6550C

[Julia]

As I said elsewhere.... holy glass, batman!!! :shock: These things are huge. These are Ruby 6550C that arrived today from Doug's Tubes.

I let them warm up for about 15 minutes with all the vols and gains at zero. Then did the biasing. I was going for 39.5 or 60%, but they kept drifting a little higher. So I relented and found where they wanted to go. I got them to stabilize from left to right:

V1 = 40.4 mV
V2 = 41.4 mV
V3 = 40.8 mV
V4 = 40.8 mV

They held it for about an hour before I shut it down. Wish me luck with this set.

I don't know how you guys get KT-88s in these amps.

 

[Jaded Faith]

I don't know how you guys get KT-88s in these amps.

Very carefully! :lol:
It's even more fun with the spring retainers and trying to push those to the side and squeeze them in.

 

[Julia]

I don't know how you guys get KT-88s in these amps.

Very carefully! :lol:
It's even more fun with the spring retainers and trying to push those to the side and squeeze them in.

I think these have the same size base. I ended up removing the spring retainers since due to the weight of the thing, this amp isn't going anywhere. Unless I get someone with a strong back and weak mind to do that regularly.

 

[aeroic]

I love the Svetlana 6550C also. I've been using them in the RT2/50, Mod50 for a long time, and just plain love them! I had to remove the spring retainers too. Definitely a very versatile tube. Glad you are digging them.

I'ved used 6550s in tons of different amps, and I've had 1 pair fail on me in 8 years.

I personally run my 6550s around 46-47 and that's where I like them the most.

Eric

 

[jmgman70]

I love the Svetlana 6550C also. I've been using them in the RT2/50, Mod50 for a long time, and just plain love them! I had to remove the spring retainers too. Definitely a very versatile tube. Glad you are digging them.

I'ved used 6550s in tons of different amps, and I've had 1 pair fail on me in 8 years.

I personally run my 6550s around 46-47 and that's where I like them the most.

Eric

This Dude made me put a quad in the Mod 100, :shock: Huge sounding tubes for sure!!!48/50 on the bias

 

[Julia]

46.2 mV is 70% max plate dissipation with the RM100. They say this is the sweet spot.... I'll shoot for that after they've broken in.... maybe.

I just finished playing. This is the tone I've wanted since the beginning. Big, FAT, tight bottom, distinct highs, and not harsh. I found big glass = big tone.

I ended my first day with these by playing with my JTM module, a Keeley Java Boost, my Mustang on the neck pickup to some "Sweet Home Chicago". Nice and clean. Big, beautiful tone.

 

[kylendm]

Is the change drastic? Like can you distinctly tell the difference? I really want Kt88s but i don't know which ones to get :?.

 

[james.fugate]

I've got some Svet 6550's in my RM 100. But i'm reluctant to bias them any higher than 41.

 

[JKD]

Is the change drastic? Like can you distinctly tell the difference? I really want Kt88s but i don't know which ones to get :?.

Ypu absolutely cannot miss the difference with KT-88s and 6550s....it's like the first time you experience stereo or DolbyHD....very different to an EL34 and much bigger sounding than a 6L6

 

[KillTone]

Ok, so you all have me interested in the "big glass". Can anyone explain the tonal characteristics of KT-88 vs 6550? I need to know which one to try.

NEVERMIND - After doing some reading it looks like they are basically the same tube.

Thanks,
Ron

 

[bruce egnater]

Good choice Julia. Hope you have better luck with these. You do obviously need to remove the retainer rings. Put the 8 screws back in as they aid in supporting the board.

 

[aeroic]

I've got some Svet 6550's in my RM 100. But i'm reluctant to bias them any higher than 41.

I've been running my VHT 2/90/2 around 46 for years (which I've sold now). Been running my Mod50 w/ 6550s at 46-47 for nearly 2 years no problems. Gonna be loading up the big bad Mod100 w/ 6550s and running them the same, as well as my RT2/50 for the last 2 months. You aren't going to blow anything at that level. It will just lower the life of the tube, but increase the tone!

