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In Reply to: RE: Class-A most of the the time, and also... posted by Al Noakes on May 27, 2009 at 11:03:23
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Edits: 05/29/09 05/29/09 05/29/09Follow Ups:
Thom , I'll stay away from you in future I can see where this is going . I'm no beginner to this game and I'm not interested in pissing contests regarding what you consider to be good . I'd rather build for my own tastes , thanks !
Al
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Well you're flat out wrong in that respect , read my original post . I have no requirement for a 3.5 watt amp and no longer have suitable output transformers so sorry I'm not going to build anything with EL84's . I have over a hundred EL84 in my stash , mainly Mullards , so saying I have prejudices against this type is laughable . Besides , like I stated before I use DHTs , for both driver and output stages so there is no place for your MSG seasoned 12AU7 input stage either
Don't expect further replies .
Al
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They're a fine VA tube, or as LTP a fine PI stage too; nice g2/anode current ratio, and with gm to deliver gain from *VERY* reasonable plate loads( 5-7kOHm ). A pair of EL84 can only deliver a bit more percieved volume than a pair of 2A3, and with efficient speakers, it is a hard arguement for more power. Why rail against DHT's? Is there a single Way to good sound? ( it is a rhetorikal question, if you answer anything but 'no', there are bigger issues than power tube choice with your PoV ). Very similar to the One Way to build power supplies put forth by idealogical fanatics, yes?
I can't say I've ever had better results with IDH tubes for some reason...DH pose a whole bunch of troubles not seen with IDH...and yet for lots of us it is indeed worth the trouble( I've got two sets of DH amps, and two sets of IDH, right now I run one of each, bi-amped ). Attempting to convince somebody they're doing it wrong can be a lot of effort, yes?
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
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see the link. At least that looks rather like slander. You also claim to have presented a 'reasonable technical arguement', and I see that nowhere...as well as this distasteful accusasation of having some 'veiled agendas'. Give me a break...there is nothing but you doing just what you accuse Al of...it's personal, why not just admit it, and be up front about it? ( another rhetorical question; no response needed)
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
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your answer sums you, and yr thought process up quite well.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
The best policy with false prophets is to back off and let them have their fun with all the newbies .
Don't worry about me I can fight my own battles
Thom is just another cheap-jack , blinkered and full of himself
Enough said , time to crack on with Friday afternoon :)
Al
ps the WE388A's are in the post , I'll drop you a mail once I have the fils fired up ;)
I tried to trace 6 samples but alas 2 were dead so here are the 4.
now toss out the extremes and look at the two in the middle.
edit oops Grid is 0 to -50V in 5V steps!
and those were the two I listened to. I cranked them up to a juicy operation point and listened and that carbon wedge was nice! Here is a crappy pic of the basic construction.
Now lets diverge from the science. The sound was awesome but a few days later it quickly lost its charm. When I checked the operating points of the two tubes they were far off the curves I plotted. So I had a $8 tube that was dead and I thought why not bump the filaments a bit to get emission and 2.2V brought me back to the curves. The sound was back and I listened for a few days and things were nice but I needed to move on since one can only be so anal. That was a year ago but interestingly enough a similar situation that parallels this situation has come up hence my post.
dave
Edits: 05/30/09
Thanks for that ! This current batch of sillyness is Douglas' fault , after all those 388A curves look a bit 316A-ish . I've got a basic idea of how I'm going to use these but not what I'm going to use them in ;) Luckily I'm sitting on some 0.2mH 20A chokes and have a few other 8mH @ 10A and 2mH 20A so the nasty part is more or less catered for . Filament bias will be a bitch , putting more power in the cathode resistor than into the filament is not exactly going to help global warming LOL .
Al
the obvious choice for your filament bias is 3 12V 110W xenon bulbs in series.
A better choice is to build a small toaster oven to operate off your bias voltage. 650W will do some serious cooking :-)
dave
When I was running the 388's i actually put the filaments in series and grounded the center connection :-)
dave
Like the 316, if you run them hard they lose emission quickly. About 4 days ago I started listening to some mesh 2A3's and they were tired. Just for kicks I set the B+ to 250 and the bias to -40V and was only getting about 25ma of current and a Gm of 1500. I remembered the 388A experience and up went the filament voltage and at 3.8V I had 60ma and the Gm was up to 3000 (which is what the tubes measured as new). after a day of use I was running 80ma and I dialed the filament voltage down to about 3.5V. another day and it was 3.2V until eventually one of the tube was pulling proper current at 2.5V and out it went and another tired tube went in. Thus far 2 tubes are much closer to normal and a third is a good way there. The 4th one is putting up a good fight and we may justfind out how long the filament will last at 4V :-)
dave
oh yeah...blame it on me...Al, here are some neat tubes. Now if I didn't tell you, it'd go the other way...'why didn't you tell me?' Can't win no how.
The experience did set a record; out of 8 4E27 he had, 7 were good. In order to get that many, even if they're NIB/NOS I'd expect a third of that between filament damage and gas.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
hey-Hey!!!,
I am considering some for myself; I've been looking for a reason to visit him again...:) Maybe get a ride in his new Shelby Cobra whilst I am there...:)
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
I'd get my mits on them ASAP if I was you . $12 a pop is super value for a WE . All you need are some meaty fil chokes/schottkys and some high ripple caps and you're away . A few turns on top of a core with some beefy ECW is all thats needed for the fil tx . Filament bias may be problematic though LOL !
I'd have a field day if I was your side of the pond , could easily see a lot more of my hard earned getting pumped into 'investments' like 388A's :)
Al
heh-heh-heh...you should see this Cat's basement...:)
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
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