tube amp?

[Stan2292]

currently rocking a first gen schiit modi + magni stack from flea market. i'm looking to introduce some more colour into the sound. i've been looking at schiit vali 2++ but when i tested one in my local audio store, i could hear a clear white noise background when using IEM. do tube amps all have high noise floor? would it improve if i use an impedence plug on the IEM?

 

i'm planning to use the tube amp with my r70x and blessing 2 dusk. might also buy a sundara soon. would like some suggestions that don't break bank. budget USD$300-ish plus maybe $50 for a new tube if the stock one isn't great. cheers.

[Bananasplit_00]

Modern headphones, especially IEMs have an extremely high sensitivity, meaning any noise will be extremely noticeable and that its very hard to get a black background.

 

Using higher impedance headphones usually yeilds better results as tubes have high output impedance.

 

I'd probably turn to head-fi for good suggestions

[cmndr]

Not my area of expertise but have you considered just applying a filter to degrade the quality of your sound to make it more tube-like?

 

here's a thread on ASR that has some info and it looks like a few links to filters. 

 

https://www.audiosciencereview.com/forum/index.php?threads/is-it-possible-to-make-a-solid-state-amp-sound-like-a-tube-amp-pc-dac-speakers-setup.42245/

[Psittac]

Hybrid tube amps are your best bet, where just the pre-amp is tube and the amp is solid. xDuoo MT-602 and MT-604 are another option (I have the 602 and enjoy it on my lower impedance headphones).  But the Vali is hybrid so it shouldn't matter what impedance your IEM's are, being as the amplification is done solid state.  I don't own IEM's so I can't speak to that but I don't think they're commonly used with tubes.  Another option is to add a tube preamp to your stack with something like the MU-603

[spartaman64]

tube amps under 1000 arent really worth it imo unless you can diy. im building a sangaku right now and its around 400 dollars of components but some of them are hard to find. another popular one is bottlehead crack though ive never heard it so i cant speak on it

[Spuriae]

On 5/14/2023 at 6:34 AM, Stan2292 said:

do tube amps all have high noise floor?

Mostly yes, at least compared to similarly priced solid state amps. For example:

• Most tube amps have minimal noise rejection. This means that much of the power supply noise is injected directly into the signal.
• Tubes are large, low bandwidth, and low gain, meaning you can't use much feedback to reduce noise issues.
• Tubes require high voltages on the anode, which means that the power supply noise is typically significantly worse than on solid state amps due to how expensive and impractical those components are.
• Tubes are microphonic, turning physical vibrations into noise in the signal.
• Most tube amps use large transformers which can accidentally pick up or emit EMF if not well accounted for.
• Most tubes have a low current rating, which requires high value (high noise) resistors elsewhere in the circuit.
• Tube amps run hot, which increases thermal noise.

Tubes themselves aren't necessarily significantly noisier than transistors; it's the other compromises in the circuit design that are mostly responsible for the noise difference. For tube hybrid designs like Vali, it becomes highly dependent on the circuit itself, as there are ways to mitigate many of the tube's drawbacks by using other active components to compensate (though at that point the tube-ness of the amplifier can become questionable).

 

The Vali 2++ shouldn't have much noise in low gain (-114dBVrms); is it possible the model you tested was in high gain or had a bad tube?

 

On 5/14/2023 at 6:34 AM, Stan2292 said:

would it improve if i use an impedence plug on the IEM?

Usually yes. For most amplifiers the noise level is mostly independent of output level. If the impedance plug attenuates the signal by 20dB and you raise the volume by 20dB to compensate, then the noise level will fall by 20dB while the final signal level stays the same.

 

On 5/14/2023 at 6:34 AM, Stan2292 said:

would like some suggestions that don't break bank. budget USD$300-ish plus maybe $50 for a new tube if the stock one isn't great. cheers.

Would recommend trying more tube amps if possible before committing to a purchase, if the Vali was problematic. Vali is a fairly safely designed hybrid so if you had any issues with it, it's possible that a more purist tube amp might be problematic in other ways.

 

4 hours ago, spartaman64 said:

tube amps under 1000 arent really worth it imo unless you can diy. im building a sangaku right now and its around 400 dollars of components but some of them are hard to find. another popular one is bottlehead crack though ive never heard it so i cant speak on it

Nice, I hadn't kept up with what Pete Millett was doing in a while. Cool to see that he's still making new stuff.

