tangent, now i have already fixed the amp by replacing the 2 new Q3 into it. and the offset now is: L: -3mV G: 3mV R: 0mV (with volume turned down and DT880 plugged in) and the offset will rise with the volume, about 20 mV when the volume is 50% is it normal? and why that is a...

Quote: Originally Posted by tangent I can only speculate. Is there anything else you can tell us that would help us guess? thanks tangent~ um... i used to turn on the PPA overnight, will it be too hot so that the Q3s are damaged? if so, why only the Q3s of the right channel get...

i have using my PPA v2 for a month already, but yesterday, when i turn on the PPA, the right channel has no sound at all, at first i think that it may be the problem of the opamp, but i found that it is not true after i replace the 3 opamps with each others. so i measure the DC voltage across...

does any know the output power of PPA? how many watt is it? can it drive DT880? or i should say, can it driver DT880 well?

Quote: Originally Posted by n_maher Let's be fair here, you followed some of the instructions, but not all of them. And believe me, I'm guilty of this as well. Just search this forum for "STEPS temp" and you'll find my thread about this. If you read through all the documentation on the...

Quote: Originally Posted by steinchen definitely 1. ! if you want to run your steps at 24V pick the 2x12V Amveco transformer tangent recommends 2. won't help at all, you have to decrease the voltage drop across the regulator 3. install the heatsink tangent recommends, it's...

my aim is to reduce the heat generated by the regulator or to cool down the regulator, so which method is better for me? 1. replace the transformer with a lower voltage output 2. replace the regulator with a lower thermal resistance 3. replace the heat sink with a larger one 4. put a fan...

Quote: Originally Posted by tangent Changing out the regulator doesn't change the voltage drop across it. It will dissipate the same amount of heat in this situation. The only time LDOs help with heat is when you're operating it with a lower voltage drop across it than the equivalent...

Quote: Originally Posted by n_maher Based on that calcuation, no it doesn't seem like too much. Mine has to deal with a lot more watts than that and I'm not worried about the heat. Why are you running 24V to a PPA? What opamps are you running? Have you actually measure the current draw...

Quote: Originally Posted by n_maher Well then you've got a couple options that I can help you with: a. turn up the juice, i.e. increase the output voltage. If your reg is getting too hot you're asking it to drop too much voltage (combined with current draw of course). b. get a...

Quote: Originally Posted by tangent 2000uF is not fine with an LM108x family LDO, in my experience. The regulator will not power up reliably with that much capacitance on its output. Oh, you could do something ugly like put a 1 ohm resistor inline with the regulator's output to allow...

Quote: Originally Posted by motherone This might seem like an obvious question, but do you have C6G installed? If not, that may be what's causing your offset to rise in the ground channel. I didn't see any mention of this in the thread, so I thought I'd ask... The offset in the other...

Quote: Originally Posted by steinchen LDO type regulators are sensitive to excessive rail capacitance, you should keep the total capacitance below 3.000uF, 2.000uF is fine for ESR reasons it is better to take several medium sized caps (e.g. 4 or 5 caps of 470uF or 680uF each) than 1...

Quote: Originally Posted by steinchen yes, but take care of your rail capacitance http://www.tangentsoft.net/elec/teps/pguide.html#IC1 does it mean if i use just 1 cap. with 2000uF on the PPA, i cant use the LDO type regulator? how about if i use 9 X 470uF cap.?

may i use LT1085CT instead of LM317T as the regulator to drive my PPA?

here is the photos of my PPA http://photo.ustage.com/ce?d=/584e3/5a78f by the way, do i need to apply heat sink on Q24, Q34?

Quote: Originally Posted by tangent This is probably normal. If you have access to a DSO, you can capture it. If it's just a volt or two, it's harmless. but can it be avoided? though it is harmless to the headphone, i dont want to be shock whenever i switch it on or off

i now find that even i dont put any signal in and just power up the amp., the three channel offset will rise! L: -0.3mV -> 1.2 mV G: 4.7mV -> 5.7 mV R: 1.4mV -> 2.8 mV and the Q34 and Q24 will also get hotter and hotter why the offset will rise automatically?

i have checked that the soldering connection has no problem, and i swap and swap the op-amp, the result is the same, the voltage offset of the ground channel still is the highest, this time, the measure is (no input): L: 1.1mV G: 4.7mV R: 1.4mV and this time i have also measure the...

Quote: Originally Posted by amb DC offset is not good, and should be as low as possible regardless of which channel. It just so happens that in the PPA (as well as Pimeta and M³), the ground channel operates in unity gain, so it typically has the least DC offset amongst the three...

Quote: Originally Posted by MisterX Yup, same here. That is kinda why I would like to see what happens when he moves the opamps around. i use AD8610 for all the three channels. when i swap the opamp among the 3 channels, the result is the same, the highest offset is still the...

Quote: Originally Posted by MisterX Yup, that is normal but the offset on your ground channel is pretty high. Switch them around and see if it changes. you mean the difference of the offset between L and R channel is normal? will it lead to the difference volume between L and R...

could anyone help?

thanks all, after i have installed the op-amp, i can measure and adjust the buffer bias, howevere, another question raises, when i go to step 11, measuring the voltage from the ground plane to the output of each of the three channels, i found that the 3 channels will have different voltage, L...

i want to buy DT880, but don't know where is the cheapest, can anyone help?