Ref 5 / 5se and different 6550 tubes

[jpspock]

Originally Posted by Barry1

My Ref Anniversary 40 originally shipped with 6550 C's for the power supply. Replacements were the 6550 WE variant. I don't think they sound as good. Highs are just a little harder, almost crystalline, after 80 hours of use. Any one else hear a difference or have an opinion?
Does anyone know the plate & screen voltage values for the 6550s so I can better match them when ordering from other than ARC?

Hi Barry,

how does it sound now with the 6550we??

[Barry1]

Actually, after 150 hours, it sounds really good and I have no complaints. What I need to do is compare the 6550WEs to the originally shipped Sed 6550C directly. I just happen to have a new matched pair of the "Cs" waiting for trial, but it'll take me awhile to get around to it.

[sander]

I'm curious if you have the same experience as i had.
After 200 hours i also thought the 6550we was not so bad after all. It was pretty good actually.
But when i installed the original 6550c it was a different story.

What if you have the same experience?
Should we all complaine and protest against ARC for this 6550we tube?

[Amado]

Originally Posted by Asterisk

At a little over 1000 hrs, one of the 6550C's in the PS of my Ref Anniversary failed. The replacements I got from the dealer were 6550WE. Have the same observations. The midrange has nice detail and the high's seem cleaner at moderate listening levels but the balance tilts when you push up the volume. Like you say a bit brash. Was hoping they would still change as it accumulates more hours ( have just about 40 hrs now). In some systems it might be a welcome change.

While I have to stick the dealer supplied replacements for warranty reasons, I'm getting a bit impatient. Didn't think that it would affect the sound that much.

Interesting though is that my Ref phono 2SE came with 6550WE as opposed the 6550C's specified in their brochure. The Reference 750 also uses 6550WE.

Whether its due to availability, reliability or performance reasons, I don't know.

I contacted Customer support about the tubes and this was the answer :

"The Owner's manual has a typo error. It should read 6550WE. The 6550C has been out of production for about one year."

I have a REF10 with the 6550we and no issues, I love the sound, no cons.

regards,
Nelson

[Barry1]

So... have run in a pair of SED 6550 "C" for 50 hours, and without doing a back to back comparison with the WE's (don't want to overflex the main board), I like the "C's" better. WE's are neutral; C's are natural. The WE's are not bad. They are just a little dry sounding in the upper mid and treble, don't have quite as much 3-D body, and not as big a soundstage. The WE's may have just a bit more leading edge definition. Tonal balance seems roughly about the same despite the difference in presentation.

[Lunchy]

Originally Posted by Barry1

So... have run in a pair of SED 6550 "C" for 50 hours, and without doing a back to back comparison with the WE's (don't want to overflex the main board), I like the "C's" better. WE's are neutral; C's are natural. The WE's are not bad. They are just a little dry sounding in the upper mid and treble, don't have quite as much 3-D body, and not as big a soundstage. The WE's may have just a bit more leading edge definition. Tonal balance seems roughly about the same despite the difference in presentation.

Just curious, how many hours did you have on the WE tube?

Sent from my iPhone using A.Aficionado

[Asterisk]

Originally Posted by Amado

I contacted Customer support about the tubes and this was the answer :

"The Owner's manual has a typo error. It should read 6550WE. The 6550C has been out of production for about one year."

I have a REF10 with the 6550we and no issues, I love the sound, no cons.

regards,
Nelson

Thanks for the heads up Nelson

[microstrip]

As far as I know, Audio Research selects the 6550 tubes for optimum values of transconductance and plate intensity in the power supply. Alternative tubes can have a wide variation in these parameters. How can we be sure you are listening to sound differences due to the tube type and not to the tube parameters when swapping tubes?

[Barry1]

Good question and a possibility. Tubes I used are very tightly matched at 450V @ plate/screen (ARC PS measured value - tube appears to be used as a triode mode regulator) with a G1 bias for both tubes almost within 1%. They have identical matching GMs. I was not able to measure the cathode or plate current at idle which would be highly desirable (I'm working on it) and that would answer your question. Can you measure the idle cathode / plate current or can you interpret values marked on the ARC tubes?

The WE's had about 60 hours on them when I listened and did improve a bit with break in.

[microstrip]

Originally Posted by Barry1

Good question and a possibility. Tubes I used are very tightly matched at 450V @ plate/screen (ARC PS measured value - tube appears to be used as a triode mode regulator) with a G1 bias for both tubes almost within 1%. They have identical matching GMs. I was not able to measure the cathode or plate current at idle which would be highly desirable (I'm working on it) and that would answer your question. Can you measure the idle cathode / plate current or can you interpret values marked on the ARC tubes?

The WE's had about 60 hours on them when I listened and did improve a bit with break in.

I built a tube measuring jig just for the 6550s and KT120s. I usually measure Vg1 and transconductance for IP= 65 mA and VP=420V for checking tube matching. Still did not have the time to think about preamplifier tubes.