A Sunfire True Subwoofer Signature has developed amp problems that I would consider bypassing instead of repairing.
I am considering eliminating the Sunfire plate amp and using a FOSI M03 subwoofer amp in it place.
The carver manual says it has 2 drivers, if so are they both active with voice coils? That would make it more complicated I suppose.
Has anyone done anything like this? Any suggestions please?
I am considering eliminating the Sunfire plate amp and using a FOSI M03 subwoofer amp in it place.
The carver manual says it has 2 drivers, if so are they both active with voice coils? That would make it more complicated I suppose.
Has anyone done anything like this? Any suggestions please?
i don't know about the signature but I thought one of the drivers is a mass loaded passive radiator. I have had my original true subwoofer for over 30 year now maybe a bit more. I have had the amp repaired twice and its usually the big Caps that need to be replaced, well at least on mine that was the issue. there is a place to send just the amp here is the link:
https://www.ebcelectronics.com/sunf...wU8UbHSOSj5gIZQ60gp4IRBnmYhpxG-JzlsqLzrZ_wnym
mine is for home theater duty.
https://www.ebcelectronics.com/sunf...wU8UbHSOSj5gIZQ60gp4IRBnmYhpxG-JzlsqLzrZ_wnym
mine is for home theater duty.
Hi tiverson, EBC price is reasonable, I think this is a good course.
Did the sub you have experience the same issues twice over time?
Thank you very much for your advice.
Did the sub you have experience the same issues twice over time?
Thank you very much for your advice.
The Sunfire plate amp has ~2700 watts peak power and is equalized, band passed and limited specifically for the driver, the FOSI M03 only 200 watts peak.
That's more than a 10dB difference, which would sound only about 1/4 as loud down in the 20Hz range.
One driver is active with a DCR of around 3.3 ohms, the other is a passive radiator with around 1.7 pounds of weight.
Takes a lot of power to throw that much eight around 😉
If you can't get the amp repaired, you would need to look for something with similar power plus DSP (digital signal processing) to replace it.
It has been done, but would take some measurement to "dial in" the DSP to match the response of the Sunfire's processing.
Isnt driver Sunfire servo controlled? That would make replacement difficult, if not impossible?
Warm Regards,
WonderfulAudio
Warm Regards,
WonderfulAudio
Thank you everyone for your replies.
I will have the Sunfire plate amp rebuilt.
I will have the Sunfire plate amp rebuilt.
Here's how Bob Carver describes the Sunfire amp, which would generally be known as a Class H design:
https://forums.melaudia.net/attachment.php?aid=19987
CIRCUIT DESCRIPTION – AMPLIFIER SECTION
The input stage is a low noise FET operational amplifier operated in a forced Class A single
ended mode. The output of this stage drives balanced Class A level shifters and a balanced
Class A voltage stage that swings the full rail of 250 volts peak to peak. The remainder of the
current gain stages run full balanced with a constant VCE of 6 volts to the loudspeaker. It is
heavily biased into the Class A region for small signals and Class AB region for large signals.
Since the power dissipation in the output stages under simple quiescent bias conditions is 15
times less than a regular amplifier for the same output power, much more idle current can be
used. The issue of how to bias this amplifier becomes moot – all but irrelevant. All of the biasing
issues simply evaporate because of the 6 volts. Even though it has a vacuum tube output
characteristic on the current source output terminals, there is not a vacuum tube inside at all – it's
fully solid state.
CIRCUIT DESCRIPTION – TRACKING DOWNCONVERTER
Coming in from the outside world we find a conventional main power supply; a large power
transformer and filter capacitors. The output of this power supply feeds the Tracking
Downconverter. The output of the Tracking Downconverter is fully regulated and tracks the audio,
receiving its input signal from the same signal that drives the main amplifier. Essentially, the
Tracking Downconverter is another power amplifier because its output voltage is in synchronism
with, and tracks the audio signal, constantly remaining 6 volts above it. The input to the
Downconverter is a small signal Class A Motorola transistor. The output of this transistor drives a
Texas Instrument PWM digital comparator. The output of the comparator drives a Hewlett
Packard precision optocoupler which level shifts the digital control pulses to the gates of 12
International Rectifier Hexfets. The final output is smoothed into a continuously varying tracking
voltage by the main energy storage Downconverter inductor wound with large gauge #12 wire on
a low-loss, non-saturating, ferrite inductor. The final energy storage capacitor is a 6.8 microfarad
low ESR unit and 12 dB of feedback is taken from this capacitor to the input stage. Finally, a
Shotky free wheeling diode Downconverter inductor. Finally, a Shotky free wheeling diode provides the energy return path for the Hexfet side of the Downconverter inductor.
https://forums.melaudia.net/attachment.php?aid=19987
CIRCUIT DESCRIPTION – AMPLIFIER SECTION
The input stage is a low noise FET operational amplifier operated in a forced Class A single
ended mode. The output of this stage drives balanced Class A level shifters and a balanced
Class A voltage stage that swings the full rail of 250 volts peak to peak. The remainder of the
current gain stages run full balanced with a constant VCE of 6 volts to the loudspeaker. It is
heavily biased into the Class A region for small signals and Class AB region for large signals.
Since the power dissipation in the output stages under simple quiescent bias conditions is 15
times less than a regular amplifier for the same output power, much more idle current can be
used. The issue of how to bias this amplifier becomes moot – all but irrelevant. All of the biasing
issues simply evaporate because of the 6 volts. Even though it has a vacuum tube output
characteristic on the current source output terminals, there is not a vacuum tube inside at all – it's
fully solid state.
CIRCUIT DESCRIPTION – TRACKING DOWNCONVERTER
Coming in from the outside world we find a conventional main power supply; a large power
transformer and filter capacitors. The output of this power supply feeds the Tracking
Downconverter. The output of the Tracking Downconverter is fully regulated and tracks the audio,
receiving its input signal from the same signal that drives the main amplifier. Essentially, the
Tracking Downconverter is another power amplifier because its output voltage is in synchronism
with, and tracks the audio signal, constantly remaining 6 volts above it. The input to the
Downconverter is a small signal Class A Motorola transistor. The output of this transistor drives a
Texas Instrument PWM digital comparator. The output of the comparator drives a Hewlett
Packard precision optocoupler which level shifts the digital control pulses to the gates of 12
International Rectifier Hexfets. The final output is smoothed into a continuously varying tracking
voltage by the main energy storage Downconverter inductor wound with large gauge #12 wire on
a low-loss, non-saturating, ferrite inductor. The final energy storage capacitor is a 6.8 microfarad
low ESR unit and 12 dB of feedback is taken from this capacitor to the input stage. Finally, a
Shotky free wheeling diode Downconverter inductor. Finally, a Shotky free wheeling diode provides the energy return path for the Hexfet side of the Downconverter inductor.
I've owned 2 of those Sunfire subs. They weren't built that well. I had to place extra weights on them so they wouldn't move around. That predictably made them sound a bit better being coupled to the floor more firmly. The other issues were poorly designed drivers with foam surrounds that cracked along the outer edge.
The amp was directly powered from the rectified AC coming in from the wall socket, which meant the speaker output isn't isolated. Because of this they only isolated the input signal, but there still was leakage, to the point the sub would have a faint line frequency buzz all the time.
The amp was directly powered from the rectified AC coming in from the wall socket, which meant the speaker output isn't isolated. Because of this they only isolated the input signal, but there still was leakage, to the point the sub would have a faint line frequency buzz all the time.