Its not a limitation but what SPL levels are you trying to acheive? What cans are you intending to use with that output level?
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March Audio HPA1
- Thread starter Dialectic
- Start date
I don't think I have cans needing more than 4V RMS, but it's not about myself, it's about the specs that sells the product. Now, depends to what "audience" you want to sell the HPA1 headamp, but from what I see on the market "more is better", no matter it will distort on the highest gain setting. 
Whilst I am sure you can find a pathologically insensitive headphone if you try, I think 4 V rms is more than enough for the vast majority of cans
A few examples @ 1v
HD650 103dB
HD800 102dB
LCD-X 108dB
Oppo PM1 110dB
HiFiMan HD500 99dB
Beyer DT880 101dB
B&W P3 114dB
Grado SR80 116dB
A few examples @ 1v
HD650 103dB
HD800 102dB
LCD-X 108dB
Oppo PM1 110dB
HiFiMan HD500 99dB
Beyer DT880 101dB
B&W P3 114dB
Grado SR80 116dB
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Fostex T50RP-mk3 power needed, based on Tyll's measurements and calculated with Digizoid.
Hifiman HE-560 power needed, based on Tyll's measurements and calculated with Digizoid.
Beyerdynamic DT880 600 Ohms version - power needed, based on Tyll's measurements and calculated with Digizoid.
Peaks of around 115dB for few ms are sometimes welcome, when some of us want to listed louder for few minutes. Also, when listening to normal average levels of 80-85dB SPL, that still means peaks between 95-105dB SPL, depending on music's compression rate. A good to read article would be here: http://nwavguy.blogspot.com/2011/09/more-power.html, although is more related to the output power and to the actual gain, which might be better to be related to 1V RMS input source instead of 2V RMS sources (seems that HD600 needs 4.16V RMS to hit 115db SPL based on Digizoid and https://www.innerfidelity.com/images/SennheiserHD600.pdf).
You might want to make HPA1 compatible with 1V RMS input sources as well. I listen to lot of -3dB music (jazz, classic etc.) that really need a higher gain, especially when listening to HE-560, but also on Fostex T50-RP mk3 and DT880 600 Ohms cans.
A headamp should be more powerful that the headphones, so amp's distortions to not sum up with headphones distortions. There's a great article on that matter on Audioholics, where they explained very well why a power amp needs to be more powerful as the speakers. Also, I really think a headamp should be able to get all of my cans up to the insane 120dB SPL level, even if I'll never use such an amount of power. It's about that power reserve that most of us sleep better if we know it's there; it's like when you purchase a car able to speed up too 250 km/h, even if you never get over 160km/h on the highway.
If you have an easy way to increase the gain on the HPA1, then doing this might be a good thing, at least from a marketing perspective. After all, most customers will only read the specs and compare them with other headamp.
P.S.: I have a headamp around LME49720 + LME49600 that outputs a clean output 1KHz power of 7.02V RMS at max. gain. With HE-560, but especially with the DT880 600 Ohms, when I listen to old jazz music (around -3...-4dB SPL) I sometimes find myself that the volume knob got to the max., even if in my ears the power if not so high. It happens with classic, rhythm & blues and other genres too (usually with music recorded before the "loudness war").
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View attachment 25391
Fostex T50RP-mk3 power needed, based on Tyll's measurements and calculated with Digizoid.
View attachment 25389
Hifiman HE-560 power needed, based on Tyll's measurements and calculated with Digizoid.
View attachment 25390
Beyerdynamic DT880 600 Ohms version - power needed, based on Tyll's measurements and calculated with Digizoid.
Peaks of around 115dB for few ms are sometimes welcome, when some of us want to listed louder for few minutes. Also, when listening to normal average levels of 80-85dB SPL, that still means peaks between 95-105dB SPL, depending on music's compression rate. A good to read article would be here: http://nwavguy.blogspot.com/2011/09/more-power.html, although is more related to the output power and to the actual gain, which might be better to be related to 1V RMS input source instead of 2V RMS sources (seems that HD600 needs 4.16V RMS to hit 115db SPL based on Digizoid and https://www.innerfidelity.com/images/SennheiserHD600.pdf).
You might want to make HPA1 compatible with 1V RMS input sources as well. I listen to lot of -3dB music (jazz, classic etc.) that really need a higher gain, especially when listening to HE-560, but also on Fostex T50-RP mk3 and DT880 600 Ohms cans.
A headamp should be more powerful that the headphones, so amp's distortions to not sum up with headphones distortions. There's a great article on that matter on Audioholics, where they explained very well why a power amp needs to be more powerful as the speakers. Also, I really think a headamp should be able to get all of my cans up to the insane 120dB SPL level, even if I'll never use such an amount of power. It's about that power reserve that most of us sleep better if we know it's there; it's like when you purchase a car able to speed up too 250 km/h, even if you never get over 160km/h on the highway.
