I picked up a couple of tube mono blocks a little over month ago and I want to make sure I'm setting the bias at the correct level. The previous owner told me to set the bias to 90 but he also said some people prefer running them at 70. The bias is set externally and is shown on a digital readout. I've tried to set it as close to 90 as I can. The bias seems to float between 85-95. I'm using them with a pair of Wilson Watt Puppies 3/2 and when I push the amps the bias will go up to about 150. I know these are demanding speakers so I'm careful not to push the amps too much. Does this sound about right? Should I be setting the bias to something else? Thanks for any help you might be able to give me.
The amps are Antique Sound Labs KMP60-FOX DT 6C33 "Bella 60 Custom" mono blocks modded by Response Audio around 2006. I've spent hours trying to track down a user manual but have had no luck so far, it doesn't sound like there are too many of these amps out there and even fewer modded like mine.
The mods listed below appear to be what was done to my amps but could be slightly off.
**SoniCap Platinum Teflon coupling capacitors
**AuriCap film interstage coupling capacitors
**Upgraded power supply capacitors now housed inside the chassis.
**Mills non-inductive grid resistors.
**6C33 output tubes x4 pieces
**Sovtek 6SN7 input/driver tubes X10 pieces.
And these are the listed specs:
OUTPUT POWER -- 50W per channel (conservative)
Frequency responsible at 1W -- 18Hz--25000Hz + 1dB
Frequency responsible at full power ---20Hz--22000Hz + 1dB
Circuit Design --- Push-Pull - zero feedback, Cathode follower output
Distortion at 1W/45W-- <0.8% / <2%
Distortion at full power --- <6%
S/N Ratio -- 86dB (1mV) ( with A weight 95db 0.6mV)
Input impedance -- 100K
Output impedance -- 4, 8 & 16 ohm
Power request -- 340W MAXIMUM 115VAC
Input sensitive -- 1.2V
Dimensions in inches -- 15.75" X 10.6" X 9.5"
Net Weight 42 lbs. ea.
Photos!
The amps are Antique Sound Labs KMP60-FOX DT 6C33 "Bella 60 Custom" mono blocks modded by Response Audio around 2006. I've spent hours trying to track down a user manual but have had no luck so far, it doesn't sound like there are too many of these amps out there and even fewer modded like mine.
The mods listed below appear to be what was done to my amps but could be slightly off.
**SoniCap Platinum Teflon coupling capacitors
**AuriCap film interstage coupling capacitors
**Upgraded power supply capacitors now housed inside the chassis.
**Mills non-inductive grid resistors.
**6C33 output tubes x4 pieces
**Sovtek 6SN7 input/driver tubes X10 pieces.
And these are the listed specs:
OUTPUT POWER -- 50W per channel (conservative)
Frequency responsible at 1W -- 18Hz--25000Hz + 1dB
Frequency responsible at full power ---20Hz--22000Hz + 1dB
Circuit Design --- Push-Pull - zero feedback, Cathode follower output
Distortion at 1W/45W-- <0.8% / <2%
Distortion at full power --- <6%
S/N Ratio -- 86dB (1mV) ( with A weight 95db 0.6mV)
Input impedance -- 100K
Output impedance -- 4, 8 & 16 ohm
Power request -- 340W MAXIMUM 115VAC
Input sensitive -- 1.2V
Dimensions in inches -- 15.75" X 10.6" X 9.5"
Net Weight 42 lbs. ea.
Photos!
> when I push the amps the bias will go up to about 150.
IDLE bias!
Some types of amplifier are *supposed* to draw more current when working hard. From 1.5X to over 10X. 1.5X or 2X is not unusual for text-tones. Seems a bit big for speech/music playing; check the load impedance.
IDLE bias!
Some types of amplifier are *supposed* to draw more current when working hard. From 1.5X to over 10X. 1.5X or 2X is not unusual for text-tones. Seems a bit big for speech/music playing; check the load impedance.