k5881 mods part 1.

[Ianm2]

ok, my newly found k5881s have arrived.

Both are monoblocked, so one is now converted to 8 ohms, the other will be and will be a reference, keeping it as k5881 mk1, and changed to the current best mod., whilst the other is 'experimented' upon...ooherrrr

First 'mod' was to drop in el34s, vs the k5581s, no argument really, I preferrred the 5881s, more neutral, clearer, el34 has a mid metallicy hash, and 5881 sounds powerful.

Count 1 down. Happy as well, as 5881s are available cheaply

Now, input stage mods. this is a proposal, and there is a poll!!

I haven't done it yet, but these are the triode connected ef86s.

so, we go...

1/ stock k5881, triode connected ef86

2/ input changed to pentode as in true mullard 5-20, I have the wad circuit.

3/ k5881 mk 2, with the srpp ecc83 input

4/ mu this input.

5/ I may go on to do just a anode follower ecc83, keeping the gain the same as the k5881mk2 so no feedback adjustment will be required.

cast your votes as to which will be best, I am voting for number 2, but I am tempted for 5 as weill. I have no prior knowledge to this.

Feedback and cap will be ajusted as per the circuit, there is no change from 1to 2, I will keep the gain the same for 3,4 and 5, and wad gives the feedback bits so should all be ok.

Incidentally, I don't find the amps bright as alluded to for the srpp change, they are pretty natural sounding, punchy, gritty in the bass on rock, quite good

If I havnen't had enough after that, I will do Neal's input bass feedback mod.

[Paul Barker]

2 stages o1a followed by one of 112a?

[Ianm2]

wtf are those valves I only know the common ones

how do I edit the poll? I was going to make public if people are ok with that?

[Paul Barker]

Oh they're common

http://search-completed.ebay.co.uk/0...t=2&sofocus=bs

They aren't used much by the modern breed who replicate other peoples website circuit designs and
puke them out with a minor change into their own design.

Her's a tip, the globes are best.

[steve s]

your not wrong paul....

I have a pair of 0a1s.. but i wonder if they are the best...., paul i think you've been on too many US sites...like ian..

I am running an old pair of globe mullard mesh plate 354V at the moment
they sound damm good..

but i would suspect Lp2s or px230's,will be better... if i am to belive DH is an improvement ?..globes of course,... i'm sure they will beat the yanks.
trouble is an extra stage is required.

James d was trying some L2's, i think, don't know how he got on...james?

I also want to go back to ml4>ml4 again to see if theres any bottom end improvements..also need to try px4/25 in place of pt15.. just to be sure?
my px4 box is getting obscene...

will have to commit to something soon to get a amp together properly for the next eggfeast.. the last meet was a disaster for my amp....

we could do with a best driver thread.... Ian you can cross a trioded ef86 off that... does sound good.. just lacked bottom end compared to ML4/ 41MP

i will have to get the soldering iron out.....
cheers
steve