Posted by Pooge on June 25, 2004 at 18:46:40

In Reply to: Re: Good Thread posted by Dave Davenport on June 25, 2004 at 16:38:57:

Passive I/V can sound better, and vice versa. Both can be done badly. I'm not trying to put myself out as an expert on this stuff. I'm just trying to find the best for myself. I am not trying to negate any of the development so far, as I don't know what on this RAKK, the experience of the developers, the full requirements of the D/A chip, etc. I have been looking for a new DAC to replace my very old one. I got out of touch with the technology, because I didn't want to buy a new DAC until all this hi-rez, DVD, multichannel stuff started to settle out. I'm not a DAC-a-month buyer, and I didn't want to buy something that would be obsolete the next week (which may be impossible in digital, anyway.) Anyway, pardon me if I sound like I'm second guessing all your judgements. I don't even know enough about what you've done yet. I contemplated buying a used DAC that was state-of-the-art two or three years ago to get good value. In doing so, I study the engineering, which for the most part I understand) AND what people say sounds good. But I don't buy something just because some people say it sounds good. I want to know why it sounds good or bad.

That being said, the posts I posted explained why an opamp based I/V could sound bad, even worse than a passive. That being said, current output chips have a voltage tolerance, and badly designed passive I/Vs will not allow the D/A chip to perform at its lowest distortion. Also, the noise level due to a resistor load would be higher than a zero input impedance I/V. The distortion in the D/A chip may be less, and more tolerable, than slewing in an active I/V. Also, at 16bit, the noise due to a passive I/V may be very tolerable. However, if you a going to go with a 24bit system, this noise MAY be wasting some of lowered noise floor of the 24bit d/a, which is one of the main reasons for going to 24bits. The same goes with distortion of the D/A with resistive loads. It MAY be that the new D/A is designed with a higher voltage tolerance that would make a resistive load tolerable, from the standpoint of D/A chip distortion. I don't know yet. But if you can achieve a perfect D/A chip environment and find an I/V that sounds great at the same time, why not? I don't have the answers yet. I'm just trying to jump in and offer information to the developers that they may not be aware of. I don't have the time to try things out. I wish I did. I'd rather do that for a living. Anyhow, I'm just trying to help.

As to the I/V circuits in the postings, I haven't tried those. From an electrical standpoint, they look good. Some people have tried them, and thought that they were better. I don't know if they were listening at the 24bit level, though. I'm not against passive. I have a TVC and Jensen input transformers on my power amp. But passive isn't always the best answer just because it is passive.

In the threads I posted, active I/Vs were dumped on. But there were sound engineering reasons for doing so. 24bits and 192khz make them even tougher to work. Settling times are even stricter than before. Maybe a passive solution would be best. However, if a cheaper active solution could be found that meets or exceeds the passive, that would be good for a lot of people, even the sellers, if it brings a better profit margin. In sum, yes, active I/Vs can sound bad for explainable, unmysterious reasons; but the best can sound pretty good. I just offered info I found on what the best active might be. You can do what you want with it.

BTW, I found yet another recommendation using an IC for I/V.

• OPA660 I/V   (Open in New Window)