Re: New born
Congratulations, Bill.
Good news from me too: yesterday my balanced f4 was born, the twin should be ready next weekend, I hope.
I would like to express my admiration for Mr. Nelson Pass project. Absolutely no problems with startup. I reach thermal stability during 25-30 minutes (50-55 C), with 250 mV bias and final excellent 0 V offset. No cracks, no bumps during power ON/OFF, cold or warm. Bias and offset adjustments are stable, every amp is like self-regulating system.
I listened it for a while, the sound is clear and nice, but at the moment this is one channel only and to quiet, driven directly from DAC by typical balanced line-level signal. As I suspected I must think about pre-amplifier, I decide to use ZenMod hand-made schematic (Post #1641), I will appreciate very much any suggestions regarding Power Supply (+60/-20V, DC).
I would like to share one of my adventures especially with novices. I start all four amps one by one separately, carefully checking voltages, bias, offset, heatsink temperature. Then I put together two amps as one balanced (goodbye my SOZ). When I switch power ON I discovered +23V at all metal parts of housing. That was a short-circuit through insulation pad caused by a piece of metal filing. In other words one of IRFP240 was connected directly to the heatsink by a very small piece of metal. Fortunately nothing wrong happened, I replaced the pad and everything is okay now. Here is the proposal dedicated to all novices (and old-hands smart guys like me): before switching power ON check if drains of all power MosFets are electrically well isolated from heatsink.
Best Regards,
Andrzej
wirewiggler said:
Congratulations, Bill.
Good news from me too: yesterday my balanced f4 was born, the twin should be ready next weekend, I hope.
I would like to express my admiration for Mr. Nelson Pass project. Absolutely no problems with startup. I reach thermal stability during 25-30 minutes (50-55 C), with 250 mV bias and final excellent 0 V offset. No cracks, no bumps during power ON/OFF, cold or warm. Bias and offset adjustments are stable, every amp is like self-regulating system.
I listened it for a while, the sound is clear and nice, but at the moment this is one channel only and to quiet, driven directly from DAC by typical balanced line-level signal. As I suspected I must think about pre-amplifier, I decide to use ZenMod hand-made schematic (Post #1641), I will appreciate very much any suggestions regarding Power Supply (+60/-20V, DC).
I would like to share one of my adventures especially with novices. I start all four amps one by one separately, carefully checking voltages, bias, offset, heatsink temperature. Then I put together two amps as one balanced (goodbye my SOZ). When I switch power ON I discovered +23V at all metal parts of housing. That was a short-circuit through insulation pad caused by a piece of metal filing. In other words one of IRFP240 was connected directly to the heatsink by a very small piece of metal. Fortunately nothing wrong happened, I replaced the pad and everything is okay now. Here is the proposal dedicated to all novices (and old-hands smart guys like me): before switching power ON check if drains of all power MosFets are electrically well isolated from heatsink.
Best Regards,
Andrzej
I am building the Pumpkin preamp with balanced output as mentioned in the other thread. I also intend to use a balanced DAC as the source.
I do have 2 pairs of F4 PCB but am intending to only build a stereo pair for the time being. The reason being I listen to music at relatively low volume and my speakers are 93db sensitive. I hardly use the 8W from my old tripath amps for these speakers and I'm sure the 25W from the F4 is more than enough.
Also have 2 huge heatsink chassis of Class A amplification is probably not sit well with my wife.
So how big a improvement will a dual mono-block setup be if I don't need the power?
her shann
I do have 2 pairs of F4 PCB but am intending to only build a stereo pair for the time being. The reason being I listen to music at relatively low volume and my speakers are 93db sensitive. I hardly use the 8W from my old tripath amps for these speakers and I'm sure the 25W from the F4 is more than enough.
Also have 2 huge heatsink chassis of Class A amplification is probably not sit well with my wife.
So how big a improvement will a dual mono-block setup be if I don't need the power?
her shann