If you have an easy way to increase the gain on the HPA1, then doing this might be a good thing, at least from a marketing perspective. After all, most customers will only read the specs and compare them with other headamp.
P.S.: I have a headamp around LME49720 + LME49600 that outputs a clean output 1KHz power of 7.02V RMS at max. gain. With HE-560, but especially with the DT880 600 Ohms, when I listen to old jazz music (around -3...-4dB SPL) I sometimes find myself that the volume knob got to the max., even if in my ears the power if not so high. It happens with classic, rhythm & blues and other genres too (usually with music recorded before the "loudness war").
Having been a qualified noise officer, dealing with people with hearing damage and trying to prevent it, I would with the greatest of respect suggest that you *really dont* want your cans to go up to 120dB or even 115dB as you suggest above. The exposure time before potential damage at those levels is surprisingly short. In many countries the HSE 8 hour exposure (LAeq,8h) limit is 85 db(A) . Every 3db increase above that you half the time.
So 115dB(A) will be 30 seconds !
I have tested the amp with a range of cans and it certainly goes loud !
@Dialectic
I had to make a late revision to the design to account for the requirements of a potential professional customer and provide a selectable 0dB and +6dB gain options to cover them and the wider domestic requirements. The final production candidate PCB was finished on Monday and should be arriving here tomorrow.
I will need to do final testing but Im expecting that board to be final design to go into production. Due to adding the gain switch I have also had to revise the milled aluminium casework. Final drawings should be going off the the machining company also tomorrow. Their lead time is 2 weeks. After receiving the cases we are good to go
Pricing is not finalised yet as I need to know the final BOM for the quantity I am going to manufacture, but expect it to be in the region of $350 US
I had to make a late revision to the design to account for the requirements of a potential professional customer and provide a selectable 0dB and +6dB gain options to cover them and the wider domestic requirements. The final production candidate PCB was finished on Monday and should be arriving here tomorrow.
I will need to do final testing but Im expecting that board to be final design to go into production. Due to adding the gain switch I have also had to revise the milled aluminium casework. Final drawings should be going off the the machining company also tomorrow. Their lead time is 2 weeks. After receiving the cases we are good to go
Pricing is not finalised yet as I need to know the final BOM for the quantity I am going to manufacture, but expect it to be in the region of $350 US
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Render minus power switch and headphone socket
Thank you, I'm aware of that, but probably most of us are getting peaks over 110dB when we listen at high volume (for few minutes or so). I say few ms peaks, not average.
My average listening loudness is somewhere around 80-85dB, which might create peaks up to 105dB.
105db - 110db peak is about right when cranking it up. Normally under 95db peak. It's also depending on dynamic ofnthe music. RMS should be 85 or so. Using the peak value to calculate amp power is ok.
Most headphones are actually rated at 100mw. So theoretically and practically 100mw low distortion with all types of load is good enough.
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I think he meant the equipment. BK is known to have very high precision and can last for years without big shift after one calibration. Cheap mics can't last and cheap level calibrators are inaccurate themselves.
BK = professional tool
Looking, finding very expensive...
Looking, finding very expensive...
They are indeed super expensive.
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Question. If there's no volume knob... can you use bitperfect audio? Say in Windows or Linux.
Not using BP audio would be a no go for me...
Not using BP audio would be a no go for me...
If your computer does a reasonable job with digital volume control it should be fine. In some cases you can have the volume control in the DAC. So if your DAC has volume control you can send BP to the DAC and then the DAC will do stuff to control the volume. Most DACs are Delta-Sigma so it gets transformed anyway.
I'm using jRiver with ASIO (not on MarchAudio DAC, but similar XMOS transport chip) and I am able to control the internal volume. I think ESS's datasheet worth reading: http://www.esstech.com/files/3014/4095/4308/digital-vs-analog-volume-control.pdf.
P.S.: I guess you could add a cheap passive preamp between your DAC and headamp, if really worried or...old school.
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I'm using jRiver with ASIO (not on MarchAudio DAC, but similar XMOS transport chip) and I am able to control the internal volume. I think ESS's datasheet worth reading: http://www.esstech.com/files/3014/4095/4308/digital-vs-analog-volume-control.pdf.
P.S.: I guess you could add a cheap passive preamp between your DAC and headamp, if really worried or...old school.
Yes, or... you know, use an AMP with volume knob? I'm not looking forward to putting more devices on the signal path.
I get that 32 bit representation makes the errors in turning down the digital volume negligible. But I still would like BP to avoid interruptions from other sound sources and avoid remixing when there's more than one event taking place.
I'm not sure if I can turn the digital volume down on Linux, too
I guess this is exactly what HPA1 designer had in mind too: less devices in the signal path.
Of course you can, just give it a try on a Linux live distro.
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