[MattGray]

Hey Ben, man first off please don't take any offence to my comment regarding the converter test at Sonamax. I realise we didn't have a lot of time & it was difficult enough just to get it patched in, so I appreciate all the effort you went to in order to hear it. Personally its just not how I would go about auditioning converters.

Originally Posted by Ben F

Hi Matt,
You are making a lot of assumptions there! How do you know that the Prism clock is worse than say the Forsell or Lavry? There are no conclusive tests regarding this, and Prism are renowned for their clock accuracy.

I'm sure the Prism clock is excellent, there is no doubt in my mind at all & I'm not saying otherwise but when it comes to AD conversion, I've always believed that a great A/D will sound its best set as the master clock (call it me being pedantic if you will). Of course this is assuming the AD converter is well designed & that it has a high quality internal clock. In the case of testing or comparing an AD converter I always start with making it the master clock because you don't know how an external clock could effect the results of a test. I'm not saying the Prism clock effected the result of the Forssell negatively (you're right I can't quantify that) but I also can't be sure that it may have improved or slightly degraded one or both of the converters so for me its an 'unknown variable' that doesn't need to be there. When you use an external clock to test 2 converters, you're not going to hear exactly what you're paying for. Take out the external clock (prism or otherwise) & then the boxes are on an even playing field because you're hearing it how the designer of the converter heard & tested it & ultimately deemed it 'done' to their ears.

Another reason I prefer internal clocking is that I found with my Cranesong HEDD that its very fussy about clocking & can even introduce ticks in the audio signal if its not happy with an external clock source (it prefers its own). This is not the only box that I've heard do this either. Of course Prism, Lavry, PM Model 2 or Forssell are very high end units & may not be as fussy on external clocking but in my experience if the A/D is set as the master clock it can often sound better than external clocking imo.

There is a lot of BS floating around regarding master clocks, remember when Apogee introduced 'BIG BEN' it was touted to make any digital system sound better Apogee Electronics > Products > Big Ben & sure it can improve the clocking & conversion quality on converters that aren't well designed but this is often a band aid fix for converters with a sub par clock or clocking related issues. Depending on the quality of the converter clock it can either improve things or slightly degrade things.

The second is levels- we matched them very close in the end, certainly within 0.1dB. Are you certain that the files that you are presenting here do not suffer from the same problem? It looks like you are matching them the same way as we were using Sequoia.

I don't think it's just a question of matching levels perfectly using digital gain. With all the converters I personally tested, I set them all up to have the same operating level (analog trim pots or jumper pins) & the conversion was a straight wire transfer (no console or other mastering gear in between). With the tests at Sonamax the Prism DA was a couple of dB hotter than the Forssell (different analog calibration level) & the Lavry AD input level was of course lower to compensate (different analog calibration level) & in between the converters was a Crookwood Mastering console & a Neve 2087. So gain needed to be adjusted digitally for it to hit the console/Neve in the same way when the Forssell was patched in. It introduces further unknown variables... but again I understand that in the time we had it was not realistic to re-cal converters to match & to change clocking etc.

I mean you could go into all sorts of aspects such as cabling, AES routing etc. But I think we still got an idea of what the Forsell sounded like.

Its true you would've still got a decent vibe on the Forssell. I just question whether it was in an ideal test case situation. When I test something I want to hear it without any unknown variables & how the designer intended it to be heard. The listening tests I've done still aren't going to showcase each converter in a real mastering workflow experience but the test is certainly very controlled (with the exception of one of the files which was done outside my room & was 2.1dB lower). As I said in my quote to William, "Its easy to pick up the bigger differences but it certainly took me sometime & some regular A/B'ing in unattended sessions on jobs to appreciate all the subtle differences between them." I certainly didn't find an hour or two enough to truly appreciate the differences. Remembering that my 1st impressions of the Forssell was much like yours until I began comparing it with my usual converters as DA & AD. That's not to say there is a clear winner every time... I'm sure the polls will definitely show that! One thing you'll hear with my test files is that one converter may sound better on one mix but not as good as a different converter on another mix & as you mentioned at Sonamax even in the same song one converter could favour a verse over a chorus on the same track.

I understand for some that it may be a case of a simple workflow wins... if you've already got a high end set of converters why do you want the hassle of integrating a second set.. more cost, more rack space, more time patching & comparing etc. However this is quite common practice in bigger facilities & even some of the smaller ones. I also like the idea of having a back up set for redundancy should one set need to go out for servicing & I don't want a compromised set of converters as my back up.

Anyway thanks for bringing the converters down for a listen!

Any time Ben... I'd still like to hear the rest of the gear at Sonamax sometime.. The 2087 sounded cool but I want to hear the Tube-Tech's next time.