[cmndr]

On 5/14/2023 at 6:34 AM, Stan2292 said:

 do tube amps all have high noise floor?

By definition yes. 
By objective measures such as SINAD solid state has been ahead of tube amps for decades. 

Some people LIKE how the distortion sounds. Think of it from a wabi-sabi perspective. 

It's the same reason why some people get distortion pedals for electric guitars... except you're doing it to your headphones. 

 

20 hours ago, Psittac said:

Hybrid tube amps are your best bet

I've heard that this can end up being the worst of both worlds, at least in some implementations (e.g. Schiit Vali 1). I have the vali 1 and am using it right now with HD800 headphones. I was young and impressionable when I got it... and it still works.  It's "fine"

 

 

 

[Psittac]

1 hour ago, cmndr said:

I've heard that this can end up being the worst of both worlds, at least in some implementations (e.g. Schiit Vali 1). I have the vali 1 and am using it right now with HD800 headphones. I was young and impressionable when I got it... and it still works.  It's "fine"

 

To the best of my knowledge hybrid's are the only way to get tubes on low impedance headphones, I might have heard of a few super high end tube amp's that could run low impedance but I wouldn't know what that requires from a design perspective short of going hybrid.  I have 3x full tube amp's and they're great, the xduoo is perfectly acceptable but the full tube experience is certainly OTL

[Spuriae]

1 hour ago, Psittac said:

To the best of my knowledge hybrid's are the only way to get tubes on low impedance headphones, I might have heard of a few super high end tube amp's that could run low impedance but I wouldn't know what that requires from a design perspective short of going hybrid.

There are plenty of full tube power amplifiers designed to power 4Ω and 8Ω speakers. The main difference is the use of power tubes instead of (or in addition to) the preamp tubes typically used in headphone amps.

1 hour ago, Psittac said:

the xduoo is perfectly acceptable but the full tube experience is certainly OTL

OTL = output transformer-less. Transistor output amps are technically a subset of OTL. Many of most popular full tube amps (e.g. Valhalla, Crack) also tend to be OTL, largely because good output transformers are expensive.

 

Tube purists will insist that the "full" tube experience is a single-ended triode amplifier with an output transformer.

[Stan2292]

7 hours ago, Spuriae said:

Mostly yes, at least compared to similarly priced solid state amps. For example:

• Most tube amps have minimal noise rejection. This means that much of the power supply noise is injected directly into the signal.
• Tubes are large, low bandwidth, and low gain, meaning you can't use much feedback to reduce noise issues.
• Tubes require high voltages on the anode, which means that the power supply noise is typically significantly worse than on solid state amps due to how expensive and impractical those components are.
• Tubes are microphonic, turning physical vibrations into noise in the signal.
• Most tube amps use large transformers which can accidentally pick up or emit EMF if not well accounted for.
• Most tubes have a low current rating, which requires high value (high noise) resistors elsewhere in the circuit.
• Tube amps run hot, which increases thermal noise.

Tubes themselves aren't necessarily significantly noisier than transistors; it's the other compromises in the circuit design that are mostly responsible for the noise difference. For tube hybrid designs like Vali, it becomes highly dependent on the circuit itself, as there are ways to mitigate many of the tube's drawbacks by using other active components to compensate (though at that point the tube-ness of the amplifier can become questionable).

 

The Vali 2++ shouldn't have much noise in low gain (-114dBVrms); is it possible the model you tested was in high gain or had a bad tube?

 

Usually yes. For most amplifiers the noise level is mostly independent of output level. If the impedance plug attenuates the signal by 20dB and you raise the volume by 20dB to compensate, then the noise level will fall by 20dB while the final signal level stays the same.

 

Would recommend trying more tube amps if possible before committing to a purchase, if the Vali was problematic. Vali is a fairly safely designed hybrid so if you had any issues with it, it's possible that a more purist tube amp might be problematic in other ways.

 

Nice, I hadn't kept up with what Pete Millett was doing in a while. Cool to see that he's still making new stuff.

thanks for the detailed answer. i watched a bit more vali reviews on youtube. apparently there's a switch on the back that toggles between high and low gain (presumeably switching bwteen tube mode and ss mode?). it's very possible that i tested IEM on high gain. i would love to test listen a wider variety but that will have to wait until i'm on holidays as i live in a medium small city with not much choice in terms of audio gear.