Hi, I have a situation that’s driving me crazy, it’s quite complicated but I’ll try to be as clear as possible for you guys, so maybe you can help me find a solution.

My setup is Lynx Hilo —-> McOne B Monitor Controller ——-> feeding: Bryston 4B with NS10s, and Genelec 8030s.

The thing is: When I try to use the combination Hilo-McOne-Bryston-NS10, I have a very loud hiss clearly audible that won’t let me mix.

Things to consider:

-With the same setup but a Stewart Amp instead of the Bryston : NO HISS. So, NS10s are out of the equation (Also tried ProAc Studio 100s and work fine so it’s not an impedance problem).

-Using the Genelecs. NO HISS. So Lynx Hilo is out of the equation and McOne are working fine.

-Bryston is connected directly to the wall.

-Bryston has just been serviced and working great elsewhere.

-Bryston 4B is one of the older ones, UNBALANCED with RCA connectors. The Stewart amp is balanced.

-I’m using 2 TS-RCA cables, which work fine as I get no hiss when connecting the Bryston directly to the Hilo.

-Unplugging the inputs from the Bryston, NO HISS when turned on. So Bryston is working fine.

And here comes what’s driving me crazy. When I connect the Hilo directly to the Bryston (no monitor controller) it works great, NO HISS. BUT, using the monitor controller with any other Monitor or power Amp, like the Stewart (which is balanced), everything works fine.

The only combination where I get this Hiss is when using the McOne monitor controller AND the Bryston.

Can you guys help me to find a solution? Can the problem be that the McOne has balanced connections and the Bryston is unbalanced?

Thanks a lot!

must be a level mis-match between gear: check the specs for max. i/o before clipping in dBu and then either use line level attenuators for a fixed level solution of trim down levels on outputs or inputs.

Forgot to say, hiss happens even when the monitor controller’s volume is at zero. So just by being connected to it I get the hiss, so I guess that an attenuator between the monitor controller and the power amp won’t help??? Anyhow isn’t the monitor controller supposed to be the attenuator between Lynx Hilo and the Bryston?

Another funny fact, this model of early 4B power amp has no volume or input trims at all.

Any possible solution?

A quieter amp? Power amps without level controls are usually set to +26 db gain. My Adcoms are also set to +26 db gain. They are totally silent, zero hiss 2" from the tweeter.

As i said before, when I plug the Bryston directly to my converters there is no hiss at all!!! Wonderful sound.
The hiss comes when I plug the Bryston to my converters with the monitor controller in the middle of the chain. And yes, with another power amp, and the same monitor controller, no hiss at all.

jim is faaar more knowledgeable on gear than most of us so maybe pm him for detailed information?

of course the monitor controller gets used to decide on the actual spl level at which you're going to listen but my experience is that regardless of what you feed into a 'weak' input (say +18dBu), if it's getting fed from a device which is capable of sending much higher output (say +24dBu) and even if you don't use it to it's full level, there is some amount of hiss...

did you try a (un-)balancing unit?

This happened to me actually. I had an old Bryston 4B that would be hissy when hooked up to my passive Coleman monitor switcher. When I swapped it out for some cheap Behringer Class D amps no hiss. Similar wattage top. I eventually got rid of it, just couldn't figure it out and decided to get something quieter and more modern. I believe mine was one with balanced inputs, and I also had it serviced to spec by an authorized technician. Wish I could help!

Could be the unbalanced connection.

I had loads of noise in my home stereo at varying levels ie noise when the heating kicked in, noise when fridge did etc.
All has been deadly silent when I replaced the last unbalanced connection (in this case a QUAD 520 amp) with a balanced one.

One of the first thing I thought was trying to make the output of the monitor controller unbalanced. Don’t know if that might help. Maybe it’ll be even worst. the thing is I don’t know how to turn a balanced output to unbalanced

Ouch, that’s bad news!

Well eventually that’s the last option, but I would like to find the way to keep the Bryston quiet, as I love how it sounds.

