dortreo
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- Jun 22, 2020
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Hello all,
First time post here but long time lurker. I've been following the conversation on Hypex and Purifi amps as closely as I can considering that I have no background in EE whatsoever. With that caveat, it seems that there are benefits to eliminating the input buffer stage as seen in the Amir's Purifi review or in the low gain mode measurements for the Benchmark AHB2 amp. It also seems that there's little difference between discrete "audiophile" op amps and certainly there's debate about whether or not these op amps present any value over stock chips. So, would there be a benefit to eliminating the input buffer if you had a pre-amp that had an appropriately high output voltage? I'm fortunate enough to own one, the Benchmark DAC3, which by default outputs 24 dBu (12 volts RMS).
With that in mind, I asked @Alan March if he could install a switch or jumper to bypass the input buffer on the NC1200. Here's what he wrote:
"It is possible to configure the module to bypass the input buffer however it is done by configuring soldered links on the board. So yes we can supply an amp configured that way but it is not a simple switch operation to revert it. However thinking about it we could fit jumpers on the board to make it easier.
"Buffered the amp gain is 27.8dB which requires 2.2v RMS input to reach full power output into 4 ohms. Unbuffered the amp gain Is only 11.6dB so will require an input voltage of 14.8 volts RMS to reach full power output. The DAC 3 at +28dBu is 19.4 volts RMS so yes this would work fine. This would indeed provide lower noise and distortion."
And here's what he installed: A push switch (in blue) to bypass the input buffer on the NC1200. Brilliant!
From what the NC1200 datasheet states, that should improve the SNR for 1W at 8 ohms from 103 to 112 dB. The Benchmark DAC3 is putting out more than enough voltage to drive the amp and speakers to ear splitting volumes. And the sound is smile-inducing.
So, hats off to Alan for building and modifying a terrific amp. I realize that eliminating the input buffer isn't practical in most cases, but if you have the potential to do so, why not? What's the downside?
First time post here but long time lurker. I've been following the conversation on Hypex and Purifi amps as closely as I can considering that I have no background in EE whatsoever. With that caveat, it seems that there are benefits to eliminating the input buffer stage as seen in the Amir's Purifi review or in the low gain mode measurements for the Benchmark AHB2 amp. It also seems that there's little difference between discrete "audiophile" op amps and certainly there's debate about whether or not these op amps present any value over stock chips. So, would there be a benefit to eliminating the input buffer if you had a pre-amp that had an appropriately high output voltage? I'm fortunate enough to own one, the Benchmark DAC3, which by default outputs 24 dBu (12 volts RMS).
With that in mind, I asked @Alan March if he could install a switch or jumper to bypass the input buffer on the NC1200. Here's what he wrote:
"It is possible to configure the module to bypass the input buffer however it is done by configuring soldered links on the board. So yes we can supply an amp configured that way but it is not a simple switch operation to revert it. However thinking about it we could fit jumpers on the board to make it easier.
"Buffered the amp gain is 27.8dB which requires 2.2v RMS input to reach full power output into 4 ohms. Unbuffered the amp gain Is only 11.6dB so will require an input voltage of 14.8 volts RMS to reach full power output. The DAC 3 at +28dBu is 19.4 volts RMS so yes this would work fine. This would indeed provide lower noise and distortion."
And here's what he installed: A push switch (in blue) to bypass the input buffer on the NC1200. Brilliant!
From what the NC1200 datasheet states, that should improve the SNR for 1W at 8 ohms from 103 to 112 dB. The Benchmark DAC3 is putting out more than enough voltage to drive the amp and speakers to ear splitting volumes. And the sound is smile-inducing.
So, hats off to Alan for building and modifying a terrific amp. I realize that eliminating the input buffer isn't practical in most cases, but if you have the potential to do so, why not? What's the downside?
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