Originally posted by EJolson:

I've got just the opposite problem (I think?). If I send a digital output from my 888/24 to my HEDD, and use the Hedd's converters to listen to the mix, if I A-B it with the analog out directly from the 888/24, the mix coming from the HEDD is at a MUCH lower volume.

This is totally consistent with my experience. Both nominal input AND output levels on the HEDD (and STC-8) seem to be calibrated substantially lower than the rest of my gear. Still haven't had time to troubleshoot this, but I will get to it soon. It's almost like Dave Hill decided he wanted "0 VU" on his stuff to be 10 dB quieter than the rest of the world. Oh well, it still sounds great... but the level mismatch IS annoying tho.

Glad to know it's not just me. :confused:

Yo! I did a bit of research on the HEDD level question and figured it was time to resurrect this thread.

From the HEDD 192 operator's manual:

Analog Input: Digital zero is +16dBm. This allows 12 db of headroom above a +4dBm 0 VU

And from the AD-8000 manual:

A/D CONVERTER - Input Level, Maximum (No Gain) 27dBu

So if I am reading it right... the HEDD (at factory calibration) likes its input levels 11dB quieter than the Apogee's. Interesting. The numbers for the D/A side are comparable on both units as well, which probably 'splains Littledog's analog level mismatch between HEDD and 888.

Moving on.... I see that Dave Hill has thoughtfully included individual level trims next to the analog in's and outs on the HEDD rear panel. Ideally I would want to match the HEDD's operating levels to the AD8K's, so that I can shuffle sources between the two without resetting levels everytime. My question is, will I get into trouble jacking those trim pots by >10dB over the factory setting? Would it be better to ease back on the AD-8000 trims instead, rather than bump up the HEDD's?

One last parting shot: All you HEDD-as-main-converter guys, are you using the HEDD's internal word clock as master, and then sending it round your studio via a clock DA? Or are you slaving to an external WC, and if so which one? (My clock choices currently are HEDD, Aardsync, Lucid GENx6, and AD-8000... Aard is master at the moment... but may soon be dethroned in favor of Lucid, OR Lucid-distributed HEDD.)

And please don't tell me to audition every single source individually with each of my available clocks every time!! (Where's that Jon Atack guy.......)

EJolsen,

Although there is a difference in db between the two converters, its not quite as big as you say.
I'm not that good at this decibel conversion thing so experts, please chime if i totally boch this up.

I say the difference isn't quite as big because you are comparing two different decibel systems

* dbm compares electrical power at a reference level of 1milliwatt
* dbu compares the difference in voltage at .775V

so,

16dbm = 10 * log(Power /1mw)
which results in 39.81mw which = 30.85V

27dbu = 20 * log(voltage / .775V)
which equals 17.35V

and finally:

20 * log(30.85 / 17.35) = 5db!

So the difference between the two should only be 5db (unless i screwed up which is quite possible! :) ).......since a difference of 6db is considered to be "twice as loud"(or quiet!)...
5db difference would still be definately audible!

Experts please correct me if i'm wrong....
Just my $0.2

S1LVER

Depending on which version of Hedd there are gain trims
HEDD-192 on the back panel
non 192 Hedd's on the inside However the first few have input gain trims only
The max level in or out is about +20dbm

Some thoughts: A few consoles and the higher end out board gear can go to +24 or +27dbm or more. But most gear has a max level of +20. When using a compressor and/or limiter in front of any converter the compressor-limiter needs to have more head room than the converter's input to allow for processing. Example if the max level that a limiter could handle is +20 and the following converter's gain was set so that +20 analog is digital 0 than the limiter may prevent digital clipping or it may have problems. Without some headroom in the compressor-limiter, there could be some internal clipping some where in the compressor-limiter's audio path or side chain. This may or may not be good depending on what ones goal is

What the big pitchure problem problem is the lack of standards as to how analog 0 relates to digital 0. some like to use 12 db above +4 which is +16dbm some like to use 14db above which +4 which it +18dbm. Some have no relationship in mind.
There is a dat player on the market that has an output circuit that when it becomes un balanced looses 6 db of headroom due to internal clipping. This makes it risky to use the maximum balanced level if you have a patch panel and some unbalanced gear

If you think of it in terms of analog tape the 12 to 14 db of headroom works. however this could be giving up some digital head room depending on what the source material is. A wood block needs more headroom and has a wider dynamic range than a distorted guitar or electric bass. It is important to know what your signal levels are and where clipping is
Dave Hill

Wow, this is great!! When's the last time Dave Hill stopped by YOUR place?!?

Dave, thanks for the info. I did cool off the HEDD inputs to roughly match the Apogee's, and everything seems happy.

Is there any kind of gain trim on the STC-8 as well? It still seems like the STC is unhappy with the levels coming off my console 2-bus. Not that I hear distortion or anything, it's just that I can _barely_ touch the threshold knob without getting into serious GR. The thing sounds great, but it just seems like I must be running hotter than it likes. All of my other bus comps have a decent amount of 'play' on the threshold knob, before compression starts to kick in... and even then, I can bring it in gradually, as opposed to the STC, where just moving the knob a millimeter from its endstop gets me 10dB of compression. OK, I'm exaggerating somewhat but it does seem odd.

By the way, I was born in Wisconsin. Hence, one of the many reasons why I love Cranesong! Go Packers!!

I'm still curious about word clock. Between HEDD, Apogee, Aardsync, Lucid, what are you HEDDites doing for a master? Jules? Anyone?