[FumblingFoo]

I have a quick question about the amount of power the v281 is able to deliver. Obviously I don't plan to listen any where near the max power the v281 is rated to deliver; I'm simply curious about what the testing is showing. So, the maximum input level for the amp is +21dbu, right? My v850 is set to deliver +18dbu balanced into the v281. For the test I had the amp set to +14.5db gain (6db + 12db pre-gain set). I used the Beyerdynamic T90 headphones 250ohm with a sensitivity of 102db/mw.

So, the v281 is rated to deliver I'm guessing around 4000mw per channel @ 250ohms balanced, right? That translates to about 2000mw per channel unbalanced, right? Well, at 2000mw the max spl should be around 135db, but by running the headphones with the volume at -30db in foobar2000 and the volume pot cranked all the way up on the v281, I was getting compensated max db figures around 140db (up to about 142db) out of my spl meter, which puts the per channel power at about 6300 - 10,000mw. I think I'm getting accurate measurements positioning the meter right next to the transducer, because listening levels become slightly unpleasant for me right at around 85db measured volume (the threshold for potential hearing loss) in the same position, and listening at 110db measured volume is EXTREMELY loud and very uncomfortable (120 db spl is supposed to be the threshold of discomfort, but a chainsaw at 1m is pretty uncomfortably loud too) . Also, even though the inner part of my ear canal is further away than the measurement instrument, the mass of my ear and skull are capturing a wider field of sound more efficiently than air from the transducer and concentrating that on my eardrum. Still, though, my methodology could be flawed and the actual spl a couple or so db lower.

I'm not about to field test that amount of power into my headphones, but the data presents a bit of a contradiction. Even with the extra 2.5db of power over what the manual specifies for the pre-gain, technically the v281 is running .5db within its limits because the signal I'm feeding into it via the v850 is 3db below max spec. So, the question is, will the v281 indeed deliver 6300mw per channel unbalanced @ 250ohms, or will the amp clip / severely distort or are my measurements just too loud?

 

[zhgutov]

I have a quick question about the amount of power the v281 is able to deliver. Obviously I don't plan to listen any where near the max power the v281 is rated to deliver; I'm simply curious about what the testing is showing. So, the maximum input level for the amp is +21dbu, right? My v850 is set to deliver +18dbu balanced into the v281. For the test I had the amp set to +14.5db gain (6db + 12db pre-gain set). I used the Beyerdynamic T90 headphones 250ohm with a sensitivity of 102db/mw.

So, the v281 is rated to deliver I'm guessing around 4000mw per channel @ 250ohms balanced, right? That translates to about 2000mw per channel unbalanced, right? Well, at 2000mw the max spl should be around 135db, but by running the headphones with the volume at -30db in foobar2000 and the volume pot cranked all the way up on the v281, I was getting compensated max db figures around 140db (up to about 142db) out of my spl meter, which puts the per channel power at about 6300 - 10,000mw. I think I'm getting accurate measurements positioning the meter right next to the transducer, because listening levels become slightly unpleasant for me right at around 85db measured volume (the threshold for potential hearing loss) in the same position, and listening at 110db measured volume is EXTREMELY loud and very uncomfortable (120 db spl is supposed to be the threshold of discomfort, but a chainsaw at 1m is pretty uncomfortably loud too) . Also, even though the inner part of my ear canal is further away than the measurement instrument, the mass of my ear and skull are capturing a wider field of sound more efficiently than air from the transducer and concentrating that on my eardrum. Still, though, my methodology could be flawed and the actual spl a couple or so db lower.

I'm not about to field test that amount of power into my headphones, but the data presents a bit of a contradiction. Even with the extra 2.5db of power over what the manual specifies for the pre-gain, technically the v281 is running .5db within its limits because the signal I'm feeding into it via the v850 is 3db below max spec. So, the question is, will the v281 indeed deliver 6300mw per channel unbalanced @ 250ohms, or will the amp clip / severely distort or are my measurements just too loud?

Your T90 can accept up to 200 mW according to specification. Haven't they exploded yet?

The manual tells what when you set the pre-gain to "+" values, the maximum level becomes less.

When you have 18 dBu at the inputs and +14.5 dB pre-gain you also have the amplifier gain, which is 8 dB in unbalanced mode, and 14 dB (8 + 6) in balanced mode.
So, you can get in theory 46.5 dBu = 163 V RMS = 107 W = 152 dB SPL in balanced mode. It is impossible in practice, because V281 has 40 VA for everything.
So, to prevent such conditions it has (at least) the current limiter. It also has half of the amplifiers in unbalanced mode, which may have it's own limits.

