[kiertijai]

here is more info.  I pasted what he has written to me. Please take a look.
 
I did a detailed test with  VT52’s. They are much closer to a 45 tube, than a 300B tube. In the EC2A3 amp with 6 volts on the heaters, 330 volts on the plate and pulling 12 watts of plate power they will only do about 3 watts. I put a pair of E.A.T 300B’s in the same circuit turned the heater down to 5V and they put out 6.25 watts. In the BA running with the VT52 tubes on 5 volt heaters they will only do about 1 watt. They are very much like a 45 tube, but with better bass. I would say in a properly designed headphone amplifier setup to support the VT52 they would be more pure, clear, detailed without losing a deep soundstage. They will not work that way in the BA no matter what tubes you roll.
    They are probably more appropriate with the 2A3/45 Balancing Act more than the 300B/PX4 Balancing.  The output when working at 5V from 300B Ba is only 1 watt,
not enough to drive the AKG K1000, HE6.  I may use them with the more sensitive headphones.

 

[cacatalysis]

Many thanks for the information.  A 45 tube with deep base would be very exciting, sounds like an ideal tube for HD800.  To use them for sensitive phones seems to be a good idea.  I am wondering how they will sound in EC2A3.  

 

[Radio_head]

Quote:

 I put a pair of E.A.T 300B’s in the same circuit turned the heater down to 5V and they put out 6.25 watts. 

Has Craig commented on the EAT's vs EML?  I was leaning towards the former until I saw some horror stories about reliability.  
 
 

 

[balderon]

Recently I had ordered a BA from Craig. He was interested in listening to the EML 300B mesh. Prior to Craig shipping my amp I sent my 300b's to him. The following was his initial response.
 
Quote (Craig Uthus):

Here is my take on the tubes. The driver tube makes a huge difference. The output tubes make a more subtle difference when listening with the new production Russian made Tung Sol 6SN7. Listening was referenced to with the Raytheon 6F8G tube. To make this easy on my head I will just list the tubes overall as favorite to least favorite understanding each tube has strengths and weaknesses, and this is just one listeners opinion.
 
All tubes are new production with 40 hours run time.
 
KR PX4
Sophia Royal Princess 300B
EML mesh 300B
AVVT 300BLS
KR 842
EH platinum matched 300B
EAT 300B
Full Music mesh 300B
Sophia PX4
Shuguang 300B metal plate
Shuguang 300B carbon plate

 
A few days layer I received this followup message from Craig. I did notice the difference switching the bias to the PX4 position.
 
Quote (Craig Uthus):

I had a chance to play around with the EML mesh 300B tubes. With the rear panel bias switch in the PX4 position the EML 300B tubes really come to life. One PX4 owner was over listening, and felt the EML sounded better than the KR PX4. The tubes still operate well below their safe current, and plate power rating so try both settings and see if you agree.

 

 

 

[Radio_head]

Thanks for the rundown.  Wow, at the prices the Sophia's are going for you could get some WE's or go the NOS Osram/Marconi route some here seem to be taking...

 

[vcoheda]

@ balderon
 
good info. thanks for posting.

 

[purrin]

 
Quote:

Recently I had ordered a BA from Craig. He was interested in listening to the EML 300B mesh. Prior to Craig shipping my amp I sent my 300b's to him. The following was his initial response.
 
A few days layer I received this followup message from Craig. I did notice the difference switching the bias to the PX4 position.

 
Awesome, you got it out of him in writing!
 
I had a talk with Craig on the bias positions, and indeed it seems that tubes tend to open up when run more aggressively with more current. With my initial PX25 mod when I put in what parts I had, the resistor in the bias circuit was about 280 ohms. After I got my parts order and set the proper value at 250 ohms, I felt the tubes sounded better - the sound really opened up and got more dynamic. Similar experience at the recent meet when I had left the switch in the down position. I was sort of like What, maybe the tubes needed to warm up; until I realized the switch was in the wrong position.