Today I’m trying with an audient nero controller. It’s active. Hope that solve the issue.

Even in a short cable an unbalanced connection can be that bad? What I can’t explain is why when I connect the Bryston directly to my converters, still unbalanced, no hiss at all.

My connection was 0.5m from a crossover directly above the amp in a rack.

Not saying that is the problem, merely suggesting a possibility.

as mentioned previously, it's not only about un-/balanced connections but about level matching (or gain staging) between gear: any gear in front of your bryston amp with lower max. output in dBU before clipping will produce less hiss...

Well that’s good information. This applies for passive units to?

This are the specs of my actual monitor controller:

New Old Sound McOne-B Features

Zero volume loss, balanced in to out (pot fully clockwise = unity gain)
3 TRS input (balanced or unbalanced)
3 TRS output (balanced)
Stereo/Mono switch
Mute/Dim/Unmute switch
All Passive, no power supply needed
Compact desktop enclosure
Technical Specifications

Input impedance: 2kOhm
Output impedance: 2kOhm (does not depend on your monitor impedance)
Dim value: -20dB
Dimension: Width 7.75" x Depth 6" x Height 3.25"
Weight: 2.5 LBS

And this are the specs of the controller I’m willing to try (audient nero):

BALANCED LINE INPUTS:

NOMINAL INPUT LEVEL:
+4dBu
MAX INPUT LEVEL:
+18dBu
CMRR:
> 50dB
MIC EIN:
-128dBu
CMRR:
>80dB @ 1kHz


UNBALANCED AUX INPUTS:

NOMINAL INPUT LEVEL:
-10dBV
MAXIMUM INPUT LEVEL (minimum trim):
+27dBu
TRIM RANGE:
±12dB


DIGITAL INPUTS:

INPUTS:
TOSLINK and Coaxial
FORMAT:
S/PDIF
SAMPLE RATES:
44.1kHz - 192kHz
BIT DEPTH:
up to 24bit


TALKBACK INPUTS:

MAXIMUM IPUT LEVEL:
2dBu
GAIN:
4-44dB
PHANTOM POWER:
+48V


SPEAKER OUTPUTS:

MAXIMUM OUTPUT LEVEL:
+12dBu


HEADPHONE OUTPUTS:

MINIMUM LOAD:
12.8Ohms


PERFORMANCE



SPEAKER OUTPUTS:

THD+N:
0.0015% 0dBu 1k input
SNR:
100dBu
CROSSTALK (SPEAKERS):
>100dB
FREQUENCY RESPONSE:
20Hz - 22kHz ±0.5dB
ATTENUATION AT MIN VOLUME (SPEAKER OUTPUTS):
>110dB


DAC:

THD+N:
<0.0017%
DYNAMIC RANGE:
113dB
FREQUENCY RESPONSE:
20Hz - 22kHz ±0.5dB


HEADPHONE OUTPUTS:

THD+N @ 0dBu (output level):
0.009% - 30Ohm

0.009% - 60Ohm

0.008% - 600Ohm
PEAK POWER OUTPUT:
90mW - 30Ohm

56mW - 60Ohm

7.35mW - 600Ohm
CROSSTALK:
>62dB
ATTENUATION AT MIN VOLUME:
>96dB

if this refers to the controller's nominal output level, then chances are good - most pro gear is way higher (+18 to +24 or even +27dBu), some can get swiched or continuously get trimmed to specific settings.

feeding a weak output into a hot input does no harm (you just loose some level), feeding a hot output into a weak input causes hiss at best (even without any signal present) or can overload/clip the input: you don't want this to happen with your amp/speakers!

Are you sure? On mine the trim pots are accessible via two small holes on the front and require a tweaker screwdriver to adjust.

I read this too somewhere else, but I can’t really find them.

This is the model I have, it’s the same as yours? Where are the trim pots located?

My Amp has them on the front - it almost looks like a little faceplate securing type deal. The older Brystons didn't come with them AFAIK - which seems to be the case with yours. You apparently have a really old one.