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  #1  
Old 22nd February 2006, 09:26 PM
Ianm2 Ianm2 is offline
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Default just built the most amazing preamp

my basie was wired with a std voltage gain direct coupled into a cathode follower.

It sounded not good, no bass at all, no idea why.

The circuit is the stock basie psu, with the bottlehead foreplay mk 3 circuit.

I took the cathode follower out, which improved things no end, bass, I also removed the led bias, and re-biased it myself, with first an unbypassed resistor, which seemed to lose some of the beautiful top end. this was then bypassed to increase gain and reduce output impedance.

Now, I have changed it again, and its sounding killer, I am running, yes, an ecc83 as a preamp valve, VERY hot, 90 odd percent maximum current, very low anode load. It sounds better than with the ecc82 which in comparison sounds a bit of a mess, very impressive b4 I dropped in the ecc83 though.

no noticable treble loss, apparently, its a pretty bad asymmetrical voltage out, so maybe a redesign necc, but sounds fab

sounds, killer, as Philip would say fokking awesome, really impressed

std gain stage with 200 volts on the b+, 22k anode load, 390 ohm resistor if you want to have a go. ( this may have to change to around 1k)

I couldn't get an rca phonostage circuit going, but I rather like my new preamp, perhaps simple is best after all, and get rid of all these srpp's, cathode followers and all that? It has significanlty bettered the musical fidelity x-pre which uses 2x 6922s with feedback, so that's going to be ebayed soon

I quite like ecc83 run hot, I may try it driving a 300b, totally against the grain, but the sounds the thing

Last edited by Ianm2; 22nd February 2006 at 09:36 PM.
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  #2  
Old 22nd February 2006, 10:09 PM
IslandPink IslandPink is offline
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Default Re: just built the most amazing preamp

Wow,
What's got into everybody ? DIY going on all over the place at the moment .
Good work Ian .
I can't remember for sure but Dave Dove and I rewired something of this sort a year or two back and got easy improvements .

MJ
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Old 22nd February 2006, 10:25 PM
dave dove dave dove is offline
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Default Re: just built the most amazing preamp

well done ian

yes mark
we got rid of the basie feedback loop
and just had a single ecc82 gain stage
-that basie isn't very good-
then i went mad and tried simon shilton's
preamp project:

http://www.users.globalnet.co.uk/~valveamp/

he likes loads of current too

this was all BA of course - before aikido.....

keep going ian

dave
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Old 22nd February 2006, 10:31 PM
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david counter david counter is offline
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Default Re: just built the most amazing preamp

well done Ian,
it's not too far off the SJS one which I'm still using with 6n1p, one day I must get round to rebuilding it as an Aikido
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Old 23rd February 2006, 10:16 AM
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The Shadow The Shadow is offline
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Default Re: just built the most amazing preamp

Well done Ian.
There sure is plenty of action on the DIY front at the moment. If this little lot gets to EggFest 3 it should be a fascinating day.

Give us some pics and a description to my email address and I'll feature it on the website. You could be the first member to get things off the ground with an article.

My gaze has now shifted to my PreII; could be a CF conversion or a redesign CF hardwired in the same case using a 6SN7 if the PSUII is capable of powering it.

Cheers

Steve
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Last edited by The Shadow; 23rd February 2006 at 02:34 PM.
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