Author Topic: Quad II mono-block amplifier question  (Read 2053 times)

Offline MusicMan_ZA

Quad II mono-block amplifier question
« on: January 03, 2021, 02:49:20 PM »
I have obtained a scruffy-looking pair of QUAD II amps, S/N 30773 and 30679.
They are going to need a lot of cosmetic work, but all the resistors and capacitors have been replaced in 2014,
(for a total component cost of R82 from Communica in Cape Town!) :-)
I will check all the values, and make sure they are as they should be.
I have connected them up to my Sansui AU101 in pre-amp mode, and they sound wonderful!
But my first question/main concern is the following:

Valves are (for each mono-block):

1 x GZ32
2 x GEC KT66
1 x Telefunken EF86

and

1 x Telefunken ECC83!?!

I know there should be 2 x EF86 (original ciscuit).
I have heard of Triode in Cascode mode mods - but I think then both EF86 valves are replaced by ECCnn valves,
after the necessary circuit modifications?

So what is going on here?
If no circuit mods, would they even work / sound good (as they do) with an ECC83 just "dropped into" an EF86 circuit?
Could this have damaged anything?

If any mods have been made - which I can't see - what will happen if I remove the ECC83 and put in an EF86?
I am happy to try this, if it won't do any damage, and either just work, or not work.

Any advice?

Thanks,
Johan


I love music - analog and digital. Even listening to the Blues makes me happy. During the day I coach and counsel, after hours I indulge in my second passion - listening to vinyl and restoring turntables. Some I keep, some I sell...

Offline MusicMan_ZA

Re: Quad II mono-block amplifier question
« Reply #1 on: January 03, 2021, 02:54:11 PM »
Just another thought:

I might be wrong, and the second valve is not an ECC83!

I based this assumption on the empty valve boxes, and the fact that it looks completely different to the first EF86.

I will post pictures of the 2 valves now, for clarity.  :nfi:
I love music - analog and digital. Even listening to the Blues makes me happy. During the day I coach and counsel, after hours I indulge in my second passion - listening to vinyl and restoring turntables. Some I keep, some I sell...

Offline MusicMan_ZA

Re: Quad II mono-block amplifier question
« Reply #2 on: January 03, 2021, 03:01:49 PM »
The two valves:



Are they actually both an EF86, or what is the one on the right? I must admit it also looks like no ECC83 I have ever seen...

Thanks,
Johan
I love music - analog and digital. Even listening to the Blues makes me happy. During the day I coach and counsel, after hours I indulge in my second passion - listening to vinyl and restoring turntables. Some I keep, some I sell...

Offline norm

Re: Quad II mono-block amplifier question
« Reply #3 on: January 03, 2021, 03:14:09 PM »
Hi Johan,
As far as I can make out, both your valves are EF86's.
One on the right is a Telefunken grey plate and the left one is a Russian made EF86.
Regards,
Norm

Offline Family_Dog

Re: Quad II mono-block amplifier question
« Reply #4 on: January 03, 2021, 03:26:12 PM »
They should both be EF86, but manufactured by two different manufacturers. They will be interchangeable. The ECC8* series is NOT interchangeable with an EF86.

Valves manufactured by Philips & Mullard favoured the perforated anode but other manufacturers settled for a more conventional anode.



More here:  https://en.wikipedia.org/wiki/EF86


-F_D



-Eric

That Guy in South Africa...
*************************************
http://groups.yahoo.com/group/vintage_tube/
*************************************

Offline MusicMan_ZA

Re: Quad II mono-block amplifier question
« Reply #5 on: January 03, 2021, 03:28:02 PM »
Thanks Norm and Eric,

You have put my mind at rest!
And - although I feel pretty stupid now - I am glad I asked, rather than not!

Cheers,
Johan
I love music - analog and digital. Even listening to the Blues makes me happy. During the day I coach and counsel, after hours I indulge in my second passion - listening to vinyl and restoring turntables. Some I keep, some I sell...

Offline MusicMan_ZA

Re: Quad II mono-block amplifier question
« Reply #6 on: January 03, 2021, 03:55:27 PM »
Just for interest's sake (and my educations, what will happen if a rectifier valve
stops working? In any circuit, but particularly in this QUAD II?

Will anything be damaged, or will just a fuse blow, or will the amp purely stop
 working (playing music)?

 :teach: :thumbs:
I love music - analog and digital. Even listening to the Blues makes me happy. During the day I coach and counsel, after hours I indulge in my second passion - listening to vinyl and restoring turntables. Some I keep, some I sell...

Offline Family_Dog

Re: Quad II mono-block amplifier question
« Reply #7 on: January 03, 2021, 06:03:49 PM »
A rectifier with an open circuit filament will lead to total failure of the amplifier, nothing will work but no damage will occur. If it goes weak emission, the amplifier will play, but poorly, with low volume and possible distortion. The fuse will not blow in either case.

