ADAT HD24 output level mismatch with Blackfaces

[JamesBRey]

Group,


I just installed a new ADAT HD24 and have a problem with the output levels.
The levels coming from the HD 24 are 0 VU and appropriate. The levels coming
from my original Blackface ADAT's are down -6db compared to the HD24.

This is with the same digital signal feeding both units, and both units wired
with +4 outputs.

Question is ... did Alesis change something on the output side wiring to make
this happen? I am running unbalanced into my board so this would account
for the -6db on the Blackfaces -- but why are the two units acting differently
with the same wiring scheme?

Has anyone else installed an ADAT HD24 and had this problem?

Any info would be appreciated.

[Mike Rivers]

In article > writes:

> The levels coming from the HD 24 are 0 VU and appropriate. The levels coming
> from my original Blackface ADAT's are down -6db compared to the HD24.

> Question is ... did Alesis change something on the output side wiring to make
> this happen? I am running unbalanced into my board so this would account
> for the -6db on the Blackfaces -- but why are the two units acting differently
> with the same wiring scheme?

There are different wiring schemes. It could be that the output of the
HD24 is actually single ended (impedance balanced) where the output of
the ADAT is differential. By grounding one side of the output pair of
the ADAT to go into the unbalanced input, you're only seeing half the
signal level, hence the -6 dB.

Just a guess, having never seen what comes out of an HD24.


--
I'm really Mike Rivers - )

[JamesBRey]

Thanks for the reply, it makes a lot of sense. Do you know some way I could
check for this?





---------------------------

There are different wiring schemes. It could be that the output of the
HD24 is actually single ended (impedance balanced) where the output of
the ADAT is differential. By grounding one side of the output pair of
the ADAT to go into the unbalanced input, you're only seeing half the
signal level, hence the -6 dB.

Just a guess, having never seen what comes out of an HD24.

[Andy Peake]

(JamesBRey) wrote in message >...
> Group,
>
>
> I just installed a new ADAT HD24 and have a problem with the output levels.
> The levels coming from the HD 24 are 0 VU and appropriate. The levels coming
> from my original Blackface ADAT's are down -6db compared to the HD24.
>
> This is with the same digital signal feeding both units, and both units wired
> with +4 outputs.
>
> Question is ... did Alesis change something on the output side wiring to make
> this happen? I am running unbalanced into my board so this would account
> for the -6db on the Blackfaces -- but why are the two units acting differently
> with the same wiring scheme?
>
> Has anyone else installed an ADAT HD24 and had this problem?
>
> Any info would be appreciated.
>
>
>

You should be able to reach Alesis at (310) 821-5000 (not a toll-free
call but less wait for tech support as a result). I've had excellent
results with their tech-support dept., a rarity in this day. I'm sure
they can help you.
peakester

[WillStG]

<< (JamesBRey) >>
<< I just installed a new ADAT HD24 and have a problem with the output levels.

The levels coming from the HD 24 are 0 VU and appropriate. The levels coming
from my original Blackface ADAT's are down -6db compared to the HD24.

This is with the same digital signal feeding both units, and both units
wired with +4 outputs.

Question is ... did Alesis change something on the output side wiring to make
this happen? I am running unbalanced into my board so this would account
for the -6db on the Blackfaces -- but why are the two units acting differently
with the same wiring scheme? >>

You are plugging 1/4" balanced TRS jacks into unbalanced TS 1/4" mixer
inputs, yes? You might say the HD24 outputs "sees" you going into the
unbalanced input and is compensating for that ( 's why the manual says "may be
connected to balanced *OR* unbalanced mixers") , but the Blackface ADAT's
outputs are not as smart, and you are just losing one leg of the balanced
output on that device.

