PrimaLuna EVO and Tube Rolling
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trainbuftony
Electron Herder
Often, they don't.
There's nothing different about anything, many power tubes use the same pin out, if the builder selects the cathode resistor or sets the bias such that the amp will work and bias up with any power tube in it from that series.
Better amplifiers will give you a means of adjusting bias so that each tube can work its best in circuit.
Better still is an amplifier that was designed to make low distortion, hi fidelity sound with a specific tube type.
Often the transformer is chosen and the circuit optimized for a specific type of output tube, you should use that tube type rather than sub in something that's going to disturb the apple cart with regards to the original builders intentions.
My advice.
Tube rolling is a slippery slope to a mental disease. If you can afford it, great, many people who can't afford it get sucked in by the flowery language but have no way to objectively tell if the tubes they just carelessly stuffed in are even working. Often they're not. They are often mismatched old, worn out, tubes. For these people the magic is in the distortion and artifacts left by running grossly mismatched and downright dead tubes. These folks amplifiers often can't make even 1 watt before distortion. They'll throw a fit if you try and tell them they need new tubes. They spent thousands rolling to find the perfect set, but the perfect set doesn't work, produces terrible distortion and rounds off the frequency extremes. My long winded advice. Don't get involved. Before you spend any money on rolling tubes, you should spend a few bucks on the equipment with which to test your equipment. If you're not taking measurements, you're not making improvements. Once you own this equipment, I think you'll find that the whole topic is a bunch of hot air.
There's nothing different about anything, many power tubes use the same pin out, if the builder selects the cathode resistor or sets the bias such that the amp will work and bias up with any power tube in it from that series.
Better amplifiers will give you a means of adjusting bias so that each tube can work its best in circuit.
Better still is an amplifier that was designed to make low distortion, hi fidelity sound with a specific tube type.
Often the transformer is chosen and the circuit optimized for a specific type of output tube, you should use that tube type rather than sub in something that's going to disturb the apple cart with regards to the original builders intentions.
My advice.
Tube rolling is a slippery slope to a mental disease. If you can afford it, great, many people who can't afford it get sucked in by the flowery language but have no way to objectively tell if the tubes they just carelessly stuffed in are even working. Often they're not. They are often mismatched old, worn out, tubes. For these people the magic is in the distortion and artifacts left by running grossly mismatched and downright dead tubes. These folks amplifiers often can't make even 1 watt before distortion. They'll throw a fit if you try and tell them they need new tubes. They spent thousands rolling to find the perfect set, but the perfect set doesn't work, produces terrible distortion and rounds off the frequency extremes. My long winded advice. Don't get involved. Before you spend any money on rolling tubes, you should spend a few bucks on the equipment with which to test your equipment. If you're not taking measurements, you're not making improvements. Once you own this equipment, I think you'll find that the whole topic is a bunch of hot air.
WOW! This is contrary to an awful lot of the conversations here and elsewhere, but I appreciate your perspective. My EVO 300i is coming with stock EL34s and I was wondering, and frankly a little skeptical, If I would hear the difference KT150s would make (as others have suggested I consider doing).
trainbuftony
Electron Herder
I'd be concerned that the power transformer designed for EL34s is not likely to have the extra capacity on the heater supply to feed those tubes on a long term basis. (they draw more current)
The bias surely will not be optimal.
If you're not prepared to modify the amp to alleviate these problems then you're probably best served by the tubes that it ships with. If your goal is High Fidelity, leave it alone.
If you want to create a personalized distortion generator, then nothing I or anyone else can say will deter you.
Do these people who claim these massive improvements give you any data? The evidence is easy to produce and interpret if in fact there is an improvement. My guess is that most of them don't own any measurement equipment with which to quantify the changes. They're relying on their ears and what the internet told them they're supposed to hear. When you begin to investigate these bizare claims on your test bench they collapse like a house of cards.
The bias surely will not be optimal.
If you're not prepared to modify the amp to alleviate these problems then you're probably best served by the tubes that it ships with. If your goal is High Fidelity, leave it alone.
If you want to create a personalized distortion generator, then nothing I or anyone else can say will deter you.
