Why tube rolling advice doesn't work

[StepheK]

One of the things I am discovering is: how one specific tube model/brand sounds is dependent on so many other things. The circuit and the voltage it's put into, the amount of NFB or the lack thereof, the output transformers used, the speakers being used etc etc.

Another big factor is what tube is it being partnered with. I'm finding part of the secret sauce for me has been finding the right driver tube to pair with a specific output tube (or vice versa). A driver tube that sounds muddy with an EL34, might sound great with a KT77 in the same amp. And in reverse, a tube that sounds too bright and harsh with the KT77 might mellow out and sound great with an EL34.

I recently found a great pairing between a Sylvania 6JC6A and a Gold Lion KT88 in my SE UL amp after trying a bunch of different driver tubes and tweaking the Schade feedback resistor value by ear to this pair. I bought a pair of the KT88-z treasure tubes to try out and just dropping them in, the bass is a bit overpowering and some of the top end crispness is missing. Still burning them in but don't expect them to drastically change after 10 hours of use.

But then I thought about other driver tubes I tried with the Gold Lion KT88, that were a little thin in the bass with a brighter top end, that might pair perfectly with these KT88-z output tubes. Then I'd need to compare those brighter 6EJ7 tubes and the KT88-z with the 6JC6A and Gold Lion KT88.

The point I'm trying to make is just because someone says X tube sounds fantastic in their amp, doesn't mean it will sound great for you. And that trying different variations of tube combos could be endless lol.

 

[gadget73]

Agree. Depends on too many variables to draw any useful conclusions from. My two EL34 amps like different output tubes, but everything about those amps is different so its not all that surprising that they respond differently. And personal preference of course. The tubes I happen to like the least in one amp, a friend who was listening with me liked best.

 

[tonyg88]

I barely hear a difference between the JJ 7591s and the tung-sol 7591 even thou they are very differently designed. A good designed amp will deal the tolerances of other manufactures tubes just fine.

 

[StepheK]

I barely hear a difference between the JJ 7591s and the tung-sol 7591 even thou they are very differently designed. A good designed amp will deal the tolerances of other manufactures tubes just fine.

I agree, some amp designs don't seem to care what tube is in them. Other amps tone might change drastically. I feel like the very simple SE amps are the most likely to change their sound with different tubes, which can be a good thing or a bad thing depending on how you look at it. I feel like PP amps with a lot of NFB are the least sensitive to tube rolling. It's probably why you see some people saying what you did, and other say they sound drastically different.

 

[Nixxuz]

Agreed, and sometimes it's just the right synergy.
I recently got a pair of GE 6SJ7's in the mail for my 805A based amp. After settling in, they were kind of bright at the very tippy top of the HF range, (at least the part I can hear). I had been running the Sino stock 5881's that came with the amp, as I previously found a pair of new production Tung Sol to be somewhat "laid back". Great tone, but just lacking in a sort of forcefulness the Sino display. Pairing the GE with Tung Sol created a cohesion that seems to be giving almost all of the benefits of both tubes, with none of the weaknesses.

 

[tonyg88]

I agree, some amp designs don't seem to care what tube is in them. Other amps tone might change drastically. I feel like the very simple SE amps are the most likely to change their sound with different tubes, which can be a good thing or a bad thing depending on how you look at it. I feel like PP amps with a lot of NFB are the least sensitive to tube rolling. It's probably why you see some people saying what you did, and other say they sound drastically different.

I think you are right about single ended.... It is one of the few things I haven't tried yet besides a portable record player that is a hot chassis design.

 

[gadget73]

yeah some things aren't awful sensitive to it. Gear with a fair level of global feedback tends to not care so much, and thats basically everything I own. Tube rolling for me is all fairly minor changes unless I happen to be replacing a bad tube.

