Advice: Amp building
 

I would love to build my own HiFi Amp.

Actually Powers amps, maybe valve.

I've had a quick Amazon search and Google search and found a few articles
but I wondered if anyone had bought and used a book, or followed any
particular plans.

Id like to maybe Bi-Amp and defo Bi-Wire

Cheers

Tim

Advice: Amp building
 

Tim Guy wrote:
I would love to build my own HiFi Amp.

Actually Powers amps, maybe valve.

I've had a quick Amazon search and Google search and found a few articles
but I wondered if anyone had bought and used a book, or followed any
particular plans.

Id like to maybe Bi-Amp and defo Bi-Wire

Audio Electronics by John Linsley Hood - your public library should have a copy.
It makes interesting reading and has a few interesting power amp circuits.

For your first amp you might be better using a kit such as:
http://www.williamshart.com/classa.htm
You will end up spending more than you would by just buying a decent amp
but any hobby takes time and money, and listening to your own work gives
a certain satisfaction.
As you learn, you will learn that biwiring is pointless, and biamping is
equally pointless without an active crossover such as:
http://www.bmm-electronics.com/Produ...roduct_ID=2300 .
So for a decent first project, you could build an amp with 4 power amps,
2 active crossovers (and ditch the crossover in your speakers) and have
something that will sound decent for the rest of your life.
My Linsley Hood 75w amp is 30 years old and still sounds as good as anything
you could buy today.

--
Eiron

No good deed ever goes unpunished.

Advice: Amp building
 

In article , Eiron
wrote:

Audio Electronics by John Linsley Hood - your public library should have
a copy. It makes interesting reading and has a few interesting power amp
circuits.

I'd add that if you wish to explore this topic, and perhaps be able to
design/understand/modify then the other books by JLH, and those by Doug
Self may well be useful.

For your first amp you might be better using a kit such as:
http://www.williamshart.com/classa.htm You will end up spending more
than you would by just buying a decent amp but any hobby takes time and
money, and listening to your own work gives a certain satisfaction.

Their kits are also useful as an easy starting point for some of the 'bits'
if you want to experiment. You may be able to find most of the items
cheaper elsewhere, and find a wider diversity, but they can be useful as a
'first stop' for things like a case or heatsinks, etc, if you don't want to
search for all the bits needed.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
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Advice: Amp building
 

In article . com,
wrote:
You might want to look into Gainclone type chip amps.There are plenty of
these type of kits available now using Panasonic chips.These are very
simple affordable kits that deliver unmatched bang for your bucks. I
have a LM3876T amp that is really superb sounding.Its 56 watts RMS seems
adequate power for most mainstream speakers.Believe all the rave reviews
-they are genuine high end sound at a bargain price.

If investigating such designs, beware of one snag I encountered when
looking at them some time ago. At least one of the 'designs' I saw
described on the web uses power supply reservoir caps that have far too low
a capacitance value. This may well affect (degrade) performance, depending
on circumstances, etc.


You might want to search under 47 Labs which started all this. Their
sound is very fast ,clear and dynamic and a lot of this must be due to
their simple design and short signal paths.Imaging is really 3D.The vast
majority of transistor amps sound very hazy,slow and compressed by
comparison.

FWIW My experience with both designing and listening to 'transistor amps'
over the decades is that I've not really encountered anything which could
be described by saying the 'majority' of them sound "hazy, slow and
compressed". The vast majority of those I've designed/built/used don't
sound like that at all - or at least that is my impression, and that of
others who have listened to them.

If the 'gainclone' you build sounds distinctly different to most of the
transistor amps you have heard I would be inclined to suspect that the
gainclone design you built has a problem - e.g. using reservoir caps that
are too small as per the example I mention above.


They approach the sound of a good SET amp in many ways
although lack a little of their harmonics and tonal colour.

The above may perhaps confuse the OP.

Note that most transistor amp designs tend to have a flat response, low
distortion, and a low output impedance. Whereas zero-feedback 'SET' designs
tend to have a tailored response, distortion that rises rapidly with
output, and a relatively high output impedance. All of these factors may
cause the SET design to change the signal patterns and cause audible
changes in some circumstances.

Up to you which you prefer. :-)

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Advice: Amp building
 

Note that most transistor amp designs tend to have a flat response, low

distortion, and a low output impedance. Whereas zero-feedback 'SET'
designs
tend to have a tailored response, distortion that rises rapidly with
output, and a relatively high output impedance. All of these factors
may
cause the SET design to change the signal patterns and cause audible
changes in some circumstances.

