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Recent Purifi EVAL1 build

Rick Sykora

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Having just sold my Buckeye Purifi amp, realized I had all parts available to build an EVAL1 except the case. Had been searching for a case with serious heat sinks but Ghent’s case is nice heavy aluminum and the back is cutout for the EVAL1 with nice silkscreening. I opted for the version with Speakon connectors but ended up just mounting them unwired (more on this later). As it may help others, here is some notes from this build.

Ghent generally does a nice job of kitting all the needed hardware and wiring. Instructions are not included but having built many Hypex versions already, I relied on my experience. In one case, this cost me as should have mounted the feet right away. In older builds, would have mounted the feet last and the feet screws had threading on the case bottom. This was not done for the EVAL1 case and the screws need to be added from the inside. This is key as one screw is under the buffer board and cannot be inserted if the buffer has been attached.

Here is a pic of the bottom with the feet attached…
IMG_0737.jpeg


Notice despite the feet having been machined for countersinking the screws heads, the screw heads are invisible as they are inside the case. The left back foot is the tricky one but the rest can be removed and reattached readily.

Otherwise, this is a fairly straightforward build. One notable exception was a miswired control cable. This kept the amp from powering up initially but so did forgetting to switch the SMPS jumpers from regulated to unregulated. Once I corrected the wiring (which now includes the AmpON and FATAL wiring), noted the standby switch no longer matters. This is probably best as it is of marginal utility mounted on the back panel. Here is a look at the finished internals…

IMG_0734.jpeg


My only additions were the high voltage cabling wraps and a knurled washer for the chassis ground. Not sure whether Ghent missed or does not include, so I added the washer underneath the crimp connector to be sure the ground wire keeps good contact with the case. As the case will accommodate the higher voltage MicroAudio power supply, I tried one I had from Buckeye, but his did not have the connector for the power LED and opted for the simpler wiring as I may sell this one in the future.

My last note is on the Speakon connectors. If I a future owner wants them wired, am willing. Since I have good banana plugs, I chose not to heat up the buffer board as the connections need to be soldered. While the wires would be short, was also not clear about the output feedback sense wiring. Ran my usual tests to ensure the amp build was good. Will include some of those later as the pics are not on my iPad.

Here is a final pic…

IMG_0735.jpeg


Although this is same as you would see on Ghent site, thought some my like to see. The front panel is nicely machined but plain. Seems appropriate as this is a nice simple amp (no trigger input or front panel switch).

EDIT: realized this thread lacked a pic of the back panel, so borrowed the Ghent one...

Ghent-Audio-Purifi-EVAL1-b.jpg


Hope this helps and plan a listening test alongside my Buckeye NCx500 next.:)
 
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Start of posting some measurements, here is THD vs Power (each channel driven individually, 1 kHz, 4 ohms)...
1692359741695.png


Nice low distortion and meets expected output power at 1% THD. Now, let's look at 100 Hz...

1692273762871.png


Not as well matched, but fine. Next a look at noise with input shorted...

1692357597341.png


This is very close to noise floor of my test rig. Just a sanity check as not really set up to measure really low noise diffs.

p.s. sounds great too!
 
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Btw, can use the inexpensive board shown here to add a trigger. :)

Just use AMPon signal from the buffer board and ground from power supply to connect to J1.

NOTE: if a (correctly wired) Ghent harness is used, can use the supplied wire. This will also restore the back panel standby switch. which needs to be turned on when a trigger is not inserted.
 
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