[cgrums]

Quote:

Originally Posted by tomb Yes - pics, please. Did you wire to the proper INputs? That messed me up once. The inputs next to the "PIMETA" text and smiley face only work for the RK097 pot. All others use the square-shaped set of pads over in the corner. The other trip-up is leaving out the jumpers for R8. You won't get any sound unless you put a jumper in those positions (assuming you don't use the R8 resistors - most don't).

Tomb's right again! Left those jumpers out of R8...lets see what this does

 

[cgrums]

It works!! After jumpering R8 I found that the browndog adaptor for the L/R Opamp were bent and improperly inserted in the socket. Instead of mounting a new AD8620 on another adaptor last night (it was late) I decided to just throw in a spare 2123.

This amp sounds amazing. I'm listening to the Ipod through an ALO bling-bling line out and the amp is driving a brand-new pair of SR-60s. I'm very impressed with the sound quality of this combination. I by no means have an 'experienced' ear but I can definitely pick out some huge improvements in the detail in the sound. The Grados respond very favorably to my different musical moods and do exceptionally well (as is most often reported) with my selection of rock (of all types). While I expected great rock performance, I'm most impressed with the way these phones handle hip-hop/electronica. They are bright and at times can border on being harsh treble-wise but they work very well with the vast majority of my music.

Now that I've got the amp making sound I'm going to turn my attention to the detail work on the case. One question comes to mind: I'd like to have the option to use both stereo RCA inputs as well as a 3.5mm mini for the Ipod...how do I tie both in? Is it acceptble to just double up the input lines to the board?

Beyond that I think everything else should go fairly smoothly as I've gotten new bits for the dremel and a Uni-Bit set for the drill. I should be able to have pictures up this evening if everything goes well.

 

[tomb]

Glad you got it working.

There are a couple of options for multiple inputs. Ordinarily, you wouldn't just parallel them. There is always the chance that two inputs could be powered at once, and that would be bad.

1. Use switched mini's. The signal wires for the RCA's are routed through the switched legs of the mini's. That way, the RCA's are in the circuit by default, but get switched out when a mini is plugged in.

2. Use a DPDT switch. If you have isolated your power ground (best), this only requires switching the single signal leg of L & R. All the signal grounds are tied together with the case (if a metal case). That means two wires each: mini and RCA's, so a DPDT switch can handle it. Those are cheap and available anywhere. If your case is plastic, then you can still tie together the signal grounds and use a simple DPDT switch.

In any event, remember that signal ground and power ground are not the same thing in a virtual-ground amp such as the PIMETA: never the twain shall meet.

 

[cgrums]

Quote:

Originally Posted by tomb Glad you got it working. There are a couple of options for multiple inputs. Ordinarily, you wouldn't just parallel them. There is always the chance that two inputs could be powered at once, and that would be bad. 1. Use switched mini's. The signal wires for the RCA's are routed through the switched legs of the mini's. That way, the RCA's are in the circuit by default, but get switched out when a mini is plugged in. 2. Use a DPDT switch. If you have isolated your power ground (best), this only requires switching the single signal leg of L & R. All the signal grounds are tied together with the case (if a metal case). That means two wires each: mini and RCA's, so a DPDT switch can handle it. Those are cheap and available anywhere. If your case is plastic, then you can still tie together the signal grounds and use a simple DPDT switch. In any event, remember that signal ground and power ground are not the same thing in a virtual-ground amp such as the PIMETA: never the twain shall meet.

Good info. How do you best recommend isolating the power and signal ground?

 

[tomb]

The simplest method is to use a plastic power jack - either 2.1mm or 2.5mm, depending on your walwart's plug.

 

[cgrums]

I've had a few hours of listening to get a feel for this amp and am very impressed. I'm still trying to adjust to the Grado sound with my SR-60s (I may not be a Grado guy) and the AD8620/8610 was far too analytical/bright/harsh with those cans. The OP2132PA/132PA combo is much better suited to the brighter headphones.

I'm planning a purchase of the HD-580 next month and am very eager to hear those with the AD8620/8610 in the Pimeta versus the Grado. I'm also curious about the Beyer and AT sound...this place is killing my wallet

Next up is a Millett Hybrid w/Diamond Buffers...I've also ordered the boards for the PPAV2 and Dynahi...and an AlienDAC. I think it's safe to say I'm hooked.

 

[tomb]

You should probably add the M3 to that list. It's on the level of the PPA, and requires a power supply common to the others you mention: ~24VDC TREAD or STEPS. The PPA uses a diamond buffer output stage, the M3 uses MOSFET's. Amb sells the M3 board and has his own site similar to Tangent's, just different.

Your choice of the Millett as your next build is just right, IMHO. Be sure to save some of those BUF634's from your PIMETA, or get a couple of OPA551's or Intersil's. That will get you up and running pretty quick with the Millett, letting you enjoy 80-90% of the sound quality while you're working on the DB's. The SOHA is also a good choice if you want to pursue tubes further. Or, you can wait for the Millett III when they get ready to Group Buy it.

What is they say? Welcome to Head-Fi ... sorry for your wallet.