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Audio amlifier. - Page 2

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Anonymous
August 13, 2005 2:42:04 PM

Archived from groups: rec.audio.tech (More info?)

On Sat, 13 Aug 2005 09:58:58 GMT, MZ <mark@mdz.no-ip.org> wrote:

>> >$100 might be a lofty goal, yeah, but $500 is a little over the top unless
>> >you're spending the bulk of that money on the case, fancy connectors, or
>> >"designer" components. An *excellent* audio amplifier will incorporate
>> >more small signal components than what showed up, for example, in that ESP
>> >schematic that someone posted the link to. It'll incorporate maybe an
>> >added pair of output transistors (so you're not living on the edge), a
>> >good transformer (probably the most expensive part of the amp), and
>> >probably relatively large air core inductors at each output. Even so, it
>> >shouldn't cost up to $500 as far as components go.
>>
>> Why on earth would you put large inductors at the output?
>
>OPS/global NFB stability. As I said, it's not essential but some people
>do it. Really, the only time I'd do it is when the amplifier will be
>operating up to 20kHz (eg. not a dedicated sub or midbass amp) and if I
>wasn't using a typical EF OPS design. I used some in my last amp mostly
>because I had a bunch of large inductors kicking around in my closet that
>I had purchased a couple years ago for a passive xover I didn't end up
>building.

I guess it depends what you mean by 'large'. You certainly do *not*
want any more than a few microHenries in series with the output. Yes,
that's *microHenries*. One milliHenry has a series reactance of 125
ohms at 20kHz - not something you really want in series with your
speakers!

>> And yes, a
>> decent '100 watt' 2-channel amp will cost $500 in parts, and that's
>> without a particularly fancy case. Remember, to do it right will
>> require a *minimum* 600 VA power transformer, and everything else that
>> entails.
>
>I guess we'll just have to agree to disagree on cost. If you know how to
>shop, then you won't be spending $500 on a transformer, rectifier,
>capacitors, and output transistors. Not for a 100 watt amp. Everything
>else is relatively cheap if you shop wisely.

Buying top-quality new parts, as you should be doing if you want
honest pricing information, most certainly will set you back $500 for
the whole kit. Sure you can buy used parts for less, but what does
that tell you about the reality of manufacturing costs?

--

Stewart Pinkerton | Music is Art - Audio is Engineering
Anonymous
August 14, 2005 12:27:38 AM

Archived from groups: rec.audio.tech (More info?)

> >> Why on earth would you put large inductors at the output?
> >
> >OPS/global NFB stability. As I said, it's not essential but some people
> >do it. Really, the only time I'd do it is when the amplifier will be
> >operating up to 20kHz (eg. not a dedicated sub or midbass amp) and if I
> >wasn't using a typical EF OPS design. I used some in my last amp mostly
> >because I had a bunch of large inductors kicking around in my closet that
> >I had purchased a couple years ago for a passive xover I didn't end up
> >building.
>
> I guess it depends what you mean by 'large'. You certainly do *not*
> want any more than a few microHenries in series with the output. Yes,
> that's *microHenries*. One milliHenry has a series reactance of 125
> ohms at 20kHz - not something you really want in series with your
> speakers!

Agreed. By large, I meant on the order of 10 uH.

> >I guess we'll just have to agree to disagree on cost. If you know how to
> >shop, then you won't be spending $500 on a transformer, rectifier,
> >capacitors, and output transistors. Not for a 100 watt amp. Everything
> >else is relatively cheap if you shop wisely.
>
> Buying top-quality new parts, as you should be doing if you want
> honest pricing information, most certainly will set you back $500 for
> the whole kit. Sure you can buy used parts for less, but what does
> that tell you about the reality of manufacturing costs?

Huh? Why would you use "top quality new parts"? And, in this context,
what do we care about manufacturing costs? How much Onkyo pays for
100,000 BJTs is irrelevant.
Anonymous
August 14, 2005 1:44:47 PM

Archived from groups: rec.audio.tech (More info?)