Anyway, taking in account 8 dB amplifier gain, you can get your ~142 dB, as measured with compensation.
Please note what the sensitivity of the headphones is not flat, and depends on the frequency.

 

[FumblingFoo]

Your T90 can accept up to 200 mW according to specification. Haven't they exploded yet?

LOL! They didn't explode but they were vibrating intensely (I only drove them to 110db spl @ 10mw).

The manual tells what when you set the pre-gain to "+" values, the maximum level becomes less.

Bummer, I was hoping to get a little extra juice into the amp without the risk of overloading it. But still the risk is negligible for me because such a level is far beyond my preferred listening volume. Still potentially useful for quieter music though.

When you have 18 dBu at the inputs and +14.5 dB pre-gain you also have the amplifier gain, which is 8 dB in unbalanced mode, and 14 dB (8 + 6) in balanced mode.
So, you can get in theory 46.5 dBu = 163 V RMS = 107 W = 152 dB SPL in balanced mode. It is impossible in practice, because V281 has 40 VA for everything.
So, to prevent such conditions it has (at least) the current limiter. It also has half of the amplifiers in unbalanced mode, which may have it's own limits.

Anyway, taking in account 8 dB amplifier gain, you can get your ~143 dB, as measured with compensation.

Thanks . According to my calculator at 140db for the T90 the load on the v281 would be 158.9 milliamps RMS @ 39.72 volts RMS, so I reckon that's still within the limits. My primary points of curiosity were that the Lyr 2 is quite a powerful amp, but the v281 on higher gain is not just a bit but a LOT more powerful than even the Lyr 2. Also, with 25W + 15W at, say, 70% efficiency for a class A/B amplifier (I believe the v281 is, right?), that leaves about up to 28,000mw of peak power (I know this isn't the same as RMS obviously, but I wonder if that translates to being what the peak db can be). All very interesting stuff, the v281's quite a bit more powerful than I thought it could be.

 

[zhgutov]

Bummer, I was hoping to get a little extra juice into the amp without the risk of overloading it. But still the risk is negligible for me because such a level is far beyond my preferred listening volume. Still potentially useful for quieter music though.

As I understand, the pre-gain stages are situated after the volume control, which only decreases the input signal.
So when you set the pre-gain higher to "get more juice", you also decrease the volume by the volume pot to get the same loudness.
In this case you have a smaller signal in the chain. And this brings the noise floor up (measurements confirm that).
I think that's why the general recommendation (which may be found at the first page of this thread) is to prefer lower pre-gain levels when possible.

Also, with 25W + 15W at, say, 70% efficiency for a class A/B amplifier (I believe the v281 is, right?), that leaves about up to 28,000mw of peak power (I know this isn't the same as RMS obviously, but I wonder if that translates to being what the peak db can be).

There are more things to power. Not only the power amp itself. And how can you get such large peaks?

 

[FumblingFoo]

As I understand, the pre-gain stages are situated after the volume control, which only decreases the input signal.
So when you set the pre-gain higher to "get more juice", you also decrease the volume by the volume pot to get the same loudness.
In this case you have a smaller signal in the chain. And this brings the noise floor up (measurements confirm that).
I think that's why the general recommendation (which may be found at the first page of this thread) is to prefer lower pre-gain levels when possible.

Yes, I almost always use -14dbu in normal listening, which leaves the volume at about 11 - 2 o'clock except for quiet recordings .

There are more things to power. Not only the power amp itself. And how can you get such large peaks?

Yeah, I'm definitely no electrical engineering expert, so I don't know how much power gets dissipated by the other circuitry (even when given a schematic). But as far as large peaks go, I think if, say, an amp has 1000mw RMS, then the necessary peak power is generally something like 2000mw. So if I was driving the v281 at 1400mw or 6300mw RMS, it would have to have to have enough reserve power to deliver 2800mw or 12600mw instantaneously for the peaks of the signal to avoid clipping. I'm sure that with the voltage at voltage and current RMS in spec, then the amp is designed for higher instantaneous values in peak loads.

 

[zhgutov]

Yeah, I'm definitely no electrical engineering expert, so I don't know how much power gets dissipated by the other circuitry (even when given a schematic). But as far as large peaks go, I think if, say, an amp has 1000mw RMS, then the necessary peak power is generally something like 2000mw. So if I was driving the v281 at 1400mw or 6300mw RMS, it would have to have to have enough reserve power to deliver 2800mw or 12600mw instantaneously for the peaks of the signal to avoid clipping. I'm sure that with the voltage at voltage and current RMS in spec, then the amp is designed for higher instantaneous values in peak loads.

