So, some of you may remember this thread from a few years ago;
http://www.diyaudio.com/forums/tube...d-ii-all-original-condition-restore-sell.html
My great uncle gave me his old Quad gear including a pair of untouched Quad IIs and the 22 control unit.
A house move, a kitten, a puppy, a wedding and a baby later, I've finally had a chance to look at them again.
After a few shandies and feeling cocky - I decided to take a gamble and plug the whole lot in. I know, I know, reckless - but I knew the risks and thought I'd roll the dice.
Long story short - they work. I wouldn't say they are healthy but they definitely work and I've had them driving my speakers for a short period.
Which brings me to the restoration. I've been keeping an eye on eBay prices for these for the intervening years, and restored Quads that are ready to play definitely command a higher price. So my mind is made up, I am going to restore them and listen to them for a while before ultimately rehoming them.
Hence why I am posting here today as I am after some advice from you all about various decisions that will form the path of this restoration.
Here are my objectives.
First off - I want them to be 100% electrically safe.
I want to replace old components with contemporary equivalents that will have a long service life ahead of them.
I want to keep as much of the "Quad sound" as possible.
The Plan
Replace all resistors
Replace all capacitors
Replace speaker outputs with binding posts (can be done without drilling)
Add chassis earth from the bulgin plugs (possibly change to IEC)
Add single RCA input
Clean casing and respray if deemed necessary
Resistors
I'm planning to go with 1w metal oxide for R1 - R11. Yes I could be more faithful and choose a modern carbon comp or NOS carbon comp resistors but I feel the risk to the rest of the amp is too great. Using metal oxide should give the units the best life expectancy possible.
R12 - I'm going to use a 10w wire wound resistor.
Capacitors
Now here is my main conundrum. What to use what to use...
I'm going to pull the grey can C4/C5 and replace with an ARS 32uf+32uf
https://www.watfordvalves.com/product_detail.asp?id=2889
C1/C2/C3 - I'm thinking about replacing with these 0.1uf 630v Mallorys
https://www.watfordvalves.com/product_detail.asp?id=3146
C5 - looking at using Ansar 22uf
Ansar Supersound Audio Polypropylene Capacitors | eBay
C2/C3 replacements are non-conductive cases so don't have the impedance that the original circuit is designed to have. I have seen some restorers appear to wrap the cases in copper tape. Is this a viable way of recreating that impedance?
Why no PIO NOS? I've thought long and hard about this. NOS always worry me. The O means old, and even unused capacitors can degrade with age. It just doesn't seem worth the risk to me. Objective 2 is a long service life ahead of them.
Notes & Feedback
I will be labelling and bagging all the original parts as I remove them so that when I come to sell them - all the original parts will be included.
I'd really appreciate some feedback about my capacitor choices and any recommendations and suggestions for them before I start purchasing parts.
If I make it through the Quad IIs then we can start thinking about the fiddly 22 Control unit.
Thanks for reading.
http://www.diyaudio.com/forums/tube...d-ii-all-original-condition-restore-sell.html
An externally hosted image should be here but it was not working when we last tested it.
My great uncle gave me his old Quad gear including a pair of untouched Quad IIs and the 22 control unit.
A house move, a kitten, a puppy, a wedding and a baby later, I've finally had a chance to look at them again.
After a few shandies and feeling cocky - I decided to take a gamble and plug the whole lot in. I know, I know, reckless - but I knew the risks and thought I'd roll the dice.
Long story short - they work. I wouldn't say they are healthy but they definitely work and I've had them driving my speakers for a short period.
Which brings me to the restoration. I've been keeping an eye on eBay prices for these for the intervening years, and restored Quads that are ready to play definitely command a higher price. So my mind is made up, I am going to restore them and listen to them for a while before ultimately rehoming them.
Hence why I am posting here today as I am after some advice from you all about various decisions that will form the path of this restoration.
Here are my objectives.