 

[kiertijai]

I finally has the B4B5/UX4 adapters and they are working.
I am now trying with the Visseaux 501 using PX4 setting ( the Visseaux 501=Telefunken RE604) and
there are no problems whatsoever and the Visseaux 501 sounds nicer than their value of 200$/ pair .  I will try more tubes
before I decide to modify to the PX25 settings ,  I think it will be much improved and I would like to know how much
change will it be.  Here is some of the answers that I got from Craig about the VT52 and the EAT300B.
 
The BA 2A3/45, or BA PX4/300B are the same except for heater voltage so the VT52 would sound the same assuming the heater voltage was correct for the tube.
The VT52 sounds like a 45 tube with better bass.
Like I said in a previous email you can use the VT52 in the BA but the tube is starving at 5 volts on the heater, and needs at least 6 volts to sound good.
Yes try it on the Grados.
The EML 300B mesh should be used in the BA with the bias switch at the PX4 position.
The mesh tube is slightly richer, and more musical than the EAT 300B tube. The EAT tube has a dryer, but still pleasing sound.
I don’t know why the EAT tube would have reliability problems so far the two pairs I have here have been good.

 

[balderon]

¿

 

[Mr.Sneis]

Makes sense the EML 300b Mesh would require more current, fits with the "not a direct replacement" for 300b; it's a really good thing then that the BA has the adjustable voltage!

 

[bdh]

Hmm, I'll have to ask Craig if I can use VT52's in my 2A3/45 BA without any modifications.

 
Quote:

here is more info.  I pasted what he has written to me. Please take a look.
 
I did a detailed test with  VT52’s. They are much closer to a 45 tube, than a 300B tube. 
...
They are probably more appropriate with the 2A3/45 Balancing Act more than the 300B/PX4 Balancing.

 

 

[kiertijai]

Craig are sending back the Osram PX25 globe and Osram PX4 ST type as well as the Tungsram and Mullard 6SN7
I also got a hand on the B4/UX4 adapters so I can now use the other NOS PX4's, PX25's and equivalents.
My initial impression is that tube rolling of the power tubes also has significant impact on sound quality of the Balancing Act ,
if not more than tube rolling the driver tubes.
    I have tried the NOS Mazda PP5/400 (similar to Osram PX25 globe) in the 4V, 300B switch setting (without modification) and the
NOS Mullard AC044 (similar to Osram PX4) in the 4V PX4 switch setting and found that both of them are really good .  The Mazda
are very smooth sounding, good tonal balance, more laid back, very clean sound and good bass,  while the Mullard AC044 is more
dynamic, more suitable to pop and rock music.  I think the sound is quite similar to KR PX4 IMO but thicker sound so I like them more
for these kinds of music than the KR PX4 and they are also cheaper but more difficult to find. Listening to Adele 21 "Rolling in the deep"
was a pure joy.  I  used the Mullard ECC35 short brown  base for the tube rolling of the power tube.
 

 

[kiertijai]

I have got the Hytron VT 52 (similar to Sylvania VT52) back and have tried to use
in the BA with 300B setting and set the filament voltage at the PSU at 5V (actually it can go to 5.4V)
I use the Sylvania 6SN7W metal base as the driver because Craig said that the starved VT52 may have less bass
I find that the sound that came out  is very good comparing to their price of 200$  I will try to get WE VT52
to get more impressions.  I don't know the long term effect but for the time being they work quite well in the BA,
The bass is good for me , I am listening to Pink Floyd " A foot in the door"

 

[cacatalysis]

Kiertijai, Thanks for your impression of the VT-52.  Could I ask which headphones you have tried them with? 

 

[kiertijai]

I used the R10 , LCD2 R1 and HD800.
I don't have the LCD3 now because I sent them back for driver check.
The HD800 treble did not sound too bright with the VT52 even I listened to Chinese music
with high recording level.  However I need to listen  to the HD800 with the super 7 to see which is better.
However I have to stress that I don't know the long term effect of the VT52 with the Balancing Act , for now
it has no problem.