It may be useful to seperate out some of the commonly used expressions
regarding SETs and valve amps, since I know several have been confused.

a) One of the common characteristics of SETs (though NOT implicit in
the term "single ended triode") is the use of a DHT (directly heated
triode) in the output such as 2a3, 6B4G, 300B and 845 - this can be a
major positive factor in the overall sound, against which can be set
the drawbacks Jim has listed above. .
b) When we come to DHTs we are in another ballgame, in my opinion.
Those who habitually use DHTs, do extended listening tests with DHTs,
and are familiar with their characteristic sound will claim they offer
quite audible gains in clarity over indirectly heated valves. This is
only partly a question of output valves, but in practice only a small
handful of people will have used small signal DHTs for preamps, input
and driver stages of amplifiers. Reason being that while output DHTs
are available in current production, there are zero small signal DHTs
(except one or two rare boutique ones at huge prices). They are
available on ebay since they were used in countless old radios from the
20s and 30s, and there are good but dwindling stocks still to be had.
Some on the other hand have become quite rare. As you might guess, I'm
a huge fan and use them in preference to anything else.
c) DHTs and zero feedback can be used in push-pull amps with different
results from their use in SETs. Each of these factors contribute -
feedback, push-pull/single ended, indirectly heated or directly heated
and so forth (we could go on)

I don't personally use SETs and never have, and it is useful in terms
of general attribution theory to consider what we attribute to which
factors. In particular DHTs and SETs are absolutely not equivalents -
one refers to valve construction and the other to circuit topology. One
might consider that SETs with DHTs are a bit of a curates egg - both
good and bad factors. I'd personally opt for all-DHT push pull amps
given the choice. We haven't even come to another common SET feature -
interstage transformers - but that's enough to be getting on with. Andy

Advice: Amp building
 

In article .com,
Andy
Evans wrote:
Note that most transistor amp designs tend to have a flat response, low

distortion, and a low output impedance. Whereas zero-feedback 'SET'
designs tend to have a tailored response, distortion that rises rapidly
with output, and a relatively high output impedance. All of these
factors may cause the SET design to change the signal patterns and cause
audible changes in some circumstances.

It may be useful to seperate out some of the commonly used expressions
regarding SETs and valve amps, since I know several have been confused.

a) One of the common characteristics of SETs (though NOT implicit in the
term "single ended triode") is the use of a DHT (directly heated triode)
in the output such as 2a3, 6B4G, 300B and 845 - this can be a major
positive factor in the overall sound, against which can be set the
drawbacks Jim has listed above. .

You may have to explain why. Since I am not particularly expert on valves I
am unsure why you believe direct heating is a "major positive factor" in
terms of the results. I had though that valve designers largely abandoned
direct heating of the cathode for various reasons. Hence the comments you
made (that I snipped) about having to search for small-signal direct heated
valves mainly from 80 year old stock.

It is obviously up to the OP to choose what they prefer. However I suspect
he would find it rather easier to get good results using a design that does
not rely on such.

Similarly, if he wanted to build his own AM radio, I'd be inclined to
suggest he used modern detector diodes, not a 'coherer'... :-)


b) When we come to DHTs we are in another ballgame, in my opinion. Those
who habitually use DHTs, do extended listening tests with DHTs, and are
familiar with their characteristic sound will claim they offer quite
audible gains in clarity over indirectly heated valves.

The problem for the OP here is that you may simply be giving opinions for
which there is no reliable evidence. As, indeed, you warn. Hence there is a
risk that what you say will simply impede his progress.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Advice: Amp building
 

"Andy Evans" wrote in message
oups.com...
Note that most transistor amp designs tend to have a flat response, low

distortion, and a low output impedance. Whereas zero-feedback 'SET'
designs
tend to have a tailored response, distortion that rises rapidly with
output, and a relatively high output impedance. All of these factors
may
cause the SET design to change the signal patterns and cause audible
changes in some circumstances.

It may be useful to seperate out some of the commonly used expressions
regarding SETs and valve amps, since I know several have been confused.

a) One of the common characteristics of SETs (though NOT implicit in
the term "single ended triode") is the use of a DHT (directly heated
triode) in the output such as 2a3, 6B4G, 300B and 845 - this can be a
major positive factor in the overall sound, against which can be set
the drawbacks Jim has listed above. .
b) When we come to DHTs we are in another ballgame, in my opinion.
Those who habitually use DHTs, do extended listening tests with DHTs,
and are familiar with their characteristic sound will claim they offer
quite audible gains in clarity over indirectly heated valves. This is
only partly a question of output valves, but in practice only a small
handful of people will have used small signal DHTs for preamps, input
and driver stages of amplifiers. Reason being that while output DHTs
are available in current production, there are zero small signal DHTs
(except one or two rare boutique ones at huge prices). They are
available on ebay since they were used in countless old radios from the
20s and 30s, and there are good but dwindling stocks still to be had.
Some on the other hand have become quite rare. As you might guess, I'm
a huge fan and use them in preference to anything else.
c) DHTs and zero feedback can be used in push-pull amps with different
results from their use in SETs. Each of these factors contribute -
feedback, push-pull/single ended, indirectly heated or directly heated
and so forth (we could go on)

I don't personally use SETs and never have, and it is useful in terms
of general attribution theory to consider what we attribute to which
factors. In particular DHTs and SETs are absolutely not equivalents -
one refers to valve construction and the other to circuit topology. One
might consider that SETs with DHTs are a bit of a curates egg - both
good and bad factors. I'd personally opt for all-DHT push pull amps
given the choice. We haven't even come to another common SET feature -
interstage transformers - but that's enough to be getting on with. Andy

What is the theory behind an indirectly heated valve, having an inferior
performance to a directly heated one ? Not being contentious - just
interested ...

