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.
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.
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.
Regards,
JG
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.
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Thanks, I know that, but I'm surprised there is no thread here, which is independent.
Regards,
JG
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.
Can anyone recommend a DIY Balanced (XLR in) Headphone Amplifier for under $400? I am using Audeze EL-8 (open-backs), SoundMagic HP150 headphone, and Shure SE425 IEMs.
I have multiple DACs with XLR outputs (DSC1.Difference & ES9038Pro based DAC) and I am looking to use them as intended. I do not care to hear people debate the merits of balanced vs unbalanced amplifiers. I found it obvious that XLR has much better noise rejection properties and completely balanced DACs (DSC1) will never be as good converting XLR to RCA (even my Douglas Self designed XLR to RCA converter/pre-amp can't match true balanced DAC -> balanced Amp).
Thanks in advance for any recommendations! If there aren't really any in a kit that are up to the task, I am fine with a schematic and parts list.
I have multiple DACs with XLR outputs (DSC1.Difference & ES9038Pro based DAC) and I am looking to use them as intended. I do not care to hear people debate the merits of balanced vs unbalanced amplifiers. I found it obvious that XLR has much better noise rejection properties and completely balanced DACs (DSC1) will never be as good converting XLR to RCA (even my Douglas Self designed XLR to RCA converter/pre-amp can't match true balanced DAC -> balanced Amp).
Thanks in advance for any recommendations! If there aren't really any in a kit that are up to the task, I am fine with a schematic and parts list.
Dual Class-A II Line Output and Headphone Amplifier
Uses THAT 1240 (or 1246) balanced line receivers.
Help with DIYing an AMP
Hi all! I´m new o his forum. I recently bought an SHP9500, and I´m about to buy this DAC . Since I'm about to start school holidays, I think I might tackle on a little project and build the amp myself (I know about electronic, have basis on Altium Designer and OPAMP theory, and I can print the PCB with ferric chloride) . The thing is, the 4xTDA1543 DAC says in it's description that it can output 2Vrms. Using this explanation (Designing headphone amplifier circuit, need help - Do It Yourself - PS Audio), I calculated that I would need 7,5 mW to push 110dB, so the amp should be able to give 0,5V. So there are two things: 1)If I only need 7,5 mW to push 110dB, why the headphones specs says that it can take up to 220 or 240 mW. 2)What can I do, since the voltage I need is lower than the output of the DAC itself without an amp (I thought of putting a resistor in serie, but forums says it ruins the frecuency response)
Hi all! I´m new o his forum. I recently bought an SHP9500, and I´m about to buy this DAC . Since I'm about to start school holidays, I think I might tackle on a little project and build the amp myself (I know about electronic, have basis on Altium Designer and OPAMP theory, and I can print the PCB with ferric chloride) . The thing is, the 4xTDA1543 DAC says in it's description that it can output 2Vrms. Using this explanation (Designing headphone amplifier circuit, need help - Do It Yourself - PS Audio), I calculated that I would need 7,5 mW to push 110dB, so the amp should be able to give 0,5V. So there are two things: 1)If I only need 7,5 mW to push 110dB, why the headphones specs says that it can take up to 220 or 240 mW. 2)What can I do, since the voltage I need is lower than the output of the DAC itself without an amp (I thought of putting a resistor in serie, but forums says it ruins the frecuency response)
The headphone power limit is the physical limit of the transducer, not a recommended listening level!
The TDA1543 is a current-output DAC that has a very small voltage compliance (0.25V), as far as I can work out the 4x TDA1543 circuits are bogus and distorting as they take the device out of its compliance range. Such current output DACs require a current to voltage converter stage on their outputs to achieve datasheet performance.
Each chip is rated for +/-2.5mA, so 4 parallelled only gives upto 7mA rms anyway, so perhaps for low impedance load its not going to leave the compliance range. But still the lowest distortion is achieved by clamping the output voltage to the reference voltage as with the standard IV converter, and for high impedance load its just going to clip. (Probably soft-clip at least).
And I can't see how changing 3 of the DACs for a dual opamp is anything but a win-win on all fronts?
The TDA1543 is a current-output DAC that has a very small voltage compliance (0.25V), as far as I can work out the 4x TDA1543 circuits are bogus and distorting as they take the device out of its compliance range. Such current output DACs require a current to voltage converter stage on their outputs to achieve datasheet performance.
Each chip is rated for +/-2.5mA, so 4 parallelled only gives upto 7mA rms anyway, so perhaps for low impedance load its not going to leave the compliance range. But still the lowest distortion is achieved by clamping the output voltage to the reference voltage as with the standard IV converter, and for high impedance load its just going to clip. (Probably soft-clip at least).
And I can't see how changing 3 of the DACs for a dual opamp is anything but a win-win on all fronts?
Well, thank you for yout answer! I'm studying electronics, and still only know the basics, so I got a little lost with yout explanation, haha. So, if you don´t recommend that DAC, is there other one at that price range that you would recommend. Also, if every chip outputs 0.25V, isn't the output getting buffered to get to 2V.
Thanks in advance.
Thanks in advance.
Actually that DAC isn't really such a bad choice - I've experimented with very similar ones and found they have an easy-going kind of sound. It cannot put out 2VRMS though because its power supply is just the USB bus power (nominally 5V) and the compliance range of the DAC chips is about half that. But if you've the inclination you can increase the power supply voltage to the DAC chips to 8V and then you can get close to 2VRMS output. You will though have to increase the I/V resistors which isn't a difficult task.
Thank you. The thing is, I don't need the 2Vrm ourput. I´m looking forward to build an AMP, but the thing is that I don't know how to do it, because the theorical DAC voltage outout is higher than the voltage I would need in the AMP output (Theoricaly, 0,5V, but going for 0,8V for having some headroom). What can I do?