If the rectifier develops internal arcing, that is bad and the fuse should blow thus preventing any possible damage, specifically to the HT winding of the power transformer and electrolytic caps in the HT smoothing circuit. Bad!

That been said, this seldom happens.


-F_D



-Eric

That Guy in South Africa...
*************************************
http://groups.yahoo.com/group/vintage_tube/
*************************************

Offline MusicMan_ZA

Re: Quad II mono-block amplifier question
« Reply #8 on: January 03, 2021, 06:43:36 PM »
Thanks Eric, that is comforting to know.
It may sound crazy, but I am asking because
the one rectifier is a GZ32 and the other rectifier is a 5V4G,
and the one shows two glowing (more) orange "dots" from above, and the
other shows two glowing (more) yellow (dots) from above.
Paranoid, much?
They both work perfectly, and sound the same to me.
 :thumbs:
I love music - analog and digital. Even listening to the Blues makes me happy. During the day I coach and counsel, after hours I indulge in my second passion - listening to vinyl and restoring turntables. Some I keep, some I sell...

Offline MusicMan_ZA

Re: Quad II mono-block amplifier question
« Reply #9 on: January 03, 2021, 06:49:47 PM »
Here is another "for my education" question:

How hot should a QUAD II Power Transformer get?

It is currently 18.45pm, and 29dC in my living room.
I have been playing the QUAD II amps non-stop since 3.30pm, so a little more than 3 hours. (fairly low volumes).
If I now put my hand on top of the PT, it is hot, but I can keep
my hand there for 20+ seconds before I "have" to take it away -
not burning, just uncomfortable.
And this is right next to one big KT66 and the GZ32.
I don't think this is bad, at all?

I love music - analog and digital. Even listening to the Blues makes me happy. During the day I coach and counsel, after hours I indulge in my second passion - listening to vinyl and restoring turntables. Some I keep, some I sell...

Offline Family_Dog

Re: Quad II mono-block amplifier question
« Reply #10 on: January 03, 2021, 07:19:55 PM »
Thanks Eric, that is comforting to know.
It may sound crazy, but I am asking because
the one rectifier is a GZ32 and the other rectifier is a 5V4G,
and the one shows two glowing (more) orange "dots" from above, and the
other shows two glowing (more) yellow (dots) from above.
Paranoid, much?
They both work perfectly, and sound the same to me.
 :thumbs:

Essentially the same valve insofar as the Quad II is concerned. The 5V4G draws slightly higher heater current then the GZ32 so keep an eye on the temperature of the Mains transformer of the Quad using this as a rectifier. The correct choice would be GZ32 for those amps.


-F_D



-Eric

That Guy in South Africa...
*************************************
http://groups.yahoo.com/group/vintage_tube/
*************************************

Offline Family_Dog

Re: Quad II mono-block amplifier question
« Reply #11 on: January 03, 2021, 07:23:09 PM »
Quote
How hot should a QUAD II Power Transformer get?

See my previous reply iro Power Transformer with a GZ32. I doubt the 300mA higher heater current will be a major problem but I also do not think there is much reserve built into those transformers. As long as you can place your hand on the transformers you should be fine.

-F_D



-Eric

That Guy in South Africa...
*************************************
http://groups.yahoo.com/group/vintage_tube/
*************************************

Offline MusicMan_ZA

Re: Quad II mono-block amplifier question
« Reply #12 on: January 03, 2021, 07:23:43 PM »
Thanks again, Eric!
Info much appreciated.
 :thumbs:
I love music - analog and digital. Even listening to the Blues makes me happy. During the day I coach and counsel, after hours I indulge in my second passion - listening to vinyl and restoring turntables. Some I keep, some I sell...

Offline charles

Re: Quad II mono-block amplifier question
« Reply #13 on: January 03, 2021, 07:40:30 PM »
Congratulations with your Quad II valve amplifiers.

I restored a fair amount of these good sounding amplifiers.

Some advise. Try to Keep it completely original. Do not cut holes in the chassis.

Keep the original Jones sockets and power Bulgin power plugs.

Offline MusicMan_ZA

Re: Quad II mono-block amplifier question
« Reply #14 on: January 03, 2021, 08:46:22 PM »
Congratulations with your Quad II valve amplifiers.

I restored a fair amount of these good sounding amplifiers.

Some advise. Try to Keep it completely original. Do not cut holes in the chassis.

Keep the original Jones sockets and power Bulgin power plugs.

Thank you, Charles. I will do my best!
I love music - analog and digital. Even listening to the Blues makes me happy. During the day I coach and counsel, after hours I indulge in my second passion - listening to vinyl and restoring turntables. Some I keep, some I sell...