LM1117 V Reg for my mini CMoy (6 Pics)

[bpribadi]

My first headphone amp, built to test the sound quality of the OPA2134. I'm quite happy with the result, this op-amp has good bass and midrange.

To be objective with the sound of OPA2134, I tried to use the best possible (possible for me

) components, with simple circuits to minimize the effect of other components.

So no pots, only Solen - Polypropylene coupling caps at the input. And I use LM1117 voltage regulator to regulate the DC supply. I choose LM1117 because it is a low-dropout (Vin - Vout) voltage regulator. The fix series and the adjustable one has around 1.1 V dropout voltage (Vin - Vout). Lower than the 78xx series, and much lower than the well known LM317.

I use the LM1117T-ADJ, set the output to around 7 V. Measured 7.16 on my DMM. I use a protection diode on the input to protect the LM1117 from reverse voltage. So 0.5 V (for the diode) + 1.1 V (Vdo) = 1.6 V total Vdo.

So the minimum supply is 7.16 + 1.6 = 8.76 Vdc, just nice for 9 V battery, but I use a normal 9-12 VDC adapter most of the time. And when I tested it with battery, it is amazingly still works even though the battery voltage has drop to around 8 Vdc

.

Below is the circuits, and some photos of my mini (5x5 cm with 3 cm heights Hammond alluminium case). It is very dense inside the casing

 

[jasonhanjk]

Hey hey. Nice work. Hows the sound?

7 v should be enough for your AT, but not for HD600.

 

[bpribadi]

I need a pot

I can hear the hiss from my iRiver iMP-150 (PCDP) line out. The gain is only 5.7, yet it is high enough to reveal the hiss of the iMP-150 line out.

Initially my idea is to use iMP-150 volume, which is used for the line out as well. But since it is a low end PCDP, I hear the hiss when it is amplified 5.7x. The hiss is not affected by the volume, vol 0 or max, the hiss remain the same level. It is not from the headphone amp as I initially suspected, but from the PCDP. I have troubleshoot in a few ways, including adding the blue ALPS pot. The headphone amp is very silent without input signal, and well shielded from RF or AC line hum. No problem with it.

I think for my iMP150, what I need is just a buffer (gain 1x) like BUF634P, to keep the headphone amp small without the need of pot (use the iMP150 volume).

Well, for the sound of the OPA2134, my comment is:
Good and weighty bass and midrange, but not as fast as I expected. I would like to have a more detailed sounding amp. But for the price, it is a very good op-amp indeed.

I would like to try the OPA627/637 but they are very expensive (SGD 40.33 at Farnell Singapore). Probably the AD845 also another good choice (SGD 20.58 - Farnell). Do you have any suggestion?

I plan to build something like PPA amp, biasing a good op-amp into class A operation. But I will do it slowly, no rush.

Anyway, Jason, do you have any idea what happen with "sgheadphone" forum? I just joined a few weeks, now it seems dissapear

I tried with my PC at home & 2 PCs in office, all no luck, cannot go the the sgheadphone website. I read that some people have difficulties accessing sgheadphone forums.

 

[jasonhanjk]

Still down......

 

[Dreamslacker]

Add a 10uF Tantalum cap on the output of the regulator going to the negative rail. Alternatively, if you've the space, using a 100uF/ 20v Sanyo Oscon would do as well. Although you'd need more space and will need a diode going from output to input across the regulator.

 

[bpribadi]

Thanks! I take your advice for my next headphone amp

This one has no more space in the casing.