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Old 13th September 2013, 11:04 PM   #1331
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Originally Posted by 2 picoDumbs View Post
Have you sent Variac, Jason, or The Store a message?
I reached out to the helpdesk and they're working on getting me a replacement. Thanks all!
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Old 13th September 2013, 11:19 PM   #1332
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Originally Posted by JP14 View Post
I reached out to the helpdesk and they're working on getting me a replacement. Thanks all!
Excellent news mate
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Old 14th September 2013, 02:22 PM   #1333
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I finished my ACA build last night and have listened to it for about six hours so far (and left it on all night to see if anything would catch on fire). First of all, a big thank you to Nelson Pass! What a wonderful resource he is!

My main reason for posting, other than bragging about finishing the amp, is to let potential builder/owners know how it sounds with a modest horn system. I had a problematic Yamaha M4 amp that I never liked the sound of very much, so I reckoned I could "reuse" it as a new amp, especially since it had some decent-sized heatsinks.

I drilled out some new holes for mounting the ACA boards and also s***canned the crappy spring-loaded speaker binding posts. A heavy plastic cutting board provided a nice support for the new binding posts. The build went smoothly until my wife pointed out that I had forgotten to order the trim pots from Mouser. So we made a quick trip to RS and bought a pair of audio 5k pots. Funky, but it's a reasonable substitute. My wife had never soldered or drilled metal before, so she was delighted to learn how. And of course I had my own nefarious plan to get her hooked on this DIY thing . . .

My speakers are eWaved Barzilays: Barzilay cabinets topped with Altec 811B horns. My speakers employ 15" Stephens TruSonic woofers and Radian 450PB compression drivers. Crossover is the eWave design by Zilch (RIP). I can only guess what the sensitivity is, but the Radian is >100dB and the TruSonic is probably about 95dB. Preamp is a NAD C 162 and I usually listen to music with a Rega Apollo-R CD player.

So how does it sound? My overriding impression is that it is smooth, with a relaxed (but not lazy or sluggish) presentation. It's like a superior athlete who doesn't need to show off. Bass is present, but a tad subdued, so maybe dub, reggae and explosion enthusiasts should look elsewhere or build giant horn woofers--or use subwoofers! I don't care for subwoofers. But bass is there and it is very accurate. The main thing for me is that I can just enjoy the music with analyzing it. Analyzing sonics is a sure sign that the music isn't doing its job. Of course we listen for sonic characteristics and signatures in the beginning, especially after we build something. But I'm into this primarily for the musical magic.

Okay, I need to substantially revise my impressions vis--vis bass. Listening to Black Uhuru's Red. Bass is there and it sounds good. And I cranked it up because I wanted more of a good thing. Leading edge transients are super quick, as are decays. Most important, the bass swings and is beautiful and nuanced. You know: musical.

My best-ever sound (okay, I should say favorite sound) was with a 6B4G amp fed by an Audible Illusions 2B, into a pair of Klipsch Cornwalls with the excellent (and essential) Crites XOs. I only have the AI preamp now, which I need to resurrect. The tube amp had a holographic imaging ability that the ACA cannot hope to duplicate. But the ACA does almost everything else as well, and perhaps is more detailed. It's certainly quieter and has zero hum via horns. The ACA sounds much better than the Yamaha M4 did. It sounds somewhat better than my Classe CA-100, which is more of a personal preference than a slam dunk "better than" comparison, unlike the Yamaha comparison. Bottom line: my Classe will be relegated to the bedroom.

I listen in a pretty big room with high ceilings. My system gets plenty loud for my tastes. I generally listen to classical music, but I cranked up some Jane's Addiction last night and it got loud--check mark for that.

I'll sleep well tonight. I was up late last listening, and couldn't sleep in because I was so excited to listen some more this morning. Again: thanks, Nelson!
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Old 14th September 2013, 02:55 PM   #1334
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Hello,
I am putting together an amp camp amp and I lost one set of the 2sk170bl for a channel.
SO,what else can i use in a pinch?It'll take a while for the next round of jfets to arrive,which will be the end of this month.
But,i do have a few 2sk117 left over,so can i use them?

Thanks
Suraj
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Old 14th September 2013, 03:31 PM   #1335
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test their Idss

if it's above 6mA , then use them temporary

170 are better , having much greater xconductance
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Old 14th September 2013, 03:54 PM   #1336
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Thanks!I have about 20 of those,so,i hope i'll find a pair with that Idss
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Old 15th September 2013, 02:51 AM   #1337
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Originally Posted by Zen Mod View Post
test their Idss

if it's above 6mA , then use them temporary

170 are better , having much greater xconductance

What about those Philips jfets. Are they still being manufactured?
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Old 15th September 2013, 09:08 AM   #1338
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which ones , exactly ?
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Old 15th September 2013, 10:28 AM   #1339
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which ones , exactly ?
BF861 or BF862
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Old 15th September 2013, 11:55 AM   #1340
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off course ......
but , as always , you need to balance between Idss , biasing technique (value of Rs) , dissipation

when Jfet is biased with CCS , then you have "one" thing less to worry (Rs versus Idss versus S versus gain)

but , when biased with Rs , as in ACA , some acrobatics is needed for adequate substitution
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