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Simple High Performance DC Coupled Class A HPA with sub PPM THD
Simple High Performance DC Coupled Class A HPA with sub PPM THD
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Old 31st January 2019, 04:17 AM   #381
bkdog is offline bkdog
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Simple High Performance DC Coupled Class A HPA with sub PPM THD
Just had a quick look and it looks like a common source jfet amplifying device that is cascoded, with a cascode jfet current source as a load.
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Old 9th February 2019, 01:26 PM   #382
avtech23 is offline avtech23  Australia
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Simple High Performance DC Coupled Class A HPA with sub PPM THD
Just wondering how other people in this group buy are getting on with their builds.

I've finally completed the power supply (as well as the misc boards).

Spent the past 2 hours tracing a short to C235 (0.1u) that took out V232 on the positive rail. Amazingly, Mouser had accidentally sent me 2 of those Fets instead of one, so no waiting for a minimum order for that one!

Power supply is now rock solid on both rails and all that's left is the amp board and probably copious amounts of troubleshooting!



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Old 10th February 2019, 08:00 AM   #383
yourownbuzz is offline yourownbuzz  Australia
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If I find I missed ordering something/broke something I usually get it from RS (free delivery no min order) or Arrow (free express delivery, no min order, and you can usually find discount coupons floating around the place).


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Originally Posted by avtech23 View Post
Just wondering how other people in this group buy are getting on with their builds.

I've finally completed the power supply (as well as the misc boards).

Spent the past 2 hours tracing a short to C235 (0.1u) that took out V232 on the positive rail. Amazingly, Mouser had accidentally sent me 2 of those Fets instead of one, so no waiting for a minimum order for that one!

Power supply is now rock solid on both rails and all that's left is the amp board and probably copious amounts of troubleshooting!



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Old 10th February 2019, 08:58 AM   #384
avtech23 is offline avtech23  Australia
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Simple High Performance DC Coupled Class A HPA with sub PPM THD
Thanks, I never realised RS was no minimum order for free delivery!

Kinda sick of getting stung with a 'foreign transaction' bank fee whenever I order from Mouser (plus their lead time from US) and Element14 let me down every time I order with missing or delayed components.
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The ever growing project list.. :NAP140 Clone, NAD 3020i & 3225PE, JLH1969, TDA2050, Fender 5F2A Princeton, NE5532 Preamp | : VSQC Phunk Style, Retro 50W | Filmosound 601 | SHPA | : