The Reference 6J5 Thread (L63, 6C5, 12J5, 6P5, etc.)

[triod750]

they are quite nice, the STC 6J5G.

Where does that put them, compared to other tubes you have used?
Many of my tubes are quite nice, more being different than better. When I find a good, or very good, pairing I only have to change to another recording to change my mind. Well, kind of....

 

[L0rdGwyn]

Where does that put them, compared to other tubes you have used?
Many of my tubes are quite nice, more being different than better. When I find a good, or very good, pairing I only have to change to another recording to change my mind. Well, kind of....

I think they are very good, if my S tier is L63 and Fivre 6C5G, I would put them perhaps in A tier at the moment. More listening is required!

 

[triod750]

Thanks. Listening is always required. I try hard to love L63. They are good but 'L' doesn't mean 'Love' so far. More listening is required.

 

[L0rdGwyn]

It will depend on the circuit too, in my amp the differences are not enormous, most all 6J5 sound good, but some are slightly better than others. Bigger difference is heard changing power tubes. I have to wait a long time if I want to swap them though, unless I want second degree burns.

Now Fivre 6J5GT.

 

[triod750]

Yes, I suppose a lot is circuit dependant. (Not written from own experience but from reading).

Restaurant chefs use to say that 'fingers are there to be burnt'.

 

[L0rdGwyn]

I need to get an oven mitt

 

[whirlwind]

I need to get an oven mitt

Ha, grab two, chances are you will burn in hole in one of them

 

[L0rdGwyn]

Here is sort of a weird one, Mullard-made GEC labeled 6C5G. As I recall, I didn't think much of these tubes when I listened to them in the past, but going from Fivre 6J5GT to to Mullard 6C5G shows BIG step up in bass heft and instrument separation. A great pairing with the 6528! Which I have found are a little more picky to match with compared to the 6336 in this circuit.

 

[mordy]

Here is sort of a weird one, Mullard-made GEC labeled 6C5G. As I recall, I didn't think much of these tubes when I listened to them in the past, but going from Fivre 6J5GT to to Mullard 6C5G shows BIG step up in bass heft and instrument separation. A great pairing with the 6528! Which I have found are a little more picky to match with compared to the 6336 in this circuit.

Perhaps the reason why the 6528 is harder to match is because the 6528 has much more gain than the 6336.

 

[L0rdGwyn]

Perhaps the reason why the 6528 is harder to match is because the 6528 has much more gain than the 6336.

Well it is operating as a cathode follower in this circuit, so the gain for both the 6336 and the 6528 is roughly 1. The higher transconductance of 6528 as a cathode follower results in lower distortion and output impedance. The contribution the 6528 makes to the harmonic distortion is very low, whereas the contribution by the 6336 is slightly higher. My suspicion is that there is some distortion masking effect occurring between the 6336 and the input stage, which is less pronounced by the 6528, so the harmonic profile of the 6J5 input with a 6528 output is more audible than it is with the 6336. Just my theory at the moment.

 

[mordy]

Well it is operating as a cathode follower in this circuit, so the gain for both the 6336 and the 6528 is roughly 1. The higher transconductance of 6528 as a cathode follower results in lower distortion and output impedance. The contribution the 6528 makes to the harmonic distortion is very low, whereas the contribution by the 6336 is slightly higher. My suspicion is that there is some distortion masking effect occurring between the 6336 and the input stage, which is less pronounced by the 6528, so the harmonic profile of the 6J5 input with a 6528 output is more audible than it is with the 6336. Just my theory at the moment.

Thanks - which 5A tube results in a more pleasing sound?

 

[L0rdGwyn]

Thanks - which 5A tube results in a more pleasing sound?

My impression so far is that the 6528 is the more detailed and resolving of the two, not surprising as it has lower distortion and output impedance. BUT like I said, I think it is a little bit harder to pair with an input tube. When the pairing is good though, it is incredible, the resolution and airiness is astounding. With a good 6J5, I have measured 0.007% THD 1mW into 300ohm with the 6528 and a 15ohm output impedance.

The 6336 is the more smooth and rounded of the two, I wouldn't call it gooey or anything like that, it is also very detailed, perhaps a bit more easy-going than the 6528, and not so picky about tube pairing.

So the complement each other well, the 6528 has a high "wow factor" ceiling but is more picky whereas the 6336 is easier to put on and enjoy out of the box. As an analogy, it's similar to what using a quality 6AS7G versus a 5998 does in a 6AS7G-type amplifier.

There are some earlier versions of the 6336 I intend to try that have metal plates as opposed to graphite, we'll see if that is a good or bad thing!

 

[L0rdGwyn]

I did some rapid fire tube rolling to get some first impressions of how each 6J5 fits with the 6528 in this amplifier. None of these tubes sound bad, differences are quite subtle, but they can be heard. Going with my gut first impressions on this one, I don't have time to do extensive comparisons, critical listening is a chore!!!

RFT 6J5 - these are quite good, well-balanced top to bottom, maybe a little more lean than the Mullard 6C5G, but very detailed, satisfying treble without stridency, great bass resolution. A top 6J5 for me.



