[project86]

I find that really interesting, as I've heard variations of that same idea from other folks over the years - but to me it doesn't seem to work that way. I generally hear it as sounding the same regardless of gain settings, though once in a while I hear the lower settings as sounding better.

I wonder if the volume control involved makes a difference? We could be getting different results based on the Alps pot versus the Relay-based design. Who knows.

 

[S Crowther]

I find that really interesting, as I've heard variations of that same idea from other folks over the years - but to me it doesn't seem to work that way. I generally hear it as sounding the same regardless of gain settings, though once in a while I hear the lower settings as sounding better.

I wonder if the volume control involved makes a difference? We could be getting different results based on the Alps pot versus the Relay-based design. Who knows.

I have an idea that the different voltages of the pre-gain settings affects the output impedance and so the performance of different headphones.

 

[project86]

I have an idea that the different voltages of the pre-gain settings affects the output impedance and so the performance of different headphones.

Interesting theory, but the output impedance is so low as to be a non issue in pretty much all situations. Even if it increased/decreased by a significant percentage, it wouldn't make a difference. Unless it is changing by a factor of 10x or something.

 

[fdg]

Hello everybody.

The Pre-Gain setting will no have any influence on the output impedance of Niimbus US 4 (+) amps.

I also often heard that people like the "sound" of a specific gain setting better than other settings - but not neccessarily 0 dB.
For my opinion there is no technical reason for that behavior.
But there might be a reason for a different sound for differing positions of the volume control.
This concerns the standard one with the potentiometer, not the relay controlled volume.

The Pre-Gain is affecting the gain of the pre-amp stage. More gain will affect the gain-bandwidth-product, meaning the upper frequency corner.
But the Pre-Gain levels are so low that these effects will take place at frequencies of 200 kHz or above.
Less gain will not have any effect on the frequency reponse of circuitry.

Cheers, Fried

 

[fdg]

... by the way, please see attached the manual from Niimbus HPA US 4+
US 4+ Manual 2018-en-2.pdf

 

[Pharmaboy]

Yup Violectric amps strangely sound better on higher gain settings... I tried many time -6db setting on my V280 and it never sounded as good as 0 setting no matter what volume i set on -6db. Maybe not demanding headphones sound good on any setting...

Wow. You guys are concerning me here. I had to knock down the gain of my V281 a lot (-12 dB on both gain-switch arrays) to make it bearable/usable as both pre-amp & headphone amp. My DAC's output (NOS 19) is 2.5V, which is ~25% higher than typical...regardless, I lived w/a "gainy" system for too long, had too few of those 128 steps actually usable. It had to change.

I have a very good sounding passive volume controller...suppose I could wire it in between the DAC & V281 to knock down the input gain, allowing the gain on V281 to be adjusted upwards. But usually adding gear/wire risk making the sound worse.

??

 

[Pharmaboy]

Interesting theory, but the output impedance is so low as to be a non issue in pretty much all situations. Even if it increased/decreased by a significant percentage, it wouldn't make a difference. Unless it is changing by a factor of 10x or something.

It's not like I did focused listening at high vs lower gain on V281--to specifically compare sound at gain settings. That would be pretty challenging, requiring gain matching (for equivalent levels) on top of the gain matching I began with.

• For what it's worth, I recall no striking/apparent sonic differences at higher gain than low...

I adjusted gain purely as a tactic to knock down overall system gain & make the V281 more usable IMS. Thanks to the V281's superb feature set & flexibility, it was easy to do for both the pre-amp out and the headphone outs. And now it sounds terrific, as usual.

 

[ken6217]

It’s a coincidence for me reading these posts regarding the gain settings. I had been using -12 since I received the V281 about 6 months ago and never tried any other setting. This is with the Ether Flow Open and a DAC with 6V output. So the other day I had listened to a friends LCD4 and needed to change the gain setting as it wasn’t loud enough. So after I switched back to my Ether Flow, I left the amp at -6 pre gain. The difference in sound was dramatic. Huge sound stage and smoother. Almost like I was listening to speakers. I listened the next day with fresh ears and the same thing. I played a lot of songs that I am very very familiar with from both Tidal and ripped CD’s and they all sound so much better. I haven’t tried it at the 0 gain setting yet but I’m extremely happy how it sounds now.

I spoke with Arthur at Violectric to tell him and be said there were similar posts on Headfi now regarding this subject.

Wow, I have new found love of this amp.

 

[ken6217]

I should add that my amp does not have the relay.

 

[project86]

Interesting, thanks for your impressions.

