Multiamp

kgdynalobal5

Thread 

on +-15V power supplies it will do about 30vpp balanced

on +/-20v power supplies it will do about 40vpp balanced

on +/-15v power supplies its 200ma per channel.

would need to adjust the bias resistors to reduce the current

for 20v.

200 ohms should be about right for 20V

works out to at least 2.5 watts rms pure class A into 50 ohms

 

mwl168 said:

 I am currently running 18VDC rails  and 312 ohm for R38/R39 for my Dynalobal which, after warm-up, results in about 19mA per

output device (380mV voltage drop on the 20 ohm emitter resistors). The MPSWx6 output devices run very warm but not hot to

the touch.  I think the silkscreen calls for 255 ohm for R38/R39 which results in about 10mA per device with16VDC PS rails,

seems very conservative to me. 

I also posted a few other R38/R39 settings using 16VDC rails on page 7 of the Multiamp
 thread. 
EDIT: With 255 ohm bias resistor on 20 VDC rails, the temperature on the output devices reached 95C after 90 minutes running with the chassis cover on. At that temperature the MPSWx6 max dissipation is derated to about 440mW. Even though they may be still running at the edge of their operating range, the amp sounded lean and harsh. Had to lower the bias resistor to 235 ohm which, upon fully warmed up, yields about 14mA current and the BJT case temperature is at a more reasonable 75C.   

                                                         SETUP

you pull the opamps, and start with all the pots in the center.

the pot by the led's is the input section offset pot. you adjust so that the outputs

are centered around zero. Then you adjust each other pot to

bring that output to zero. then you put the opamps back in.

you can probably get away with 18ma per output transistor.

in balanced mode the gain is Rf/Ri *2
you don't want to change the 5k input resistors, so
change the feedback resistors. Unlikely the compensation
cap needs to be changed
each ssdynalobal board pulls about 180ma at 20v

rv3 is the common mode offset pot. with the 2 other pots in the center, and the servo's
removed you adjust for minimum between both outputs and ground.
then you adjust the other 2, then add the servos

what I do is float everything in the chassis. The chassis is connected to earth ground.
everything else floats and the audio ground does not touch the chassis ground.

those are bipolar inputs, with a bit of offset current, so you really need a 10k input pot, or 10k
resistors to ground. other than that I listened to my latest set of boards on the new power supply,
and there is definitely a noticeable difference in noise with iem's.

 

 

 

ubaltobald3