wardbeck m460-hiss with no mic connected?

[nosebleedaudio]

You need a load on the input; 150 ohms is typical when checking noise..
And those pres are a little hiss'y anyway..

[rogerbrain]

Originally Posted by nosebleedaudio

You need a load on the input; 150 ohms is typical when checking noise..
And those pres are a little hiss'y anyway..

yep.. a lot of the low noise specs are generated with the input shorted and not actual in use loading.. open will be the 'hissyest'

[beatsnblunts]

thanks mike, would you say that this is 'normal'? i just don't recall noticing this with other preamps.

[beatsnblunts]

thanks for the replies guys! It's a pretty crazy difference from loaded and un-loaded. Like one snake to a basket full of snakes!

[nosebleedaudio]

Originally Posted by beatsnblunts

thanks mike, would you say that this is 'normal'? i just don't recall noticing this with other preamps.

It depends..
Two things to comfirm this:
One: Have to be sure the gain is the same for two mic pres that you are comparing, if both are just cranked to max one might be 66dB of gain, the other 58dB for example..the 66dB will have more hiss..regardless..

2nd: terminate both with a 150 ohm resistor..
To make sure we are talking about the same pre, do you have a schematic?
Is Q1 and Q2 2N4401"s?

Plus a RE20 is a low level mic..

[beatsnblunts]

Any though other thoughts on these pre's?? I haven't had opportunity to really use em yet-seems like they have a crap load of gain. I bought em thinking they would be cool for rock n roll drums and guitar.

[nosebleedaudio]

Originally Posted by beatsnblunts

Any though other thoughts on these pre's?? I haven't had opportunity to really use em yet-seems like they have a crap load of gain. I bought em thinking they would be cool for rock n roll drums and guitar.

There's your answer, the more gain a pre has the higher the noise will be...
For drums you will NEVER notice it..
Try'em and see..
I would guess you may need a pad, but I believe those had one on the PCB...
The schematic I have shows a pad..

[beatsnblunts]

mike,
they are the m460A-not sure of the rev. i guess i'll open it up and get back to ya. the schematic i have has Q1 & Q2 as 2n5209 on the pre amp card and pn3569 on the output card. Im getting in over my head here! Curiosity killed the cat-or shocked it.

and Yes it does have a pad switch.

thanks for the replies.

[nosebleedaudio]

Originally Posted by beatsnblunts

mike,
they are the m460A-not sure of the rev. i guess i'll open it up and get back to ya. the schematic i have has Q1 & Q2 as 2n5209 on the pre amp card and pn3569 on the output card. Im getting in over my head here! Curiosity killed the cat-or shocked it.

and Yes it does have a pad switch.

thanks for the replies.

OK, I may have the 460b schematic, may or may not be very different..
Either way just give it a good listen...

[Warren Beck]

Hello.

The M460 series is a very low-noise module superior in design to the later M470 series. You certainly do need to terminate as described by nose. The M460A and B are essentially the came module, just different routing options.

Please visit Tony's site the Ward Beck Preservation Society for all the help you need to get these wonderful units back to life properly.

Regards,

[beatsnblunts]

thanks for adding Warren!
I've checked out wbsps-thats where i got the schematics. I will revist.

i've attached couple of pics

it looks like there's no resitor on the output and they are using the 'right out' for the output connection.

Excuse my lameness(im here to learn and hopefully pass along some knowledge in the future) but where would i connect the resitor-across hi and low or to ground??? ANd this would bring my output level down too?-which would prob help going into my AD.

thanks guys!

[beatsnblunts]

Bumpy bump for more termination info.

[beatsnblunts]

for your comments and to check termination. looks like my camera was upside down! doh!
cheers

[DrTom]

On some (most?) 460s the output wired "right out" makes the pan pot function as a trim. Engage the pan switch and that should give you a bit more flexibility dealing with the headroom/hiss issues. Worth a try anyway. That's how I always wire them up and, if I recall correctly, it was Dave T who turned me on to that quite some time ago.
Best,
DrTom

[beatsnblunts]

Originally Posted by DrTom

On some (most?) 460s the output wired "right out" makes the pan pot function as a trim. Engage the pan switch and that should give you a bit more flexibility dealing with the headroom/hiss issues. Worth a try anyway. That's how I always wire them up and, if I recall correctly, it was Dave T who turned me on to that quite some time ago.
Best,
DrTom

Thanks for that. Makes perfect sense now that you mention it. I will give it a turn.

[analogtodd]

I'm racking up a pair of M460-LA, and ran into a similar/same issue.

I've got both of them racked up, running on the same power supply (JLM)
Voltages are good.
If I turn either one on and run signal, its clean and perfect.... When I turn the second one on and turn the gain up, I get a ton of noise (hissy snake noise) in the unit I've got my mic plugged into.

I've got the resistor network built in to compensate for the fader gain, and I'm using A out pot so I've got an output trim.

[brianroth]

Todd, use a scope to be sure the unit isn't breaking into oscillation at some ultrasonic frequency.

Bri

[dandeurloo]

I have a number of Ward Beck pres and eq's. If they haven't been re capped any of those could be bad. Or an Opamp could be bad. They are worth getting going however. Cool pres!