On Sat, 13 Aug 2005 20:27:38 GMT, MZ <mark@mdz.no-ip.org> wrote:

>> >> Why on earth would you put large inductors at the output?
>> >
>> >OPS/global NFB stability. As I said, it's not essential but some people
>> >do it. Really, the only time I'd do it is when the amplifier will be
>> >operating up to 20kHz (eg. not a dedicated sub or midbass amp) and if I
>> >wasn't using a typical EF OPS design. I used some in my last amp mostly
>> >because I had a bunch of large inductors kicking around in my closet that
>> >I had purchased a couple years ago for a passive xover I didn't end up
>> >building.
>>
>> I guess it depends what you mean by 'large'. You certainly do *not*
>> want any more than a few microHenries in series with the output. Yes,
>> that's *microHenries*. One milliHenry has a series reactance of 125
>> ohms at 20kHz - not something you really want in series with your
>> speakers!
>
>Agreed. By large, I meant on the order of 10 uH.
>
>> >I guess we'll just have to agree to disagree on cost. If you know how to
>> >shop, then you won't be spending $500 on a transformer, rectifier,
>> >capacitors, and output transistors. Not for a 100 watt amp. Everything
>> >else is relatively cheap if you shop wisely.
>>
>> Buying top-quality new parts, as you should be doing if you want
>> honest pricing information, most certainly will set you back $500 for
>> the whole kit. Sure you can buy used parts for less, but what does
>> that tell you about the reality of manufacturing costs?
>
>Huh? Why would you use "top quality new parts"? And, in this context,
>what do we care about manufacturing costs? How much Onkyo pays for
>100,000 BJTs is irrelevant.

Not when the question was whether you'd get better value by building
or buying. It should be obvious that a complate novice is highly
unlikely to be able to build a top-class amp for the price that he'd
pay for say a used Yamaha AX-592 - or a Denon 3804 if he needs
surround-sound capability.

--

Stewart Pinkerton | Music is Art - Audio is Engineering
Related resources
Anonymous
August 14, 2005 3:15:57 PM

Archived from groups: rec.audio.tech (More info?)

"Stewart Pinkerton" <patent3@dircon.co.uk> wrote in message
news:7ajrf1lp8jr8pplqh9b0skkkuac8qj48rp@4ax.com...

> Buying top-quality new parts, as you should be doing if you want
> honest pricing information, most certainly will set you back $500 for
> the whole kit. Sure you can buy used parts for less, but what does
> that tell you about the reality of manufacturing costs?

As I remarked earlier, I costed the ESP Project 3A amplifier at $150 for two
channels, using all new parts at published prices (but excluding case.)

Personally I'd have guessed that most people would be more than satisifed
with the quality of that amplifier. It certainly seemed adequate for the
intended application (powering computer speakers).

Still, as I also remarked, anyone can take a published project and cost it
themselves.

Tim
Anonymous
August 14, 2005 5:57:05 PM

Archived from groups: rec.audio.tech (More info?)

On Sun, 14 Aug 2005 11:15:57 GMT, "Tim Martin"
<tim2718281@ntlworld.com> wrote:

>
>"Stewart Pinkerton" <patent3@dircon.co.uk> wrote in message
>news:7ajrf1lp8jr8pplqh9b0skkkuac8qj48rp@4ax.com...
>
>> Buying top-quality new parts, as you should be doing if you want
>> honest pricing information, most certainly will set you back $500 for
>> the whole kit. Sure you can buy used parts for less, but what does
>> that tell you about the reality of manufacturing costs?
>
>As I remarked earlier, I costed the ESP Project 3A amplifier at $150 for two
>channels, using all new parts at published prices (but excluding case.)
>
>Personally I'd have guessed that most people would be more than satisifed
>with the quality of that amplifier. It certainly seemed adequate for the
>intended application (powering computer speakers).

BWAHAHAHA! Hardly any need for a 'top quality' amplifier there,
however.............................

I already stated the base spec as 200 watts continuous into 4 0hms.
--

Stewart Pinkerton | Music is Art - Audio is Engineering
Anonymous
August 15, 2005 12:16:01 AM

Archived from groups: rec.audio.tech (More info?)

"Stewart Pinkerton" <patent3@dircon.co.uk> wrote in message
news:qoduf1l2gaof19jo4tkromv50qmemjnd9q@4ax.com...

> I already stated the base spec as 200 watts continuous into 4 0hms.
> --

That's your spec for your amplifier. And I'm sure you know what you're
doing and have come up with the optimum price performance for your needs.

You're obviously skilled sat designing, speccing, and building amplifiers.
I expect you have considerable experience.

Can you remember the first one you built? Was it a high-quality $500
amplifier capable of delivering 200 watts continuous into 4 ohms? Or did
you start wih something simpler and cheaper?

