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Zkit1 (SE84DIY) problems (Read 9111 times)
dank
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pair of dual 18
Imperials

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Re: Zkit1 (SE84DIY) problems
Reply #15 - 02/22/09 at 22:48:58
 
Now we are getting somewhere!  Thanks Henk.  I connected pin 6 of the output tubes to pin 3 (not ground) and the output before clipping across 8 ohms changed from 7.5 vptp (.88 w) to 8.7 vptp (1.18 w).  This is an increase of 34%, yea!

Its getting almost loud enough so I can listen to it...trouble is that it sounds so darn good that I naturally want to turn it up, and when it won't go up any more its so frustrating I just don't listen to it.

I think my next step will be to put in a negative bias to the grid of the output tube(s) so I can do away with, or at least reduce, the common cathode resistor, which is now at 500 ohms.

After that, I have plans to try a "boosted triode", inspired by an EDN Design Idea published in June of 2003.  www.edn.com/article/CA302240.html
if anyone is interested.  I will let you know what happens.

DanK
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Steve Deckert
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If the 1st watt
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Re: Zkit1 (SE84DIY) problems
Reply #16 - 02/23/09 at 16:17:38
 
Connecting pin 6 (grid 3) to pin 3 (cathode) on a 6P15P-EV makes more sense.  An EL84 has grid 3 and the cathode internally connected leaving pin 6 unused, where a 6P15P has them separated.  This is why you see a performance gain similar to using an EL84.

Dan - if you're getting close to the volume level your after, try running a preamp with gain in front of the amp, and turn the volume on the amp down a bit, then turn the volume on the preamp up a bit to compensate.

Steve
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henk
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Re: Zkit1 (SE84DIY) problems
Reply #17 - 07/12/09 at 17:12:56
 
Dear Steve,
After my remarks (02/21/09 ) about pin 6 from the tube 6N15N-EB, I connected pin 6 with a 120 K carbon resistor to ground.
120 K is sufficient for the grid load discharged and prevents distorsion and compression, but gives a nice better sound.
In your last modification information you mention the use of  an non-polarized film cap. What type and value you use this?.

Henk.
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Alan H
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Re: Zkit1 (SE84DIY) problems
Reply #18 - 07/12/09 at 19:56:54
 
Hi Henk,

I ordered 10 (by mistake) non-polarised film caps of the appropriate value for the "Christmas" mod, so have 8 left over. If you are in the UK or Europe I would be happy to send you a couple.

Alan
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henk
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Re: Zkit1 (SE84DIY) problems
Reply #19 - 07/13/09 at 18:32:49
 
Hi Alan,

Thanks for your response,
If you send me a couple capacitors, I am grateful.
My address is in the Netherlands.
I can still not through the forum mail at this time.
If you want to email me a message, I can give you my address.
Thanks,
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dank
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pair of dual 18
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Re: Zkit1 (SE84DIY) problems
Reply #20 - 07/13/09 at 18:35:05
 
HenK

I too have a bunch of extra Christmas Mod caps (.1 uf 400v).  Would gladly send you a couple if you are in the USA.  Just PM / email me with your address.

Dan
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Alan H
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Re: Zkit1 (SE84DIY) problems
Reply #21 - 07/13/09 at 21:28:55
 
Henk - pm'd.
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FLAC via Ethernet-over-Mains
Squeezebox 3
Valab 6N Solid Silver Coax
GD-Audio DAC19 DSP
Decware SE84DIY (V-Caps + CCE mod)
Solid silver / teflon cables
Scotmoose Sachiko FE206En Horns
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henk
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Re: Zkit1 (SE84DIY) problems
Reply #22 - 07/17/09 at 18:48:28
 
Problem solved,

Alan sent me the chrismas C
I have this assembled and indeed, this sounds much better. !!!!
Strongly recommended !

My earlier suggestion a 120 K resitor use is only part of the solution
With the C you have a better signal decoupling at Suppressors grid.
Compliments for Steve.

Alan thanks for sending the C and Dan thanks for your reaction.

Regards,

Henk.
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