Guitar amp tubes or 'hifi' tubes? (Mullard or Sovtek)

[MeloManiac]

I need a backup set of tubes for my Leben Hifi CS300. Originally, this Japanese tube amp came with NOS Sovtek tubes (pre-amp and power tubes). The previous owner replaced them, when one of the originals went bad, with a complete set of Genalex Gold Lions.

 

The CS300 was engineered with the Sovtek tubes in mind, so that seems to be the rational path to follow. The Sovtek EL84M (M stands for military grade) are my choice, together with the 12AX7LPS (longplates). These are highly appreciated for hifi, and are great value for money, and built to last. These are new tube.

 

I 'm also looking at Mullard tubes. These are popular among guitarplayers  because of distortion in the highs. This to me seems the opposite of what a hifi tube should do, but some people have posted positively about the mellow sound they add to the music in their hi-fi amp. And this, of course, has triggered my curiousity. The CS300 has a tendency to reduce the highs, I should add.

 

So... Mellow Mullard or Neutral Sovtek?

I'd love to here your opinion and experience on this matter.

 

PS

I put two Sovtek EL84M tubes in my CS300, and they glow brighter and get warmer than the original Sovteks. Would that be an issue?

 

 

[seti]

Mullard tubes are NOT distorted in the highs. It is all in how tubes are used driven. Certainly guitar amps are not built to same end as hifi.

 

 

[captainbeefheart]

These questions are a can of worms but I will give it my best.

 

The EL84M is really 6P14P Russian tube which is electrically similar to the EL84 but has higher voltage and dissipation ratings. The EL84M/6P14P is similar to the 7189 tube.

 

I am not sure if you are talking about the current production Mullard or vintage Mullard but they are apples and oranges. If you are talking about the current production Mullard then I would hands down choose the EL84M/6P14P tube as it will last the longest in the amplifier. If you are trying to purchase vintage Mullard EL84 tubes they are very expensive and do not think you will gain any sonic improvements with that amp, so again the EL84M/6P14P is the smart choice.

 

As for sound, you have a hifi amplifier that uses more feedback vs guitar amplifiers, also guitar amplifiers are driven into overdrive which is where the chimey high frequency comes into play with any true pentode. You will not be driving this amp into overdrive. Your amplifier is designed to meet a specification with any functioning EL84, the feedback keeps the slight tolerance differences at bay which is hallmark of good engineering. I.e. I highly doubt you will hear any sonic differences between the two types of power tubes once correctly installed and biased the same.

 

As for the Sovtek tube that ran hotter and glowed brighter, the glowing most likely has nothing to do with anything, depends how much of the heater is showing from within the cathode, some tubes are just brighter than others unless you are talking about the plates glowing red which is bad but I doubt your situation. You cannot just swap power tubes without checking bias and making sure it is within the design parameter. The Sovtek you installed most likely were running higher bias current and needs to be biased after installation. If you cannot perform this safely I suggest you bring your amp to a tech that can properly install and bias your new set of power tubes.

 

In short go for the Russian 6P14P-EV variant, the EL84M is a 6P14P but not the same as a 6P14P-EV, the EV is long life and more rugged, sturdier construction with slightly even higher ratings vs the 6P14P/EL84M. Or if you have the money get some really nice NOS RCA 7189 tubes and they should last a very long time, but the 6P14P-EV are damn close and will also last a very long time.

 

 

 

 

[thebes]

If it's already a mellow sounding amp, swap out the long plates for some Telefunken's.

 

IMO, the real major sonic differences in tube swapping lie in the driver tubes, not the power tubes.

[mjcmt]

On 11/29/2021 at 2:27 AM, MeloManiac said:

I 'm also looking at Mullard tubes. These are popular among guitarplayers  because of distortion in the highs. This to me seems the opposite of what a hifi tube should do, but some people have posted positively about the mellow sound they add to the music in their hi-fi amp. And this, of course, has triggered my curiousity. The CS300 has a tendency to reduce the highs, I should add.

 

So... Mellow Mullard or Neutral Sovtek?

I'd love to here your opinion and experience on this matter.

 

I have Mystere EL34 tube amp made by PrimaLuna and have tried ElectroHarmoix and Mullard. ElectroHarmonix have a warmer and easier listen, the re-issue Mullard have a more detailed and cutting sound w/ my amp. I prefer the EH w/ my amp and 3 different speakers. I've always thought Mullard were supposed to be warm but the new re-issue are not. I've read the new EH have that old Mullard sound and I believe it from my experience.

[pepper3589]

I'd lean towards sticking with Sovtek for the neutrality, especially given the amp's engineering with those tubes in mind. The brighter glow and warmth could indicate higher output or biasing differences, but it shouldn't be an issue as long as performance remains stable and sound quality is unaffected.

Edited February 20 by pepper3589

[MassiveG]

I had to choose between different tubes for my amp and it wasn't easy. You want something that sounds great, lasts long, and is worth the money. I found a forum online full of people who understand amps and tubes. They explained how Sovtek tubes are super reliable and give a clear sound, while Mullard tubes have a warmer, softer sound that some folks really like because it add a special vibe to the music. This helped me decide to go with Sovtek because they were originally made for my amp and seemed like a safer bet.

 

 

 

Edited February 25 by MassiveG