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john buckland 14th August 2007 10:33 PM

Mullard px25 - need matched pair
Anyone have or know where I can find a matched pair of Mullard px25 valves. Will buy or trade.

316a 15th August 2007 10:10 AM

Re: Mullard px25 - need matched pair

Originally posted by john buckland
Anyone have or know where I can find a matched pair of Mullard px25 valves. Will buy or trade.
Good luck finding a 'Mullard' PX25 , they never made them !!!!!



ianc13 15th August 2007 11:31 AM

Mullard did do the DO24 tube that is somewhat similar to the PX25 and certainly in eBay auctions you will see PX25's listed as DO24 as well.

The DO24 runs max 400V, -34V, 63mA, amp factor ~10 which is very similar to one of the standard PX25 op points 400v, -31V, 62.5mA with amp factor ~9.

The main difference that I can see is that the DO24 max anode voltage is 400V, whereas the PX25 will take 500V (albeit at lower current ~50mA).

I would say that you could quite easily drop in a PX25 in place of a DO24 but would be a little hesitant the other way round unless you knew that the operating point is suitable for the DO24.

PX25, VR40, CV1040, NR47 types can be had from some eBay shops or you could look at EIFL .

I have not seen any DO24 for sale anywhere and googling turns up nothing.

NOS PX25 are going to set you back though.


kevinkr 15th August 2007 04:09 PM

TJ makes a very good clone of the PX25 - I'd check that out, a pair of NOS PX25 would probably cost well over $400.. The TJ's are available and somewhat less, and available here: (I have no affiliation with this vendor.)

I have heard the UX4 version of this tube fairly recently.

PX25 was originally made by Osram which became M-OV. (Marconi Osram Valve)

Here's a link:

ianc13 15th August 2007 04:30 PM

I think that you may be looking more like $400 per tube for NOS PX25 at present prices.

One quick note is that diyhifisupply have the B5 based PX25 at around $390 per pair on their website at present but they were having a sale on these in the last couple of weeks and the sale price of $240 per pair seems to still stand on their eBay shop.

I too have no affiliation with them, just seems like a pretty good price.

kevinkr 15th August 2007 04:38 PM


Originally posted by ianc13
I think that you may be looking more like $400 per tube for NOS PX25 at present prices.


Yeah, I was curious about the most current going price so I was looking at and found a bunch of them at 260. (Well over $500 each.)

The TJ even not on sale are a relative bargain at <40% of the price, and they sound very good.

john buckland 16th August 2007 07:04 AM

Hmm, seems I read somewhere that Mullard did make some, oh hum. Thanks for all your replies on this. I can't send e-mails yet. Anyway looks like the XP25 idea is going to be too expensive. FYI I'm currently building a Mr Liang 845. Which is growing to be a bit of a monster. I had all the iron upgraded and it's very heavy. Also had to make the chassis much larger than previously intended to accommodate point to point wiring (no pcbs or mini components) Also needs space to prevent arching from the 1200V. This thing is lethal, I hope I survive the experience. A few of my buddies suggested I quit, sell or trade the 820V transformer and build something else. Then someone else suggested the PX25 route..
Thanks again

john buckland 16th August 2007 07:04 AM

Duh! Just re-read the article on the PX25 it was Marconi. Oh the path to old age....!

7N7 16th August 2007 09:35 AM


Pretty aren't they?

Please note this is not my picture, but I do not know the source; I will happily acknowledge it if the owner lets me know

dave slagle 17th August 2007 01:48 AM

from what i have seen, the only new manufacture PX25's that match the original spec are the KR's. The curve traces i have seen from the Chinese seem to mis the PX25 mark by a fair bit.


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