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Build Report: EF86 AC15 with *6V6* outputs


 
11/10/2003 2:09 AM
Dutch
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Build Report: EF86 AC15 with *6V6* outputs
Hi all--  
Just wanted to jump in here and let you know that Ian Anderson was the *KING* of understatement when he said last year that this circuit sounds great.  
 
I finally got around to rebuilding an old junker hi-fi chassis with this arrangement, and it kicks @$$!! Mine's got a couple twists to the circuit, mostly due to limitations of the chassis I'm building it in, and the PT that I had to work with.... I supplied the screens and the PI from the same power supply node to save room, the B+ is a little higher than usual for cathode-biased 6V6es (it's around 415V even when using the 5V rectifier winding in series with the PT primary to knock down the line voltage a bit), so I had to use my Zener bias trick to cool it down, even with a 300 ohm Rk, and I replaced the brilliant switch with a 10M-RA pot to give a continuously variable amount of low end. It's a tiny bit louder than a typical Tweed Deluxe and sounds *RIGHTEOUS* through a pair of alnico Blue Dogs.... It does clean better than any amp I've ever played through, with plenty of sparkle and jangle, a bit of compression, great note definition within chords, and plenty of bass if you want it. Turn up the volume and it just keeps sounding better and better. Think Beatles meet AC/DC, Smitereens meet Ted Nugent, REM on steroids, or something like that--the growliest, angriest pop guitar sound you could imagine. Great dynamics, and even when balls-out, it still has nice note definition and cleans up well with a change in pick attack. If only the chassis layout was better, as the EF86 is right next to the PT, and it picks up a bit of hum. It's definitely wrth a rebuild in a properly laid out chassis, though, and I may just go with 6V6es instead of 7591As when I build my rack-mount channel-switcher (with EF86 clean channel and Dumble ODS dirty channel) since this sounds so good.  
 
C ya,  
Dutch
 
11/10/2003 10:53 AM
Chris ( CMW amps )
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Hi Dutch  
 
Woah , cool !  
 
I do have a set of transformers over here from an old hifi-amp and they're f*ckin' great . Voltage is a bit too high for cath. biased EL84s and the OT is UL . Hope to build a 6V6 ( UL ) pp-amp with an EF86 or EF184 ( diff. pin-out ) pre .  
 
I did do some experimenting with a pot instead of the brilliant-switch too .  
 
Have fun , keep on building & rockin' !  
 
Chris
 
 
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11/10/2003 4:57 PM
Dutch
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quote:
"Voltage is a bit too high for cath. biased EL84s and the OT is UL ."
 
 
Then it sounds like a killer application for 7591As.... I can't wait to get started building my rack-mount channel-switcher so I can use the Heyboer Hygrade 18W clone OT that I bought last January. It has the UL taps, and I intend to use 'em.... Open loop UL rocks! :^)  
 
 
quote:
"EF86 or EF184 ( diff. pin-out )"
 
 
Is the EF184 more or less the same tube with just a different pinout, or does it work differently than an EF86?  
 
C ya,  
Dutch
 
11/10/2003 5:05 PM
Chris ( CMW amps )
email

Hi Dutch !  
 
quote:
"killer application for 7591As.... "
 
 
What brand do you suggest ? I've never used those tubes ..... Are the new EHs/Sovteks good ones ?  
 
 
quote:
"Is the EF184 more or less the same tube"
 
 
I did see some comments saying it does sound "better" then EF86s . I do have a couple of NOS ones over here but I love to use "easy-to-get-tubes" :) .  
 
Thanks !  
 
Chris
 
11/10/2003 7:45 PM
Dutch
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quote:
"What brand do you suggest ? I've never used those tubes ..... Are the new EHs/Sovteks good ones ?"
 
 
Chris--  
I like 'em. They're pretty reasonable compared to NOS prices, but are a bit more expensive than most tubes in their power range. I still want to do an AC30 type output section with no changes to the stock layout except swapping 7591As for the EL84s and UL outputs (that OEI Plexi OT would be pefrect if it had 40% UL taps!!). That'd be a bit of fun, and it'd be neat to have an AC30 that didn't eat tubes.... :)  
 
quote:
"I did see some comments saying it does sound "better" then EF86s . I do have a couple of NOS ones over here but I love to use "easy-to-get-tubes" :) ."
 
 
Me too, for the most part. I'm *way* happy with the sound of the EF86, so I guess there's no real reason to mess with EF184s, except for the sake of curiosity. When I get a better paying job (which may be soon--I applied for a job on friday last week--wish me luck!! :D), I'll be more curious....  
 
C ya,  
Dutch
 
11/10/2003 9:14 PM
Chris ( CMW amps )
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Dutch  
 
Best luck with getting a new / better paid job !!!  
Thanks for your notes ,  
 
Chris
 
11/11/2003 12:19 AM
michael_m
Hi!  
 
quote:
"Then it sounds like a killer application for 7591As.... I can't wait to get started building my rack-mount channel-switcher so I can use the Heyboer Hygrade 18W clone OT that I bought last January. It has the UL taps, and I intend to use 'em.... Open loop UL rocks! :^)"
 
I actually replaced the EL84s in my would-be Matchless DC30 clone with 6V6s first and then changed to 7591As. I like the tone very much. Has got a very thick quality to it. I'm thinking about replacing the power tranny, though. The current one only gives me a B+ of about 300V. Anyway, I like the tone more than with EL84s: less ice-pickle, more oomph. ;-)  
 
Michael
 
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