just built this....

[Ianm2]

taken out my active preamp, and changed it.

BTW, took it around to a hifi world reviewer, industry expert, speaker manufacturer, and vinyl addict/expert, who's worked everywhere and really can talk me into the ground, he lives a mile from my door!!

He liked my preamp, better than a commercial one he liked a lot, and bear in mind he has modified crown amplifiers he has tweaked himself, too, high praise indeed!!

anyway, just built this in its place, the previoius circuit is pretty easy so its possible to revert, there was more work than meets the eye, lots of connections...

sounds....dunno, just plugged it in this minute, will report, it works first time!! so I must've done something right.

http://www.geocities.com/rjm003.geo/...ls6dj8_cir.gif

I know Paul and Nick probably won't approve.

[NealG]

As long as you like it Ian then it's OK! However......

[Ianm2]

curate's egg, good in parts, not as airy or open up at the top end, I don't think its a keeper, but will take it to my friend first b4 destroying, looks like the mc head tube amp is worth a build...I have a circuit...

http://users.otenet.gr/~athsam/hampt...oving_coil.htm

will be similar

anoyone enlighten me as to what's happened to the bias, and how much current each triode draws?

[NickG]

I know Paul and Nick probably won't approve.

Not something I have a view about. Why not try the same approach as the ecc83 pre with a few different valves?

[James D]

Ian,

Bias is on the 0V line so some grid current flows and that may shift the bias slightly positive. ECC88 is one of those valves that doesn't show a lot of grid current until about 0.5V positive so this is quite safe and it moves it into lots of anode current very quickly. With B+ at 84V you probably have around 45-50V as Va so around 12-15mA of Ia. You need a lot of Ia to keep Gm up which translates to lower noise.

James

[Paul Barker]

Glad you've given up trying to please me.

This is a lot better than the last multiple parallel valve thing you found, but still has no redeeming features.

[Paul Barker]

Just get a 112a per channel and rc couple it to the output, it will sound lovely, then stop plaguing us with all these stupid parallel valve circuits.

Select an loverly sounding triode and do something simple with it!

[Greg.]

Ooo,err Ian, god has spoken. Deviate at your peril............

Paul is a very dry and blunt man. I like him. He's to the point here, but much gentler after a pint or two on an eggfest meet, and then, in the middle of a clip lead build of a 1200V 212 amp, he'll casually stroll over to you and wisper in your ear, 'your amp sounds good with these speakers.....' and then he wanders away back to his high voltage 'Twister' party game whilst the rest of us look on from a (safe) distance.

Oh well, it's another dimension I probably won't aspire to and won't want to, but this PB man can certainly build kit that sounds very right and dynamically live and correct.

Hmmm, ok Paul, the first drink is on you

Best wishes,

Greg

[Paul Barker]

Yes, I think Ian and I understand each other, we have chated on the phone and at Eggborough; there are so many ways people find to make a sound. No harm in my expressing an opinion on it, doesn't mean I don't like the person behind it.

[Ianm2]

aha, yes of course, no cathode resistor means that grid to cathode voltage is zero.

won't valve behave strange as no difference between v-g-k?

anyway, I have just realised, with these mc amplifiers, you could put the bias anywhere and the swing would be so small it would be perfectly linear, so you could run at 50 volts or 300, makes little odds??

interesting Paul, you called 6922 a nasty valve, last 2 incarnaan tions I have heard it have been a tad soft in the top, even tubecad predicts its not massively extended with those 4 paralleled at the top end, and I can hear it, too!! But it does seem to lose some focus and is more 'diffuse' than the simple ecc82.

Actually, my 4x6922 preamp will make an excellent mc step up stage, with virtually no tweaking, and my theory that it doens't matter where its biased distortion wise means I should get a good idea with minimal trouble, will try with around 470 ohms load and report soon.

Can you use an lo output mc into 47k?

Those weird unknown valves sort of scare me, no idea where to get them, and I may turn into Paul and Nick next if I go down that road.

I have acquired a new turntable, a home made jobby, and its just wasted my humble rega, so that's going on ebay. If I can get to turntable fest it will be there for sure, I am sure many will be interested.