TASCAM UH-7000 as headphone amp (or how to understand amp specs)
Jul 5, 2020 at 11:27 AM Thread Starter Post #1 of 9

RGBeatman

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Hello, audiofolk. Fisrt time posting here, and I have a doozy for you all.

My interface is a TASCAM UH-7000 and My Headphones are Sennheiser HD600. The Tascam has no problem driving the HD600's, and by that I mean that I rarely have to turn the volume knob past 12 o' clock. But I never verified whether the Tascam was a good fit for the Senn's before buying. So a few days ago I got curious and read the Tascam manual and found that the only information regarding the headphone amp is this tiny and confusing (for me) sentence:

Maximum output: 45mW + 45mW or higher (THD+N 1% or less, into 32 ohm load)

Now, I know that this isn't a dedicated headphone amp but I was still surprised that that is the only information provided on the manual.

So my main question is: Are those specs good for the HD600 or do I benefit from a Schitt amp or something similar to get the most of my HD 600?

But beyond that, What does "45mW + 45mW or higher" mean?

I used a Headphone Power Calculator (https://www.headphonesty.com/headpho...er-calculator/) to better understand de HD600 power needs. It states that the SENNs, with
a sensitivity of 105 DB(1VRMS) and 322 OHMS impedance, require 10 mW or 1.82 volts RMS to achieve 110 DBSPL of loudness or 34mW (3.19 volts RMS) for 115 DBSPL.


Somewhere I read that 115db of loudness is ideal for soft/old music (and I do listen to a a lot of old jazz, samba, tango)

Are the stated 45mW in the Tascam per channel (45mW left and 45mW right)? Is it 45mW divided by two?

The Magni 3 specs in contrast: Maximum Power, 300 ohms: 410mW RMS per channel. Thats less than 1/2 a watt per channel.

How many wats per channel are ideal for the HD600 and can we know how many wats per channel the Tascam has based on: 45mW + 45mW or higher (THD+N 1% or less, into 32 ohm load?

Woe is me.

I know thats more than one question and a bit all over the place, but I hope its fun enough for those of you with a good understanding of these technical concepts to help out a newbie.
 
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Jul 5, 2020 at 2:32 PM Post #2 of 9

gimmeheadroom

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If the output is linear which often it is not, then we expect around 4,5 mW / channel at 300 ohms. SPL for the 600s is shown on Sennheiser site as 97dB, much less than the 105 dB you quoted. On paper, the device is extremely underpowered.

The Sennheiser 600 is unusual in that it often gets loud enough without enough amp but sounds lifeless or dull. I cannot recommend entry level schiit but a used Valhalla 2 with the right tubes is a good match. The HD 600s scale incredibly, the more quality power the amp has, the better they will sound.
 
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Jul 5, 2020 at 6:28 PM Post #3 of 9

RGBeatman

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The Sennheiser 600 is unusual in that it often gets loud enough without enough amp but sounds lifeless or dull
Dang. I've been using this setup for 3 years now. I feel like a fool. I figured since they were loud enough, the amp was ok. Whats more, I recently ordered a pair of LCD-X, looking for something more detailed than the HD600, but it sounds like I will have to invest in a dedicated amp if only for the HD600 (the LCD-X are suposed to be way easier to drive).

Which tubes would you recomend for the Valhalla? Would the Little Dot MK2 be a good choice?
 
Jul 6, 2020 at 2:51 AM Post #4 of 9

gimmeheadroom

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Dang. I've been using this setup for 3 years now. I feel like a fool. I figured since they were loud enough, the amp was ok. Whats more, I recently ordered a pair of LCD-X, looking for something more detailed than the HD600, but it sounds like I will have to invest in a dedicated amp if only for the HD600 (the LCD-X are suposed to be way easier to drive).

Which tubes would you recomend for the Valhalla? Would the Little Dot MK2 be a good choice?

