FAQ (Frequently Asked Questions)
about repairing OLD valve amplifiers.

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"Because ?they? told me so !"
You may not realizes how much you have been brainwashed by 
hundreds of dealers in Internet Forums
(disguised as innocent members of the public)
selling / hyping up their stock of old unreliable valves amplifier
(usually bought from boot fair or house clearance for a song)
until I ask you 2 question.
Are the Quad II and Radford STA-25 good amplifiers ?
You will answer, "Yes, they are great valve amplifier"
Have you heard both of these valve amplifiers ?
How do you know that they are great amplifier,
if you have never heard these amplifiers.
You answer will be "Because ?they? told me so !"
I will ask another question.
Are 40 years old British valve amplifier
better than Modern Chinese amplifier ?
Your answer will be "Of course."
Have do you know that,
unless you have auditioned dozens of 40 year old British amplifier
against dozens of Modern Chinese amplifier.
and your answer is "Because ?they? told me so !"
Please think for yourself,
or do you listen to everything that
"?they? told me so."

I apologise for being blunt,
but hundreds of dealers in Internet Forums (disguised as innocent members of the public)
have been selling / hyping up OLD UNRELIABLE British amplifier, that are
dangerous (usually does not does not have CE safely cage
(e.g. Quad II might produce 15 watts in the midrange,
but the transformers are too small to produce 10 watts of deep bass),
uses inferior "automatic cathode bias", 
so you get lousy power of 10 watt or less of DEEP BASS,
high output impedance, lousy woolly bass, slow recover from overload, etc
uses tiny valves like ECL86 or EL86 or KT66.
(We use the superior bigger version of these valves like)
( EL34 instead of EL84.                                              )
( like KT88 instead of KT66.                                      )
Many lousy design of phase splitter
(unbalanced at high frequency, e.g. Radford STA-25 and Quad II),
that anybody who knows anything about valve amplifier design
would NOT have designed the Radford STA-25 and Quad II.
If the phase splitter of Radford STA-25 and Quad II are so good,
why haven't more people copied them ?
Please look at the amazing similarity between MANY valve amplifier 
to the design of the Mullard 5-20 !

Question on 17 January 2006 = 

I have a pair of valve monoblocks, hand built by Peter Lindley (I would imagine specialists within your field would recognise his name). 

The mono blocks have been completely reworked and the only donor component from the original Quad II are the transformers. One power amp has developed a fault which by process of elimination is pointing to an unstable HT transformer. Fuses on the mono block in question keep blowing, but the mono block can work fine for some time without trouble. 

I cannot make contact with Mr Lindley, but I have someone locally who is able to complete repairs, but I would like to ensure I am able to source a high quality transformer as the component, design and build quality of the Lindley monoblocks are to a very high standard. 

Are you able to supply a high quality transformer? 

Will I need to match transformers in both mono blocks? 

What is the cost per transformer? 

What is the availability? 

Any advice or guidance would genuinely be welcome and appreciated. 


