"Eeyore" wrote in message
...
I have the schemtics for the A10 and A20 amplifier-equalizers here before
me. They are loaded with 4558s, no 4136s in sight. I looked inside my A10
and found that they were indeed 4558s.

YUK ! Pro ? That's a joke.

When were these designed ? At least drop some 4560s in.

Graham


Hi Graham,

I have A20's which I use in my home audio system and cannot fault them. I
have no issues with them that would make me say the IC's should be changed.

Some people say they are too forward, some have said they are too bright for
their liking. I am quite happy with them.

What difference would you expect a different IC to make over the 4558's?

APR

APR wrote:

"Eeyore" wrote

I have the schemtics for the A10 and A20 amplifier-equalizers here before
me. They are loaded with 4558s, no 4136s in sight. I looked inside my A10
and found that they were indeed 4558s.

YUK ! Pro ? That's a joke.

When were these designed ? At least drop some 4560s in.

Hi Graham,

I have A20's which I use in my home audio system and cannot fault them. I
have no issues with them that would make me say the IC's should be changed.

Fair enough if you're happy but audio designers like me vomit at the mention of
4558s.


Some people say they are too forward, some have said they are too bright for
their liking. I am quite happy with them.

What difference would you expect a different IC to make over the 4558's?

Less noise and less distortion for two. The NJM4560 is an 'improved' 4558 by an
arm and a leg or two. They're actually pretty repectable. I must have designed
in several million of them.

Graham

APR wrote:

What difference would you expect a different IC to make over the 4558's?

Just to put this into perspective, the 4558 is little better than the rightly
maligned (today) 741 op-amp.

4558s are most commonly found in low-rent DJ gear.

Graham

Eeyore wrote:

APR wrote:

What difference would you expect a different IC to make over the
4558's?

Just to put this into perspective, the 4558 is little better than the
rightly maligned (today) 741 op-amp.

Hnmm ... it doesn't have enough treble to actually distort, unlike the 741
that had too much, otoh it is not spitty, just plain boring. There are
plenty plug and play alternatives ... but whomsoever plays the opamp upgrade
game should unsolder what is there CAREFULLY, you may need that exact opamp
for the circuit to work, and put good sockets in to avoid having to solder
multiple times on the pcb.

Graham

Kind regards

Peter Larsen

In article , Peter Larsen
scribeth thus
Eeyore wrote:

APR wrote:

What difference would you expect a different IC to make over the
4558's?

Just to put this into perspective, the 4558 is little better than the
rightly maligned (today) 741 op-amp.

Hnmm ... it doesn't have enough treble to actually distort, unlike the 741
that had too much, otoh it is not spitty, just plain boring. There are
plenty plug and play alternatives ... but whomsoever plays the opamp upgrade
game should unsolder what is there CAREFULLY, you may need that exact opamp
for the circuit to work, and put good sockets in to avoid having to solder
multiple times on the pcb.

Graham

Kind regards

Peter Larsen



And a scope to see what its getting up to in the MHz region;!...
--
Tony Sayer

"APR" I_don't_Want_Spam@No_Spam wrote in message


I have A20's which I use in my home audio system and
cannot fault them. I have no issues with them that would
make me say the IC's should be changed.

Some people say they are too forward, some have said they
are too bright for their liking. I am quite happy with
them.

Both the A10 and the A20 were well-received on the professional market when
introduced, and still seem to be holding their value in the used equipment
market.

What difference would you expect a different IC to make
over the 4558's?

Why the NHT designers used 4558s would be an interesting question. As a
group, they were very well-informed engineers with any number of sucessful
designs for speakers and amplifiers already under their belt.

If you avoid very high and very low signal voltages, 4558s can work out just
fine. I wonder if the NHT engineers were making a statement against the sort
of bias that makes so many fly off the handle when they see 4558s in an
audio signal path.

Personally, my bespeak audio designs are mostly based on 5534s. and 5532s. I
think some LM353s snuck in a few places where impedances were high.

tony sayer wrote:

And a scope to see what its getting up to in the MHz region;!...

Too true. Circuits that may be stable with junk op-amps may respond differently
when given the chance.

Graham

Arny Krueger wrote:

"APR" I_don't_Want_Spam@No_Spam wrote

I have A20's which I use in my home audio system and
cannot fault them. I have no issues with them that would
make me say the IC's should be changed.

Some people say they are too forward, some have said they
are too bright for their liking. I am quite happy with
them.

Both the A10 and the A20 were well-received on the professional market when
introduced, and still seem to be holding their value in the used equipment
market.

What difference would you expect a different IC to make
over the 4558's?

Why the NHT designers used 4558s would be an interesting question. As a
group, they were very well-informed engineers with any number of sucessful
designs for speakers and amplifiers already under their belt.

If you avoid very high and very low signal voltages, 4558s can work out just
fine. I wonder if the NHT engineers were making a statement against the sort
of bias that makes so many fly off the handle when they see 4558s in an
audio signal path.

Personally, my bespeak audio designs are mostly based on 5534s. and 5532s. I
think some LM353s snuck in a few places where impedances were high.

Never bad choices. If you have access to NJR/JRC parts many of the NJMs are very
respectable too. Notably the 4560 and 4580.

Graham

"Arny Krueger" wrote in message
. ..
"Eeyore" wrote in
message
Chronic Philharmonic wrote:

"Arny Krueger" wrote
"Marky P" wrote


LM741 (pretty sure this is an op amp)

Yup and a real oldie. Slow and noisy, not to mention
power hungry and a weak output for what it does.

This was arguably the "breakthrough" IC op-amp. It was
one of the first popular devices that was actually a
monolithic design, and not a hybrid like some of the
original Burr Brown modules. It was compensated for
unity gain, which made it much too slow for anything but
a buffer for audio work. It had a slew rate of 0.5
volts/microsecond. With a +/- 12 volt power supply, 6
kHz rail-to-rail was about it for non-slew rate limited
signals. You could get 20KHz through it if you were
content with about 4 volts peak.

I think it had more applications in analog computing,
integrators, low frequency function generators, servo
controls, etc.

True but it DID get used in audio. Its companion, the 748
was uncompensated internally (like the 5534 vs the 5532)
and always seemed less noisy to me, so I used quite a few
of those.

The on-chip compensation cap for the 741 was a well-known source of noise.

I'm curious, what mechanism caused this noise? I suspect it must have been
realized in silicon, a reverse-biased P/N junction or something. Does
anybody know?

"Eeyore" wrote in message
...


tony sayer wrote:

And a scope to see what its getting up to in the MHz region;!...

Too true. Circuits that may be stable with junk op-amps may respond
differently
when given the chance.

Random thoughts... Could it be that the original designers were aware of the
device's limitations, and took care to stay within those parameters? If they
used them in low-gain, low-voltage applications, with minimal gain
downstream, I can see how they could comfortably stay within the product
design specifications. And the intrinsic stability might have been a bonus.

I wonder what made them choose that part in the first place. Could it be
cost? Or stability problems that went away by subbing a part without the
need to rev the PCB?