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In Reply to: Re: Chip regulator may not sound so musical to many discerned ears, unless ... posted by . on May 9, 2007 at 08:17:44:
Hi.Or it just your own way of describing it?
c-J
Follow Ups:
it's LCL and I just have ! CLC does not isolate the filament from the last cap in the filament supply . The final choke isolates the smoothing cap from the signal which passes through the filament . For reasons which I do not understand , a solid state CCS , with it's huge impedence sounds inferior to a passive LCL supplied filament which relies on the reactance of the final choke . This is a well known practice of DHT afficionados . You obviously have never tried or even considered this
For reasons which I do not understand , a solid state CCS , with it's huge impedence sounds inferior to a passive LCL supplied filament
DN2540 and LM1084 for 250mA fils running from a battery supply , had problems with the drop across the DN2540 . LM1084 and LT1085 for currents above that . I'm yet to try mosfets . So far I've found that the CCS reg followed by a cap to 0V and a choke feeding the filament provides the best sound when a chip reg is in the chain . LM317 sound horrible , are noisy and the filament needs to be bypassed with a cap . The heavy , bulky LCL approach wins hands down every time ;)
Thanks for the info. The LM317 is indeed horror. Can I ask what kind of choke you use and where do you get them from? Thanks.
LM317 is fine for heaters ;) Chokes are mainly from radio rallies , where else could you find a 10mH 10A choke for example ? So far I've been lucky and been able to pair up many of the singles I've found . Ebay is also a good place to find stuff , although postage price can make some deals unattractive . I'm beginning to think that rewinding and gapping mains transformers may be a worthwhile alternative . Chokes in my linestage are 280mH 2.7A (more like 100mH at the 1A I'm using these at) from Display Electronics in the UK
So what would be a good LCL filament supply for a 26..? Just wanting to learn.
what filament chokes do you have in stock or access to ? DCR of a hot 26 filament is 1.5 ohms , finding an isolation choke with sufficient reactance should be fairly easy . Just treat the LC part as you would a choke input supply . My main advice regarding implementing this is to use an outboard supply , keep all the iron well spaced and well away from the valves , use schottkeys for rectification . You could always go the silly route and use a pair of CV5 MV rectifiers instead of the schottkeys if you want to avoid solid state altogether :)
The MV route has me intrigued, I am a silly type guy anyway. So how ould one implemiment the cv5 MV..? & what is the equivalent # of a CV5, I really like running the vr75's for reg, so why not go MV..even if a hassle, I care not.. Chokes I have on hand are 1- Hammond 193L-5H @ 300ma, 2- 17H with unknown ma @ 300ohm DCR made by National Radio Company & are potted. I have access to any of the new production Hammonds & can source what ever might be needed.I also have the 2- 9H 40ma chokes that are in my 27's PS that I could use also.
You need low inductance , low DCR , high current chokes rather than the other way round . CV5 is a beast , 4 volt 10 amp filament , mogul base and are about the size of an 845 . I have a pile of CV5 going spare if you're keen ;) I have never used an MV for filaments , although a pair should easily light up a 26 . Definitely silly 'silly' , 80 watts + CV5 volt drop all to light up 1.5V @ 1A :) Maybe a pair of 866A would be a more conservative option ? (hehehe)
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