At this point you can

1. Buy a 8 channel balanced to unbalanced connection converter box for the
ADAT. (naaah)

2. Use the digital outs on the ADAT with a better D/A converter that HAS got
balanced outs (well...)

3. Turn up the line trims on your mixer channels where the ADATS come back,
calibrated by the tone you stripe at the top of each and every tape. ( Aha! A
good practice and cheap too... )





Will Miho
NY Music & TV Audio Guy
Fox And Friends/Fox News
"The large print giveth and the small print taketh away..." Tom Waits

[Mike Rivers]

In article > writes:

> The black ADAT's balanced outputs use a standard phase reverse stage
> for 'pin 3'. If you run it into an un-balanced mixer input, you short
> out the 'pin 3' or ring output through a 560 ohm resistor and
> therefore drop 6 db. The HD24 48k uses an impedance matched output
> that carries no signal on the ring output and will appear 6 db down
> from a Black Adat wired balanced.

I figured it was like that, but usually single end driven balanced
outputs carry the full nominal signal level on the driven lead. If
that's 6 dB down from the differential output of an ADAT, that means
it's a non-standard, probably nominal -2 dBu level.

I would expect that you'd see that level out of half of the ADAT. But
I guess you've studied this out. Did they perhaps change the digital
reference level for +4 dBu on the HD24 to make up for the lower output
level?



--
I'm really Mike Rivers - )

[Flea Man]

(Jim Williams) wrote in message >...
> ...SNip Snip...
> The HD24XR uses a 'cross-coupled' balanced output that corrects for
> the -6 db drop you get with the black ADAT outputs. It is the same
> level balanced or un-balanced.
> Install the EC-2 upgrade converters and these level changes will go
> away. You will also have superior sonics due to better converters. The
> A/D section is nearly identical to the Radar 96 at $13,000
>
> Jim Williams Audio Upgrades


Wow, now that's a statement! Of course one's "Nearly identical to the
Radar 96" might be someone else's "not a chance!"

Of course its such a new unit...I can't imagine many being able to
have both units to compare. Wonder what the Fletcher/Mixerman tribe
thinks of this...

One of the comments about the Radar 96 (Or higher) is how great it
sounds at 48k (over the 48k version Radar). I wonder if the HD24XR is
also improved at 48k (over the regular HD24)?

How about the D/A section? I dear to ask if it's in the "Radar"
league?

Fleaman

[Mike Rivers]

In article > writes:

> Wow, now that's a statement! Of course one's "Nearly identical to the
> Radar 96" might be someone else's "not a chance!"

In this case, the one saying it's nearly identical has built his
farily long career from studying, measuring, and upgrading audio
equipment. He didn't say they sounded nearly identical, but I'd trust
that the circuitry and basic components are pretty similar if Jim
Williams said so.



--
I'm really Mike Rivers - )

[Flea Man]

(Mike Rivers) wrote in message news:<znr1059398859k@trad>...
> In article > writes:
>
> > Wow, now that's a statement! Of course one's "Nearly identical to the
> > Radar 96" might be someone else's "not a chance!"
>
> In this case, the one saying it's nearly identical has built his
> farily long career from studying, measuring, and upgrading audio
> equipment. He didn't say they sounded nearly identical, but I'd trust
> that the circuitry and basic components are pretty similar if Jim
> Williams said so.

Yeah, I know who he is. And I know who you are! I have to say, the
way you translated it makes it sound a little more believable.

Then again, sometimes the differences between many of these machines
can seem pretty small...especially if you're only comparing a couple
of tracks (Stereo).
Although hard to evaluate, comparing all 24 tracks at a time starts to
show a little more (or a lot more) differences.

Fleaman

[JamesBRey]

Just a follow up as I started this initial thread.

My suspicions were confirmed today talking to the helpful and informed Alesis
tech.

All ADAT models since the XT (everything but the Blackfaced originals) have a
"Servo" output balancing scheme that keeps the levels at +4dbm with an
auto-sensing type feature.

Only the original ADAT's are down 6db running into an unbalanced board on the
ELCO +4 outs.

I guess a simplle solution here is to swap out a Blackface for an XT20 or M20
or something. Just to keep parity between all levels matched to the ADAT
HD24.

Thanks for all the input folks.

[Mike Rivers]

In article > writes:

> I guess a simplle solution here is to swap out a Blackface for an XT20 or M20
> or something. Just to keep parity between all levels matched to the ADAT
> HD24.

Remember that the data polarity is opposite for the original ADAT than
all later models. So your levels will match, but the polarity of the
audio will be inverted. Don't forget where the "phase" switches on
your console are.

