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and now for something completely different part 3


kevin gilmore
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15 hours ago, starcat said:

Planning on using for the GRLV the OPA134PA, if it is ok.

Also, which LT1021 exactly have you been using, any p/n by the hand? This one is with 0.05% tolerance.

opa134pa is exactly what i am using and is fine

the LT1021DCN8-10#PBF is about half the price of the version of the reference your are proposing. 

The output accuracy is a function of the accuracy of the LT AND the divider network (which sets the output voltage) by taking the output and dividing it down to a nominal 10V. This is fed to the opamp which acts as a comparator between this and the LT. Unless you are going to use 0.1% or better tolerance hand picked resistors for the divider network there is not much point in spending $$$ on a very accurate version of the reference when the divider resistors  are 1% and will drown out any extra accuracy a more expensive version of the LT will provide....

If you want high accuracy and don't want to spend $$$ you can always hand measure and match the resistors to get a more accurate output voltage (if you need that level of accuracy).

 

 

Edited by jamesmking
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Long time between drinks, been working on this for a few months and finally got my panels back. It’s going to be a dual mono GRLV PS with a quartet of CFA2’s, balanced in and out using a Goldpoint 10k 47 position stepper.

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Edited by johnwmclean
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  • 1 month later...
13 hours ago, Kerry said:

SMD version of the CFA3 dynamic

Ah Awesome!

@Kerry @kevin gilmore - what would you gents consider to be the ultimate overkill build for this CFP/A?  4x CFA2 boards or 2x CFA3 boards in 2 separate chassis, with 2 separately enclosed GRLV psu? Or is this new SMD animal you have designed the way to go, assuming the same multiple separate chassis & PSU overkill plan?

Separately, I've read the entire thread and can't seem to get my head around the difference between using 4x CFA2 boards or 2x CFA3 boards - are there additional PCBs that need to be printed if I go the 4xCFA2 route (scheming going down this road and 2 dissipante cases such that each pcb has its own heatsink). 

Or do I just wait and go for the SMD boards you're working on?

Many thanks in advance for the help and guidance

Cheers

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Just go 2x CFA3 boards and 2x GRLV (on one or even two transformers). For the amp you do not need to separate the + and - per channel, so 2x CFA3 boards is more than good to go. No need to put the CFA3 boards in separate cases, if you want to separate the L and R channels, put an aluminium divider in the mid of the amp case and use per channel umbilical on the back (off separate GRLVs and transformers in the PSU case), so basically going strict dual mono in two chassis in total. That's already more than overkill. 

You can have the headphone protector as well (for dynamic headphones, stats don't need that) and eventually the ZF/SS selector (which I didn't do). 

Edited by starcat
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18 hours ago, mwl168 said:

Care to share a few listening impressions? 

I do need a planar... but HD800S are amazing with the CFA2. Comparative to the mini dynalo it’s more refined, open, bass has better detail and impact. I’ve not heard the HD800S sound this good, not quite as good as the SR-007 with a Carbon, but could be very content with the small compromises. 

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I was comparing the HD800 to a HE-6 planar on a RSA The Dark Star. Both phones were pretty close, the HE-6 won by a small amount. And I still have this combo. 

Gorgeous build, John, congrats. 

Btw, what are the transformer covers that you are using? And what are the PCBs on the back and the one mounted on the front panel right next to the phones jack? 

Edited by starcat
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9 hours ago, starcat said:

Btw, what are the transformer covers that you are using? And what are the PCBs on the back and the one mounted on the front panel right next to the phones jack? 

The transformer and covers both from from Antek:
https://www.antekinc.com/ca-100-steel-cover/

The rear panel has a diyaudio soft start circuit (blue pcb) and also amb audios ε24 power switch driver circuit/small transformer for the momentary switch on the front.

Next to the output on the front is Kevins balanced headphone protector.  

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14 hours ago, johnwmclean said:

I do need a planar... but HD800S are amazing with the CFA2. Comparative to the mini dynalo it’s more refined, open, bass has better detail and impact. I’ve not heard the HD800S sound this good, not quite as good as the SR-007 with a Carbon, but could be very content with the small compromises. 

Interestingly, my experience very much mirror yours - HD800 was the first can I used with my CFA2 and I could not stop listening to that combo. The control, speed, clarity are amazing and addictive.

The second can I grabbed to try on the CFA2 was my Audeze LCD2 🙂 

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Anyone here tested the PecanPi XLR-out/DAC with the Pi as roon (or LMS) endpoint?

Measurements look pretty amazing and I am thinking about ordering one and if it passes the listening test, putting it in a nice custom case with a GRLV. So... ETH in and XLR analog out. To be used with all the amps here. Nice control via iPad. 

Edited by starcat
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1 minute ago, Sherwood said:

Looks sweet, Starcat.  Let me know if it works well, it would be a very cool remote source for the inevitable separate system locations we all accrue.

Sure, ordered parts and building a 9V 1.5A positive only GRLV for it. 

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