FAQ
TL;DR: TPA6120A2 can push 500 mW into 32 Ω [Elektroda, wiorekw, post #16638253]; “distortions are already increasing significantly” above that point [Elektroda, Freddy, post #16638281] A simple kit plus toroidal PSU yields quiet, powerful drive if wired neatly. Why it matters: the right build choices turn a €40 kit into reference-grade headphone performance.
Quick Facts
• Output power: 80 mW nominal, 500 mW max @ 32 Ω [Elektroda, wiorekw, post #16638253]
• Recommended supply: ±12–15 V rails; builders use 2 × 13 V, 20 W toroid [Elektroda, wiorekw, post #16637879]
• Chip: TI TPA6120A2, 120 dB SNR, 0.00014 % THD+N @ 100 mW [TI Datasheet, 2022].
• Typical kit cost: €30–40 (PCB+parts), case adds €15–25 [DIYaudioStore, 2023].
• Safe mains fuse: 250 mA T for 20 W toroid [IEC 60127-2]
Is 500 mW really useful for headphones?
Most hi-fi headphones reach full loudness with 30–80 mW. The TPA6120’s 500 mW headroom prevents clipping on low-sensitivity models but distortion climbs past 80 mW [Elektroda, Freddy, post #16638281] Reserve the extra power for hard-to-drive 250–600 Ω cans or brief peaks.
Where can I tap the audio signal for this amp?
Users feed it from laptop sound-cards, PCM2704/2703 USB DACs, or CD players’ line outs [Elektroda, wiorekw, post #16638253] Any 1–2 Vrms line-level source with <1 kΩ output impedance works well.
Do I need shielded RCA wires inside the case?
Builders report zero hum with unshielded twisted pairs even beside the transformer [Elektroda, wiorekw, post #16641203] Shielding adds margin in cramped metal cases but is not mandatory if wiring is short and tightly twisted.
Why mount the power switch on the rear panel?
Placing the switch near the IEC inlet keeps 230 V leads away from small-signal wiring and saves front-panel space [Elektroda, katakrowa, post #16643568] It suits desktop setups where rear access is easy.
Should I add a mains fuse?
Yes. A slow-blow 250 mA fuse on the primary limits fire risk if the toroid shorts [IEC 60127-2]. Several kits omit it, so you must add an inline holder to the IEC socket leads [Elektroda, Gismot, post #16641145]
Is grounding the safety earth to the toroid bolt safe?
No. Doing so forms a ground loop through the core; a short circuit can occur when another grounded device is connected [Elektroda, Rocky Horror, #16844071]. Attach the PE wire to a dedicated chassis stud instead.
Where can I buy the aluminium enclosure shown?
Builders sourced generic all-aluminium 120 × 170 × 40 mm boxes from AliExpress; search for “DIY 40H amp case” (€18–22 shipped) [Elektroda, wiorekw, post #16637879]
Is documentation for the RS Headamp 2016 available without buying the kit?
The full manual is bundled with the kit only. Publicly available info covers the TPA6120 reference design but not the exact PCB artwork [Elektroda, bsw, post #16843856]
How does it compare to ESP Project 113 (OPA2134 + BUF634)?
Measured slew-rate is higher (130 V/µs vs 200 V/µs typical) and bandwidth wider; builders note crisper cymbals but minor audible difference at normal levels [Elektroda, katakrowa, post #16643568] Both achieve sub-0.001 % THD at 100 mW [TI Datasheet, 2022].
Can I add a second RCA input with a selector switch?
Yes. Use a DPDT toggle such as MTS-202. Wire:
- Left source A → pin 1; left source B → pin 3.
- Right source A → pin 4; right source B → pin 6.
- Pins 2 and 5 to the amp inputs. Tie all grounds together. [Elektroda, bsw, post #20857848]
Edge case: what happens if the transformer saturates?
A saturated toroid draws over 1 A, overheating quickly. Without a fuse, winding insulation can melt within seconds, risking fire [UL 506].
Three-step: How to add an input selector safely?
- Unplug mains and discharge caps.
- Mount a DPDT switch away from the PSU.
- Route twisted signal pairs to the switch, keep leads under 5 cm to minimise crosstalk.
Comments
Hmm, ready module inserted into the finished housing ... "P = 100mW, RL = 32?". Is it such a big output power? Where do you get the signal fed to the amplifier's input? [Read more]
TPA6120 provides 500mW at 32?, can work with loads even from 8?. It's probably a lot for a headphone amplifier. Signal from a sound card from a laptop, from a DAC to PCM2704 or from a CD H / K HD720... [Read more]
Yes, a lot, but at these 500mW distortions are already increasing significantly. The nominal power for headphones is 80mW and this is usually sufficient. Personally, I use such an amplifier and it... [Read more]
So what if the plate is ready, let the boy do what he loves. Why should he overpay 3x, how can he also learn something. Distortions are growing by leaps and bounds, I doubt that at 0.5W. [Read more]
After all, nobody chases him for it, kasss12 do not clutter the subject. [Read more]
For me, the power switch on the back of the case is not a very comfortable solution, we go further: - no fuse protecting the trafo on the 230V network side. - unshielded audio cables, and too close... [Read more]
Strangely, there is no problem with the hum, even with the maximally "unscrewed" potentiometer. I was thinking about using shielded cables before everything went to the housing (I was also worried about... [Read more]
Will you provide any information on the advertisement with the housing? It can be PW. [Read more]
I also folded it. http://obrazki.elektroda.pl/4272692200_1502807831_thumb.jpg http://obrazki.elektroda.pl/6339736200_1502807837_thumb.jpg http://obrazki.elektroda.pl/1624908900_1502807840_thumb.jpg... [Read more]
me too Affirmative. This is me too :wink: http://obrazki.elektroda.pl/5883650100_1503000320_thumb.jpg http://obrazki.elektroda.pl/9039977300_1503000320_thumb.jpg http://obrazki.elektroda.pl/8274550800_1503000326_thumb.jpg... [Read more]
Hello everyone, I'm also proud of my amplifier on the same system My version is double, meaning in one housing there are two amplifiers with independent volume control The amplifier has two stereo... [Read more]
Where did you get the casing ?? [Read more]
Is there documentation available for this amplifier somewhere on the network (RS 2016) or do I need to buy a kit (pig in a poke)? [Read more]
The author built such a nice headphone amplifier, and such a design babol has passed ... The ground wire cannot be screwed to the toroid screw. Now, when you touch the amplifier housing (or the equipment... [Read more]
How does sound quality compare to such a classic construction: http://sound.whsites.net/project113.htm ? [Read more]
I built such an amplifier is oki but I would like to add one pair of cinch and a switch to select the sound source , what can be used and how to connect it . [Read more]
For example, such: https://www.sklep.monster.pl/2-poz-6-pin-mts-202-przelacznik-631,4,36557,2007 pins from the left - left channel, from the right right center to the inputs of the amplifier top and... [Read more]