I think a lot of people are not getting the most out of their 600s. Wait and see :)

I don't have tube recommendations and the Valhalla 2 is ok for a used price, just mentioned it since you asked about schiit. There is a huge tube rolling thread for the Valhallas here, if you get one you will get lots of good advice. I don't know about the Little Dot amps. Depending on your price range people can make suggestions, check in the full size amps threads.

I have LCD-2C and they are easier to drive. But I still think an Audio Interface is not going to do a good job with most hifi headphones.
 
Jul 6, 2020 at 9:57 AM Post #6 of 9

gimmeheadroom

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I will do that. Thanks for the advice.
What do you use to drive your HD600 (assuming you own them)?

Yes, I have the 600s and 800s. I run them both out of a Violectric V280. They 600s also do well out of a Meier Corda Jazz-ff and ok on a Valhalla 2.
 
Jul 7, 2020 at 9:25 AM Post #7 of 9

tomb

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Hello, audiofolk. Fisrt time posting here, and I have a doozy for you all.

My interface is a TASCAM UH-7000 and My Headphones are Sennheiser HD600. The Tascam has no problem driving the HD600's, and by that I mean that I rarely have to turn the volume knob past 12 o' clock. But I never verified whether the Tascam was a good fit for the Senn's before buying. So a few days ago I got curious and read the Tascam manual and found that the only information regarding the headphone amp is this tiny and confusing (for me) sentence:

Maximum output: 45mW + 45mW or higher (THD+N 1% or less, into 32 ohm load)

Now, I know that this isn't a dedicated headphone amp but I was still surprised that that is the only information provided on the manual.

So my main question is: Are those specs good for the HD600 or do I benefit from a Schitt amp or something similar to get the most of my HD 600?

But beyond that, What does "45mW + 45mW or higher" mean?
No, those specs are NOT good. 45mW + 45mW is simply a way of showing that the amplifier has two channels (stereo) and they are quoted with power per channel.

More importantly, those power figures are quoted at 1% THD. This means that is the power available at clipping and 1% is well within the range of actually seeing the clipping distortion of the wave on a scope. That is one of the least stringent ways available to specify amplifier power. 1% distortion from an amplifier is probably not even listenable with a pair of reasonable quality headphones. So, the actual power (most stringently rated at RMS power from 20-20kHz) is much less, perhaps by as much as one-half of that 45mW.

Further, the power specs are quoted at 32ohms. The Senn is 300 ohms (nominal). That implies that the Tascam is oriented toward lower impedance loads. All combined, the low impedance orientation plus the quoted power at 1% distortion means the power could be as low as 11mW per channel, a very low amount.

I used a Headphone Power Calculator (https://www.headphonesty.com/headpho...er-calculator/) to better understand de HD600 power needs. It states that the SENNs, with
a sensitivity of 105 DB(1VRMS) and 322 OHMS impedance, require 10 mW or 1.82 volts RMS to achieve 110 DBSPL of loudness or 34mW (3.19 volts RMS) for 115 DBSPL.

The headphonesty site says to take that calculator with a pinch of salt. I recommend you use at least a fistful. I tried increasing the loudness value in that calc for the HD600 to equal the sensitivity rating and got 4mW required. Why is that when the sensitivity is shown as 1mW at 105dB (the same?). Does this mean the dB for sensitivity is not the same as the dB for loudness? That must be the case if the calculation is correct. There are many different ways to specify dBs. However, if they are different, then what is the usefulness of the calculation? Which is telling you how loud the headphone will go and what does that mean? It seems senseless to use one type of dB rating for sensitivity and then use another for loudness. How does that help anyone?

What is also not mentioned is that impedance in the Senn is not constant. It hits a peak of around 550 ohms at 100Hz. This means if your headphone amplifier is not prepared to respond with volts instead of current, you are going to hear the headphone as bass-deficient. It is notable in your situation that an amplifier (such as the Tascam) is optimized for producing current with low impedance loads, rather than voltage with high impedance loads.