STC 6C5G - the only one I really did not like. I found vocals to sound slightly harsh and unnatural on the tracks I was listening to, which pretty much made it a no go. This was probably the 6C5G I remembered not liking, not the Mullard.



Visseaux 6J5G - I've always liked these tubes, this pair is slightly noisy, but once they settle down they are very resolving, airy, and smooth. Up there for me with the best.



Sicte 6J5GT - pretty uncommon tube, they are pretty good, similar character to Fivre tubes, slightly warm leaning and smooth. I like them, very easy listening, but not the last word in resolution. Above average, I think I prefer them over the gray plate Fivre 6J5GT.



Ken-Rad 6J5GT - these are quite good, excellent body, warm leaning, good bass heft, and smooth upper midrange. Very easy to listen to and quite detailed.



Tung-Sol 6J5G - these used to be one of my favorites, but not quite as impressive as I remember them being. Maybe they are getting old? I felt the midrange was a little uneven, but a nice full low end. I would put the middle of the pack in this circuit.



Sylvania 6J5GT - I have thought highly of these in the past, still do now, they are nicely balanced, nice full low end, sparkly highs, but not harsh, and good resolution. They don't seem to do anything "wrong", but perhaps don't separate themselves from the rest to be called top tier, but above average.



Nippon Electric 6J5GT - one thing I have found about Japanese tubes, they all seem to be exceptionally quiet. These are no different. Another middle of the pack tube I would say, midrange could be a tad smoother, but a nice low end, detailed highs.



Right now my personal tier list goes something like this.

S - MOV L63, Fivre 6C5G, Mullard 6C5G, Visseaux 6J5G, RFT 6J5
A - Ken-Rad 6J5GT, Sylvania 6J5GT, Sicte 6J5GT, STC 6J5G
B - Tung-Sol 6J5G, Nippon Electric 6J5GT, Fivre 6J5GT
C - STC 6C5G

That's right, my scale only goes to C, every tube gets a passing grade. Cs get degrees!

I know I have more 6J5 somewhere, but that's what's in the drawer next to me lol maybe I'll update the list as time goes on.

 

[leftside]

Those silver RFT 6J5 are top notch tubes. Also the Philips. I think I might have another brand as well. I'll have to double check.

 

[raindownthunda]

I did some rapid fire tube rolling to get some first impressions of how each 6J5 fits with the 6528 in this amplifier. None of these tubes sound bad, differences are quite subtle, but they can be heard. Going with my gut first impressions on this one, I don't have time to do extensive comparisons, critical listening is a chore!!!

RFT 6J5 - these are quite good, well-balanced top to bottom, maybe a little more lean than the Mullard 6C5G, but very detailed, satisfying treble without stridency, great bass resolution. A top 6J5 for me.



STC 6C5G - the only one I really did not like. I found vocals to sound slightly harsh and unnatural on the tracks I was listening to, which pretty much made it a no go. This was probably the 6C5G I remembered not liking, not the Mullard.



Visseaux 6J5G - I've always liked these tubes, this pair is slightly noisy, but once they settle down they are very resolving, airy, and smooth. Up there for me with the best.



Sicte 6J5GT - pretty uncommon tube, they are pretty good, similar character to Fivre tubes, slightly warm leaning and smooth. I like them, very easy listening, but not the last word in resolution. Above average, I think I prefer them over the gray plate Fivre 6J5GT.



Ken-Rad 6J5GT - these are quite good, excellent body, warm leaning, good bass heft, and smooth upper midrange. Very easy to listen to and quite detailed.



Tung-Sol 6J5G - these used to be one of my favorites, but not quite as impressive as I remember them being. Maybe they are getting old? I felt the midrange was a little uneven, but a nice full low end. I would put the middle of the pack in this circuit.



Sylvania 6J5GT - I have thought highly of these in the past, still do now, they are nicely balanced, nice full low end, sparkly highs, but not harsh, and good resolution. They don't seem to do anything "wrong", but perhaps don't separate themselves from the rest to be called top tier, but above average.



Nippon Electric 6J5GT - one thing I have found about Japanese tubes, they all seem to be exceptionally quiet. These are no different. Another middle of the pack tube I would say, midrange could be a tad smoother, but a nice low end, detailed highs.



Right now my personal tier list goes something like this.

S - MOV L63, Fivre 6C5G, Mullard 6C5G, Visseaux 6J5G, RFT 6J5
A - Ken-Rad 6J5GT, Sylvania 6J5GT, Sicte 6J5GT, STC 6J5G
B - Tung-Sol 6J5G, Nippon Electric 6J5GT, Fivre 6J5GT
C - STC 6C5G

That's right, my scale only goes to C, every tube gets a passing grade. Cs get degrees!

I know I have more 6J5 somewhere, but that's what's in the drawer next to me lol maybe I'll update the list as time goes on.

Great list and nice comparisons! It just goes to show how much of a difference amps, tube synergy, and ears can make in tube rankings. Personally STC 6J5G are quite possibly my all time favorite in the Bottlehead Crack w/ SB with the Chatham 6AS7G, with Visseaux 6J5G being one of my least favorite. Completely agree it’s all relative and all of the tubes in this family are enjoyable to listen to, some just more magical and better power tube synergies than others.