Rail splitter TLE2426

The Curent drain of your opamp is unimportent to the virtual ground driver. The Load current delivered to your Headphones is the Controling factor for the rail Splitter. I would suggest using Large capacitors from each rail to Gnd so as to offer a Reserve of Current available for your phones. 1,0000uf or above per rail should work. Then One TLE2426 will work because it will split the supply and the capacitors will supply the Current as well as offering a low AC impedance.

ppl-

If the virtual ground driver current is unimportant, why do you use two BUF634s in your maxed out portable? Cross-talk?

I think he's sayin that compared to your load, the Idrain the opamps add isn't really important.

Nothin' like a malformed question to waste thread space.
This was probably in a Headwize thread but...

Let me rephrase it a number of ways, primarily so I don't have to waste more BU634s.

I believe ppl's amp uses on one channel a single buf634 for a virtual ground driver to supply 3 buf634s in the output stage. So I got 1 BUF634 rated at 250 ma capable of supplying output to a load up to 750 ma. I assume that the average or RMS current draw of the amp doesn't exceed 250 ma and that caps are used to supply peak current above 250 ma, up to the 750 ma output capability of the 3 BUF634s. Is this reasoning correct?

Put another way, what prevents me from simply using a tle2426 as a ground driver in the same circuit and adding a massive amount of capacitance?

Is there a rule of thumb to determine the amount of capacitance to use? With power amps there's kinda a rule of thumb based on output power but with some very large variations.

Finally, in your experience, how do these virtual ground drivers behave when you exceed their current rating? I've had some shut down, some oscillate, and some, well, smoke. Think I will.

Thanks for the info!

I've just been testing a circuit containing two AD843 and two BUF634. Total current draw is 50mA - so you can be fairly sure that one BUF634 as the virtual ground will be sufficient. If you used two EL2009 or other very hungry buffers you might want multiple BUF634.

sneard: your Logic is correct in that the capacitors Provide the Peak Current well in excess of what the Virtual ground driver alone can provide, That's why i have used 2 BUF-634's as the Virtual Gnd. Driver and 3 BUF-634's on each output stage. This is augmented with 30,000uf Per rail of capacitence.

The Current Drain of your Amp is of no importence since the Current flow of your amp No signal or load is from V+ to V- and thus the rail splitter's current is uninportent up to this point.

What is importence and the only thing to concern your self with is the Current Delivered to the Load in this case the Amp and it's virtual gnd. driver are in series with the Load as well as the Power supplies. In theroy the Virtual ground driver should have the same Current rating as the Output stage but by adding capacitence to handel the peaks then a lower current Vir gnd dr. can be used.

aeberbach: I am interested in your findings with the AD843 & BUF-634? I found the BUF-634 to not be the best sonic match for the AD-843. This combo sounds good but the BUF-634 lacks the Bass Punch to take Full advantage of the AD-843. I used an EL-2009 with the AD843 to great sound. On another note the AD-843 likes or shall i say demands at least +15 & -15 volt to 18 volt rails to sound evean Good otherwise another opamp like the AD-825, or AD823 is what i would use.

Regarding the TLE2624 vs the BUF-634 i would use the BUF-634 if at all possible. The tle 2624 is good for an opamp driving a high impedance load. Headphones are a low impedance load. Another thing i do not like about the TLE2624 is the Limited bandwidth resulting in the Impedance to rise well into the Audio band requireing at least 100uF of capacitence just to evean the Imppedance out over the 20-20,000Hz. Audio range.

If it wasn't clear to everyone yet, the following will make it very clear - I'm a software guy. The 843 & 634 circuit I built was working nicely with the 634s inside the feedback loop driving HD600s but with my Grado SR-60s awful distortion was the result. I set out to fix it this morning. Ten or so circuits later I stumbled across the answer - wrong resistor values in the voltage divider I was using to get supply rails. I had used a pair of 100K with a pair of 100uF caps across them - these could maintain just enough voltage for clean sound into a 300R load but not the 32R Grados! So, down to 500R voltage divider and it's fixed.

What I'm mostly noticing now is a slight hissing brought on by the highs. Probably this is a question of voltage again, since my NiCd pack must be down to around +-5V by now. Now that you've said the 843 likes 15 to 18 volts I'm going to have to make the bench supply a temporary addition to the stereo rack. I have noticed that I like the sound of the 843s a little more at the same (+-9) voltage.

Have you measured current draw from your 843/2009 amp? I have some on the way (from Gerber) and have not completely ruled out using them in my portable amp - I have a 600mAH NiMH pack.

Could you give a circuit for using the 634 in place of the 2426?

aeberbach: Your Problem with the Voltage devider illistrates what i have been trying to get across to Headwizers for quite awhile, The Current required by the Load not the Current required by your amp is what's importent for the Virtual ground Driver.

The Virtual ground driver using the BUF-634 is on Page 9 in Figure 6 of the BUF-634 data sheet I use 47K ohms rather than the 10K ohms.

If the AD-843 is supplyed by only +5 & -5 Volts the opamp is on the verge of sutting down. I don't use the AD-843 for a Portable amp because of this and also considering it's 13 Ma Current Drain. Also since the BUF-634 is used within the Feedback Loop in your circuit you will have to use the Wide bandwidth Mode of The BUF-634 Pin #1 conect to V- as stated on the data sheet for the BUF-634. I use the AD-843 in One of My AC powered Headphone amps. with the EL-2009 in the Output Stage. This Draws 150 Ma of Current No load or signal. This is Not a battery Frendly Circuit.

I gess you could use the AD-843 in a portable and maby Keep the Amp's ICq around 50-60 ma. However there will be alot of Problems doing this. One is as the battery deplets the available output swing at the Amps output is greatly reduced. Considering that the AD-843 put's out about 2 or more volts less RMS voltage swing than almost every other OPA i have used When All OPA Tested are operated on the same Supply voltage with the Exception of the LT-1122. The LT-1122 puts out about the same as the AD843. What will happen is if the Supply Voltage is marginal to start with and a Loud listening Level is required then the Amp may Clip. The AD-843 is Nasty sounding when it Clips and Will latch up to one of the Supply rails. This is why i dont use it for a Portable amp. Another Concern is when the AD-843 dose drop-out it will put about 1.3V - 2.0V DC into your Phones. So I use a shorting relay in My AC amp using this Opamp.

I dont mean to Discourage you, The AD-843 when operated Correctly is a wonderfull sounding OPA and i have toyed with the Idea my self but the Above Mentioned Problems have resulted in My going with an AD-825. The AD-825 is Mutch Better Behaved in this regard.

As for the His you mentioned I have not noticed this so the answers to the following questions would help. (1) What bandwidth is the BUF-634 operated at? (2) what is the DC offset voltage at Min Volume and no load? (3) Dose this offset voltage change with a load connected. (4) What gain are you using? (5) What is the Supply Voltage? (6) is the Hiss Costant or dose it change with the Signal?
The answers to the above will be needed to futher post on what you should do.

HI

Will one TLE2426 be enough to supply two OPA2132 ? with 32R load ??

This has to be power supply for this project http://www.decware.com/newsite/zenheadrev6.pdf

Or maybe BYF634 would be better ??

A TLE2426 should be enough for this circuit.

The DIP8 version seems to provide more current

than the TO92 version even though they are supposed

to use the same die.