Do these people who claim these massive improvements give you any data? The evidence is easy to produce and interpret if in fact there is an improvement. My guess is that most of them don't own any measurement equipment with which to quantify the changes. They're relying on their ears and what the internet told them they're supposed to hear. When you begin to investigate these bizare claims on your test bench they collapse like a house of cards.
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PrimaLuna advertises that the EVO 300 and 400 units are compatible with KT88, KT120, KT150s in addition to the stock EL34s but they do not claim that the amplifiers somehow morph to take full advantage of the bigger tubes. That was the genesis of my original question. I sure do not want to spend the $$$ for new tubes, which may operate, but not to their full potential.
Your question about others showing their data was rhetorical, correct? I have not seen any data to support their suggestions. To be fair to them, I always understood their suggestions to be subjective and not objective.
Musictubes
Isaac
My rebuttal is this, tube rolling is fun. If having fun is “hot air” then I guess I live in the desert lol. Admittedly tube rolling puts you squarely into the audio gear as a hobby part of the audiophile world. I tend to switch between being a gear head and getting lost in the music. Once again, your hobby should be fun. If I were looking for better measurements I’d use solid state amps. The beauty of tube rolling is that I can have a system that sounds different by simply swapping tubes. Why have one system when I can have many? Plus you can often times save money by using alternative tubes. Many mainstream tubes have become crazy expensive.
From a technical perspective, rolling tube types will definitely change the amount and nature of the distortions the amp makes. Output tubes in particular specify the transformer load they perform “best” at. Here’s the thing, measurements are typically done into static, resistive loads whereas speakers are reactive, dynamic loads. They will typically have a range of impedances depending on the frequency and so present a constantly changing load to the amp. On top of that, every speaker is different and so can have a different effect on an amp. The key is that the tube is always the thing that is driving the voice coil, the transformer is just there to put it in the general ballpark of the appropriate load. This dynamic is why I believe there can be good technical reasons why different output tube types can sound better despite there being a mismatch on paper. The same goes for switching the transformer taps from 8 to 4 ohms.
To be clear there are three levels of tube rolling in my mind.
1) You try different versions of the same tube type. This is the safest and easiest thing to do. This is usually easier to do with input than output tubes. Different tubes sound different. IMO this exposes the lie that tube amps can be “tuned” to a specific tube type. I have yet to hear two tubes from different manufacturers sound the same even if they are the same type. I think some high feedback amp designs can minimize the difference but it is always there.
2) You can roll in equivalent tubes. For input tubes you can do things like use an adapter to use a pair of 6j5 or 6c5 tubes instead of a 6sn7. Electrically they are identical. 6550 instead of KT88? Go for it. The el34, kt77, and 6ca7 are all supposed to be the same. You could even go further afield and get adapters that run a pair of 6j7 or 6sj7 in triode instead of a 6sn7. Those are electrically identical to a 6c5. Adapters will also allow you to use 6kg6 instead of 6aq5/el84. If you want to go even crazier you can buy adapters that allow you to use different voltage heaters. 12sn7 are much less expensive than 6sn7. 4v, 11v, etc. Are even cheaper. Why go to all this trouble? Fun! See point 1, different tubes sound different. Plus these alternatives are usually quite a bit less expensive and can usually equal or surpass the more expensive options.
3) You can use different tube types altogether. This is most safely done with amps that the maker has given their blessing to do so. Dennis Had goes out of his way to tell you about all of the different tube types you can use in his KT88 Firebottle for both input and output. On the other hand, the maker of my preamp laid down the law and said that using anything other than 6sn7 (and equivalents) could damage it. It’s on you to do your homework to make sure you are staying within the limits of your power transformer (don’t just pop an ecc32 or bl63 into that 6sn7 socket!). This route is the riskiest and I usually don’t recommend going beyond what the manufacturer says you should do. On the other hand there is a whole world of possibilities…
Musictubes
Isaac
Typically amps that can use KT88 can also use the newer variants of kt90, kt120, kt150, etc. but they won’t generate any more power because you’re still using the same power supply. The same thing goes for using a 6l6gc or 7581a instead of a 5881. Just make sure you don’t go the opposite way! Don’t put in kt88 if the amp was made for kt120!
