Matching a 470 ohm headphone to 300 ohm headphone amp

[johny_2000]

I do wish that the phono preamp generated a bit more volume over the headphones

Here's where it come from:

• Headphone output power: 125mW(32Ω)/62.5mW(64Ω)/30mW(128Ω) * Ampapa A1 specs

Continuing this power/impedance line for your headphone range, we get the following: 125mW(32Ω)/62.5mW(64Ω)/30mW(128Ω)/15mW(256Ω)/8mW(470Ω). Based on the Audio-Technica ATH-R70x's 98 dB/mW sensitivity, we get the following sound pressure level at maximum volume for the Ampapa A1: 98 dB +20*log(8) = 98 dB + 18 dB = 116 dB. This is sufficient for most listening scenarios, in my opinion.

 

[johny_2000]

Then what is the "linear output" graph supposed to mean? I'm curious.

The Ampapa A1 has a headphone output jack on the front panel and line-level (RCA) output jacks on the rear panel. They use different amplification circuits and have different output parameters. The latter have worse characteristics than the former.

 

[solderdude]

Here's where it come from:

• Headphone output power: 125mW(32Ω)/62.5mW(64Ω)/30mW(128Ω) * Ampapa A1 specs

Continuing this power/impedance line for your headphone range, we get the following: 125mW(32Ω)/62.5mW(64Ω)/30mW(128Ω)/15mW(256Ω)/8mW(470Ω). Based on the Audio-Technica ATH-R70x's 98 dB/mW sensitivity, we get the following sound pressure level at maximum volume for the Ampapa A1: 98 dB +20*log(8) = 98 dB + 18 dB = 116 dB. This is sufficient for most listening scenarios, in my opinion.

Using Amir's measurements the R70X calculates to 104dB/V. Given the max. output voltage of 2V (headphone out) I calculate 110dB peak. That said given the compression I would say around 109dB peak SPL.
Still this is enough for most listening scenarios.

 

[johny_2000]

That said given the compression I would say around 109dB peak SPL.
Still this is enough for most listening scenarios.

Right! I calibrate my headphones' SPL to about 105dB for pink noise. For typical music mastered at -10dB(+/-) peak headroom, that's 85-95 dB max SPL, which is enough for fairly long listening periods (Permissible Exposure Time) without permanently damaging my hearing.

 

[solderdude]

that's 85-95 dB max SPL

you mean 85-95 average SPL with peaks reaching 105dB SPL with well recorded music.
Those peaks (depending on the recording) can be very short.

At these levels one usually doesn't listen to a whole album though (when you have some sense of protecting the hearing) but probably just one favorite song or so.

People listening to an entire album, on average, will be at around 70-75 average at 'active listening levels' and around 60-65 when listening to a few albums to relax.

Playing 'Texas holdem' for instance has merely 3dB dynamic range at several moments in that track.

105dB white noise is 105dB SPL average.

 

[johny_2000]

you mean 85-95 average SPL with peaks reaching 105dB SPL with well recorded music.

Yeah, right.

 

[DRich65]

Holy shit, that's really bad. Easily perceivable, severe lack of subbass. Isn't that one of the main points of using good headphones? Getting super deep bass response for cheap, the kind you'd have to pay thousands for if you wanted that from speakers and subwoofers? Hell, my old 8" bookshelves, 1000€ in 1999 moneys can do better than 45Hz at -3dB in a room.

The Ampapa, as Johnny 2000 mentioned, is just fine at attenuating bass and treble to my liking. Bass is nice but not everything. There is also things like soundstage, clarity and instrument separation which are impacted by too much bass. But if your listening preference is heavy sub bass, more power to you! We all are different. In my case, age also plays it's part as I have trouble hearing higher frequencies.

 

[johny_2000]

The Ampapa, as Johnny 2000 mentioned, is just fine at attenuating bass and treble to my liking. Bass is nice but not everything. There is also things like soundstage, clarity and instrument separation which are impacted by too much bass. But if your listening preference is heavy sub bass, more power to you! We all are different. In my case, age also plays it's part as I have trouble hearing higher frequencies.

If you like the sound profile of the Ampapa A1 Tube Phono Preamp but want a louder headphone response, you can pair it with a good headphone amp like the TOPPING L30 II or the JDS Labs Atom Amp 2. Both are excellent, compact, and affordable amps that will take your headphones to any sound pressure level you desire.
Both devices were reviewed here and showed excellent results:

Topping L30 II Review (Headphone Amp)

This is a review, detailed measurements and listening test of Topping L30 II. It was sent to me by the company and costs US $149. It comes in a number of colors. Usability could not be better with positive clicking switches for power/pre and gains. Three gains are provided with the low gain...

www.audiosciencereview.com

JDS Atom Amp 2 Headphone Amplifier Review

This is a review, listening tests and detailed measurements of the JDS Labs Atom Amp 2 headphone amplifier. It was sent to me by the company and costs US $129. The solid metal case makes an instant impression, erasing memories of the plastic case of the previous generation. A white LED...

www.audiosciencereview.com

 

[DRich65]

Thanks Johnny 2000. Perhaps soon I will look at one of those options. For now, Everytime I put these cans on my head, I am absolutely stunned by how great they sound on the A1. To think that they haven't even truly been pushed to their limits is enticing., to say the least. At $350 this is the most that I have spent on headphones. The most expensive that I have owned beforehand were the Hifiman HE 400's at, $109 I believe. These are amazing!

 

[johny_2000]

To think that they haven't even truly been pushed to their limits is enticing, to say the least.

There is such a possibility. Judging by the photo of the AMPAPA A1 board, the headphone amplifier is assembled on 6 planar transistors. I don't have exact information about their circuit diagram, supply voltage, and maximum output current. According to the specifications, the output voltage of the headphone amplifier reaches 2V max. It is likely that using a more powerful headphone amplifier (in terms of output voltage/current) will allow the Audio-Technika ATH-R70x headphones to produce a richer and more lush sound, especially during dynamic moments of music.

 

[DRich65]

The JDS Atom amp is the one I am leaning towards.

 

[johny_2000]

The JDS Atom amp is the one I am leaning towards.

This is a great amp. The Atom Amp 2's octo-buffers achieve over 2.6W (9.28Vrms) per channel! Much more headroom than the AMPAPA output.

 

[johny_2000]

The JDS Atom amp is the one I am leaning towards.

Based on its specifications:

With an output voltage of 9.2Vrms, it can deliver up to (9.2 * 9.2 / 470) * 1000 = 180 mW of power to your headphones. Compare this to the 8 mW output of the AMPAPA A1 .

 

[solderdude]

9.25V = 123dB peak SPL with dynamic compression I would expect 120dB peak with enormous amounts of distortion ... but at least the supplied signal will be clean