John Sayers' Recording Studio Design Forum Archive

Thanks for all your info and advice! Maybe if you would be so kind as to lend a little more. I have been using Mosvalve MV-962 power amp that was manufactured by Tubeworks, I am using it to power a pair of Event 20/20 passive monitors. Anybody have anything to share on this amp/ speaker combo (Mosevalve/Event 20/20) I'm all ears! My worst complaint with the Mosvalve amp so far as I'm concerned is fan noise, followed by the fact that there seems to be a little noise comming through even when no material is present. Not sure if the latter would still be the cases with say a HaflerTA1600, Alesis RA150 or not since I have no other experience. Once again any and all advice would be much apreciated!

Thanks
Jeff

Mosfets tend to exhibit more "tube-like" properties due to their electrical characteristics, but other than that there shouldn't be any noise (fan excepted) - have you tried shorting out your INPUTS to the power amp with a pair of 1k ohm resistors and seeing if the noise is still there? Steve

First off, thanks so much for your help Steve! I understand the idea behind mosfet behaving more like tube amps but is that a good thing in my situation or not? I'm not going to worry about the resistors at this time, any ideas about fan noise?

Thanks Jeff

Tubes tend to distort (when they do distort) with more pleasing sounding harmonics; since MosFets, unlike bipolar transisistors, amplify VOLTAGE, they are claimed to have similar characteristics. I've not had occasion to do a head-to-head comparison, but if this is true then MosFets should have a "warmer" sound when pushed than an amp with only bipolar transistors would have.

Fan noise - if you can't turn it off without cooking the amp, I'd sell it and find an amp with convection cooling and NO FAN... Steve

Thanks Steve! What's your recomendation?

Thanks!
Jeff

That would partly depend on your financial situation; if you're
a) running the amp at relatively low gain settings, say under 30%
b) technical enough to figure out how to unplug the fan
c) able to buy a replacement should you fry this one

Under those conditions, I would try just unplugging the fan and seeing if the amp lives or dies. MosFets are self-regulating current-wise (as opposed to bipolar transistors, who "run away" at the slightest provocation) - so if they get too warm they should "self regulate" and shut down.

Just in case they do NOT do this, however, I'd only try unplugging the fan if ALL the conditions above are true; otherwise, sell it on ebay and find something that's designed to run without a fan.

Any decently designed power amp, when used WELL UNDER its design rating, won't appreciably color the sound - and you do NOT want to use a low powered amp anyway; when an amp's output stages go into clipping, they produce DC which can take out the HF elements in a speaker... Steve

Thanks Steve! I got the fan unhooked & so far so good! Looks like you might have saved me from puchasing a new amp , as I've never had an issue with its sound or performance!

Thanks Again!
Jeff

I have a 250w version of the same amp, and it is not the best sounding thing. I ended up using it bridged for my guitar. Works well for that.

Hello:
Depending on the fan design you may be able to put a resistor in series with it and slow it down. It would make little noise and provide some air movement to keep the amp cool enough.

I am not in favor of too much coloration in the monitoring system. I prefer stark reality as much as possible. 20-20s are sweet sounding monitors but they hide a lot. Add that to an amp that colors / makes things sound better than they are and mixing is difficult. There is a big difference between a listening room and a critical listening / working control room.