Anyone familiar with the 6h30 tube layout in the ARC Ref 5SE?
 

My ARC Ref 5SE has developed a low level hiss and crackle in the right channel. It is volume dependent, but cannot be perceived at the listening position at normal listening level, only with an ear close to the midrange driver. I have removed the tubes and cleaned the pins and sockets with no change in the noise. So, I have a couple of old 6H30 tubes on hand that I can swap in and out of the four sockets in the preamp to try to identify a possible noisy tube. The four 6H30s installed are labeled V1, V2, V3, and V4 on the main circuit board. Does anybody know which pairs of tubes serve the right and left channels? I can easily change one tube at a time, but knowing the general circuit design would help with interpreting the results. Thanks in advance.

Noise that can only be heard by putting my ear up to a midrange driver doesn't trouble me. If a tube does develop an issue, I replace all four of the signal tubes at the same time. I reason that once one fails the remainder cannot be far behind and there's no fun in fiddling with them. If the tubes reach around 5,000 hours with no issue I simply replace them all prophylactically.

Thank you, Cleeds. Sound logic. But I do like to fiddle from time to time and isolated V1 as the noise maker. I am surprised to hear how good the system continues to sound with the "old" 6h30s installed. They came out of my prior LS 25II. Nevertheless, after the first of the year I will be ordering a complete new tube set for the unit.

Here's a related question. I just purchased a set of replacement 6H30 tubes for my REF 5SE. They came in matched pairs. Does anyone know if matched pairs are actually necessary in the REF 5SE? If they are, what are the matched tube positions (V1,V2,V3,V4) for each matched pair?

Good question. I can guess from looking at the circuit board and the input leads from the Ref 5SE rear panel that V1 and V3 serve the right channel and V2 and V4 serve the left channel. If I was going to install two pair of matched tubes, assuming that the pairs are slightly different from each other, I would put the first matched pair in sockets V1 and V2, and the second matched pair in V3 and V4, to balance the contribution of the tube pairs between the right and left channels. But I could be completely wrong about this. I will probably buy my new tube set from Upscale Audio, and plan to ask this same question when I place my order. Where did you buy your new 6h30s?

I got my 6H30's from Upscale. I also think that V1 and V3 are for the right channel and V2 and V4 for the left channel, based on the board layout. However, I was thinking of keeping the matched pair in the same channel, which would be one pair for V1/V3 and the other pair for V2/V4. But I'm not absolutely sure about this, which is why I was asking the question.

So, give Kevin Deal a call at Upscale. I'm sure he would be happy to answer our question, since you are a customer and I expect to be one soon. Post his answer and you will save me a phone call. My guess is that he will say that all 4 tubes are matched to one another and that it makes no difference where you put them. But again, I could be wrong. Thanks.

The answer I got from Upscale is that one matched pair should be used for V1/V2, and the other pair for V3/V4. I'll also ping Audio Research for their recommendation.

Thanks, I will be interested to hear what ARC recommends.

This is what ARC says about tube matching in the REF 5SE:

"The 6H30's do not need to be matched like they do in the power amps but you do want to make sure they are well balanced on each part of the triode."

The 6H30 is a dual triode, so I presume the balance that they refer to is the matching of each triode within the individual 6H30.