I am not an electrical engineer too. Maybe someone will disagree with me, and will explain why.

HE-6 need ~500 mW to get 110 dB SPL. It is hard to get peaks higher than 3 dB above 0 dBFS.
So, it is enough even in the case when we have a movie set to 106 dB SPL.
It will be able to play the loudest, explosive parts of the movie easily, with power and transparency, because it has low THD, IMD, etc. at this levels.
And it plays such fragments exactly this way, but this is much much less than 10 or 20 W!

 

[sahmen]

I am not an electrical engineer too. Maybe someone will disagree with me, and will explain why.

HE-6 need ~500 mW to get 110 dB SPL. It is hard to get peaks higher than 3 dB above 0 dBFS.
So, it is enough even in the case when we have a movie set to 106 dB SPL.
It will be able to play the loudest, explosive parts of the movie easily, with power and transparency, because it has low THD, IMD, etc. at this levels.
And it plays such fragments exactly this way, but this is much much less than 10 or 20 W!

Since you bring up the extraordinarily hard to drive He-6 (50 ohms, 83.5db sensitivity), I wonder if you can help me determine what pre-gain setting would be ideal to drive it optimally. Currently, I use mine on the unity gain setting, and get to comfortable loudness levels at 11-12 o'clock on the volume dial. I like the way the he-6 sounds overall with these settings except for the bass, which sounds ever-so-slightly underextended, as compared to when the He-6 is playing either on my Bryston 2b LP via speaker taps, or on my Audiogd NFB1 amp. It is not really a problem I can't live with, as the bass is adequate at that level, and the rest of the frequency spectrum sounds sufficiently balanced. However, given the power and quality of the V281, I wonder whether I can draw a slightly more weighty bass response from it if I were to tweak the pre-gain settings a bit, either by increasing or reducing them by a few decibels. Up to this point, I have only ever used the V281 at unity gain.

 

[sahmen]

Here's a first response from Violectric USA to this query... He doesn't think the deterioration always occurs, but he needs to crosscheck my case with Fried and get back to me:

*************
"...I'm not sure I'll have to ask Fried who designed it.

Keep in mind he said "slight sound deterioration might occur depending on the following devices connected". He is saying 'might' with 'some' devices. If there is miss match in the combined load there could possibly be small degradation in sound quality.

A lot of very picky audiophiles use the V281 in the same fashion with speakers and subwoofers simultaneously utilizing both your RCA and XLR outputs at the same time. No one has ever noticed any degradation in sound quality. I really wouldn't be overly concerned about this.

I'll let you know what Fried says.
*******************

I shall post the follow-up response from Fried, if/when I receive it.

I have been told that Fried might post a response to this inquiry on this thread, and I can't wait to read what he has to say.

 

[zhgutov]

Since you bring up the extraordinarily hard to drive He-6 (50 ohms, 83.5db sensitivity), I wonder if you can help me determine what pre-gain setting would be ideal to drive it optimally. Currently, I use mine on the unity gain setting, and get to comfortable loudness levels at 11-12 o'clock on the volume dial. I like the way the he-6 sounds overall with these settings except for the bass, which sounds ever-so-slightly underextended, as compared to when the He-6 is playing either on my Bryston 2b LP via speaker taps, or on my Audiogd NFB1 amp. It is not really a problem I can't live with, as the bass is adequate at that level, and the rest of the frequency spectrum sounds sufficiently balanced. However, given the power and quality of the V281, I wonder whether I can draw a slightly more weighty bass response from it if I were to tweak the pre-gain settings a bit, either by increasing or reducing them by a few decibels. Up to this point, I have only ever used the V281 at unity gain.

Looks like you have perfect gain settings already.

As I remember, you have standard volume control on V281, right?

Unfortunately, I have not heard Bryston 2b LP or Audiogd NFB1.
What do you mean about underextended bass?
What do you mean about more weighty bass?

Have you tried to localize the problem?
Do you use the same DAC/outputs when you compare this units?
Do you have the same bass with both units, and different bass with V281?
Do you have the same loudness when you compare this units?

 

[sahmen]

Looks like you have perfect gain settings already.

As I remember, you have standard volume control on V281, right?

Unfortunately, I have not heard Bryston 2b LP or Audiogd NFB1.
What do you mean about underextended bass?
What do you mean about more weighty bass?

Have you tried to localize the problem?
Do you use the same DAC/outputs when you compare this units?
Do you have the same bass with both units, and different bass with V281?
Do you have the same loudness when you compare this units?

