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Amir's TODO thread

amirm

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#81
Good news. It got the purchases it needed to hit $179 so there is good demand for this. Will be a very interesting comparison to Topping D30.
 

drconopoima

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#82
One of the units I find most interesting is the SMSL Sanskrit Pro-B, it is as fully featured as a DAC gets, with coax, SPDIF, Bluetooth, and has what as far as I've reviewed specifications is the most popular DAC chip inside, the AK4490EQ also present in the JDS Labs OL DAC, SMSL M8A. If the Pro-B it's as good as the Topping D30 it's the ultimate dedicated DAC, nothing more to ask for.

Another review that may be interesting is testing the output impedance of SMSL amps. I've stayed away from their amps as some unsourced Amazon reviews pop here and there saying they all have 10 OHM output impedance, and I plan to use several 32 to 60 ohm headphones with them, only headphones I have that wouldn't be affected by the sound signature or the bass is my HD 600 and my upcoming on April HD6xx. I also plan to buy a DT880 but as a Venezuelan just getting out of my country last year I have to get a bit of responsibility and wait to earn more money to pull the trigger (don't worry, as an engineer living in Spain I'm not on risk of welfare or anything).

From the products you already have, I would be interested if the JDS Labs published results for the OL DAC hold up. I've already ordered it to test subjectively myself.
 

amirm

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#83
Thanks for the suggestions. I am measuring the output impedance of all headphone amplifiers.

I have other requests for JDS Labs OL DAC so I will test that next. :)
 

stunta

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#84
Amir, which DAC do you plan to review after the OL DAC? May I suggest the Topping DX7 because its in that middle-of-the-road price range which is neither "bargain" nor "high-end" but has good features. Software volume control is great, but launching the app each time to do that is a pain, so the DX7 which has a physical remote is quite attractive at this price point.
 

mindbomb

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#87
In the headphone community, a lot of people buy certain dacs, like the modi 2, topping d30, and ol dac, with their complementary headphone amps - the magni 3, topping a30, and o2 headphone amp. Now that we have reviews for the dacs (which have been tremendously valuable), if you did a roundup of those amps, we'd have the complete picture on what to recommend headphone users looking for stuff at this price.
 

amirm

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#88
In the headphone community, a lot of people buy certain dacs, like the modi 2, topping d30, and ol dac, with their complementary headphone amps - the magni 3, topping a30, and o2 headphone amp. Now that we have reviews for the dacs (which have been tremendously valuable), if you did a roundup of those amps, we'd have the complete picture on what to recommend headphone users looking for stuff at this price.
That's important feedback. Please keep on top of me to deliver :).
 
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#89
I definitely agree with mindbomb. I'm looking for a good amp now that I've read some of your DAC reviews and I'd love to see what you can find.
 

Candlesticks

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#91
The most value is going to be in budget DAC and amp products. People who are buying more expensive products that don't have a feature advantage are not going to care how good or bad the measurements are. If a Schiit Mjolnir turns out to measure poorly it's not going to matter beyond credibility to that brand.

My suggestions for products to measure for headphones would be these:

Fiio products. Good value and high portability make them a versatile product for people who just bought their first pair of decent headphones. As Fiio products have line out functionality it makes them a good stepping point to a high power amplifier for any less sensitive headphones they may purchase in the future.
  • Fiio Q1 - Portable. DAC and Amp. Own battery. 1.5Vrms line out. A lot of people want to use a portable DAC/Amp combo with their android smartphone which makes this a better choice than the Fiio E10K.
  • Fiio Q1 MK2 - Not really an upgrade to the Q1. More of a sidegrade with a balanced IEM focus and weaker unbalanced power output that makes it less attractive to people outside of balanced IEM owners. Line out is unbalanced.
  • Fiio Q5 - A lot of different inputs in a portable package. Modular amplifier section that can be swapped.
Other DAC products I'd recommend measuring are:
  • Sabaj DA2 - I think it's the same as the SMSL iDEA but I don't know. It's small, has 2Vrms output, asynchronous, <1Ω output impedance.
  • Sabaj DA3 - It has balanced and unbalanced output. It's small and has an on screen display that shows the sample rate. Only a little more expensive than a Sabaj DA2 but amazingly cheap for a balanced DAC.
For amplifiers I would recommend measuring:
  • Fiio A5 - High power, portable amplifier that isn't that expensive. There needs to be something good in this niche for people who travel away from home a lot or using low sensitivity closed headphones such as T50RP mods.
  • Fiio A3 - Quite cheap. Moderate power output for a portable amplifier.
  • Fiio A1 - Unique in that the inline microphone of the IEM connected will still pass back through to the smartphone.
  • Schiit Magni 3 - Very high power desktop amplifier. Very popular. Wonder if it is actually good.
  • Fiio K5 - The Fiio high power desktop amplifier. Not as high power as Magni 3 but Fiio has better international distribution.
Fiio BTR1 - Small bluetooth DAC and amp. There are many of these kinds of products on the market but all untested. Good to know if it is good for IEM owners who want to detach their IEMS from their smartphone.

After that it becomes about finding better products than listed above at lower price points or have some advantages. Knowing the power draw from the smartphone for portable DACS is also important and these cheap things do that well.
 
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amirm

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#92
Warm welcome to the forum Candlesticks. :) That is great feedback and exactly what I like to see. Quickly looking at your list, I already have the Schiit Magni 3 and Sabaj DA3 which I will review.

To reward you for great info :), pick one or two from your list that you like me to measure most and I will go ahead and order one or both of them. Over time I will strive to test as many as I can.
 

