Tubes for BAT VK60. Need help

I’m now looking to retube a BAT VK60. I know very little about the tubes in it or which ones are most important to address first... or at all.

Any VK 60 owners with re-tubeing experiences out there?

I surely would appreciate some input on what you wound up with and why...?

Thanks so very much for the time and efforts here, as I'm lost now.
Hi Jim ! Hope all is going well for you! Before my now 150SE's :), I used red base RCA 6sn7's in my VK60. The front two 6sn7's are the input and make the greatest change on the sound.

The 63CCb's also seem to need to be replaced yearly in my system. More dynamics and jump every time I replace them.

Regarding the 6sn7's, They need to be matched and the matched pairs put in spots 1 & 4, then 2 & 5, and finally 3 and 6. Or course these are 6 tubes in the second row. #1 from left to right in my example here.

The RCA's seemed to be smoother on the top end, a little warmer than the stock sovteks.

Also, using 400 - 600 grit sand paper, sanding the tube pins, then using contact cleaner in the tube sockets and the tube pins to me is a big help.

Good luck
thanks john
Talking to BAT today I was told one thing of import... look to get 6SN7s with at least 600v ratings... during start up that is the applied voltage ... if that is not the ratings things will wear out sooner or not work properly.

They didn't say anything about the 6c33b's... except they cost a lot. I'm not far from Cuba.. maybe I'll slip over there and find a Mig.
You can get those 6c33 tubes from Parts Connexion for $27, or from for a bit more. I believe they all come from the same Ulyanov factory regardless of distributor. As remarked by jfrech, in the BAT they lose their punch after about 1200 hours (1800 hours with Pearl Tube Coolers). About 25% of them eventually ARC out (loud popping sound followed by hum), so buy a spare or two. After sanding the pins, try Walker SST silver paste. I use EH 6SN7s in my VK75SE and they hold up well and sound fine.
The 6c33bs are a lot cheaper than good NOS 6SN7s, thats for sure!
I got all RCA in the Thor.. NOS. 12AT & 12AX... very nice.

Are the or is there some amalgamation of info on the types and their related sounds, akin to Joe's tube lore review?

Thanks much
Jim for 10K you can go to the Soviet Union and take a flight in a Mig. Just don't take any tubes out before ;)
Jim- There are a couple of good sellers of 6SN7s right here, who have pretty good knowledge of their typical sounds. Jsautter and Kalidelkol (not sure on teh spelling) come to mind, but there are also a couple of others. Of course Andy at Vintage Tube and Upscale Audio also.
Dgarretson -I do appreciate it

...a third more life expectancy using Pearl tube coolers...

Speculation, or your own experience? ...if so, that bears looking into for sure.

"EH, hold up well and sound good".

Wow. I've only had one pair of EH tubes, 12AT's, and I didn't care much for them... but they weren't new, so that played a part I'm sure.

In my 'researching' both types, 6SN7-GTB & 6c33c-b, (those numbers and designations are accurate for the VK60 application), Dan at BAT said to insure the SN7's handle 600v, or they'll run out fastER, AS 600V IS APPLIED AT START UP & DURING THE BIASING.

The least price I found so far on the 6c33c-b or cb, is right from Russia. Averaging about $8 - $10 es. less than Paarts con., but a bit more for shipping, I'd bet.

"Parts con. doesn't test them or offer warranties do they?

That would change things. I'm also finding out the 33's being sold aren't usually tested prior to the sale. Well at least it's rare.

Lastly, "Is matching needed on these big current supplying tubes?"


Thanks much. Think they'll take a check? ...for free, I can swim, uh, paddle, over to cuba and nab some there maybe... have to brush up on my Spanish though and get a dog that can swim.


Big help. Thanks. Andy doesn't do 6c33c-b. he does do Sylvania, tungsol, & RCA. he had said in that order they'll range from open and extended to more full bodied, were their sonic traits. Also that they would gain in price going back towards earlier itterations, which is expected i suppose.

For posterity, the front 6SN7's are the more important tubes in the array. use of the lowest noise and harmonic preffs here will dictate more to the amp than elsewhere on the VK60... or so said BAT.
Chris at Parts Connexion stated to me that upon request he will test each 6C33C and offer a 90-day warranty.

After many retubings of 6C33Cs in the VK75SE without Pearl Tube coolers, I noted (subjectively) about a 50% extension in tube life with the Coolers. I now use them everywhere, particularly with hot-running & valuable 6H30-DR input tubes. However I don't think the Pearl Coolers extend tube life 2x-5x as claimed.


