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OP AMP Capabilities in Supporting 24 bit bandwidth

Hello Everybody

Iam in the market in search of a Minimalist Preamp and got pulled towards Morrison ELAD, I saw this piece of message in Don Morrison Website:
(The most important thing about it is that its circuitry is designed around the Analog Devices AD797, a highly advanced op-amp made with a fully complementary IC process. This complex device, consisting of 60 transistors, settles to a full 16-bit resolution in under a microsecond, has a noise spec equivalent to a 50-ohm resistor from 10 Hz to 1MHz, and achieves lower THD + N levels than any discrete audio circuit that has come our way. The preamp consists of two AD797's with associated circuitry - including separate volume controls for each channel)

Looks like it can handle 16 bit resolution at ease, but, how about handling higher bandwidth signals at 24 bit resolution?

Any advice is highly appreciated.

Thank you

sivamayam
svenss1
2 posts
 
I completely agree with cornelius. 24 bits is a dynamic range issue, not bandwith. The 797 was designed before 24 bit digital audio existed as a regular format, which explains the published information from Analog Devices (and the ELAD spec's). I suspect you may be asking about sampling rate - 96kHz or 192kHz which are also non issues with the 797. It's bandwith exceeds the requirements of 192kHz sample rate by many times.
On a more subjective note, I've had a chance to use an ELAD and it is completely transparent. If you want minimalist, it's a good pick.
eldartford
4,262 posts
 
I checked out this preamp, and find that it has only 6dB gain, with a switch option for unity gain. It is easy to get distortionless ("transparent") performance from a low or unity gain amp. The trick is to do it with about 30 dB or more gain. I guess you could call this item a "straight wire without gain".
sivamayam OP
2 posts
 
Thank you all, your responses are giving me the most confidence in the ELAD unit. Iam going ahead with the purchase.
svenss1
2 posts
 
Re Eldartford's "30dB or more gain". 30dB of gain is the job of a power amp, not a preamp.
Let's do the math. Most CD players are capable of 1 volt rms output. Most amplifiers have an input sensitivity where 1 to 2 volts rms input will drive them to full output or beyond (and if your speakers are reasonably sensitive, that's gonna blow your head off). So if we put an additional 30dB of gain between your CD player and power amp that means we'll have 31.6 volts rms at the input of your power amp with 1V rms from your CD player. Do you smell smoke?
On another note, if it's so easy to get distortionless performance from a unity gain amp as suggested above, I don't understand why so many people have so much to say about simpler items - like connectors, wire, resistors, capacitors solder, pots, and op-amps. Oops! just built a pre-amp...
eldartford
4,262 posts
 
Svenss1...Yes, 30 dB would be a bit high for the line stage, but I was thinking in terms of a phono preamp, where considerably more than 30 dB overall is necessary. Also, the line stage usually has excess gain, which is attenuated by the volume control. The circuitry may actually be producing 4 or 5 volts, which is cut back to the 1 or so that it takes to drive the power amp.

On your "other note" I don't understand it either.
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