Arfa

Advice: Amp building
 

In article . com,
wrote:

The chip amp I was talking about uses 44,000 mF resevoir caps.I
would have thought that is adequte for a 56 watt RMS amp.

I'd agree. However I have seen 'gainclone' designs that used reservoir caps
as small as 1,000 microF. That seems way too small to me.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

Advice: Amp building
 

(DHTs sounding better than directly heated valves) You may have to
explain why (Jim).

I may not - your need for theoretical knowledge is considerably greater
than the average, and many people build equipment empirically - they
put a circuit together, listen to it and measure it, then start
changing it until it sounds better to their ears. I'm sure there is an
explanation somewhere, but on a day of 35 degrees centigrade I'm damned
if I'm going to hunt around for anything.

Since I am not particularly expert on valves I am unsure why you
believe direct heating is a "major positive factor" in terms of the
results.

As I said, I and a few others (audio designers and EEs just for the
record) have been working with DHT small tubes for quite a while now,
building numerous circuits and subjecting them to listening tests. We
believe in DHTs on the basis of the results we have found, and our
responses to listening tests have been very close. The differences are
quite marked.

I had though that valve designers largely abandoned direct heating of
the cathode for various reasons.

They indeed did - the reason, as I said, being that current production
of them stopped in the 30s for the most part. Designers use current
production parts.

I suspect he (OP) would find it rather easier to get good results using
a design that does
not rely on such (DHTs).

Absolutely true. It's an esoteric pursuit.

The problem for the OP here is that you may simply be giving opinions
for which there is no reliable evidence. As, indeed, you warn. (ed.
???? do I) Hence there is a risk that what you say will simply impede
his progress.

I advised the OP to build a simple transistor amp as a first project.
But if the OP is interested in a) valves, which he noted and b) the
best possible sound, then it is the belief of myself and a number of
others (including a large number of respected designers and EEs) that
he should investigate DHTs. I go out of my way to point out that this
is an esoteric route to take and that the small signal tubes are not
current production. I should also add that they are complex to work
with and require sophisticated filament supplies. Having said all that,
in the interest of completeness it would be a dereliction of available
knowledge not to mention DHTs since if he wants the best in sound, NOT
knowing about them would impede his progress. It took me thirty years
to start building them, and this SUBSTANTIALLY impeded my progress.
Like the OP I was originally a simple DIY builder interested in valve
equipment. My "progress" was quite simple - I rejected what sounded
worse and used what sounded better. Along the way came a lot of theory
and listening tests, but the principle of using what sounds better
remains the same. Andy

Advice: Amp building
 

In article .com,
Andy
Evans wrote:
(DHTs sounding better than directly heated valves) You may have to
explain why (Jim).

I may not - your need for theoretical knowledge is considerably greater
than the average, and many people build equipment empirically - they put
a circuit together, listen to it and measure it, then start changing it
until it sounds better to their ears. I'm sure there is an explanation
somewhere, but on a day of 35 degrees centigrade I'm damned if I'm going
to hunt around for anything.

I'm afraid that translates as "No evidence, just opinions presented as if
they were facts". :-)

Since I am not particularly expert on valves I am unsure why you believe
direct heating is a "major positive factor" in terms of the results.

As I said, I and a few others (audio designers and EEs just for the
record) have been working with DHT small tubes for quite a while now,
building numerous circuits and subjecting them to listening tests. We
believe in DHTs on the basis of the results we have found, and our
responses to listening tests have been very close. The differences are
quite marked.

So has anyone demonstrated they can:

1) hear these "quite marked" differences in a suitable test - i.e. one
whose results can be subject to statistical analysis, etc?

2) Show any theoretical analysis or measurements to give a plausible
physical reason?

I can't recall hearing any reports to this effect, or reading any. I can,
however, recall hearing all kinds of unsubstantiated opinions presented as
definitive 'conclusions' about such matters.

That you and some anonymous 'EEs' "believe in" them is a declaration of
personal faith, not evidence, I'm afraid. I suspect that many more 'EEs'
*don't* believe anything of the kind, but that wouldn't be evidence, either
- but it may put your faith into context.

I had though that valve designers largely abandoned direct heating of
the cathode for various reasons.

They indeed did - the reason, as I said, being that current production
of them stopped in the 30s for the most part. Designers use current
production parts.

I'm afraid you may have a problem with the above argument. In logical terms
it can be explained by the 'cart:horse' operators not being commutative.
:-)

I would suspect valve makers stopped making direct heated valves because
the people who wanted to buy valves started buying - and preferred - those
which were *not* direct heated.

However, as you say, you are under no obligation to anyone to provide any
evidence for your assertions. The OP and others can judge your opinions on
the basis you have chosen to provide.

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html