Tubes for BAT VK60. Need help

Good John, many thanks.

RE - K. Deals' 6c33'S
I was hoping that to be the case. Though I did see a .pdf Tube Data sheet that showed both it and the 33c-b as two different tubes. Looking at the pics of both hasn't helped. They spec differently too.

RE - fuses
"Underneath"

...according to the owner which had that experience (s). his thoughts pointed more to the application and use to the Thor pre IN CONJUNCTION WITH, rather than the BAT VK60'S '6SN7S' alone. Some reverse synergy I guess.

We are soon to find out for sure.

BAT's tech guy, 'Dan', said to that account, "the SN's need have the 600v rating to avoid that and usually it is a bad tube causing it, arced, or to low a voltage value most of the time."

As best I can remember, Dan also mentioned rolling tubes in the amp isn't a bad thing, but one runs the risk of blowing fuses and/or tubes, if the plate voltages aren't in keeping with the design parameters... saying some NOS tubes just weren't on that level years ago.

Andy of VTS said the safe bet given that info is to keep to the military grade of NOS 6sn7's.... 5761? Syl, Tung, or RCA.

have you or anyone found placing the speaker being used cables onto taps other than the speakers suggested imp load, effective, better, or no diff? (like putting a 8 ohm spkr onto the 4 ohm taps, for ex.)

I've not had any issues with my amp blowing fuses other than once during an output tube failure.

Andy's advice is good, as is Dan's. The commercial grade NOS stuff is the best place to look for 6SN7 replacement. I replaced the front two positions with RCA red base 5962s from Andy some time ago and they are still rippin.'

Best bet about the output taps is to swap 'em and see what floats your boat. I've tried connecting the 4 ohm taps to my VR4jrs, but to my ears, the presentation was a tad more effortless using the 8 ohm taps.

"...the peak power will occur into a 3 Ohm load (in the case of 4 Ohm taps) and into 6 to 7 Ohm load (in the case of 8 Ohm taps)." The jrs are nominal 6 ohms.

Dgarretson
I'll sure bear that tube integrating idea in mind. I would freak right out if upon installing a set of tubes they were to arc out on me.

Loonytunz ... You bet, thanks. try any of the Tungs or Sylvanias?

Andy had merely mentioned the Syls being way more extended on top, tungs having better body by a fair amount, and the reds being the more warm sounding but still with fine detail and imaging.

I thini Andy's description of the 3 NOS tubes is on the money. The mil spec 6sn7 is a VT231. The idea that the Thor could cause the tubes in the amp to fail seems to me to be nonsense, but it is true that if the BAT design runs the tubes at a higher voltage, it could cause shorter tube life and premature failure, esp with "NOS" tubes, that often turn out to be only overpriced "pulls". If you are buying NOS tubes from other than a trusted dealer and do not have a tube tester, you are really buying a pig in a poke. I found out the hard way and bought a tester.

Swampwalker ...sage advice. I'm in full agreement.

Fuses more so than tubes seemed the issue with the 'other' Thor/BAT user... and i think he was using a bridged pair of vk60s as vk120's. whether that matters or not i've no idea.

we'll see soon enough.

i looked into the "tube tester" briefly. Calibration is the key. Without that being accurate in the tester even with one it’s as you said, “… a pig in a poke” .

Many I saw for sale were old, out of date, unsupported, yet said to be working and recently calibrated. Several makers of tube testers told me personally even after calibration, the return shipment can put it back to it’s previous “OUT OF CAL” issues.

How does one get past that?

More importantly, finding one that is both simple to use, with a sufficiently large view meter (3” x 3” more or less), and associated electronic text (PC viewable for settings etc), and remains in calibration or can be calibrated on site… well then I’d likely be headed that way as long as it ain’t too expensive.

I’ve had the thought that in today’s digital domain there sure should be some IC set type testing gear using chips and such inside to test tube variables with and not so prerequisite of regular calibration…. And cheap.

I’ve done some of that tube buying from hobbyists… and pros…both in my exp. Have been a mixed bag, save those I’ve bought from Andy b. his have served me well, had no issues and provided good results.

Though having a tester on site does what really? Whose tester gets the nod? Mine or the sellers? I sure see it’s value for periodic testing of one’s own supply…. But as a lie detector? I don’t know about that part.

I reckon it’d be a nice thing were I out scroungeing up tubes on my own away from retail venues though.

I’m probably better served in the long run to stick with those sellers people like you point me to than attempting to become a tube monger myself.