bpribadi

Well Jason, I don't know what your reason to stick with the OPA2134 or 132 for the ground channel, to me it is just doesn't seem right in your amp Option 1 is not good theoritically. We cannot just short outputs of op-amps without any resistors. With resistor, we already discussed that it is bad for ground channel. Option 2, are you sure you want to use bended pin Op-Amp for your production amp? Come on... So, the best option for ground channel is to use single op-amp with high current (LM6171, OPA551) in unity gain config. For the gain, I think 4 is too low. Well what I can see from my 'marketing' point of view, the one who need budget headphone amp is the one using high impedance headphone. I don't think those who use 32 ohm headphone will be interested with budget headphone amp. And for high impedance headphone, for example Beyer DT-880, 250 ohm, even gain 6.6 is not loud enough when connected to PCDP line out. And the 600 ohm will need even higher gain. So I suggest you set the gain to around 8.5 - 11. Also, why do you need A47 circuit (high current circuit) for gain 4? Gain 4 means the ouput voltage is low, therefore the current is also low. A simple CMoy will be just nice for gain 4. A47 is needed when the output voltage is high, therefore you need high current output. And also if the output resistor is too high, like 47 ohm, there will be too much voltage drop on the output resistor, waisting the limited low voltage supply from the battery. I tested 12 ohm, and it work perfectly. Sorry Jason, I don't mean to question your design... I just hope you will finaly make a good production amp Why should I wrote so many if I don't care about it

Tropical, I can pass you my version for your carefull comparison Hopefully the new board sounds better, even though I think the ground channel circuit will easily oscillating and will cause instability

The main reason is to stabilize the ground, and some op-amp has higher output current than the TLE. Inside the TLE is also resistor voltage divider and an op-amp, so same thing.

Is there any good SACD player in range S$ 500 - 1000 ? Cheap SACD usually convert DSD to PCM before converting the signal to analog, therefore the SACD sound not better than normal Red book CD

Me and a few friends of mine don't really like the Sony XA3000 sound. But please bear in mind, it is up to personal preference. Some people likes Sony's sound, but not me. Try Denon DVD2910 or better the DVD3910. Or the Marantz... I'm waiting for Rotel to make SACD player

I have listen the FX6021 a few times, in Sim Lim and Sitex. Although not very objective, but personally I don't like the sound. It is just another boombox from Altec, not musical, sounds almost like the MX5021. Probably because of bad source But looking into the 'in concert' concept, it must have include a lot of cross over network. Which will cause a lot of phase distortion. So the concept doesn't looks good to me, I hate crossover

Thanks for sharing Digi! We have some comparison of Op-Amp sounds, also buffer sounds, I think we need somebody to enlighten us for the Q1 and Q2 The sound different of the various transistors. Anybody know about audiophile grade transistors? I think for this purpose, the low power types.

You should try bare naked braided PC-OCC cooper from Ahfart Get the wire from him, and braid it Should be the coolest cable ever

Wow, that's cool A bit heavy though

Exactly same or with modification? The board size please if possible... Thanks!

Cool!!! Very nice and neat mod You have a very solid music gear! Rotel is always a good bargain, performance/price ratio always good so far Where did you get those blackgates and finegolds nichihon?

I have the Grado adapter, and I saw something similar in SLS, 3rd floor, the shop name is UF Technology (green banner). I didn't check properly, buy it looks like the Grado adaptor. That shop has a lot of cables I will check again when I go there.

As always, very nice Digi Haw many amps you make in a year? Seems like a lot to me

Need translator

I found a good article about ground. Less than 3 pages http://www.passlabs.com/downloads/articles/ground-loops.pdf The summary: It is better that the Safety AC power ground (chassis) and the Signal (Audio) ground not to be connected. Disconnecting the power ground is not a good idea as it is potentially very dangerous. Taken from the article, it is about unbalance RCA interconnect, how to make the right RCA interconnect with cable that shielded with 2 conductors: "Shields are to keep stray noise out of component inputs; the common or signal return is part of the signal path, two opposed tasks. Because of these separate tasks your cables should be directional, and the shields should be part of the input circuit only. Shield ground should not be connected on the source end of the wire, only at the input component end; label them and don’t forget! This will of course mean that at the input component end of cable the shield and ground signal conductors will bond together." Happy Reading

Mini jack : S$ 3.5 RCA : S$ 5.5 They will give discount if you buy more

Nice cable Firefox! On which end do you terminate the shield to the ground? On the source or amp end? Thanks!

Thanks guys ! The connectors are OEM connectors I got from SLT basement. I forgot the shop name, but they are on display, so you don't have to go into the shop to look for the connectors. I would like to share the 4 and 3 cables braiding techniques, it is just I don't know how to display the techniques in this forum Probably later when I found how to draw it. I just imagined the technique, never learnt from any classes You are right evil zen, it is 4 cables to the mini jack, and 3 cables to the RCA. In the Y junction I added another cable to make it 3+3 for the left and right channel RCA. Digi, you got the point. Unfortunately I don't like the sound Probably the cable need burn in time.... But to me the sound lacks of dynamic. Probably it is because the RG-179 is high frequency cable, so it is heavily shielded for RFI & EMI protection. As we know, bare naked cable, not shielded, normaly has better dynamic, but when your handphone ringing you will hear ''dut.. dut.. dut.." sound in your music . To me the cheap normal Daiyo interconnects has better dynamic compare to this cable If budget permit, I would like to try it again with PC-OCC silver wire This time it is going to be bare naked wires, not shielded

Thanks! Yes, I braid it, and after that my fingers numb because the mini coax is pretty stiff

You're welcome ! That's another way. What I did, I didn't bend any pin, I cut one pcb track and short pin 7 & 8: http://www.sgheadphones.net/index.php?showtopic=2400&st=180

Testing RG-179 mini coax for interconnect. The cable is braided from 4x RG-179. The RG-179 is mini coax for high fequency signal normally use in telecom industry. The conductor is silver plated cooper. Looks like the silver layer is quite thick, I hardly see the cooper part. I think the insulator (jacket) is either PTFE of PVC, and I found to be very good, can stand the heat of soldering iron very well, didn't melt of change form.

I saw most of the mini drill come with 3 mm chuck. I also saw in Kaichin, the shop that sells used stuff near the escalator SLT 2nd floor, they are selling drill bit, for small holes, 1mm, etc. with 3 mm diameter on the lower part to fit the 3 mm chuck. They are only SGD 1.5 per bit, and looks good

You guys are very right! I'm agree with both of you! They can't claim their simple non-inverting circuit is their propietary circuit, but selling the PCB using their amp's name is also not right. It's not the circuit that matters, it's the name. The circuit is no different than a CMoy, with different resistors value. Just like PPA and Pimeta, the names are refering to the PCB not the circuits So, actually we cannot make Pimeta or PPA without the original PCB.

Aahhh you changed the knob I like the new knob

Tangent notes for audio op-amp have the recommendation: http://www.tangentsoft.net/audio/opamps.html