Any PCM54/55 type chips and R2R ladders out there ?

percy · 1st November 2006, 04:17 PM

Are there any R2R ladder dac chips in current production (other than pcm54/55).

I am interested in building a R2R dac, maybe even from the grass root level i.e. use actual high precision (0.1%), high stability, low current noise ( 1µv/V) resistors to build the ladder.

Are there any standalone R2R ladder chips readily available ? Doesn't have to be a "DAC" chip. I/V conversion and output buffering can be external, or rather I'd prefer that.

Thoughts anyone ?

jwb · 1st November 2006, 05:45 PM

You don't like PCM1704? Despite being "not recommended for new designs" they are still produced.

percy · 1st November 2006, 07:07 PM

oftmof pcm56 or pcm63 or tda1541...
But I'd just like to build it this way.

I'd just like to be able to write to a multi-bit latch that is in turn tied straight to a "DAC" (ladder). How I write to the latch, and how often, is what I'd like to see open for trying out a few possibilities. If not anything else, just for the fun of it...

Bernhard · 1st November 2006, 07:20 PM

For 16 bit you need a little better than 0,1%.
And tight Ron-matched switches.

Accuphase used ICL8019 current switches in their early DACs.

I tried 1 PCM54 / bit. Works so far.

percy · 1st November 2006, 08:51 PM

Quote:

For 16 bit you need a little better than 0,1%.
And tight Ron-matched switches.

0.1% is the max deviation. It might be quite possible to find resistors much closer than that, especially if you measure and hand pick what you like.

I have seen a few measurements you've done on various dacs but I have never seen one for the PCM54. Did you ever do any ?

Bernhard · 1st November 2006, 09:16 PM

Quote:

Originally posted by percy

I have seen a few measurements you've done on various dacs but I have never seen one for the PCM54. Did you ever do any ?

The measurement of chips does not say too much about the chip family unless you test a lot of them.

I have 16 pieces of PCM54 and one or two are quiet good with MSB adjust.
PCM56 I have about 90 and nearly 50% are very good with MSB adjust, the rest ranges from good to horrible.
PCM56 is much better than all the rest. My favorite in nonos with passive I/V.
PCM53 has no MSB adjust, I have about twenty, one is good.
PCM58, PCM63, PCM64, AD1862, PCM1702 I have a few of each but non is good.
TDA1541/1541A was never good, except one out of 10 crowns.
And I have a pair out of four ceramic/gold chips that is good, maybe I was lucky

percy · 2nd November 2006, 02:35 PM

anyone heard about or tried the AD669

Bernhard · 2nd November 2006, 02:57 PM

AD669 83dB SNR ?

percy · 3rd November 2006, 01:57 AM

http://www.semiconwell.com/r_net/swr2r.htm !

1st November 2006, 04:17 PM	#1
percy diyAudio Member Join Date: Apr 2004 Location: MN	Any PCM54/55 type chips and R2R ladders out there ? Are there any R2R ladder dac chips in current production (other than pcm54/55). I am interested in building a R2R dac, maybe even from the grass root level i.e. use actual high precision (0.1%), high stability, low current noise ( 1µv/V) resistors to build the ladder. Are there any standalone R2R ladder chips readily available ? Doesn't have to be a "DAC" chip. I/V conversion and output buffering can be external, or rather I'd prefer that. Thoughts anyone ?

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1st November 2006, 05:45 PM	#2
jwb diyAudio Member Join Date: Mar 2002 Location: San Francisco, USA	You don't like PCM1704? Despite being "not recommended for new designs" they are still produced.

1st November 2006, 07:07 PM	#3
percy diyAudio Member Join Date: Apr 2004 Location: MN	oftmof pcm56 or pcm63 or tda1541... But I'd just like to build it this way. I'd just like to be able to write to a multi-bit latch that is in turn tied straight to a "DAC" (ladder). How I write to the latch, and how often, is what I'd like to see open for trying out a few possibilities. If not anything else, just for the fun of it...

1st November 2006, 07:20 PM	#4
Bernhard diyAudio Member Join Date: Apr 2002 Location: Munich	For 16 bit you need a little better than 0,1%. And tight Ron-matched switches. Accuphase used ICL8019 current switches in their early DACs. I tried 1 PCM54 / bit. Works so far.

2nd November 2006, 02:35 PM	#7
percy diyAudio Member Join Date: Apr 2004 Location: MN	anyone heard about or tried the AD669

2nd November 2006, 02:57 PM	#8
Bernhard diyAudio Member Join Date: Apr 2002 Location: Munich	AD669 83dB SNR ?

3rd November 2006, 01:57 AM	#9
percy diyAudio Member Join Date: Apr 2004 Location: MN	http://www.semiconwell.com/r_net/swr2r.htm !

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