Answer = Sorry, but I have never heard of Peter Lindley.
I tried to find out a bit more about your amplifier on the Internet,
but my internet search did not find anything about Peter Lindley.
I apologise for being blunt,
but there has been so much nonsensical hype about monoblocks or Quad II or exclusivity,
that you will misunderstand my words, if I tried to overly polite and "beat around the bush".
The best sign of quality of a valve amplifier is 
NOT the usual hype of  monoblocks or Quad II or exclusivity.
The best sign of quality is the SIZE OF THE TRANSFORMERS. 
Our "standard" main power transformer weighs over 8 kilogram
(the weight of a 'typical' COMPLETE transistor amplifier or the weight of a COMPLETE QUAD II monoblock.)
Our "standard" main power transformers are so big,
you CANNOT fit it on a rebuilt version of the SMALLISH Quad II monoblock.
I really do not see the point of building or rebuilding SMALLISH Quad II monoblocks with small transformers.
The transformer on the Quad II monoblocks are 
TOO SMALL to produce 10 watts of DEEP BASS
(DEEP bass is a problem because the loudest sound on a recording 
is usually the bass drums or bass instrument.)
I do not see the point of building (or rebuilding) a monoblock with
transformers that are too small to cope with the insane amount of bass on modern CD. 
(There was a limit to how much deep bass you can put on a record,
before the wiggly groove 'overflowed' into the next wiggly groove).
Quad II monoblocks manages to squeeze out 15 watt in the midrange,
but that is not much use,
because a man shouting as loudly as possible produces 20 TIMES LESS THAN 1 WATT.
Please forget about the hype from Hi Fi magazines,
that sensationalize / hype up equipment to sell Hi Fi magazine,
or dealers selling / hyping up their products
in Internet Forums (disguised as innocent member of the public.)
Which do you think is better,
transformer from an amplifier that produces about 10 watt of deep bass (to 15 watts of midrange)
transformers from a 40 watts + 40 watts amplifier ?
So, if the monoblock uses transformers from the Quad II,
and it will cost a hundreds of pound to repair it,
my suggestion is to buy our
40 watts + 40 watts EL34 valve amplifier for GBP £250 + GBP £30 shipping,
with 2 years guarantee on everything (INCLUDING OUR BEST RELIABLE CHINESE VALVES. Many competitors only give 90 days guarantee on Russian valves),
with CE safety markings ,
with bolted on CE safety cage (with 'anti tamper' label, so you must NOT remove the safety cage.) and
peace of mind (no need to worry about the next repair bill) for 2 years
As for being well built,
our GBP £250 amplifier makes most British made amplifier look
as though they were built in a garden shed or kitchen table
(and some of them probably were)
with a Black and Decker drill and jig saw.
The metal joint on our chassis of our GBP £250 amplifier are so good that
you either do NOT see the joint, or you get a hairline crack. 
The build quality on the chassis of our Leak Stereo 20 and Roger HG88 III
is CRUDE and VERY POOR compared to our BEST Chinese standards, 
If Mr Peter Lindley has followed Quad II design,
then it is definitely a waste of time to repair it.
Automatic cathode bias is a waste of time because it lower power, increase output impedance
(Negative feed back when applied correctly, reduces distortion, noise and out put resistance. 
Negative feedback at the cathode reduced distortion, but increase noise and output resistance.
Please read Mr Morgan Jones book) ,
give woolly bass, slower recover from overload. 
While Quad (and McIntosh) enthusiast are telling everybody about the unique design of their transformers,
have avoid Quad (and McIntosh) style transformers !
Just because it is expensive and exclusive and different (?odd?) does NOT mean that it is the best !
Using a EF86 pentode valve (with VERY HIGH output impedance, compared to ECC82 (12AU7))
to drive the 'miller capacitance' of BIG power valves is a lousy idea.
To make matter worse, one of the EF86 has a HUGE amount of negative feedback,
so its' output impedance is totally different to the OTHER EF86,
so the a.c. balance between the 'push and pull' at ultrasonic frequency is poor.
This is important for the stability of the amplifier.
Yeah, Quad II is better than many transistor amplifiers.
Almost anything is better than "Class B biased' transistor amplifiers.
But do a 'shoot out' between the 10 watt (deep bass) to 15 watt (midrange) Quad II with SMALL transformer
against our GBP £250 40 watt + 40 watt valve amplifier with MUCH LARGER output transformers,
and the Quad II will lose EASILY
(assuming that the listening is done with High End '3 way' speakers with 10 inch woofers or 12 inch woofer,
like our GBP £450 to GBP £2,900 High End speaker)
(Assuming the listeners are not HUNDREDS OF DEALERS in an Internet forums, 
trying to 'hype up' and sell his stock of overpriced OLD UNRELIABLE used amplifier.
Regardless of hype about 6 inch speakers,
it is a waste of time testing SERIOUS valve equipment with
small 5 inch or 6 inch speakers (lousy bass, cannot handle power)
or electrostatic speaker (lousy bass, cannot handle power).
How can you test the 'bass slam' of the amplifier
with 5 inch or 6 inch speakers (lousy bass, cannot handle power) ?
Sorry, but hundreds of dealers (some big, some small) in Internet forum (disguised as innocent member of the public)
are leading thousands of people 'up the garden path',
with their absurd unbelievable hype,
so they can sell their stock of OLD UNRELIABLE used amplifier ('bought for a song' in Boot fairs and house clearance),
at silly absurd unrealistic prices.
40 year old used valve (or transistor) amplifier , cars , washing machine , man or woman
will have reliability problem (as you have found out to your cost,
whilst the dealer is laughing all the way to the bank).
Some woman will say that ALL man, regardless of age, are unreliable !

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