The light from the 300B could be a romantic setup too.
He he sorry Mark could not resist
You might be surprised.
It's kind of like a friend who had a Marshall tube amp with TL071 for FX loop buffer.
I gave him a few different OPA's to try
-> "they won't make any difference"
-> "OK, just try them anyway"
-> (Later) "you're not getting that one back, how much is it"
-> "expensive"..
(OPA627) TCD
Hi Altor,
I haven't tried those yet, but I think at least someone has used OPA1656 with AK4499. I do have some of those parts around here to try, but so far no time.
As an aside, I sort of find myself being tutored in high end audio design by someone who worked as a designer at Wadia, Cary Audio, and Pass Labs. In addition, he is someone who learned from guys like Charles Hansen, John Curl, and Nelson Pass (not that he always agrees with them). Coming from a very different background myself, sometimes my designer friend and I argue. Honestly though, when I test out his ideas they always sound better than mine even if I don't quite understand why. Maybe I am just now starting to understand it in some theoretical way. Sorry, can't get into certain details though. A few people rely on the knowledge to make a very modest living. Its about all they know how to do.
I haven't tried those yet, but I think at least someone has used OPA1656 with AK4499. I do have some of those parts around here to try, but so far no time.
As an aside, I sort of find myself being tutored in high end audio design by someone who worked as a designer at Wadia, Cary Audio, and Pass Labs. In addition, he is someone who learned from guys like Charles Hansen, John Curl, and Nelson Pass (not that he always agrees with them). Coming from a very different background myself, sometimes my designer friend and I argue. Honestly though, when I test out his ideas they always sound better than mine even if I don't quite understand why. Maybe I am just now starting to understand it in some theoretical way. Sorry, can't get into certain details though. A few people rely on the knowledge to make a very modest living. Its about all they know how to do.
Hi kimschips,
So far as I know that output stage is their most recent design, but its been out for awhile. Also, the only thing I sort of remember in the way of reviews was that it might sound a little sterile, whatever that means.
Regarding the design, the idea of using a servo to remove DC offset is not new.
Also, no reason why a servo couldn't be used to average in on the reference offset voltage (which is otherwise usually set to AVCC/2 volts). Usually, we just use a voltage divider for that and connect it to the noninverting I/V opamp inputs.
IMO the thing about servos is that they tend to affect the sound in a not in a not wonderful way, although some servo designs can work okay. In general, IMHO its probably better to avoid them unless its necessary to have one. Yet again IMHO, there isn't really a compelling need in this case.
So far as I know that output stage is their most recent design, but its been out for awhile. Also, the only thing I sort of remember in the way of reviews was that it might sound a little sterile, whatever that means.
Regarding the design, the idea of using a servo to remove DC offset is not new.
Also, no reason why a servo couldn't be used to average in on the reference offset voltage (which is otherwise usually set to AVCC/2 volts). Usually, we just use a voltage divider for that and connect it to the noninverting I/V opamp inputs.
IMO the thing about servos is that they tend to affect the sound in a not in a not wonderful way, although some servo designs can work okay. In general, IMHO its probably better to avoid them unless its necessary to have one. Yet again IMHO, there isn't really a compelling need in this case.
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Of possible interest to those designing with ESS dac chips, a discussion in the 'Bob Cordell's Power Amplifier Book,' thread (a bit before post #10240): Bob Cordell's Power amplifier book
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Well, the discussion in the other thread didn't go very far. What interested me was that time domain artifacts associated with ESS hump distortion that Scott Wurcer shared seemed to resemble what might be expected from a so-callled 'speed distortion' effect. Maybe slew limited distortion would be a closer guess. Either way, because of the pseudo random distortion seen in the time domain, it makes me think that HF/RF noise from the ESS modulator is likely one piece of the cause. At least, the only thing that comes to mind that that is approximately random is the modulator noise shaping function. Since there is some mix of analog audio, clock noise, and shaped random noise coming out of the dac analog outputs, presumably all necessary ingredients are there. Only question is under what conditions can the I/V opamp best tolerate it all.
Hi potstip,
The hump is only one consideration if one wishes to design a good sounding dac. Everything else that we usually talk about in this thread matters too. If we are interested in working on getting the best sound quality we can, its probably best to start with OPA1612 and then work on all the other problems until the dac sounds great with that opamp. It the dac doesn't sound great, its unlikely to be because of the opamp.
After that if we want to see if we think the dac might sound slightly better with another opamp, we could try it then.
The hump is only one consideration if one wishes to design a good sounding dac. Everything else that we usually talk about in this thread matters too. If we are interested in working on getting the best sound quality we can, its probably best to start with OPA1612 and then work on all the other problems until the dac sounds great with that opamp. It the dac doesn't sound great, its unlikely to be because of the opamp.
After that if we want to see if we think the dac might sound slightly better with another opamp, we could try it then.
After DAC chip usually there is I/V and/or LPF, output buffer, etc. Mostly with OP.
During the transients, like power on/power off, when the VCC/VEE are below some value, OP is are not controllable, and there is a glitch at the output.
It not depends of a DAC chip.
Relay with the dedicated control (power supervisor) at the output can solve this problem.