Do tube preamps put out noise?

[belgianbrain]

Got a new tube preamp, a Schiit Freya.

I've had my Freya for over a week and love it.

Being new to tube preamps, I do have a question, though, considering tube preamps and noise. It is typical for a tube gain stage to add noise to the signal?

Source: Yggdrasil
Preamp: Freya, connected to Yggy with balanced cables
Power Amp: either Bryston 3BSST or Yamaha B2

If I connect the Freya to either power amp with single ended cables (quality, blue jeans cables), when Yggy is idling, the speakers sound absolutely silent when Freya is in passive or JFET buffer mode. BUT, when you switch Freya to tube mode, you notice a hiss coming from the mid range and a hum coming from the woofer. It's not loud but clearly perceptible when you're standing directly next to the speakers. The noise volume does not change with volume control on Freya.

If I connect Freya to the Bryston using balanced cables, the noise is still only in tube mode there but it becomes almost imperceptible. You have to put your ear right next to the drivers to even detect it.

If I'm going to use the Bryston with this setup, I don't really care because I'll just use balanced cables. But I'd also like to use the Freya with the B2. The noise coming from the speakers with the singled ended cables connecting Freya and power amp is enough that it dissuades me from using my B2 in this setup.

I've tried swapping tubes, but it doesn't really change the noise.

Is this just par for the course with tube preamps, or should I be looking for a problem somewhere?

 

[Hi-FiGuy]

I don't have experience with your pre but I did buy a Elekit TU-8500 tube pre amplifier kit, it had a hiss that I could not figure out. I tried changing the tubes, and I got the noise to diminish a bit but it was still there and it sounded like tape hiss. I have fairly efficient speakers and sensitive ears and this was very annoying, I ended up selling the amp. I have heard other tube pre amps without noise, I guess its just the design of a few on the market.

 

[gadget73]

Noisy tubes do tend to make a hiss. Could be other components not up to snuff, or just too much gain. They are not automatically noisy though.

 

[ZOOM]

All preamps output noise, all amps period, do. It's best to omit the preamp entirely, as literally all it can do is add noise. The shorter the signal, the better.

 

[kward]

Where are the components plugged in relative to one another? The hum may be coming from a ground loop. You could try temporarily plugging all of your components into a single power strip or power source and see if that eliminates the hum. If it does, then it is indeed a ground loop caused by different ground voltage potentials between the locations where the components are normally plugged in. Freya in passive mode may not participate in the ground loop. Balanced cables may mask the ground loop because balanced circuits reject common mode nose. Seems a plausible explanation anyway, then again, may not change a thing which means problem is somewhere else.

 

[airtime]

My Conrad Johnson preamp and Latino ST-70 are dead quiet. I mean NO noise!

With RCA jumpers for the preamp inputs and NO signal going into your amp, listen if the noise is coming from your amp. Which is common even for SS amps.

Then add the preamp and see if the noise level increases with the source unplugged. Then add the source and notice the noise level.

 

[Palustris]

All preamps output noise, all amps period, do. It's best to omit the preamp entirely, as literally all it can do is add noise. The shorter the signal, the better.

OK, that's not a popular assertion in audio circles. Sadly, it is the truth.

That said, every component the signal goes through adds some noise and distortion, even though it might be infinitesimally small. Every gain stage adds some noise and distortion to the signal; so the clever audiophile will work out a gain structure for his entire signal chain. We know we have 2VRMS coming from the CD player because that's the Red Book standard. We should know what the input sensitivity of our power amp is because that is one of the basic specifications. The average power amp has an input sensitivity of about 1VRMS and in fact the manual for the Bryston 3B SST states that the input sensitivity for single ended input is 1VRMS. So, it should be obvious that if we have 2VRMS coming from the CD player is can already drive the amp to clipping (max power) with 6dB of headroom.

So why not punch a hole in the front panel of Bryston and install a 100k volume control? Well, that would ruin the re-sale value. So if the goal is the cleanest and clearest sound, then the best alternative is to use a CD player with an integrated volume control directly into the amp.

 

[sKiZo]

First things first ... try cleaning and re-tensioning your tube sockets to ensure the best possible connection. True even with a brand new piece of equipment. Also make sure any and all OEM shields are in place properly.

 

[Vint Age]

The shorter the signal, the better.

 

[sKiZo]

... but ya gotta listen real fast ... <G>

 

[nj pheonix]

I've found certain tube pres with certain amps are dead silent (ears next to driver). Other amps (with more gain) pick up hiss (thermionic emission noise). While a noisy tube can certainly make an otherwise silent system noisy. Some properly working gear can have hiss. Just my observation.

 

[belgianbrain]

All preamps output noise, all amps period, do. It's best to omit the preamp entirely, as literally all it can do is add noise. The shorter the signal, the better.

I've pretty much tried it all over the years. I've had good luck with passive preamps, but with a tube based DAC. With solid state based DACs, I find passive attenuation tends to kill the dynamics of the music.

The Schiit Freya allows you to switch between passive, JFET buffer, and tube amplifier.

Passive sounds a bit dull and lifeless. JFET buffer sounds excellent. BUT, tube mode (with good tubes) sounds positively sublime, with added dynamics and a special character to the space in the music. IMHO, a good preamp is worth the added complexity.

I just hope I can bring down the noise of the tube mode a notch so I can rotate in my B2 from time to time.

 

[mdrums]

I've pretty much tried it all over the years. I've had good luck with passive preamps, but with a tube based DAC. With solid state based DACs, I find passive attenuation tends to kill the dynamics of the music.

The Schiit Freya allows you to switch between passive, JFET buffer, and tube amplifier.

Passive sounds a bit dull and lifeless. JFET buffer sounds excellent. BUT, tube mode (with good tubes) sounds positively sublime, with added dynamics and a special character to the space in the music. IMHO, a good preamp is worth the added complexity.

I just hope I can bring down the noise of the tube mode a notch so I can rotate in my B2 from time to time.

Hi, did you ever figure out the issue with the hiss and hummm in tube mode? I'm considering the Schiit Saga or Freya preamp for my small office system. I don't want issues just want,to,plug up and it work. Thanks!

 

[belgianbrain]

Hi, did you ever figure out the issue with the hiss and hummm in tube mode? I'm considering the Schiit Saga or Freya preamp for my small office system. I don't want issues just want,to,plug up and it work. Thanks!

Yep - it just depends on the quality of the tubes! Good tubes are quiet - no hiss, no hum. Crappy tubes are noisy. You can get quiet or noisy tubes in any variety - it's just the luck of the draw. Ebayers selling cheap tubes are usually selling noisy tubes. Just buy tubes guaranteed to be quiet and you're good to go.

 

[mdrums]

Thanks belgianbrain for the response. So many will have an issue but never say if or if not and what the fix was. Thanks much appreciated!

 

[triode17]

I just looked at the specs. for the Freya and the JFET buffer has a signal to noise ratio of 110dB. The tube pre produces a SNR of 95dB. THerefore, it will sound noisier by 15 dB. Since your amp doesn't have a volume control, it's being amplified at maximum potential power, which you may hear.
My ques. to you is, how far up can you turn the preamp volume before music becomes too loud? As someone else suggested, you may need to add a volume control before the power amp. to match the levels better. That would cut down any amplified residual noise.
My own question to Shiit is, what type of plate resistors are used on the tube sections? I had a microphone pre. that got noisy at high gain settings (55-60dB). Solved the problem by replacing the carbon film plate resistors with metal film resistors.