First off - I want them to be 100% electrically safe.
I want to replace old components with contemporary equivalents that will have a long service life ahead of them.
I want to keep as much of the "Quad sound" as possible.
The Plan
Replace all resistors
Replace all capacitors
Replace speaker outputs with binding posts (can be done without drilling)
Add chassis earth from the bulgin plugs (possibly change to IEC)
Add single RCA input
Clean casing and respray if deemed necessary
Resistors
I'm planning to go with 1w metal oxide for R1 - R11. Yes I could be more faithful and choose a modern carbon comp or NOS carbon comp resistors but I feel the risk to the rest of the amp is too great. Using metal oxide should give the units the best life expectancy possible.
R12 - I'm going to use a 10w wire wound resistor.
Capacitors
Now here is my main conundrum. What to use what to use...
I'm going to pull the grey can C4/C5 and replace with an ARS 32uf+32uf
https://www.watfordvalves.com/product_detail.asp?id=2889
C1/C2/C3 - I'm thinking about replacing with these 0.1uf 630v Mallorys
https://www.watfordvalves.com/product_detail.asp?id=3146
C5 - looking at using Ansar 22uf
Ansar Supersound Audio Polypropylene Capacitors | eBay
C2/C3 replacements are non-conductive cases so don't have the impedance that the original circuit is designed to have. I have seen some restorers appear to wrap the cases in copper tape. Is this a viable way of recreating that impedance?
Why no PIO NOS? I've thought long and hard about this. NOS always worry me. The O means old, and even unused capacitors can degrade with age. It just doesn't seem worth the risk to me. Objective 2 is a long service life ahead of them.
Notes & Feedback
I will be labelling and bagging all the original parts as I remove them so that when I come to sell them - all the original parts will be included.
I'd really appreciate some feedback about my capacitor choices and any recommendations and suggestions for them before I start purchasing parts.
If I make it through the Quad IIs then we can start thinking about the fiddly 22 Control unit.
Thanks for reading.
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hi Katch
This site looks at many aspects of restoring the Quad 2
quad2powerampmods
and Keith Snook has some great information too
QUAD II Valve Power Amplifier Modernising and Modifying
I have a feeling you will end up keeping them
Cheers / Chris
This site looks at many aspects of restoring the Quad 2
quad2powerampmods
and Keith Snook has some great information too
QUAD II Valve Power Amplifier Modernising and Modifying
I have a feeling you will end up keeping them
Cheers / Chris
I would stay with good quality carbon film resistors in the Quad II amps the sound changes with metal film.
Here is a link to the modification I did to my Quad 22.
Quad 22 Preamp Challenge. - pink fish media
Sharif
Here is a link to the modification I did to my Quad 22.
Quad 22 Preamp Challenge. - pink fish media
Sharif
Any suggestions for resistors? Trying to find all 12 from the same series is proving difficult. What voltage rating do I need to meet - Keith Snook suggests 500v - is this overkill?
Hi
If you follow your own objectives
"First off - I want them to be 100% electrically safe.
I want to replace old components with contemporary equivalents that will have a long service life ahead of them.
I want to keep as much of the "Quad sound" as possible."
They should guide you to agree fully with what Keith and msdin suggests.
Alternatively you can do extensive research on ESR applying to high voltage
equipment, you will find there is more to component ratings than just
steady state conditions.
Cheers / Chris
If you follow your own objectives
"First off - I want them to be 100% electrically safe.
I want to replace old components with contemporary equivalents that will have a long service life ahead of them.
I want to keep as much of the "Quad sound" as possible."
They should guide you to agree fully with what Keith and msdin suggests.
Alternatively you can do extensive research on ESR applying to high voltage
equipment, you will find there is more to component ratings than just
steady state conditions.
Cheers / Chris
Limbering up... Quad 303 resurrected from the grave. It had no output on either channel. Replaced the PSU caps (output caps on back-order...), the electrolytics on both channels and replaced all the trimmers.
