PGA2310 buffer question

till · 18th September 2003, 08:05 PM

Now my minimal PGA2310 volume controll is working, i think about a buffer.

From the datasheet: "[...] the capability to drive 600 Ohm loads directly without buffering" -- ok, no output buffe needed.

"[...] It is important to drive the PGA2310 with a low impedance . If a source impedance of greater than 600 Ohm is used, the distortion performace of the PGA2310 will begin to degrade."

ok, my CD player is 3k Ohm. Buffer needed.

Should i use opamp stuff like buf634, or would the simple single mosfet buffer from Zen V4 work also for the PGA?

analog_sa · 18th September 2003, 08:51 PM

Just curious: why is your CD player 3k? It seems like a better plan to reduce the output impedance of the cd player rather then introduce extra stages. What's the sound like at present?

cdl · 19th September 2003, 03:33 PM

Sounds good that vol-ctrl is working!

Zen stage sounds rather tempting, but on the other hand there's an opamp in the PGA thingy anyway, so another opamp might be a natural starting point...

How about a simple opamp in unity gain...? E.g. Opa627, should work I think.

Those who like it can use a current source / pulldown resistor to bias it class A.

Should be fairly easy to try both Zen and opamp out that way,

/cdl

soren · 19th September 2003, 09:35 PM

I have made some measurements of PGA2310 and 2311 with an Audio Presicion equipment. I used both unbuffered or buffered (inverting, noninverting) output. As outputbuffer I tried OPA627 and OPA134 (which should be the same as the one inside the PGA231x).

I could not see any differences in the output spectrum wheter it was buffered or not, I tried both 100k and 600 Ohms of load impedance.

The measurements where made with a rather crappy power supply, but I met the specs in the datasheets. One thing that could be taken into account when choosing between the two is the lower noise from PGA2311, but only if you can live with the lower maximum output.

The results made it clear to me that my next preamp should not have any buffering after the PGA.

soren · 19th September 2003, 09:38 PM

Ooouups...

I read a bit too fast.

Till will make an input buffer. My measurements was of an output buffer...

till · 19th September 2003, 11:57 PM

sorry, i checked, my CDP and TDA1305 DAC isn´t 3k output impedance, but says minimum Rload = 3k.

Does this mean no buffers needed? What is input impedance of PGAS2310?

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18th September 2003, 08:51 PM	#2
analog_sa diyAudio Member Join Date: Aug 2002 Location: Sofia	Just curious: why is your CD player 3k? It seems like a better plan to reduce the output impedance of the cd player rather then introduce extra stages. What's the sound like at present?

19th September 2003, 03:33 PM	#3
cdl diyAudio Member Join Date: Aug 2003 Location: Copenhagen	Sounds good that vol-ctrl is working! Zen stage sounds rather tempting, but on the other hand there's an opamp in the PGA thingy anyway, so another opamp might be a natural starting point... How about a simple opamp in unity gain...? E.g. Opa627, should work I think. Those who like it can use a current source / pulldown resistor to bias it class A. Should be fairly easy to try both Zen and opamp out that way, /cdl

19th September 2003, 09:35 PM	#4
soren diyAudio Member Join Date: Sep 2003 Location: Copenhagen	I have made some measurements of PGA2310 and 2311 with an Audio Presicion equipment. I used both unbuffered or buffered (inverting, noninverting) output. As outputbuffer I tried OPA627 and OPA134 (which should be the same as the one inside the PGA231x). I could not see any differences in the output spectrum wheter it was buffered or not, I tried both 100k and 600 Ohms of load impedance. The measurements where made with a rather crappy power supply, but I met the specs in the datasheets. One thing that could be taken into account when choosing between the two is the lower noise from PGA2311, but only if you can live with the lower maximum output. The results made it clear to me that my next preamp should not have any buffering after the PGA.

19th September 2003, 09:38 PM	#5
soren diyAudio Member Join Date: Sep 2003 Location: Copenhagen	Ooouups... I read a bit too fast. Till will make an input buffer. My measurements was of an output buffer...

19th September 2003, 11:57 PM	#6
till Banned Join Date: Apr 2002 Location: Germany, Clausthal	sorry, i checked, my CDP and TDA1305 DAC isn´t 3k output impedance, but says minimum Rload = 3k. Does this mean no buffers needed? What is input impedance of PGAS2310?

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