Changing tubes (VH4)

[Soliam]

I own a Diezel VH4; it's the first head I've ever owned, so I'm new to this stuff, and not too long ago one of the power tubes blew, the one labeled {2} on the back of the head. Soon after, probably 2 weeks or so, the power tube labeled {1} followed suit and blew. I have a couple of questions regarding what needs to be done.

do the labels on the back of head (1,2,3,4) indicate how the tubes are paired or are diezel's paired like most heads with outer and inner matched pairs?

if those labels are in correct succession, am I correct in saying that it is only necessary (maybe not ideal, but...) to only change the 1st and 2nd power tubes?

I'm unsure what brand of tubes are currently in the head, having bought the VH4 used. I do know that they are labeled "6550c made in russia"
I bought a matched pair of SED 6550's and I'm wondering if it would be a bad idea to put those in place of the offending pair or if I should get a matched quartet and replace all 4 power tubes. also, regardless of what I do, am I going to need to get it biased?

 

[duesentrieb]

In a VH4 they are not paired. You need to buy a matched quartet and ask a tech to set the idle bias current for the tubes.

 

[racerevlon]

^^^This, x 1,000,000

 

[Ventura]

Yep. Even when just one goes, you are "strongly encouraged" to purchase a matched quartet.

As for make and model, there are a lot of cats running =C= 6550's in there instead of the currently recommended Ruby EL34BHT (I believe they are). The 6550's sound absolutely amazing, but due to a higher incidence of blow-out's, Diezel HQ is now recommending the more stable EL34's by Ruby. Entirely up to you and your ears, I for one am sticking with the SED =C= 6550's as they're just blistering sonic heaven

Good places to buy tubes:
thetubestore.com (Jon knows his business and has decent prices)
valvequeen.com (lots of + feedback from fellow forumites using her for their glass orders)

Good luck, and welcome aboard!!

V.

PS - and while you're at it, if you bought this head used, check out the preamp glass in there too. If you go with Chinese/Shuguang 12AX7B or C pre's, the amp definitely comes to life... No boutique high end NOS glass needed, the amp rips with stock Chinese and they're pretty cheap to boot

 

[mightywarlock]

for the ValveQueen. I just got my order in from her today, of my special order of Ruby EL34BHT's, and some preamp tubes to try as well.
I was having a hard time locating the BHT's, and she was able to get them for me, so big
I'm going to replace the Sovek 5881's that are in my VH4 this weekend! (I didn't even remember what was in the amp until I popped the back off tonight).

Incidentally, I ordered some of Peter's recommended tubes, the HG+ for V1&2, and when I just opened up the amp tonight, I discovered in V1 an HG+ was already in there! There was also a mix of HG's and Tad's Special Mullard reissues (selected), and one Mesa chinese in the return i think it was...
weird.
I ordered from her a JJ 12AT7 to try in V3, as I read it helps cut down some of the compression on ch.3...but...I think it has a slightly negative affect on ch.2 (says on the Diezel webpage that V3 is used by ch.2/3/4, but V2 is used by just ch.4

I always run the gain high on Ch.2, and like the way it was crunching up. I wasn't able to crank the amp tonight as it was like 1am, but I could definitely tell there was less gain.
Ch.3 seemed a little more tamed as well, at least at lower volume.
I'm wondering how this tube would work for ch.4...as I don't need as much gain is in there, and find myself not using ch.4 all that much.

Anyone have any experience with a 12AT7 or 5751, or anything other than a hot 12AX7 in V2?