I also wonder if it may have something to do with the DAC rather than the amp.... not sure what DAC you are using at the moment, but I know I've heard differences on some models when they have variable output settings. So a 2V DAC output might have a different flavor (for better or worse) than cranking it up to 4V or higher. Messing with the pre-gain on the amp just matches the incoming signal better but the change really comes down to the DAC.

I dunno, just an idea.

 

[S Crowther]

Interesting, thanks for your impressions.

I also wonder if it may have something to do with the DAC rather than the amp.... not sure what DAC you are using at the moment, but I know I've heard differences on some models when they have variable output settings. So a 2V DAC output might have a different flavor (for better or worse) than cranking it up to 4V or higher. Messing with the pre-gain on the amp just matches the incoming signal better but the change really comes down to the DAC.

I dunno, just an idea.

You may be right. Changing the V281 pre-gain settings with a chord TT made a big difference for me but with a terminator dac not much at all.

 

[ken6217]

Interesting, thanks for your impressions.

I also wonder if it may have something to do with the DAC rather than the amp.... not sure what DAC you are using at the moment, but I know I've heard differences on some models when they have variable output settings. So a 2V DAC output might have a different flavor (for better or worse) than cranking it up to 4V or higher. Messing with the pre-gain on the amp just matches the incoming signal better but the change really comes down to the DAC.

I dunno, just an idea.

The setting on the DAC didn't change. The only variable is the gain setting on the amp itself which I changed. Maybe it's a combination of the gain setting and volume position.

The difference in sound is the same as if I swapped a new (better) component.

 

[project86]

Very interesting - still not sure of the mechanism behind this, but I'm glad you are getting an improvement regardless!

 

[CoLdAsSauLt]

@ rgs9200m

Your questions:

3. Meaning of the different gain switches
Due to the very low internal gain of US 4+ (-4 dB for unbalanced operation / +2 dB for balanced operation) it is neccessary to preparea high amount of gain in case of low level input sources combined with low efficiency headphones.
This is achieved by 2 x +12 dB gain, giving +24 dB gain as a result.
All three light-on-dark switches are acting around the input circuitry
while the dark-on-light switch will push +12 dB gain inside the power amp circuitry.
By combining these switches eight meaningful gain settings are possible to cover virtually all sources and all headphones
whilst maintaining lowest noise and maximum attenuator travel - these are : -15 / -12 / -6 / 0 / +6 / +12 / +18 / +24 dBr

Thank you, Fried

I'm a lawyer, which probably explains why I have difficulty trying to wrap my mind around the technicalities.

But I was wondering what the difference is between gain and amplification.

Am I correct when I say gain is about voltage and amplification about current?

Seems like by keeping the amp section as pure and lowest noise as possible, more parts are needed in the gain (preamp) section to compensate for that? Is this a better place then for the signal to be manipulated?

Makes me think that an even more improved ultimate US4+ doesn't have the relay volume control at the end in the amp section, though controls the volume solely through the gain in the preamp (which for some reason seems to be chosen as the better option now too for the US4+, be it only 8 volume settings are available.

Or I could be plainly wrong, oversimplifying things like this.

John, @project86, I thoroughly enjoyed reading your review, as usual. Thank you for your splendid efforts that will serve as a little amp encyclopedia to me for quite some time to come. Have you had a chance to hear the Benchmark HPA4 by now for some comparison with the US4+? I'm quite curious as I keep seeing good impressions popping up on the former.

Thanks!

Stijn

 

[mlxx]

But I was wondering what the difference is between gain and amplification.
Am I correct when I say gain is about voltage and amplification about current?

No, gain is just the amount of amplification as a ratio of output to input. So 1V in to 10V out would be 10 times or 20dB voltage gain. You can have voltage gain, current gain, power gain, etc.

Seems like by keeping the amp section as pure and lowest noise as possible, more parts are needed in the gain (preamp) section to compensate for that? Is this a better place then for the signal to be manipulated?

You can have one or many amplification stages, depends what you are trying to achieve. The last stage sometimes has low voltage gain, high current gain, and low impedance.
If you had 3 stages of 10x, 10x, and 1x, voltage gain, if the 1st stage was noisy, then the noise would be amplified by all the remaining stages too. Ideally you want all low noise stages but especially the first stages. The noise gets amplified as well, a small noise the at input becomes a very large noise at the output.

Makes me think that an even more improved ultimate US4+ doesn't have the relay volume control at the end in the amp section, though controls the volume solely through the gain in the preamp (which for some reason seems to be chosen as the better option now too for the US4+, be it only 8 volume settings are available.

The gain settings are just there to better match all the different type of sources/headphones out there, not as a volume control as such but it allows for better range on the volume.
The volume control is usually at the start not the end but some actually do what you describe above, https://www.psaudio.com/pauls-posts/the-gain-cell/
Depends on the implementation what is better.