Candlesticks

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#93
Warm welcome to the forum Candlesticks. :) That is great feedback and exactly what I like to see. Quickly looking at your list, I already have the Schiit Magni 3 and Sabaj DA3 which I will review.

To reward you for great info :), pick one or two from your list that you like me to measure most and I will go ahead and order one or both of them. Over time I will strive to test as many as I can.
Fiio Q1 because it's a good budget portable combo. I really want to see what the limits of it are as an amplifier and how well that correlates to Fiio's own stated specifications.

Fiio A5 because a good high power portable amp is an attractive alternative to a desktop amp for most use cases.

The most stress placed on headphone amplifiers will be low sensitivity, low impedance planar magnetic headphones like the Hifiman HE-560 which requires 2.5mW to reach 90dB SPL. The very low sensitivity headphones range from 16Ω to 50Ω. Other commonly recommended headphones don't require much power to reach high SPL but common mid-fi headphone recommendations would be the higher impedance Sennheiser HD 600 300Ω and Beyerdynamic DT 880 600Ω so knowing the maximum power output at those impedance levels would be beneficial. So how well an amplifiers performs at an impedance of 16Ω, 32Ω, 50Ω, 300Ω and 600Ω is worth knowing because that covers the range that an amplifier would be expected to drive.
 

amirm

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#94
Great. I ordered the Fiio Q1 just now. Since I already have the Fiio A3, let's get through that review and then I will consider the A5.

And I hear you on driving less sensitive headphones. I like to have plenty of headroom and often these give me good listening level just a hair beyond their max output. I test with HiFiman HE-400i and Sennheiser HD-650.

I need to finish my multi-range headphone dummy load so that I can more easily test at different impedances. My testing so far has been at 32 ohms but I have the dummy loads for other values.
 

Candlesticks

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#95
On second thought perhaps it is better to test with the same dummy impedance loads as RAA does for comparative purposes. Sabaj PHA1 amplifier as an example.

They test at 16Ω, 25Ω, 31Ω, 62Ω, 100Ω, 199Ω, 300Ω, 763Ω.

Out of those I think 16Ω, 31Ω, 62Ω, 100Ω and 300Ω is the most important. 763Ω is too high in my opinion as the highest impedance headphone a headphone amplifier will see would be the Beyerdynamic DT880 600Ω.

An additional DAC and Amp combo to test would be the MiniDSP HA-DSP. It offers complex DSP processing to the optical or USB digital input as well as an ADC for DSP processing to an analog input.
 
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amirm

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#96
Wow, that russian site is something else. Can't believe how extensive their measurements are.

I just checked my dummy loads and looks like I made a typo and ordered some 1 ohm loads instead of whatever I wanted to order. :( Here are the values I have:

33 ohm
100 ohm
300 ohm and enough to make 600 ohm out of them
50 ohm

These are Caddock precision resistors and come in fixed values I can't get 32 for example. But that should not matter in grand scheme of things. Here are the values that are available: https://www.mouser.com/Search/Refine.aspx?Keyword=684-MP915-

Looking at your list, I can get 25 ohm. There is no 16 ohm but I see a 15 ohm. I can also put two 8 ohm in series if we need precision there but I assume not. There is a 200 ohm that I could get.
 

Candlesticks

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#97
From that list I would get 15Ω, 33Ω, 50Ω, 100Ω, 300Ω and 2x 300Ω together to make 600Ω.

The headphones I know of at 200Ω is the Audeze LCD-4, the 160Ω Sennheiser HD 700 and the 180Ω Sennheiser HD 660S. So I think you could make an argument for a 200Ω load as well. The other headphones close would be the 250Ω Beyerdynamic DT 770, 880 and 990 but I think the 300Ω load would represent them well enough.

In terms of use cases most people are looking for an amplifier to power a Beyerdynamic DT 880 or 990 250Ω, Sennheiser HD 600 and <50Ω planar magnetics. The Sennheiser HD 600 series is the most common headphone people ask amp advice for so knowing whether cheaper amps have enough voltage output is my core consideration to finding cheaper alternatives than the Schiit Magni 3 or Fiio E10K. For closed headphones it's people asking what amp to get for their Beyerdynamic DT 770 80Ω but I think the 100Ω load represents that fine.
 

drconopoima

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#99
The most stress placed on headphone amplifiers will be low sensitivity, low impedance planar magnetic headphones like the Hifiman HE-560 which requires 2.5mW to reach 90dB SPL. The very low sensitivity headphones range from 16Ω to 50Ω.
Will low impedance with low sensitivity stress the amplifier more than a high impedance similarly low sensitivity headphone? Even though the high impedance one will require more power? @Candlesticks I would be really interested in reading more about that topic if you have any source where that topic is explained.
 

drconopoima

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Ohm's law tells me that, if a headphone of 43 ohms gets 2,53 mW, a similar voltage driving a 600 ohm headphone would be only getting a power of 0,181 mW. So, if the Beyerdynamic DT 880 600 ohm requires 0,43 mW for the same 90 dB, it may seem that it is not as difficult to drive, but those 0,181 mW that are equivalent to the 43 ohm load wouldn't yield 90 dB with the Beyerdynamics. but something like 83 dB. And if instead we convert with Ohms law the 0,43 mW of the Beyerdynamic to reach 90 dB, we are providing the 43 ohm planar magnetic HE 560 with 60 mW, getting them to sound at like 107-108 dB. Is there something else at play here that I may be missing?
 
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