If I tell you about an Idht similar to px4?

Paul Barker · Post by **Paul Barker** » Thu Aug 08, 2013 9:05 pm

Will you all swear to let me have the next one we find so I can have stereo?

Not a pentode triode connected a proper triode.

I am not talking about 6A5G

I am not talking about R120

My curve trace of it.

Here it is scaled the same as and next to the PX4

The problem is finding another.

JamesD · Post by **JamesD** » Thu Aug 08, 2013 9:23 pm

Promise! I'll even look for one for you

J

Paul Barker · Post by **Paul Barker** » Thu Aug 08, 2013 9:28 pm

Lower impedance hence I could draw a 2k loadline, and OK usual IDHT distortion not a DHT.

Granted plenty of triode connected pentodes do this same job.

But it might be that proper triodes sound better? Who can say?

10 years ago a loan guy used to come on the forums and say triode connected pentodes sounded just as good as triodes, and he was laughed out of the place.

these days more than 50% swing that way.

What is the truth?

The big question is why didn't they make more IDHT's of the output valve types?

Paul Barker · Post by **Paul Barker** » Thu Aug 08, 2013 9:37 pm

The curse of the uTracer.

Thumb through old bottles, trace them, and find loads of great stuff you have one of!

JamesD · Post by **JamesD** » Thu Aug 08, 2013 9:39 pm

...because pentodes are more efficent than triodes - more power out for same Va and Ia so they ruled the marketing roost!

However triode connection was always the choice for sound quality - see Williamson et al for the proof of that.

Really interesting that Steve is finding ultra-linear better than triode for his KT120!

steve s · Post by **steve s** » Fri Aug 09, 2013 9:03 am

well paul .. i've no idea...
there's nothing in the older uk valves that makes more than 2 watts..
it either very old.. or a bit modern for me( 1950's +) or ...

well come on... spill the beans?

JamesD · Post by **JamesD** » Fri Aug 09, 2013 12:04 pm

I measure u=5.5 and Ra=750R against for a PX4 u=5 Ra=830R so very close, oh I measured at Va= 130V and Vg=-10 rather than Va=100v and Vg=0V for the PX4...

I'm intrigued all right!!!

Paul Barker · Post by **Paul Barker** » Fri Aug 09, 2013 12:41 pm

AkShirley Steve knows what they are as he mentioned them before he has some.
I have this and thats all.
35v heater Steve. 1930's era.

steve s · Post by **steve s** » Fri Aug 09, 2013 1:04 pm

6a5 is a idh 2a3... but not 35 volts and as you said at first its not the one

pp3521 ?

dont know... and i have some..? still dont know

valvey quiz - i like it

JamesD · Post by **JamesD** » Fri Aug 09, 2013 1:21 pm

Yeah, that pretty much matches it! PP3521 - new one on me.

I see if I can find one anywhere - doubt it though...

IslandPink · Post by **IslandPink** » Fri Aug 09, 2013 1:35 pm

Interesting , curves look right too - very nice !
http://www.mif.pg.gda.pl/homepages/fran ... PP3521.pdf

steve s · Post by **steve s** » Fri Aug 09, 2013 1:48 pm

IslandPink wrote:Interesting , curves look right too - very nice !
http://www.mif.pg.gda.pl/homepages/fran ... PP3521.pdf

but they are so rare.. one went on ebay for £20 last week thats the first one i've seen
i once spent a full day going through all my valves to see if i had one
that was a few years ago.. i've been looking out for them for a few years now...

Paul Barker · Post by **Paul Barker** » Fri Aug 09, 2013 4:34 pm

you got it.

I only have one.

steve s · Post by **steve s** » Fri Aug 09, 2013 5:22 pm

Wow, is it the full sized mazda pp3/250 anode?
I was not sure .. As the 2p/ 4xp anode is smaller and i was not sure what is was based on...
I'm jealous.. You just need another for a really good amp

Paul Barker · Post by **Paul Barker** » Fri Aug 09, 2013 5:59 pm

I don't have a pp3/250

Here it is next to bog standard cooking Osram PX4

Others may need to know PX4 is the one on the left.

audio-talk

If I tell you about an Idht similar to px4?

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