Do you think the beginner who originally posted this thread is capable of
matching your abilities on his first attempt?

Tim
Anonymous
August 15, 2005 1:48:39 AM

Archived from groups: rec.audio.tech (More info?)

On Sun, 14 Aug 2005 20:16:01 GMT, "Tim Martin"
<tim2718281@ntlworld.com> wrote:

>"Stewart Pinkerton" <patent3@dircon.co.uk> wrote in message
>news:qoduf1l2gaof19jo4tkromv50qmemjnd9q@4ax.com...
>
>> I already stated the base spec as 200 watts continuous into 4 0hms.
>> --
>
>That's your spec for your amplifier. And I'm sure you know what you're
>doing and have come up with the optimum price performance for your needs.

No, it's a base spec for a midrange hi-fi amplifier which will meet
the needs of most audiophiles.

>You're obviously skilled sat designing, speccing, and building amplifiers.
>I expect you have considerable experience.

Thank you - indeed I do.

>Can you remember the first one you built? Was it a high-quality $500
>amplifier capable of delivering 200 watts continuous into 4 ohms? Or did
>you start wih something simpler and cheaper?

It was a single-ended tube amp. But then, I am *very* old! :-)

>Do you think the beginner who originally posted this thread is capable of
>matching your abilities on his first attempt?

No, which was my original point.
--

Stewart Pinkerton | Music is Art - Audio is Engineering
Anonymous
August 15, 2005 2:19:20 AM

Archived from groups: rec.audio.tech (More info?)

On Sun, 14 Aug 2005, Stewart Pinkerton wrote:
<snip>

Stewart, I'm not questioning your experience or suggesting that you're
wrong. I'm just not having an easy time piecing together your cost
estimates. I'm also unclear as to why you seem to insist on buying brand
new parts. I'm sure I don't have to tell you that many hobbyists feel
that half the fun is to design around parts that are available at a good
price, either because of a good bulk price (new), ebay availability,
surplus, and in the case of bulk metal, used prices. So if you're going
to compare a homebuilt amplifier to a used amplifier, then it's only fair
to include used/clearance prices.
Anonymous
August 15, 2005 3:22:26 AM

Archived from groups: rec.audio.tech (More info?)

"Stewart Pinkerton" <patent3@dircon.co.uk> wrote in message
news:bqevf1d0lndp8geh5hn35c6mfe72aaljcq@4ax.com...
> >Do you think the beginner who originally posted this thread is capable of
> >matching your abilities on his first attempt?
>
> No, which was my original point.

OK; so, to refresh our memories, here's the opening post again

"I want to build an amplifier for listening music on my computer.
Can anyone suggest where to start? I have very basic knowledge of
electronics but probably need some theory. Any good books?

I searched around on the net and the only thing I can find are complete
schematics and books on how to build tube amplifiers. I'm really not
intersted in tube amps, but since the only information on the net is
about tube amps I dont even know what is the alternative!

Any help is greatly apprciated.
Thanks in advance."

I've suggested ESP computer systems Project 3A, which I've costed at $150
excluding case. That cost includes the ready-made PCB, which I believe will
be a considerable help in gettting the project working correctly.. The
project page includes consruction guides.

Now, can you offer the chap any better advice than that?

Tim
Anonymous
August 15, 2005 3:22:27 AM

Archived from groups: rec.audio.tech (More info?)

Tim Martin wrote:
> Now, can you offer the chap any better advice than that?

Not if he insists on building. If he wants to buy he should be able to
find an adequate amp for considerably less; much less if he's willing to
buy used.
Anonymous
August 15, 2005 9:57:46 PM

Archived from groups: rec.audio.tech (More info?)

On Sun, 14 Aug 2005 22:19:20 GMT, MZ <mark@mdz.no-ip.org> wrote:

>On Sun, 14 Aug 2005, Stewart Pinkerton wrote:
><snip>
>
>Stewart, I'm not questioning your experience or suggesting that you're
>wrong. I'm just not having an easy time piecing together your cost
>estimates. I'm also unclear as to why you seem to insist on buying brand
>new parts.

Reliability.

> I'm sure I don't have to tell you that many hobbyists feel
>that half the fun is to design around parts that are available at a good
>price, either because of a good bulk price (new), ebay availability,
>surplus, and in the case of bulk metal, used prices. So if you're going
>to compare a homebuilt amplifier to a used amplifier, then it's only fair
>to include used/clearance prices.

