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EF86 rules, EF86 rules!!!


 
10/22/1997 6:27 AM
Steve K EF86 rules, EF86 rules!!!
Ok, sorry for that title, but this  
amp is making me feel like a kid in  
a candy store. Some of you asked me  
to post the results of trying the  
EF86 preamp in an AC30. All I can  
say is WOW!!!! Totally blown away  
how great it sounds. I thought it  
would be good but never imagined it  
would be THIS good. Dynamic, tight,  
responsive, touch sensitive, subtle,  
extreme, soft, hard, etc... These  
all fit. I'm sure the class A  
output has alot to do with the  
pure magic this tube can bestow on  
a guitar signal but it just is  
such a totally pure and responsive  
tone, I can't even look at any of  
my other amps the same now. If  
there are any doubters about the  
capability of this pentode tube  
driving a guitar signal, you are  
in for a surprise by trying it!!  
It delivers alot more gain than I  
thought also. It is alot louder  
than the top boost channel or the  
normal channel in my amp. It  
totally responds fantastic when  
being fed either a strat OR a LP  
and either a Tube Screamer or a  
Bixonic Expandora OD pedal. The  
later one being, as expected, the  
better of the two. I was going  
to disable the master volume I  
installed in this amp untill I  
realized it works great with the  
EF86 channel. What a GREAT tube.  
I hope it can hold up in this amp.  
The Svetlana EF86 appears to be  
built like a Russian tank also.  
The only two speakers I've tried  
so far are an EVM 12L 200 watter  
which is very clean but delivers  
excellent bass responce with this  
amp and a Celestion G70 also works  
quite well and offers more grit  
but is lacking in the bottom.  
The brilliance switch is ok but  
only works for me with a LP  
feeding it. It adds too much  
treble to a strat. It seems to me  
that the sweet switch offers a  
somewhat similar tone to the top  
boost channel but not near as  
bell like and crisp. I could  
lose this switch and not miss it.  
If I were to recommend this  
project to someone now, I'd  
suggest starting with just the  
EF86 preamp and building in a  
Fender style reverb instead of  
the top boost and normal channels.  
I found that adding a touch of  
classic analog delay to the input  
is enough to satisfy my reverb  
levels. Though I am not a loud  
player anymore, 30 watts seems to  
be the minimum power I could live  
with for this type of amp. I  
have not finished testing all the  
levels yet and still get a fair  
preamp hum through the normal  
and EF86 channels but not the top  
boost channel at all. So I need  
to trace that down. Probably a  
high voltage wire crossing or a  
bad ground somewhere. Since the  
top boost channel is dead quiet,  
I'm optimistic its quickly  
curable... I hope...  
Sorry for the long post. I  
usually try to avoid that but I  
thought I knew most all the great  
amp tones out there but till I  
tried the EF86 AC30, I didn't  
know squat!!! It simply must be  
heard to be appreciated...  
Steve K
 
10/22/1997 8:06 AM
John Martin
email

The main reason amp manufacturers stopped using small signal pentodes was that they can be very microphonic, far more than the typical triode input stages. This creates a problem in combos. Shock mounting is recomended. Also make sure the EF86 internal shield is grounded to reduce hum.  
But, I agree they sound great. I have an amp where all the preamp tubes and driver are pentodes (6SJ7).  
 
JM
 
 
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10/28/1997 2:27 PM
Minoru
email

Hi,  
 
Could I use the EF86 in my Vox/Korg AC30 reissue without modification? If so, where would it be placed in the preamp chain?  
 
I'm currently considering some other options for tailoring the sound of my new amp, so if there are useful tips, I would appreciate any advice.  
 
Thank you.  
 
Minoru
 
10/28/1997 2:32 PM
John Martin
email

The amp would need modification. The EF86 is a single pentode. Your preamp tubes are dual triode.
 
10/29/1997 5:25 AM
Steve K
email

Hi,, I believe the new AC30 is PC bd.  
based so you'd have to jump through  
a few hoops to cut into that but if  
you have the space for another tube  
in my opinion it would be most likely  
worth it as this tube sounds great  
with this power section!!! Just add  
the EF86 circuit (only about 8  
components plus tube) and put the  
center wiper of the EF86 vol pot to  
a 220k res and add that to sum into  
the inverter coupling cap with the  
other channels 220k res. If you didn't  
want to void the warranty, you could  
just build this preamp in a small box  
but then you'd want to add a line-in  
somewhere for it but I'd bet this  
circuit as a preamp box would be  
great!!!  
Steve K
 
10/29/1997 5:57 AM
Pat
Steve - I'm glad to hear your EF86 project  
went well. Based on your enthusiastic review  
I may incorporate this tube in my next  
project. BTW, several months ago a guy (I  
seem to remember he was from Europe) posted  
here and was saying he had built an amp he  
claimed produced OP tube type distortion in  
preamp stages using the EF86. I remember  
several people asking him to contact them or  
send schematics. Were you one of the folks  
asking him for more info, and if so, did you  
ever hear from him? Just curious.  
 
Pat
 
10/29/1997 8:02 AM
Steve K
Hi Pat,, I'm not sure but I do remember  
getting some good feedback from the  
fellow from Holland I think, Yves I  
believe was his name. Sorry if I have  
that wrong but I can't locate the mail  
I saved from him. Sounded like he did  
quite abit of experimenting with this  
tube and I would love to have some of  
the values he came up with. I'll  
eventually start tweaking values on  
this myself but need to do my homework  
first to know and understand exactly  
what the hell I'm doing.... Besides,  
I'm having too much fun with this amp  
now to take it apart again anytime  
soon... I simply can't believe I  
havn't heard or seen more things done  
with this tube in the guitar amp  
world. Maybe it won't last. Maybe  
other problems will show up later,  
but I know I'm now hooked on using  
it so I'll do whatever it takes to  
keep using it...  
Steve K
 
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