Mine just says "Limited Edition 3 of 10" on the back of the amp. No other serial number that I can see on either the amp or PSU. Not that it really matters anyway, the sound proves its provenance.

Interesting I wonder why foo_me and I have silver sharpie numbers on the power supply/amp (Both the same #). I'll ask craig next time I chat with him laf

I take it you are happy with the item eh ?

So is the TS RP 6SN7 is a better sounding tube than the TS 6F8G?

I own them all and I think people's preferences are highly personal. Perhaps we can agree on what we hear 50% of the time, but preferences belong to the individual.

I would say that the VT-99 combines a lot of detail with the subtleness of the NU grey glass. It is not in your face, but is very detailed. I would not call it dead neutral, like the 6SN7W. It may be slightly - ever so slightly, dark, but is relaxing and non fatiguing. The Tall bottle 7N7 sounds somewhere in between a Vt-99 and a Sylvania Bad Bay. It is a really smooth sound that disappears in a good way, but the Vt-99 has a subtle presence in a good way.

But none of these are my favorite as a driver. That would have to be the lowly Raytheon Type 1. The T-S TSRP does nothing for me at all.

I agree with all those that found the ZDT neutral, detailed, fast, but nice to listen to, esp on those Audeze headphones!

I've been interested in the BA for some time now. Craig emailed me the following after I asked questions about the 2nd run, which should start end of of this month:

Stock BA for $3500.00 will include JJ Tesla 300B, New production 6SN7, JAN 6X4 tubes, copper output transformers, Bakelite sockets with machined gold plated pins.

The Chassis is 1/2" taller, the top plate and control panel are polished laser etched, no silver pins.

Power supply has a meter, and adjustment knob for heater supply.

I will make the amp for 307A tubes same price, 307A tubes not included, but if you send me tubes I will burn them in with your amp.

Upgrade to silver secondary outputs $200.00.

Upgrade to Teflon sockets $50.00.

Are Teflon sockets available for all versions of the BA?

Didn't know about the meter and adjustmant knob

The ZDT is an output-transformer coupled SET. What is the typology of the original ZD and the ZD balancing act? If they have OPTs, they are under the case, or are they OTL's?

I liked the ZDT a lot when I heard it with the Audeze headphones. But I at least partially (or maybe permanently) fixed my SP MPX3, thanks to help from people here and on the other site and decided to stay with it, until......? They sound very different and it sort of perplexes me that I should like them both so much. But, then, I have a custom SS headamp by Blue Circle Audio that I also like at least as much as the MPX3.

The ZD is OTL. BA is transformer coupled. The Moth stuff I believe is all transformer coupled.

I was unsure whether to go 300B or 307A for my build (though I sent in my order for 300B). I asked Craig what would suit me best, given my headphones, and he responded with the following:

KR is sending me a pair of their PX-4 tube for evaluation. This will have a 300B pin out, and may be the best tube yet in BA. Let me see how this works, it is not too late to switch over to the 307A socket if you prefer.

http://www.kraudio.cz/pic/px4.jpg

Hopefully the px4 works out well, in which case, I will go that route!

I would make sure that if you go with the PX-4 you could also utilize other 300b's. Just because it is pin compatible doesn't mean the tubes spec out the same.

I would make sure that if you go with the PX-4 you could also utilize other 300b's. Just because it is pin compatible doesn't mean the tubes spec out the same.

yea, I had thought of that already, so I responded likewise to him.

Should be doable with the meter on the power supply in the second run.

Ah, good point, I forgot about that. As long as it has a big enough adjustment range then it should be doable.

QUESTION:

Hi Craig,

I know you must be terribly busy, but just wanted to ask how the PX4 testing worked out, as in my last email I opted to go this route (if technically possible) over the 300B. I'm in no rush, so take your time to answer at your earliest convenience.

Thanks,

Alex

ANSWER:

Hi Alex

The KR PX-4's are amazing. I will be setting up the 300B amps with a bias switch to use either the 300B, or PX-4 tubes. KR, and Sopia both make a PX-4 tube in a UX-4 base like the 300B. You will need to remember to change the heater voltage to 4V for PX4, and 5V for 300B. I have a pair of Sopia PX-4 tubes on order but have not received them yet. So far I believe the KR PX-4 tube to be the best sound in the BA.

Are the ZDT and BA using single ended OPT's or capacitor coupled P-P OPT's ?