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Chip Amps Amplifiers based on integrated circuits

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Old 6th May 2003, 11:36 PM   #31
Previously: Kuei Yang Wang
 
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Koinichiwa,

Quote:
Originally posted by leadbelly
Thanks,

And after researching it a bit more, I can see that the economics are not great either, as the lm6181 is $C5 and that cheapo xfo was $C6. Just doesn't make sense at all, really.

So, you were suggesting a preference for the lm6182, would you therefore think using twice as many of the still available lm6181's would work better than lm6172's?
I am actually suggesting that used in a subwoofer filter, there is little to choose between the much maligned NE5532, TL07X/08X or any other Op-Amp. I mean don't dig the 741 out of retirement, but for such low frequencies the PSU becomes much more more important than the chip. Chip's make large difference at higher frequencies, but not so much in subwoofers.

Sayonara
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Old 7th May 2003, 03:14 PM   #32
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Quote:
Originally posted by Kuei Yang Wang
Koinichiwa,



They would sort of work, but are really by far too low impedance to work well in a lineinput. The LL7901/7902 is what you'd be better looking at, if it has to be lundahl.

Sayonara
KYW,

I am using LL7902 for mic pre's currently and they are
switchable in/out specifically for their coloration. They do
have some DDR degradation and they also flatten
dynamics somewhat.
I think the S & B or Jensen would be better option
if transparency is the goal.

T
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Old 11th May 2003, 11:45 PM   #33
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I checked a bit and it looks like the only 0.1% resistors easily available in small quantities are 1/16 watt. Would these work as feedback resistors or are they too small?
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Old 14th May 2003, 02:19 AM   #34
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OK, well if nobody likes that question, let me ask a more basic one for my knowledge: why 0.1%?

Is that a tolerance spec for the actual construction, so that the constructor must match resistance values within that range and so it is meant as a spec for mass production? (in which case matching pairs of 1% resistors would be acceptable)

Or is it a manufacturing tolerance dictating that product tolerance must be met in order to guarantee properties other than resistance, such as impedance or stability over a long lifespan? (in which case 0.1% resistors must be used)
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Old 14th May 2003, 09:37 AM   #35
Previously: Kuei Yang Wang
 
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Koinichiwa,

Quote:
Originally posted by leadbelly
OK, well if nobody likes that question, let me ask a more basic one for my knowledge: why 0.1%?

Is that a tolerance spec for the actual construction, so that the constructor must match resistance values within that range and so it is meant as a spec for mass production? (in which case matching pairs of 1% resistors would be acceptable)

Or is it a manufacturing tolerance dictating that product tolerance must be met in order to guarantee properties other than resistance, such as impedance or stability over a long lifespan? (in which case 0.1% resistors must be used)
Well, the 0.1% Spec is given as 0.1% Resistors are readily available from any decent electronic part supplier (Mouser & Digikey certainly should do them in the US, in Europe Radio Spares or Farnell).

Ideally all resistors should be zero tolerance, but the tighter toleranced resistors get the more expensive they get and the harder to find are they. And yes, you could hand select if you like.

Sayonara
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Old 14th May 2003, 04:15 PM   #36
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Thanks!

It was Digikey that I was hoping to order from, as the whole digikey.ca thing makes it so easy. But they only have 0.1% SMD 1/16W in small quantities. Mouser however does stock 0.1% leaded resistors.
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Old 19th May 2003, 02:36 PM   #37
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I've looked into this BPA. Here's my two cents.

Use the servos unless you are a miser or a sloth. I talked with an engineer at Nationals audio division about this. The servos will keep the noise level and extraneous current flowing between the devices much lower. That means it will better and louder, if you do.
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Old 19th May 2003, 07:58 PM   #38
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i use the servos....
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Old 21st May 2003, 11:22 AM   #39
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Quote:
Originally posted by cybervagrant
Use the servos unless you are a miser or a sloth. I talked with an engineer at Nationals audio division about this. The servos will keep the noise level and extraneous current flowing between the devices much lower. That means it will better and louder, if you do.
Aren't you being a bit fast in lining up with what a Nationals engineer may say?

First of all, I haven't much against servos or have had so much practice with them, but many people whose ears I trust say they can be "heard". That is they introduce behaviours that do not belong in a "clean" sound, that is they do not improve the sound or add nonlinearities that shouldn't be there.

Second, National suggests a parallel/bridging arrangement that some find not ideal, using inverting and non-inverting blocks. When I named this thread "Bridgeclone", the idea was to do something using the inverting circuit as the basic brick to work from.

So perhaps your suggestion would belong on a new thread, which I would happily follow as I am a flexible DIYer who does not believe in stone cut recipes.



Carlos
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Old 21st May 2003, 12:08 PM   #40
vic2 is offline vic2  United States
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I have reread the app note from National. It specifically says that if .1% tolerance resistors are used, then the servos can be avoided.

The .1% resistors are apparently there to keep current from flowing through the other opamp circuits. Could this be avoided by increasing the output resistances of the individual circuits thereby allowing on to get away lower tolerance resistors?

Vic
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