 

[aeroic]

I've got some Svet 6550's in my RM 100. But i'm reluctant to bias them any higher than 41.

I've been running my VHT 2/90/2 around 46 for years (which I've sold now). Been running my Mod50 w/ 6550s at 46-47 for nearly 2 years no problems. Gonna be loading up the big bad Mod100 w/ 6550s and running them the same, as well as my RT2/50 for the last 2 months. You aren't going to blow anything at that level. It will just lower the life of the tube, but increase the tone!

 

[james.fugate]

I've got some Svet 6550's in my RM 100. But i'm reluctant to bias them any higher than 41.

I've been running my VHT 2/90/2 around 46 for years (which I've sold now). Been running my Mod50 w/ 6550s at 46-47 for nearly 2 years no problems. Gonna be loading up the big bad Mod100 w/ 6550s and running them the same, as well as my RT2/50 for the last 2 months. You aren't going to blow anything at that level. It will just lower the life of the tube, but increase the tone!

In your experience, what is the average tube life biased at 46?

 

[Julia]

Like I said for this amp 46 mV is 70% which is supposed to have magic fairy dust on it. I'm doing what turns out to be about 62% which is around 40 - 41 mV. I'm leaving some wiggle room for burn in. I check and adjust periodically especially the first month, then about every couple weeks afterward just to make sure. It's not that I don't trust things.... I don't trust things. I realize not everyone has their bias settings on paranoid like I do. It's just that I have a reason.

 

[aeroic]

I've got some Svet 6550's in my RM 100. But i'm reluctant to bias them any higher than 41.

I've been running my VHT 2/90/2 around 46 for years (which I've sold now). Been running my Mod50 w/ 6550s at 46-47 for nearly 2 years no problems. Gonna be loading up the big bad Mod100 w/ 6550s and running them the same, as well as my RT2/50 for the last 2 months. You aren't going to blow anything at that level. It will just lower the life of the tube, but increase the tone!

In your experience, what is the average tube life biased at 46?

Average playing...abouot a year or a bit more. So good power tube life.

 

[aeroic]

Like I said for this amp 46 mV is 70% which is supposed to have magic fairy dust on it. I'm doing what turns out to be about 62% which is around 40 - 41 mV. I'm leaving some wiggle room for burn in. I check and adjust periodically especially the first month, then about every couple weeks afterward just to make sure. It's not that I don't trust things.... I don't trust things. I realize not everyone has their bias settings on paranoid like I do. It's just that I have a reason.

I totally understand. I've had issues with other tubes in the past also...but 6550s have been rock solid for me. So have TS 5881s and Sovtek 5881s.

 

[Julia]

Well, since you all know I'm in paranoid mode on tubes I thought I'd give an update on these.

They are sounding better, but I've noticed something and just want to ask. I know some changes are normal. Is this normal?

Here are my initial bias settings on 9/1/09 (V1-V4 left to right):

V1 = 40.4
V2 = 41.4
V3 = 40.8
V4 = 40.8

Here are my bias readings today 9/11/09:

V1 = 37.8
V2 = 37.3
V3 = 37.3
V4 = 37.7

Line voltage both days was at 116 VAC.

So is this downward drift normal. Should I bring it back up? Or should I take the "if it's not broke..." approach?

 

[kc2eeb]

I would say let them cook some more.
Tolerances in the heyday of tubes were +/- 10% with most +/- 20%.
You may want to leave the meter connected and play at usual or full volume and see what their actual dissipation is.

 

[Rod]

Like I said for this amp 46 mV is 70% which is supposed to have magic fairy dust on it. I'm doing what turns out to be about 62% which is around 40 - 41 mV. I'm leaving some wiggle room for burn in. I check and adjust periodically especially the first month, then about every couple weeks afterward just to make sure. It's not that I don't trust things.... I don't trust things. I realize not everyone has their bias settings on paranoid like I do. It's just that I have a reason.

That's very smart Julia..espiecally considering what you've gone through with tubes issues...Good luck with these tubes...
FWIW, I toured the US with a pair of Tung Sol 6550's with never an issue