Somewhere I read that 115db of loudness is ideal for soft/old music (and I do listen to a a lot of old jazz, samba, tango)

You should search for another reference on loudness. Headphonesty seems inconsistent in that regard.
Are the stated 45mW in the Tascam per channel (45mW left and 45mW right)? Is it 45mW divided by two?

As noted above, it's simply a way of specifying power for two channels. Yes, they are saying 45mW per channel. However, note again what I explained above. This is not power quoted at RMS values, but at 1% THD, which is about the most liberal way to quote power that there is (probably the same as "Music" power, an old amplifier spec trick).

The Magni 3 specs in contrast: Maximum Power, 300 ohms: 410mW RMS per channel. Thats less than 1/2 a watt per channel.

At least note that this quoted at RMS and at 300 ohms, almost 10 times what the Tascam was quoted at 1% distortion and at 32 ohms. A typical solid-state amplifier will put out twice the power at half the impedance. IOW, just changing the impedance spec for power could reduce the 45mW per channel of the Tascam down to 10W or less (depending on the actual topology involved).

How many wats per channel are ideal for the HD600 and can we know how many wats per channel the Tascam has based on: 45mW + 45mW or higher (THD+N 1% or less, into 32 ohm load?

An HD600 can be powered quite well at 250mW or less, if the voltage produced by the amplifier is sufficient at 300 ohms. You can't really know what the Tascam produces for the Senn, unless you actually measure it. However, you can make reasonable estimates as I've done above.

Woe is me.

Not really - you're asking the right questions. That's a big step. :)
Refer to this for a great reference of measurements for the HD600:
https://www.innerfidelity.com/images/SennheiserHD600.pdf

I know thats more than one question and a bit all over the place, but I hope its fun enough for those of you with a good understanding of these technical concepts to help out a newbie.
 
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Jul 11, 2020 at 1:12 PM Post #8 of 9

RGBeatman

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Yes, I have the 600s and 800s. I run them both out of a Violectric V280. They 600s also do well out of a Meier Corda Jazz-ff and ok on a Valhalla 2.

Oh wow, that Violectric V280 is so powerfull. The Valhalla, though, is right about my pricerange right now. I've spent the last few days reading reviews on it and some other amps. It's a wide ocean of amps and specs, out there! So far the Asgard 3 sounds the most appealing to me. Found an extensive thread here about it and it's seems like its apt for my headphones.

No, those specs are NOT good.

Wanna hear something funny? I got a pair of Audeze LCD-X 3 days ago. So to compare them a bit with the HD600 and my monitor speakers I plugged the Tascam interface into a small Mackie mixer I have to easily mute the monitors and switch between headphones. With both headphones I quickly noticed that the mixer was outputting more bass than the interface. On the one hand I'm shocked at myself for spending all this time without proper amplification and on the other hand I'm still surprised at how well these headphones sound even with anemic power.
 
Jul 11, 2020 at 2:19 PM Post #9 of 9

RGBeatman

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What is also not mentioned is that impedance in the Senn is not constant. It hits a peak of around 550 ohms at 100Hz

That explains why opinions on HD600 bass response are so disparate from one review to the other all over the internet; some saying it has no bass at all and others saying it has very nice lows.

An HD600 can be powered quite well at 250mW or less,

Would that mean that, ideally, I would need an amp that provides around 250mW at 550 ohm to reach the bass potential of the Senns? If so, It seems like the Asgard 3 would be a nice fit for me (Maximum Power, 300 ohms: 600mW RMS per channel, 600 ohms: 300mW RMS per channel )

I've done more math these past 2 days than in the past 2 years (heck, even 10 years!) Following the 30 Hz Square Wave InnerFIdelity chart, I was trying to convert mW to Volts to figure out how much volts amplifiers provided. I couldn't reach satisfactory conclusions as I have no idea what I'm doing :poop: haha.
 

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