You may want to read up on the iBasso D6 or PB2, lots of power from a portable amp.
Hi Miguel Portable amps are fine for low impedance headphones that aren't designed to meet those IEC specification, but when the headphones need that 120 ohm output resistance to sound balanced across the whole spectrum, you need around + and -20V to properly drive them. (As you listen at levels well below what most do, that may not worry you though. ) In that case , it's voltage swing you need, not current delivery. Better still, with headphones designed to meet that IEC spec , high voltage supply rails as well as 100mA or more current drive capabilities is even better. That's where the Aune Panda or Class A HA can really shine, and eat the Jaycar for breakfast! You can also change their output resistor values to suit low Z headphones, and drive them to destructive levels.
Sure, the iBasso D6 can do around 500mW into 32 ohms from it's 12.6V Li Ion polymer battery, but you still need 120 ohms output impedance to make the IEC specced headphones sound tonally balanced. In your case you could use external 120 ohm resistors which I think you have done before, and most likely still reach a satisfying output level.
Picked up one of these portable amps to play with. My first impression was a bit of a shock at how hot it ran, i almost couldn't pick it up after a bit of use. I had a poke around the pcb after reading this thread and discovered the heater supply resistor was a .1ohm. Yup .1ohm so the element was getting 12v across it and ran hotter than the surface of the sun, it also glowed really bright
If anybody buys one of these double check the resistor they have installed as its way too small..
I've since cobbled together a 7806 linear regulator to output 6.35v so it runs much cooler. The regulator itself runs at ~70-80c with a small heatsink clipped on, not ideal but it will do the job and fits inside the unit.
Replaced the above with a Traco unit, better battery life, less heat, definitely the way to go. If you study the PCB there are two positions for transistor packages that are unused, i assume they had planned some sort of power manangement circuitry. By chance they are perfect fit for the Traco unit pin outs when mounted sideways, as per attached pic. Coupling caps are laid out as per datasheet.
So far i have done the following mods,
-Replaced Ratheon 6111 tube with a NOS G.E. 6021A -Replaced both 10k resistors with 20k adj pots and set to 6v DC. (9.3v with 6021A tube) -Replaced all resistors with known quality metal film. -Replaced all capacitors with Elna Silmic II. -Added 10uf lytic / 100nf poly cap across Opamp power supply pins. -Replaced blue led with red. ....i hate blue leds with a passion. -Replaced NE5532 with a genuine LM4562. -Replaced volume pot with a genuine Alps. -Created linear regulated supply for heather circuit. Replaced with Traco based heater supply.
The original tube (Ratheon 6111) got roasted alive with 12v across its heater so i replaced it with a NOS G.E. 6021A. Vs the 6111 that was installed its much better, lower distortion, greater clarity, and more gain. Only issue is the two 20k pots start at 9.3v output now vs 6v, not sure if thats really an issue or just due to the added gain with this tube, either way it sounds much better now.
videoguy: Hi Jon: I am in Florida & am in frequent contact w Alex Kethel. Am in need of some single ripple eater boards. Wpuld you mind giving me the address of the pcb manufacturer; as I need ten boards. Thank You in advance. Bill Wilson
Dec 2, 2019 1:54:46 GMT