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The YARRA Preamplifier/HPA for Melbourne DB Group Buy
The YARRA Preamplifier/HPA for Melbourne DB Group Buy
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Old 22nd November 2019, 08:46 PM   #1041
JPS64 is offline JPS64  Germany
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I‘m using this one exactly with no issue.

JP
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Old 22nd November 2019, 10:33 PM   #1042
Vunce is online now Vunce  United States
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The YARRA Preamplifier/HPA for Melbourne DB Group Buy
Hi redjr,
I’ve got something for you to try.
Solder a jumper wire as per my markup of your I/O panel for the two output RCA’s.
That will fix the ungrounded outputs.
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Old 23rd November 2019, 01:24 AM   #1043
redjr is offline redjr  United States
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The YARRA Preamplifier/HPA for Melbourne DB Group Buy
Quote:
Originally Posted by Vunce View Post
Hi redjr,
I’ve got something for you to try.
Solder a jumper wire as per my markup of your I/O panel for the two output RCA’s.
That will fix the ungrounded outputs.
Hey Vunce,

Thanks for the tip. During my troubleshooting this afternoon, and once I figured out what-was-what on the back of the jacks, I realized I could strap those points and ground the jack. While that's a stop-gap approach, and I may well do it, I'd like to know why those particular jacks are wired that way. Seems to me there must be a valid reason, unless they are defective. (2 not likely) Either way, I'm somewhat surprised no one else ran into this issue. Now that I know only one jack is grounded, I will use that jack for my sub.

Also, if we 'know' the reason, it would be helpful information to someone else building this pre down the road. It sure caused me some headache today! I'm curious if this grounding is an issue with other style jacks. If it is, it would seem to me to be a PCB design decision.(?) I guess no one is using a sub - at least with these jacks in this configuration.
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Old 23rd November 2019, 02:35 AM   #1044
Vunce is online now Vunce  United States
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The YARRA Preamplifier/HPA for Melbourne DB Group Buy
Hi redjr,

Your RCA jacks are not defective. The heavier gauge pins on the RCA jack are for support purposes only and have no electrical connection. You can actually remove those pins and install them in the vacant holes on the side and bend the GND and signal pins 90° to fit in the cut grooves to use these jacks as a right angle mount. The circled pads where the ground pin solders on the I/O board are not connected to the X111 header. But it’s complementary output ground pad is. So connecting a “stereo” amplifier or a Y-adapter cable would have one ground pad connected to the X111 header and all would be fine.
You are probably the first builder to try a set of outputs with a mono cable and happened to use the un-grounded output.
The work-around for those two locations would be to solder a jumper wire between the GND pin and either of the fat support pin pads (they also make connections to the X111 header gnd pins)
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Old 23rd November 2019, 04:21 AM   #1045
redjr is offline redjr  United States
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The YARRA Preamplifier/HPA for Melbourne DB Group Buy
Quote:
Originally Posted by Vunce View Post
Hi redjr,

Your RCA jacks are not defective. The heavier gauge pins on the RCA jack are for support purposes only and have no electrical connection. You can actually remove those pins and install them in the vacant holes on the side and bend the GND and signal pins 90° to fit in the cut grooves to use these jacks as a right angle mount. The circled pads where the ground pin solders on the I/O board are not connected to the X111 header. But it’s complementary output ground pad is. So connecting a “stereo” amplifier or a Y-adapter cable would have one ground pad connected to the X111 header and all would be fine.
You are probably the first builder to try a set of outputs with a mono cable and happened to use the un-grounded output.
The work-around for those two locations would be to solder a jumper wire between the GND pin and either of the fat support pin pads (they also make connections to the X111 header gnd pins)
That explains a lot.
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Old 23rd November 2019, 08:29 AM   #1046
JPS64 is offline JPS64  Germany
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Are the Jack screws mounted?

JP
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Old 23rd November 2019, 10:22 AM   #1047
JPS64 is offline JPS64  Germany
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Bad question, sorry, as they‘ve no electrical contact!

JP
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Old 27th November 2019, 06:56 PM   #1048
aljordan is online now aljordan  United States
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Quote:
Originally Posted by Vunce View Post
My 22v Talema’s are installed, but I did test a Talema 70064K (18v) transformer with the Qmodo jig for the Yarra and came up with:
Cs: 0.15uF
Cx: 0.01uF
Rs: 24R

Yarra snubber location ID’s
Cs = C153,154,173,174
Cx = C151,152,171,172
Rs = R153,154,173,174
I don't own an oscilloscope. I followed the annotated BOM someone had posted a long time ago and it seems like my values are way too high compared to the values others have come up with. I have 15 volt transformers and I used 2.2 uF caps at all 8 locations, and 51R resistors.

What in effect am I doing to the performance of my Yarra with these values?
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Old 28th November 2019, 12:06 AM   #1049
xrk971 is online now xrk971  United States
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The YARRA Preamplifier/HPA for Melbourne DB Group Buy
I am using the stock BOM values. Unless you have and Oscope and a Quasimodo jig - it’s not essential to get a perfectly cricitcally damped pulse from the diode switch. Especially at the currents we are dealing with here.
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Old 30th November 2019, 03:46 AM   #1050
aljordan is online now aljordan  United States
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Originally Posted by thompsontechs View Post
I'll take them Al, hit me up with a number and paypal.


JT
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