 

[Lavane]

I found this out with my VTA-ST-70. I tried various EL-34's, some KT-77's, KT-88's, and EH 6CA7's. Trying various driver tubes I found I had to use a perticular driver tube with whatever power tube I was using. Examples are with the KT-77's I preferred the E80CC. The KT-88's, the RCA 12AU7 clear tops. But with the 6CA7's the 12BH7 sounds great. I agree it depends on factors like circuit design if a certain power or driver tube is going to sound better than another.

 

[BMC]

Great points about synergy & pairing power and signal tubes. I feel this is not discussed as much as individual tubes. Same for capacitors.

I have also found certain combinations where the whole is greater than the sum. I have a SE amp with 2 12AX7’s and 2 EL34’s, so it’s easy to roll. Here are the top combos:

Telefunken (smooth plate) 12AX7 into Mullard EL34 (XF2)
Mullard Long plate (f92) 12AX7 into RFT EL34
RCA grey plate 12AX7 into RFT EL34
Sonotone 12AX7 into Mullard XF2

 

[kappclark]

With classic audio gear, they must have done some tube rolling of their own, and decided on best bang for the buck. Maybe there wasn't as much of a selection..Kind of reminds me about my obsession with pickups in the 70's - Pickering, Empire, Shure, Audio-Technica, Grado etc....I enjoyed the quest, and experimenting was fun..Have not done any of this with tube rolling, outside of replacing some older, suspect tubes... not searching for the holy grail here - but am embracing the miracle of tube sound ...

 

[gadget73]

doubt it honestly. The circuits were designed around bogey examples of a tube, and brand selection was likely done just by bid. Tube rolling didn't seem to have become a "thing" until way after the hey-day of tube gear. I've read a number of old magazines and articles and never have I seen any mention of using a specific brand of tube for any sonic reason. Back then the idea was to make the components as invisible as possible, it was all about low distortion and flat response with some amount of reliability in the mix. Cap types and resistor styles were rarely specified unless it had some very specific reason.

 

[StepheK]

doubt it honestly. The circuits were designed around bogey examples of a tube, and brand selection was likely done just by bid. Tube rolling didn't seem to have become a "thing" until way after the hey-day of tube gear. I've read a number of old magazines and articles and never have I seen any mention of using a specific brand of tube for any sonic reason. Back then the idea was to make the components as invisible as possible, it was all about low distortion and flat response with some amount of reliability in the mix. Cap types and resistor styles were rarely specified unless it had some very specific reason.

Which is why I think with some of the more complex designs from the tube heyday, PP amps with a lot of NFB and their goal of transparency, tube rolling probably doesn't change things much. But for some of the simple DIY, especially SE amps that aren't so transparent, tube rolling can change the sound a lot. Honestly I personally don't want a tube amp that sounds just like a SS amp. And I love I can fine tune the sonics by dropping in different tubes.

 

[halkaloogie]

The more components in a circuit, the less each component change will make a noticeable difference. With a very simple circuit each tiny change can make a huge difference. It all depends on what you're dealing with.

 

[Palustris]

doubt it honestly. The circuits were designed around bogey examples of a tube, and brand selection was likely done just by bid.

Yes, I worked in a electronic manufacturing company 40 years ago. Engineers would design a circuit around specific parts based upon their specifications. They would tell "purchasing" who were part of manufacturing what they need as samples. Purchasing would acquire the parts as samples. The engineer would then build and test the circuits. Once the circuit design was finalize, purchasing would get bids on the part from several vendors and the design would go to manufacturing to build.

I was a lowly technician passing and failing circuit boards, but I was friends with the VP of manufacturing and the women in purchasing. Taking the opportunity, I asked purchasing to get me several different values of Sprague Vitamin Q capacitors for an amp I was building at the time. These caps were very expensive intended for aero-space and critical applications. I was embarrassed to receive a telephone call (in the printed circuit board test room in manufacturing) from the manufacturer's representative a few weeks later to find how the components were working in our "prototype" and how many units we were expecting to order. With the cacophony of the manufacturing floor in the background, I told the rep that he parts worked well, but the project had been cancelled.