I am very familiar with the desire to spend money on different tubes. Bought a Primaluna Dialogue Two integrated probably 15 years ago. Same year bought some Tung-Sol KT120s, just had to have them. Tried them, they been sitting in a box for at least 14 years. Have been running NOS RFT EL34s in it ever since.
Musictubes
Isaac
I briefly mentioned a possible technical reason why different output tubes can improve performance in a previous post. To expand on that and address the “Where is your data?” question I’ll simply ask what data confirms to what things sound like? We don’t listen to resistors. Speakers have their own distortions that add and cancel distortions as well as present a varying load to the output tubes. And all of that varies not only with frequency but what combinations of frequencies the speaker is trying to produce as well as the amplitudes of those different frequencies. The interaction of electrical signals being turned into physical ones is insanely complicated. I’m not aware of any measurements that can capture or quantify what is happening. Ultimately we are not listening to the amplifier, we are listening to the amplifier driving the speakers.
Musictubes
Isaac
Yeah, there will ultimately be tubes you prefer over others and so the rejects end up sitting around. Of course you could sell the ones you aren’t using, lots of people could use those kt120s.
trainbuftony
Electron Herder
To be 100% clear, sound quality can easily be measured and quantified. For under $1000 a person can set themselves up to measure the performance of tube amplifiers then when a change is made you can compare what you measured before the change to what you measured afterwards to see if an improvement was made.
Doing so is a lot of work.
Slapping in different tubes and then going to your favorite social media to brag about them and the euphoric sound is comparatively much easier.
Are all of these people improving the performance of their amplifiers ir just changing it?
Like I said, before you spend any money on tubes you should equip yourself to know weather you're traveling forward or in reverse. I can tell you as a matter of fact that our minds will play major tricks on us, convincing us we hear differences in the same piece of music. More often than not it's just your fallable brain, doing its best to make sense of its surroundings.
You can easily drive yourself insane trying to pin the tail on the donkey, for what?
So you can convince yourself it sounds the best in your own mind?
Why not know what's easily knowable.
There's enough mystery in life, the real performance of your tube amplifier does not need to be a mystery.
Lavane
Lunatic Member
Lots of good info has been posted for the OP.
The amplifier in question was optimized for one tube type.
Using another tube type in an amp that wasn't optimized to use them probably isn't going to sound better. Your ears are the judge in the end though.
Here is what I found with one of my amps that's optimized for EL-34 types including KT-77's and 6CA7's. I tried four KT-88's in this amp since it can be biased to use them.
What I found was the KT-88's produced better bass, but I found the midrange lacking some. It sounded a bit recessed, and plain sounding is the best way I can describe it. I put the same KT-88's into mono blocks I have that are designed to use KT-88's and they sound great.
I would suggest trying different brands or tube types that the amp was optimized for if your wanting to roll some tubes. Like different EL-34's, KT-77's, and 6CA7's.
The amplifier in question was optimized for one tube type.
Using another tube type in an amp that wasn't optimized to use them probably isn't going to sound better. Your ears are the judge in the end though.
Here is what I found with one of my amps that's optimized for EL-34 types including KT-77's and 6CA7's. I tried four KT-88's in this amp since it can be biased to use them.
What I found was the KT-88's produced better bass, but I found the midrange lacking some. It sounded a bit recessed, and plain sounding is the best way I can describe it. I put the same KT-88's into mono blocks I have that are designed to use KT-88's and they sound great.
I would suggest trying different brands or tube types that the amp was optimized for if your wanting to roll some tubes. Like different EL-34's, KT-77's, and 6CA7's.
knotscott
Super Member
Perhaps I got lucky, but my Dyna/VTA went from very good, to better, then better yet after some tube rolling. Only once did it sound like a step backwards, and those tubes were promptly returned according to supplier policy. It's subjective, but I like what I like....I'm thrilled with the transition from tube rolling from 12AU7 driver tubes to 12BH7a, and EH EL-34s to GL KT-66, then to TS 7581A output tubes. I knew going in that each of the tube changes would work and was approved by the manufacturer. You'll never know unless you try.
trainbuftony
Electron Herder
There, I fixed it for you.
