its a low sound not a whistle

[Barry]

Its a low sound not a whistle

Do you get the problem if the 6-pin Jones plug is disconnected from the suspect Quad power amp? If you do, then it looks like the problem is with the amp.

If it was an earth loop problem, the resultant hum should be quite noticable but not loud enough to be alarming.

You are correct in feeding the Quads from the OUT sockets on the Croft preamp

[hifi_dave]

Looking at the rear of the croft , it has

OUT

Line out

I have the interconnects plugged in the OUT

is this correct or am I a plonker :scratch:

Use the " out " - the last sockets on the end of the row, furthest from the " phono ".

[Audio Al]

Use the " out " - the last sockets on the end of the row, furthest from the " phono ".

OK Thanks , that's the one I am using

[Barry]

I've just noticed you live in Essex. Would you be willing to PM me your address and telephone number. If you are not too far away, I might be able to pop round and try to help you out.

Failing that, we might be able to sort things out over the phone.

[Audio Al]

PM on its way :D

[Lodgesound]

Was about to offer the same as I live next door in Surrey....

[Barry]

After verbal instructions via the phone, Al and I have now ascertained the problem lies with the 'blue', Quad II amp feeding the left-hand speaker.

The loud hum (the "blast") was due to the 'bullet' phono plug not making proper contact. (So much for the virtues of single point connection to the outer part of the phono socket!)

Nothing wrong with the Croft preamp or either of the Quad ESLs. The chassis of the Quad IIs are earthed via the interconnects and preamp.

[Audio Al]

Was about to offer the same as I live next door in Surrey....


Thanks for the offer , I am now sure its a amp fault :(

Strange as they were both working when auditioned before purchase :scratch:

Sods law :)

And a big thanks to Barry ;)

[nat8808]

If the Quad IIs are earthed via the pre-amp then these Bullet plugs are probably a very poor choice in this instance!

Surely you'd want a more substantial connection if that's the only earth?

Still, Al, you shouldn't disconnect speaker cable from amps whilst they're still on - just asking for trouble, even disconnecting at the speaker end.

Well, with solid state amps you can but still dicing with blowing up your amps for the sake of saving a little time.

Similarly, it's bad practice to disconnect the audio input to a power amp whilst they are still on. Some can go into oscillation and other stuff with the signal earth being disconnected, hence why you should plug it all up, then turn on the pre-amp first (sometimes wait until it clicks on, depending on the pre) before switching on the power amps.

EDIT: perhaps if one is now broken, it's because the output transformer has been damaged from this?

[nat8808]

After verbal instructions via the phone, Al and I have now ascertained the problem lies with the 'blue', Quad II amp feeding the left-hand speaker.

The loud hum (the "blast") was due to the 'bullet' phono plug not making proper contact. (So much for the virtues of single point connection to the outer part of the phono socket!)

Nothing wrong with the Croft preamp or either of the Quad ESLs. The chassis of the Quad IIs are earthed via the interconnects and preamp.

So the amp is still broken but no more blast? Or did sorting out the bullet connector make it work now?

[Barry]

EDIT: perhaps if one is now broken, it's because the output transformer has been damaged from this?

No, there is still a faint hiss/buzz to be heard close to the speaker fed by the faulty amp.


If the Quad IIs are earthed via the pre-amp then these Bullet plugs are probably a very poor choice in this instance!

Surely you'd want a more substantial connection if that's the only earth?

Agreed - 'bullet' plugs are probably the worse choice in this case. In the original Quad 22/ II setup, the metalwork of the Quad IIs were earthed via the screen braiding of the umbilical leads of the Quad 22 preamp. These umbilical leads were directly connected to the Quad 22, so preserving the integrity of the earth connection.

Such an arrangement is frowned upon these days, and probably does not conform with modern safety standards. The problem is the '0 volt' rail and the chassis metalwork on the Quad IIs are one and the same. Ideally the metal work should be earthed directly to the mains earth at the wall socket, though there will most certainly be an earth loop problem. Only by trying it out can the problem be assessed, and if one exists, it could perhaps be ameliorated by loosely twisting the left and right-hand interconnects together.

[Tarzan]

If you need a spare interconnect PM me Al:)

[Audio Al]

Thanks for the offer Andy

I have been in contact with Dave at MCRU and he is going to change the 2 bullets to RCA for something with better earth

Top man is our David :)

[The Black Adder]

My old Quad II's were not earthed and took the earth via the inputs. When Glenn had them back for a service n stuff he earthed them properly.

[Tarzan]

Thanks for the offer Andy

I have been in contact with Dave at MCRU and he is going to change the 2 bullets to RCA for something with better earth

Top man is our David :)

He is indeed, got shitloads of I/Cs here if you get stuck.:)

[macvisual]

Audio Al;

Glad you found the fault! What about a few photo's of your ESL57's..? Are they bronze or black? Matched pair and of what age might you know?

Hope you've them raised off the floor for best audio benefits?

Loved to see photo's please....

[The Black Adder]

I used MG G2000HD's Cu with WBT's on my Quad II's. Nice tight fit on the Socket.