?CJ Pre gain and tube life

[medward0]

Hi all,

Awhile ago, I was grousing about the tube life in my ET3SE...it seems that the tube is quiet for only a few months and then starts to get noisey.

I've got a DAC with a variable output and I usually keep the gain there relatively low and use the pre for most of the gain as I prefer that sound, especially with the new Sophias (although that is changing as they break in).

So for a moderate volume in the room is about 50 on the pre's volume indicator.

While I can get all OCD about which device provides how much gain and how that affects the sound, I wonder: Does pre gain have anything to do with tube life?

Thanks for any thoughts.

[Hatzudokiseizo]

Originally Posted by medwardo

Hi all,

Awhile ago, I was grousing about the tube life in my ET3SE...it seems that the tube is quiet for only a few months and then starts to get noisey.

I've got a DAC with a variable output and I usually keep the gain there relatively low and use the pre for most of the gain as I prefer that sound, especially with the new Sophias (although that is changing as they break in).

So for a moderate volume in the room is about 50 on the pre's volume indicator.

While I can get all OCD about which device provides how much gain and how that affects the sound, I wonder: Does pre gain have anything to do with tube life?

Thanks for any thoughts.

Hello Quote....

The Volume in the Room of 50 is very very High..In my CJ equipement in Bi-Amping,I manage at times Volume 8, maximum 20. .. but at 50 I fly off the roof ...

In the tubes with high gain it has influence on the life! The higher the shorter.
Greets Sounding Chris

[medward0]

Originally Posted by Hatzudokiseizo

Hello Quote....

The Volume in the Room of 50 is very very High..In my CJ equipement in Bi-Amping,I manage at times Volume 8, maximum 20. .. but at 50 I fly off the roof ...

In the tubes with high gain it has influence on the life! The higher the shorter.
Greets Sounding Chris

Thanks Chris...sounds like I've been shortening the tube's life by using the pre to do so much gain. Whew! Now I'm not so worried about why my pre was burning through tubes...it wasn't, but I was!

[ronenash]

Originally Posted by medwardo

Hi all,

Awhile ago, I was grousing about the tube life in my ET3SE...it seems that the tube is quiet for only a few months and then starts to get noisey.

I've got a DAC with a variable output and I usually keep the gain there relatively low and use the pre for most of the gain as I prefer that sound, especially with the new Sophias (although that is changing as they break in).

So for a moderate volume in the room is about 50 on the pre's volume indicator.

While I can get all OCD about which device provides how much gain and how that affects the sound, I wonder: Does pre gain have anything to do with tube life?

Thanks for any thoughts.

I will try to explain as this is not easily done. First and foremost you are mixing terms. Preamp or tube gain does not change with volume control. The volume control merely changes the level of signal reaching the amplification circuit in the preamp. With that cleared, the volume control has virtually zero effect on tube life in a preamplifier. Unlike power amplifiers where the volume you are listening at has a dramatic effect on the current flowing through the tubes and thus on their "life", in a preamp the currents are very low and volume will have very little effect on tube life.

Now about the gain discussion; An amplifiers gain in a tube amplifier is defined by the tube selected and the circuit design. CJ designs their preamps with zero feedback and thus the gain is relatively high (typically between 20 and 26DB). A high gain design will surface tube imperfections, such as noise coming from tube manufacturing imperfections, in a more pronounced way. The same tube that becomes noisy in the ET3 will probably work as a driver tube in a power amplifier without a problem. For this exact reason you need preamp grade tubes for use in preamps where the tubes are selected for low microphonics and low noise.

Now for the ET3 noisy tube discussion. This discussion has been going on for a while and you can search AA for the details. To make a long story short there was a defective batch of tubes from EH that became noisy after a few hundred hours of use. You can call CJ to see if your tube is from that batch and possibly get a replacement or you can purchase a good tube from vendors such as Upscale Audio and live happily ever after. A good tube should last 3-5 years based on how much time you spend listening to music.

Hope this help clarify things somewhat.

[ronenash]

One more thing. Always keep the volume level on source components such as your DAC at the maximum when going into the preamp. This will keep noise levels and resolution at the max. Lowering the volume on the DAC will limit resolution and just induce more noise.

[Joe Appierto]

Thank you, Ron, for the explanation. It was clear, useful and helpful.

[Hatzudokiseizo]

r. A good tube should last 3-5 years based on how much time you spend listening to music.

Hope this help clarify things somewhat.[/QUOTE]


At 3-5 hours daily in operation to the tubes are then replaced after 4-5 years depending on performance mode ... I changed me after 4 years the tubes in my MV75 ... Sounds Chris

[medward0]

Originally Posted by ronenash

One more thing. Always keep the volume level on source components such as your DAC at the maximum when going into the preamp. This will keep noise levels and resolution at the max. Lowering the volume on the DAC will limit resolution and just induce more noise.

Thanks Ronenash, both this and your explanation above were very helpful. I appreciate you taking the time for the explanation and I'll turn my DAC output up.

On the noisey EH tubes...ironically, the factory EH lasted longer than just about any other tube that I put in the ET3 before it started to get noisey. I think it lasted 4 months or something; a GL lasted only a few months; a gold EH has been in for about a month and is beginning to hiss now.

I'm eager to try a Matsushita / National PCC88 / 7DJ8 tube in the pre, but it sounds like I need to go the route of buying some tubes from CJ and seeing how those do before I assume that something is wrong with the pre. I think that CJ would want me to do that first.

Thanks again.

[ronenash]

At least when you buy from CJ the tubes are guaranteed for a few month. Hopefully if they turned out noisy it will be within that period.

I had to replace many tube that got noisy in the ET3SE. When I got the Matsushita 7DJ8 it lasted over 6 month and was still going strong when I sold the ET3SE to get the ACT2. The Mat 7DJ8 also sounded substantially better to my ears.

[Joe Appierto]

Originally Posted by ronenash

At least when you buy from CJ the tubes are guaranteed for a few month. Hopefully if they turned out noisy it will be within that period.

I had to replace many tube that got noisy in the ET3SE. When I got the Matsushita 7DJ8 it lasted over 6 month and was still going strong when I sold the ET3SE to get the ACT2. The Mat 7DJ8 also sounded substantially better to my ears.

If the Matsushita 7DJ8's are like their 6922's, and they probably are, they were made with Mullard tooling. It's no wonder they sound so good.