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In the Forum: Audio Discussions
In the Thread: 250 watts Parallel S.E. advises
Post Subject: Driving the direct heated and why do you need so much power?Posted by Romy the Cat on: 5/30/2018
Devo, the GM-100 for sure is a good triode to get 160 watts output power in A1. Still, it would be a good chose, from my point of view, ONLY from a prospect of embracing as good DIY audio project. There is nothing wrong then to do the good DIY audio projects, it for sure better then to drink vodka or sniff cocaine. Still, I would not recommend to confuse the enjoyment of having a good DIY audio project with opportunity to get a better sound. 
 
What I am trying say that the GM-100 is a complex project and if you have an objective to drive with this thing your entails playback then I think it is set to be failure before it started, or what I call system architectural failure. Let me to explain. You are planning to drive with GM-100 the “full range system with passive filters”. Your HF or MF or Upper bass range need no 160 watts, it hardly need 10 even if you have a large room. Your array of 4 by 18” in BPH enclosure would not need more then 20W and it is closed-bottom it means it will not consume endless power at ULF and your BPH will act as very aggressive high pass filter. If you are one of those who will get 15Hz out of BPH type of loading by driving insane power into the drivers and exert them as direct radiators then you pretty much stop read this site. :-)   
 
Now, let see what will you pay for your, in my view unnecessary 160 watts. Having the 3500 Volts on the plate and 250mA you would need an output transformation with at least rated for 5000-6000 volts. The insolation for the turn of this power will be very dramatic, so the impact to the capacitance. To get HF you will go to crazy sectioning but to do it at 6000V is a huge problem, you will still have a lot of HF destroying capacitance in that transformer. So, we do know that in your full range applier the HF will be compromised. The question why to build it…? 
 
I understand if you have open bottom ULF channel that you would like to drive into oblivion with a lot of power. Then you get LF-only, no-sections, high capacitance transformer with a lot of core mass and huge amount of inductance. Then you drive your direct heated GM-100 with some kind of super powerful current source in order to let the GM-100 to be pushed on the right side of graph and let it to run with grid currents if it incidentally needs to.  You for sure do not want to have the amp like NAT Audio where GM-100 is driver by super flimsy 1n1p. Not that it is wrong and with 160 watts you will be siting deep into A1 but if you have a playback the need to consume 160 watts to run then why do not make a provision that it will not hard-clip at 165 watts? The point if that the direct heated can run semi-fine in A2 and they do soft clipping, it is shame not use it with DHT…. 
 
Anyhow, all about is  so much not your case with 4 BPH  boxes…

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