Preamp again
Hi, here is a SMD version to the inverted preamp. There is no real reason to make the layout so small, just for fun. It is then also my limit for DIY etching. Maybe someone has fun with it.
Thanks Mile and a little late happy birthday!
regards Olaf
Hi, here is a SMD version to the inverted preamp. There is no real reason to make the layout so small, just for fun. It is then also my limit for DIY etching. Maybe someone has fun with it.
Thanks Mile and a little late happy birthday!
regards Olaf
Attachments
I did an interesting experiment in an effort to figure out how to get rid of hum in my Class A amp setup. I was having the hardest time getting rid of hum from ground loops or what not in my Class A Pass amp setup so I finally took out the Pass amps, and built a Pass F6 PSU with P2P wiring, using a 400VA 18v-0-18v trafo and qnty 8 x 33mF caps in a CRC PSU. It is important to follow the schematic exactly, especially where the ground points are. So instead of a Pass Class A amp (either M2 or Babelfish J), I put in the FX8 Bimo mod amp, but I cranked the bias up to 1 amp. It is stable, and the DC offset is maintained at circa 10mV. Bias is rock stable.
The new F6 PSU and the FX8 Bimo under Class A operation works very well. I measured 0.0mV noise at the speaker output with my Fluke 101. I have never measured 0.0mV in any speaker amplifier. Only headphone amps after much care is taken.
Anyhow, just wanted to let Apex fans know that the FX8 Bimo runs very nicely with 24v rails and an amp of bias. If you have the PSU and the heatsink, give it a try. It's refreshing to have a Class A amp that has 30dB gain vs the 15dB or 20dB typically seen over in the Pass forum.
Thanks to Mr Mile, Bimo, and Prasi for this great amp. I dusted it off after more than a year on the shelf and it is sounding great.
Here is F6 PSU schematic:
Here is test showing 0.0mV noise at speaker output with input turned off (iPhone 6s):
Here is closeup of FX8 Bimo mod running at hot 1000mA bias:
The new F6 PSU and the FX8 Bimo under Class A operation works very well. I measured 0.0mV noise at the speaker output with my Fluke 101. I have never measured 0.0mV in any speaker amplifier. Only headphone amps after much care is taken.
Anyhow, just wanted to let Apex fans know that the FX8 Bimo runs very nicely with 24v rails and an amp of bias. If you have the PSU and the heatsink, give it a try. It's refreshing to have a Class A amp that has 30dB gain vs the 15dB or 20dB typically seen over in the Pass forum.
Thanks to Mr Mile, Bimo, and Prasi for this great amp. I dusted it off after more than a year on the shelf and it is sounding great.
Here is F6 PSU schematic:
Here is test showing 0.0mV noise at speaker output with input turned off (iPhone 6s):
Here is closeup of FX8 Bimo mod running at hot 1000mA bias:
Attachments
I did an interesting experiment in an effort to figure out how to get rid of hum in my Class A amp setup. I was having the hardest time getting rid of hum from ground loops or what not in my Class A Pass amp setup so I finally took out the Pass amps, and built a Pass F6 PSU with P2P wiring, using a 400VA 18v-0-18v trafo and qnty 8 x 33mF caps in a CRC PSU. It is important to follow the schematic exactly, especially where the ground points are. So instead of a Pass Class A amp (either M2 or Babelfish J), I put in the FX8 Bimo mod amp, but I cranked the bias up to 1 amp. It is stable, and the DC offset is maintained at circa 10mV. Bias is rock stable.
The new F6 PSU and the FX8 Bimo under Class A operation works very well. I measured 0.0mV noise at the speaker output with my Fluke 101. I have never measured 0.0mV in any speaker amplifier. Only headphone amps after much care is taken.
Anyhow, just wanted to let Apex fans know that the FX8 Bimo runs very nicely with 24v rails and an amp of bias. If you have the PSU and the heatsink, give it a try. It's refreshing to have a Class A amp that has 30dB gain vs the 15dB or 20dB typically seen over in the Pass forum.
Thanks to Mr Mile, Bimo, and Prasi for this great amp. I dusted it off after more than a year on the shelf and it is sounding great.
Here is F6 PSU schematic:
Here is test showing 0.0mV noise at speaker output with input turned off (iPhone 6s):
Here is closeup of FX8 Bimo mod running at hot 1000mA bias:
Nice, I suggest AA9 or AA14 class A amps.
Regards