Personally I think you're being a little silly with this level obcession, but if it
makes you feel better, continue along your path. There are many sonic improvements
to be had with a 20-bit ADAT over the original model, but watch out for the M20. It
was never really quite finished and has some quirks that might bite you eventually.
But it DOES have input level controls, bless 'em.



--
I'm really Mike Rivers - )

[Mark Plancke]

(JamesBRey) wrote:

>Just a follow up as I started this initial thread.
>
>My suspicions were confirmed today talking to the helpful and informed Alesis
>tech.
>
>All ADAT models since the XT (everything but the Blackfaced originals) have a
>"Servo" output balancing scheme that keeps the levels at +4dbm with an
>auto-sensing type feature.

I'm not a circuit designer by any stretch of the imagination but....
I'm not sure how a servo could effect balancing because that circuit
is usually used to get rid of DC offset in a DC coupled circuit, which
I'm pretty sure the ADAT's and HD's are not. Perhaps the tech used the
wrong terminology to describe what the circuit is doing?? It's cool
that it automagically makes up for level differences regardless of how
it does it.

Mark
http://SoundtechRecording.com

"Putting the lion's share of your attention and investment out in front
of the microphones pays off every time." -- Bob Olhsson

[Flea Man]

(Mike Rivers) wrote in message news:<znr1059438099k@trad>...
> In article > writes:
>
> > I guess a simplle solution here is to swap out a Blackface for an XT20 or M20
> > or something. Just to keep parity between all levels matched to the ADAT
> > HD24.
>
> Remember that the data polarity is opposite for the original ADAT than
> all later models. So your levels will match, but the polarity of the
> audio will be inverted. Don't forget where the "phase" switches on
> your console are.

"Data polarity" is the key word here. AFAIK, the polarity was
reversed within the Blackface ADAT, before it was written to tape,
then reversed again to normal before leaving the ADAT. They didn't do
this on the later ADATs. So, you would only have a Polarity issue if
you mixed tapes (used a tape made on a Blackface in a XT) and/or had
different ADAT models linked in the same rack (with mixed tapes or not
totally going through the analog ins/outs).

If your recording and playing from scratch through the Analog
ins/outs, there will be no problems, polarity will be fine on all
units.

This is why it is a good idea to mark on the ADAT Tape what machine it
was recorded on….Blackface, XT, XT20, etc.

> Personally I think you're being a little silly with this level obcession, but if it
> makes you feel better, continue along your path. There are many sonic improvements
> to be had with a 20-bit ADAT over the original model, but watch out for the M20. It
> was never really quite finished and has some quirks that might bite you eventually.
> But it DOES have input level controls, bless 'em.

What/which quirks? I'm curious if you remember what some of them
might be? I know that even after Alesis discontinued the M20, they
still had a software update or 2. I'm wondering if you know whether
(and what) the quirks where and at what level of update they might of
been at.

May it be possible the last update might of fixed them??

??

Fleaman

[Mike Rivers]

In article > writes:

> "Data polarity" is the key word here. AFAIK, the polarity was
> reversed within the Blackface ADAT, before it was written to tape,
> then reversed again to normal before leaving the ADAT. They didn't do
> this on the later ADATs. So, you would only have a Polarity issue if
> you mixed tapes (used a tape made on a Blackface in a XT) and/or had
> different ADAT models linked in the same rack (with mixed tapes or not
> totally going through the analog ins/outs).

This is true. But there are a lot of old ADAT tapes around, and
presumably if James is using his ADAT now, he has tapes to mix.

> What/which quirks? I'm curious if you remember what some of them
> might be?

No, but a friend of mine who runs a very busy studio bought into the
M20 system, had continuing troubles with it, and eventually bailed to
ProTools. Alesis and his dealer were as helpful as they could be, but
there were some things that he found important which never worked
correctly. A casual user might not have any problems with it, like so
many other things.

> May it be possible the last update might of fixed them??

Sure, but by that time there may not have been any M20 users left to
tell. There are a lot of things to like about that machine. Too bad
they never finished it.


--
I'm really Mike Rivers - )