Super! Thanks. Does Parts Ex. do the coolers too? I'll Google 'em.

I think for the $40 diff of the Ruskies, and the time frame to get them from there to here, I'll call and order the 33's from them.
Parts Connexion has the Pearl Coolers or you can get them directly from Pearl. For the hot power tubes, make sure you get the 3" tall Coolers with the red silicone O-rings. The black rubber rings dry out and break after awhile.
...again, many thanks. Like other 'tube rings' I would think these also affect sonics some too, correct?
nO LUCK YET but I'm closing in... I now know who does not have 6c33c-b tubes for sale: Parts Express, Antique Electronics. Alan welch, & Vintage Tubes. Searching here provides zip as well.

Best so far is $40 ea + ship. More for matched
The Pearl Coolers do help with microphonics. The ones designed for small signal tubes include a carbon fiber mesh that slips between the tube & the vaned metal cooler.
As all the tubes I'm getting are or will be NIB/NOS, MF likely won't be an issue. I've used Herbies halo rings in the past and found they do affect the sound and imaging. For the better once set rightly.

I got the names mixed up, but got in touch with PCX. $35 ea. $10 ex for matched Quad. ordered a set of 4. $30 for next day air.

OK... 6c33c-b side is done... now the bigger $$$ aspect. Eight 6SN7's.
BTW I've found that when retubing 6C33Cs the occasional new output tube fails to bias up. This is usually remedied by swapping output tubes around. I've become superstitious since the time I had two output tubes on one channel arc out simultaneously during first time start-up. Since then I replace output tubes one at a time and turn up the unit for a couple of minutes before powering down and moving to the next tube. BAT recommended to me that output tubes should be discarded after two arcs-- and power output is reduced each time a tube arcs. Apparently the default operation mode of these tubes after arcing was engineered for those MIGs...

Could be. Now I just gotta pray it gets here in tact.

I'm a little late to the party, but in the future, you may want to consider ATSI for a matched & tested set of 6C33C-Bs. I bought my last quad there and have had really good luck (they have increased in price, though.) I believe he's the only game in town if you want matched tubes AND a 90 day guarantee.

I'll also second Andy at VTS. He's very knowledgable about the VK60 and which tube will get you what you are looking for.
I'll 2nd ATSI. I've bought 2 sets of 6C33b's from ATSI. Have initial failures both times, and got a prompt replacement. Great service.

They say they'll match them.

Kevin Deals joint shows 6c33 tubes available. Not 6c33c-b.

Anyone ever have issues with these VK60s blowing fuses? or blowing them as the result of which preamp is tied to it?
Especially a Thor?

Thanks people... I might get this right in spite of myself with your help.
Which fuse? The fuse on the back panel next to the power cord or one of the 4 fuses underneath the tubes? If underneath the's likely tubes arcing and failing. That is common. New tubes and a new fuse from Radioshack. Make sure it's the same type and value.

I'm pretty sure Kevin Deals 63CC tubes are really 6C33cb's. I've retubed my VK60 from him once. Tubes sounded great.

If it's the main fuse. That maybe a issue somewhere, I can't comment there...

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

...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.
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.
I'm not sure how much topology difference there is between the 60 and 75, but I switched amps a while back (still using the red bases.) That being the case, take my opinion with a healthy dose of salt. I have read lots of praise for the NOS Sylvanias and aim to snag a pair of them to try in my new(er) toy, but no practical experience with any NOS goodies beyond the reds in your amp.

The description of the reds you provided sounds plausible, but since I didn't do a side-by-side with anything other than the factory 6H8C and some standby EH 6sn7s, I don't really have a frame of reference. FWIW, to my ear, the reds are definitely a warm and articulate tube in my 75. Verrry sweet.

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.
Thanks All.

finding one of the vendors that came recomended in the above posts being closer to me I went with him on the 6c33cb tubes. Matched Quad, + tax + ship = <$200, with 90 day warranty. A bit higher than another one or two but in stock and the quckest available.

6SN7 I'll probably get from VTS. Once I figure out which version suits me for the front two, and 5692 in the six slots of the second stage.
Regarding choice of taps, with the VK60 or VK75 you can try using different taps for t & w. I found my 8R Merlins had a sweeter treble and better bass control with t on the mid tap & w on the high tap. Just couldn't get the best of both worlds without splitting the taps.

wow! Thanks. I'd have been reticent to do that myself. probaly wouldn't have used two taps at the same time.