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List of best DIY Headphone Amplifiers
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Old 22nd February 2018, 12:21 AM   #41
Pars is offline Pars  United States
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Originally Posted by TypodCrow View Post
Hey just bumping this - can anyone recommend a relatively small reference grade amp to build? It would be sweet if I could get a Class A.

I'm currently running an Objective 2. It's pretty sweet, but I could appreciate some more power to give my Alpha Prime's their slamming bass.
Kevin Gilmore's current feedback amp (CFP2?). Relatively small (still needs heatsinks), pretty cheap to build, sounds really good, and plays well with orthos as well. Use a good PSU like a GRLV with is. Can be built fully balanced as well if that is your thing.
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Old 22nd February 2018, 05:21 PM   #42
xrk971 is offline xrk971  United States
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List of best DIY Headphone Amplifiers
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it's just that the measurements didn't seem realistic considering the topology and parts.
Not sure why they would be "unrealistic", the measurements are the measurements of the real amp. Despite whether or not a 11:1 attenuator is in place, the THD below signal is still the same. I expect the measurements to be even better when done with a lower noise laptop with SSD and no fan running on the laptop.
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Old 24th February 2018, 06:52 PM   #43
Giordano is offline Giordano  Hungary
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Originally Posted by thuanth43 View Post
For dynamic DIY headamps, there won't be anything that would touch the level of Beta22 and balanced Dynahi (Dynamite). The Sjostrom QRV-08 is also fantastic, reasonable cost, but quite low powered. I also really like the Millett Hybrid Maxx, good stuff, well documented and easy build.
Hello,

Where is the Beta 22 thread?

At "Home > Forums > Amplifiers > Headphone Systems >" I switched to descending order of replies, and I could not find it. Maybe I'm overlooket, I hope, but I can't believe there is no thread for the Beta 22?

I've just decided to make one, 2 channel probably, running on 2 small 12V SLA battery. I was looking to read build experiences etc ... It is strange for me that I could not find it on a very popular amp.

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JG
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Old 24th February 2018, 07:56 PM   #44
merlin el mago is offline merlin el mago
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The β22 stereo amplifier
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Old 25th February 2018, 02:55 PM   #45
mediatechnology is offline mediatechnology  United States
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Originally Posted by 00940 View Post
Reading the thread where you posted this graph: "Ok a quick measurement with Focusrite 2i4 and 1.00vrms into 50ohm load, read out with 10:1 voltage divider."

Btw: here are the measurements open loop vs closed loop of Wayne Kirkwood DCAO2: An Improved Dual Class-A Output: The "DCAO2" - Page 4 - Pro Audio Design Forum
As expected, closed loop is needed to achieve very low distortion.
Not completely correct. To begin with the wrong amplifier was cited. The original is here: Dual Class-A Line and Headphone Output Board Documents - Pro Audio Design Forum and the beginning of the concept here: Using the THAT1646 As A Transistor Pre-Driver/Headphone Amp - Pro Audio Design Forum

For the DCAO II that was cited the THD up to about 60 mW is about the same open or closed loop. The comparisons are at 100 mW at a point feedback is providing benefit. Although the DCAO-II is a different design than the 1646-based driver the results below 60 mW are nearly identical between the original and the "DCAO-II."

Don't recall at what power level the measurements by xrk971 were done at but they were lower than 60 mW IIRC. (EDIT: Just checked 20 mW.)

The output only runs open loop, the low distortion is made possible by high class-A current relative to the load power. The only magic is stiff Vbe bias reference which does have both negative and thermal feedback.

20 mW THD does not equal 100 mW THD.

Last edited by mediatechnology; 25th February 2018 at 03:02 PM.
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Old 26th February 2018, 07:25 AM   #46
Luke is offline Luke  New Zealand
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Quote:
Originally Posted by Pars View Post
Kevin Gilmore's current feedback amp (CFP2?). Relatively small (still needs heatsinks), pretty cheap to build, sounds really good, and plays well with orthos as well. Use a good PSU like a GRLV with is. Can be built fully balanced as well if that is your thing.
Hi Pars, are boards available for this amp?
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Old 26th February 2018, 04:52 PM   #47
Giordano is offline Giordano  Hungary
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Originally Posted by merlin el mago View Post
Thanks, I know that, but I'm surprised there is no thread here, which is independent.

Regards,
JG
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Old 4th March 2018, 02:47 AM   #48
Pars is offline Pars  United States
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Originally Posted by Luke View Post
Hi Pars, are boards available for this amp?
There is a group buy going on now (closing shortly) with these boards and GRLV boards among those included.
2018 PCB Group Buy with TKD pots - Do It Yourself - www.Head-Case.org
The gerbers are readily available as well; these boards would be fairly cheap at one of the board houses (seeed, etc.) as well.
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Old 4th March 2018, 03:38 AM   #49
Luke is offline Luke  New Zealand
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Thanks Pars, thought about signing up, but I got too many projects that are not going to get done. I use a Dynalo and Saphire still not built my SS Dynalo. Is it in the same league as the Dynalo?
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Old 7th March 2018, 06:26 PM   #50
Pars is offline Pars  United States
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^ Depends on the headphones. With orthos, I think it is better. People with HD800s really like the ss dynalo with that.
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