Fair enough, if you can guarante that the parts you're buying have
never been overstressed. That's not so easy for parts where you have
no history of what they were used for.

--

Stewart Pinkerton | Music is Art - Audio is Engineering
Anonymous
August 15, 2005 9:57:47 PM

Archived from groups: rec.audio.tech (More info?)

> Fair enough, if you can guarante that the parts you're buying have
> never been overstressed. That's not so easy for parts where you have
> no history of what they were used for.

True. But the same, of course, goes for the used amplifier.
Anonymous
August 15, 2005 10:01:01 PM

Archived from groups: rec.audio.tech (More info?)

On Sun, 14 Aug 2005 23:22:26 GMT, "Tim Martin"
<tim2718281@ntlworld.com> wrote:

>
>"Stewart Pinkerton" <patent3@dircon.co.uk> wrote in message
>news:bqevf1d0lndp8geh5hn35c6mfe72aaljcq@4ax.com...
>> >Do you think the beginner who originally posted this thread is capable of
>> >matching your abilities on his first attempt?
>>
>> No, which was my original point.
>
>OK; so, to refresh our memories, here's the opening post again
>
>"I want to build an amplifier for listening music on my computer.
>Can anyone suggest where to start? I have very basic knowledge of
>electronics but probably need some theory. Any good books?
>
>I searched around on the net and the only thing I can find are complete
>schematics and books on how to build tube amplifiers. I'm really not
>intersted in tube amps, but since the only information on the net is
>about tube amps I dont even know what is the alternative!
>
>Any help is greatly apprciated.
>Thanks in advance."
>
>I've suggested ESP computer systems Project 3A, which I've costed at $150
>excluding case. That cost includes the ready-made PCB, which I believe will
>be a considerable help in gettting the project working correctly.. The
>project page includes consruction guides.
>
>Now, can you offer the chap any better advice than that?

I already did - I pointed him at lots of SS design information on the
net. However, the Project 3A is a nice simple amp to start from.
--

Stewart Pinkerton | Music is Art - Audio is Engineering
Anonymous
August 16, 2005 9:28:34 AM

Archived from groups: rec.audio.tech (More info?)

On Mon, 15 Aug 2005 16:16:42 -0400, "MZ"
<myfirstname@mdz.junk.no-ip.junk.org> wrote:

>> Fair enough, if you can guarante that the parts you're buying have
>> never been overstressed. That's not so easy for parts where you have
>> no history of what they were used for.
>
>True. But the same, of course, goes for the used amplifier.

BZZZZT! Of course it doesn't, since you know that these parts were
used in an audio amplifier! These are not typically used for welding,
or for driving traction motors.......................
--

Stewart Pinkerton | Music is Art - Audio is Engineering
Anonymous
August 16, 2005 4:49:57 PM

Archived from groups: rec.audio.tech (More info?)

> >> Fair enough, if you can guarante that the parts you're buying have
> >> never been overstressed. That's not so easy for parts where you have
> >> no history of what they were used for.
> >
> >True. But the same, of course, goes for the used amplifier.
>
> BZZZZT! Of course it doesn't, since you know that these parts were
> used in an audio amplifier! These are not typically used for welding,
> or for driving traction motors.......................

Well, I suppose if you thoroughly test the used amplifier beforehand - not
always possible, depending on where you purchase it.
Anonymous
August 18, 2005 9:19:35 AM

Archived from groups: rec.audio.tech (More info?)

MZ <mark@mdz.no-ip.org> wrote:

>> Why on earth would you put large inductors at the output?

> OPS/global NFB stability. As I said, it's not essential but some people
> do it. Really, the only time I'd do it is when the amplifier will be
> operating up to 20kHz (eg. not a dedicated sub or midbass amp) and if I
> wasn't using a typical EF OPS design. I used some in my last amp mostly
> because I had a bunch of large inductors kicking around in my closet that
> I had purchased a couple years ago for a passive xover I didn't end up
> building.

It's not really necessary anymore these days with modern output devices,
which make it possible for the HF poles to be properly staggered. Back in
the days of output devices having 2MHz bandwidth, amplifiers with lots of
loop feedback usually could be made to oscillate even if they had output
inductors. Proper staggering makes the range of theoretical oscillation so
narrow that it very difficult to induce in the physical sense.
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