Just letting it burn in for an hour or so before resetting the bias. Gonna be using a pair of these to biamp my system while I get these Quad IIs back up.
Back on topic;
Having a little difficulty finding a supplier for the resistors in my Quads. Can't seem to find a brand and series that do all the values I need and don't fancy mix and matching. Any suggestions?
An externally hosted image should be here but it was not working when we last tested it.
Just letting it burn in for an hour or so before resetting the bias. Gonna be using a pair of these to biamp my system while I get these Quad IIs back up.
Back on topic;
Having a little difficulty finding a supplier for the resistors in my Quads. Can't seem to find a brand and series that do all the values I need and don't fancy mix and matching. Any suggestions?
Started ordering some bits today;
Smoothing caps are being replaced with these ARS 32uf+32uf cans
ARS 32UF+32UF/500V RADIAL
And the coupling capacitors are being replaced by these Mallorys
Cap-Mal-150-.1uF/630 volt
Both from Watford Valves.
Still choosing what to use for C1 and C5.
Still struggling to get the resistors.
Smoothing caps are being replaced with these ARS 32uf+32uf cans
ARS 32UF+32UF/500V RADIAL
And the coupling capacitors are being replaced by these Mallorys
Cap-Mal-150-.1uF/630 volt
Both from Watford Valves.
Still choosing what to use for C1 and C5.
Still struggling to get the resistors.
A few points:
Resistors: I stay with 0,5W (alt. 0,6W) metal film resistors, mostly because the physically smaller 1/4W types look rather silly!
I would caution regarding trying to be too 'grand'. Respectfully, as an EE I cannot support the subjective experience that metal film changes or diminishes the sound, or an overrated fixation with boutique coupling capacitors. There is no good reason to replace with carbon resistors - sorry. Materials have developed with great strides over the last 6 decades; carbon resistors have been used only because at the time it was all there were.
If the original appearance is part of your goal and you do not mind doing some 'tinkering', one can replace the twin electrolytic filter capacitor inside the case with two modern ones*. One can unsolder the bottom of the square container and remove the cap inside. What with newer smaller sized capacitors it is fairly easy to replace with two separate 32µF 450V units in the same space and bring out the connections topwise. (I use brands like Hitano, Trec, Jamicon and other reliable brands - no affiliation with any brand). The inside can be filled with some urethane foam or similar to keep the caps in place and the bottom returned. One does have to do a respray job to restore the appearance.
Finally there is a slight effect from replacing C2, C3 by non-metal canned polyester types. The slight (about) 18 pF of capaciy to earth thus forfeited can be compensated for by placing a 1 NF cap across (in parallel) with R11.
Technically this causes a lead phase shift correction within the NFB loop, improving stability - the effect can be seen when viewing a square wave response on a 'scope.
One can also substantially increase C5 to 1000µF or even 2200µF 35V, thus causing fixed bias conditions for the KT66s (the so-called 'music power' conditions), again taking advantage of the modern smaller size formats. With the h.t. at about 340V for our mains supply I could get 18W music power from a Quad II before clipping.
Finally: Do move C5 away from the hot R12! Over the years I have found just about every C5 a sorry dry emaciated wreck from having lived in the heat to R12. (Heat is the enemy of particularly electrolytic capacitors.)
Best wishes; Do keep us informed of your progress.
PS: Not attentive here! You could use the exact same capacitors for C1, C2, C3.
_________________________________________________________
*Apology. I have just noticed that you have already ordered some components. Fine then; perhaps a suggestion to other would-be restorers.
Resistors: I stay with 0,5W (alt. 0,6W) metal film resistors, mostly because the physically smaller 1/4W types look rather silly!