By "underextended," I simply mean that the bass on the He-6/V281 combo sounds just a wee bit thinner, and hits with slightly less impact when compared to either the He-6/NFB1amp or He-6 Bryston 2b LP combos. The NFB1amp is paired with an Audiogd Reference 5.32 DAC with the Amanero combo USB module installed on it, and the Amanero seems to have given the bass more enhancement, although the Audiogd DAC/Amp combo's bass with the He-6 has always been satisfactory.

The Bryston 2b LP is a 60 WPS speaker amp, which I often pair with my Emotiva DC-1 for use with the He-6, using the amp's speaker taps. The sound from the speaker taps has more weight and impact than the sound which comes out of the amp's headphone jack for the He-6. In this combination, I think the He-6 derives much of its viscerally impactful characteristics from the Bryston.

I do not mean to suggest that the V281 is inadequate for the job, as it drives the He-6 very well in all other respects. I'd probably not think anything was amiss, if I was not familiar with the way the He-6 sounds on the two other amps. Consciously or unconsciously, I tend to compare the He-6's bass impact on the V281, with its impact on the Bryston and the Audiogd amps, and that is what creates that effect of slightly light bass. Sometimes, I wish that tendency to compare didn't exist, frankly, but I can't help it.

 

[zhgutov]

By "underextended," I simply mean that the bass on the He-6/V281 combo sounds just a wee bit thinner, and hits with slightly less impact when compared to either the He-6/NFB1amp or He-6 Bryston 2b LP combos. The NFB1amp is paired with an Audiogd Reference 5.32 DAC with the Amanero combo USB module installed on it, and the Amanero seems to have given the bass more enhancement, although the Audiogd DAC/Amp combo's bass with the He-6 has always been satisfactory.

The Bryston 2b LP is a 60 WPS speaker amp, which I often pair with my Emotiva DC-1 for use with the He-6, using the amp's speaker taps. The sound from the speaker taps has more weight and impact than the sound which comes out of the amp's headphone jack for the He-6. In this combination, I think the He-6 derives much of its viscerally impactful characteristics from the Bryston.

I do not mean to suggest that the V281 is inadequate for the job, as it drives the He-6 very well in all other respects. I'd probably not think anything was amiss, if I was not familiar with the way the He-6 sounds on the two other amps. Consciously or unconsciously, I tend to compare the He-6's bass impact on the V281, with its impact on the Bryston and the Audiogd amps, and that is what creates that effect of slightly light bass. Sometimes, I wish that tendency to compare didn't exist, frankly, but I can't help it.

So, it looks like you have different sources for the different amps, right?
Can you compare this amps with the one source and outputs (for example, the same RCA out and the cable for everything)?
And with the same loudness.
If you don't have a measurement equipment to match loudness, you can make a series of comparisons with the slightly different volumes, where one of the amps achieves slightly more loudness, then another amp achieves slightly more loudness, and so on..

 

[ostewart]

My review is up, I'll post it on head-fi in a couple of days: http://www.soundperfectionreviews.com/2017/10/review-violectric-v281-fully-balanced.html

 

[FumblingFoo]

My review is up, I'll post it on head-fi in a couple of days: http://www.soundperfectionreviews.com/2017/10/review-violectric-v281-fully-balanced.html

Awesome review @ostewart, especially with the Hifiman Susvara headphones . It nice to see more reviews on the v281 rolling in; it's indeed a really nice amp .

 

[ostewart]

Awesome review @ostewart . It nice to see more reviews on the v281 rolling in; it's indeed a really nice amp .

It's a shame I don't have any higher end amps on me. I was listening to the Sennheiser HDVD 820 today, and the Violectric it better, but the Sennheiser is more flexible.

Violectric doesn't really colour the sound, it has a black background and very transparent sound yet still sounds superbly natural.

The Sennheiser is slightly smoother sounding and not quite as transparent.

 

[FumblingFoo]

It's a shame I don't have any higher end amps on me. I was listening to the Sennheiser HDVD 820 today, and the Violectric it better, but the Sennheiser is more flexible.

Violectric doesn't really colour the sound, it has a black background and very transparent sound yet still sounds superbly natural.

The Sennheiser is slightly smoother sounding and not quite as transparent.

Yeah, same here. The next best thing I have to compare it to is the Lyr 2 / Bifrost Uber, which is still a killer combo especially with nice tubes, but the v281 is still in another league imo (I used to think the two sounded the same until I got more practice listening). I notice with the v281, probably because of its transparency, low distortion, and excellent overall performance, it seems to be able to bring out the particular character very well of each headphone I try. This was a lot more noticeable when I added the DAT RS 05 to the stack.