Until you own and use the test equipment you can't really contextualize how hilarious it is when people claim improvement by ear.
Once you've seen the reality of these "improvements" you can't unsee it.
So you lead the horse to water...
. Measurements and numbers are all that matter in this hobby, how you like the sounds of the changes you made does not 
trainbuftony
Electron Herder
That's not what I'm saying at all.
What I'm saying is that I've seen enough evidence on my end to suggest that we need to keep our fallable ears and imaginative minds in check by measuring things from time to time so that we can know that we're traveling in the right direction.
I've personally built an amplifier that makes 3/4 of a watt, nearly ten percent distortion, yet still sounded beautiful within its extremely limited range. It used 6sn7 as a power tube, and was built entirely of salvage. Given that I was running it on 100db/w efficient speakers it provided plenty of volume. Fact is it wasn't a very good amplifier, had I trusted strictly my ears, I'd have thought it sounded good enough and perhaps continued using 6sn7s as power tubes.
Reality: It sucked as a power amplifier and the correct thing to do is try something else.
I had to actually measure it, because to my ear it sounded OK.
This is but one example, I'll spare you the others. Protect the innocent and what not.
My personal experience dictates that owning a signal generator and distortion analyzer or a full on audio analyzer will really help to keep you on the true path and keep you from chasing rabbit holes that lead to lower performance rather than higher.
What I'm saying is that I've seen enough evidence on my end to suggest that we need to keep our fallable ears and imaginative minds in check by measuring things from time to time so that we can know that we're traveling in the right direction.
I've personally built an amplifier that makes 3/4 of a watt, nearly ten percent distortion, yet still sounded beautiful within its extremely limited range. It used 6sn7 as a power tube, and was built entirely of salvage. Given that I was running it on 100db/w efficient speakers it provided plenty of volume. Fact is it wasn't a very good amplifier, had I trusted strictly my ears, I'd have thought it sounded good enough and perhaps continued using 6sn7s as power tubes.
Reality: It sucked as a power amplifier and the correct thing to do is try something else.
I had to actually measure it, because to my ear it sounded OK.
This is but one example, I'll spare you the others. Protect the innocent and what not.
My personal experience dictates that owning a signal generator and distortion analyzer or a full on audio analyzer will really help to keep you on the true path and keep you from chasing rabbit holes that lead to lower performance rather than higher.
I know exactly what you are saying.
After operating and maintaining sound transmitting, receiving, processing, recording and playback gear as a career. Also the "how good can people hear" University studies I was involved in, and teaching the course developed from those studies. From experience, I just don't agree with your absolutism take. Human hearing and brains can be better test equipment than you "numbers" guys give them credit for.
And that's ok, we are allowed to have different opinions formed from our experiences.
I was just pointing out the obvious in my previous post. It's not a hobby for looking at test equipment, it's for using ears to listen to music.
I have done plenty of tube rolling with same type tubes, even the same type of tube from different manufacturers can have subtle differences, should they? No, do they? Yes
Too the thread, I would need to look at one of these auto bias ckts, something I have not done.
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Lavane
Lunatic Member
The 12BH7 is my favorite for the voltage gain tube in my VTA ST70.
I never did try any KT-66's, I thought about it though. In the end I liked the EH-6CA7 the best.
knotscott
Super Member
So if I'm the sole judge of how I want my system to sound, and once achieved after a 30 year pursuit, it sounds incredible to me....just the way I like it every time I listen on all the music I love most, you're suggesting I shouldn't trust my ears for that preference? I don't see the purpose of measuring at this point for my needs. It hasn't always been the case, or I wouldn't have pursued the improvements, but I'm more than satisfied.
Unlike an electronics or speaker manufacturer, I'm not marketing the sound I get, or trying to share it with others....I'm just listening to it, so how it sounds it to me is what matters most. There's no need for me to achieve a universal neutrality or compatibility so I can replicate it. I only need the components I have to work in the space they're in now. As flawed as it may actually be according to the test bench, there are no measurements necessary for me to enjoy it further, but I do get what you're saying.
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