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Hello i just finished my new amp
he played almost a year on a a board
and after al the tweaks i build cabinets from cherry wood
sounds very good.
I have already good experiences with the ux245 and i like the sound very much but i find the 2 watts where a little to low.
So i used the 45 as driver for the px25, also a very nice tube
it looks like this now:
input tube (thanks DanLaudionut!) is a 12a4 interstage coupled to a 45 interstage to px25
al the transformers are amorphouse core
The wire is all silver cotton isolated
The whole system is silver inside the amp the speaker cables and inside the cabinets the Phy km30 drivers have also silver voice coils
Follow Ups:
Very nice, nice iron too!
Where are you located in the Netherlands?
hallo Arend Jan
jose_korneluk AT bellsouth.net
hello koneluk
Thanks
i live in Limburg its a 150 km from Utrecht
could you please share the schematic?Awesome work, BTW!
this is the backside :
the silver wire:
Only this wire on the opt took me 4 hours
It are separate strands each with cotton isolated and then together again with cotton
HornyCongratulations
Looking Good !!!
Thanks Dan
you give me good advise with the 12a4 choice
jesus. now those are some amps. you wound the OPT's yourself? also, do you happen to have a schematic?
hi, thanks
The opt's are from Tribute audio here in Holland
Pieter made very good stuff!
i have no schematic
but its a very simple circuit the interstages are all 5k/5k
the first 20ma and the second 40ma
the 12a4 runs at 15 to 20 ma and the 45 on 34 ma
the px25 on 60ma and the opt is an 3k5
every stage has simple autobias.
just for kicks, you should give tap swapping a shot. You might be surprised what happens if you reflect back 7K.
hi Dave
i tried also 5k but i find it a little lifeless
also tryed 2,5 k 3k5 was best for my ears
interesting,given your moniker, i guess you are using horns.
did you try 7K with the current outputs? The reason i bring this up is all of the curve traces i have seen of the mesh plate PX-25 have them looking nothing like a true PX-25. The Mu is low (6-7) and the Rp is in the 1.8K range. Did you get curve traces with the tubes you have?
hi Dave
i use not horns anymore
i use now PHY km30 sag in Musical affairs cabinets
i ordered the opt only with only with 16 ohm taps
but 5 k was also not better sounding
the sam experience do i have with a300b i like them better with 2k5 as 5k
Robert
I auditioned the PHY km30 (copper coil) at DHT Rob's in large open baffles. Very nice open sound with a surprising amount of bass. Soundstaging was a little bit less grand but tonality was very very nice.
This makes me wonder if you simply like the sound of the 2K5 transformer independent of what is driving it. A 300B into a 2K5 is a bit more than 3X Rp and your PX25 into a 3K5 is just under 2X Rp. Maybe you should see if you can try a 1K6 OT with the 300B.dave
hi dave
The Rp of the mesh px25 is 1265 ohm
i have als a word doc of the specs and curves if you like i can sent it to you.
sent me an email then
i do not now how i can post it on this forum.
have you measured this yourself for your tubes on hand?I have been sent a similar document by various chinese wholesalers, but the actual curves of samples I have seen look quite a bit different.
hello Dave
No i dont measure it i just took ik from the paper.But 3,5 sounds very good for my ears better than 5k i tought
i looked to the transformer that i used for the test and it wat actualy 6k that i has tryed.
The transformer that i used for this test was a magnequest FS-030
Robert
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