I would caution regarding trying to be too 'grand'. Respectfully, as an EE I cannot support the subjective experience that metal film changes or diminishes the sound, or an overrated fixation with boutique coupling capacitors. There is no good reason to replace with carbon resistors - sorry. Materials have developed with great strides over the last 6 decades; carbon resistors have been used only because at the time it was all there were.
If the original appearance is part of your goal and you do not mind doing some 'tinkering', one can replace the twin electrolytic filter capacitor inside the case with two modern ones*. One can unsolder the bottom of the square container and remove the cap inside. What with newer smaller sized capacitors it is fairly easy to replace with two separate 32µF 450V units in the same space and bring out the connections topwise. (I use brands like Hitano, Trec, Jamicon and other reliable brands - no affiliation with any brand). The inside can be filled with some urethane foam or similar to keep the caps in place and the bottom returned. One does have to do a respray job to restore the appearance.
Finally there is a slight effect from replacing C2, C3 by non-metal canned polyester types. The slight (about) 18 pF of capaciy to earth thus forfeited can be compensated for by placing a 1 NF cap across (in parallel) with R11.
Technically this causes a lead phase shift correction within the NFB loop, improving stability - the effect can be seen when viewing a square wave response on a 'scope.
One can also substantially increase C5 to 1000µF or even 2200µF 35V, thus causing fixed bias conditions for the KT66s (the so-called 'music power' conditions), again taking advantage of the modern smaller size formats. With the h.t. at about 340V for our mains supply I could get 18W music power from a Quad II before clipping.
Finally: Do move C5 away from the hot R12! Over the years I have found just about every C5 a sorry dry emaciated wreck from having lived in the heat to R12. (Heat is the enemy of particularly electrolytic capacitors.)
Best wishes; Do keep us informed of your progress.
PS: Not attentive here! You could use the exact same capacitors for C1, C2, C3.
_________________________________________________________
*Apology. I have just noticed that you have already ordered some components. Fine then; perhaps a suggestion to other would-be restorers.
Last edited:
I'm not massively concerned with retaining the original appearance; how often do you look at the inside of your amp when it's playing?
I'll be keeping all the original parts in original condition should a future owner want the original look.
I've gone with a set of metal oxide resistors ordered in kit form from an eBay seller.
I've also picked up some WIMA caps for C1.
In fact - everything needed is now ordered and should arrive this week - so stay tuned.
I'll be keeping all the original parts in original condition should a future owner want the original look.
I've gone with a set of metal oxide resistors ordered in kit form from an eBay seller.
I've also picked up some WIMA caps for C1.
In fact - everything needed is now ordered and should arrive this week - so stay tuned.
Is this a crime...?
An externally hosted image should be here but it was not working when we last tested it.
No its not a crime.
People keep thinking they are restoring quad amps and generation after generation will love and care for them.
Well shock horror after this generation how many want what looks like 1960's lab equipment in there flat or sitting room?
Its a bit like a classic car.
you can keep it original and not keep up with the cost of fuel and sit in the slow lane at 20 MPH thinking I have a classic or you can do subtle mods.
The choice is up to the owner.
then you end up with what about resale value..and everyone does them up to look original..then the next buyer does the same but they are run about 2hours and go in a box while the mass produced HIFI is used every day.
So whats the point of owning them?
Would I want a pair in front of my flat screen..er..no!
You either want to use them or keep them for a rainy day that never happens..
Look at post 2# in this thread..
The whole point of the quad is the sound quality..so if they don't sound good and look C**p why own them?
They should sound as good as possible and look the part or why bother?
There is a difference between pimp my ride and a professional build..
you should be able to say Look I have a couple of quad amps..
But that's my opinion..I would use selected parts as well..HIFI world did two rebuilds using Audio note /and russ Andrews parts then did a comparison..I'm not saying you should go that way but the outcomes were interesting..
Regards
M. Gregg
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Just remember,
If you chrome you have to clean..
(it shows the dust like crazy)
Remember to photograph the original so you have a guide..for rebuild!
Regards
M. Gregg
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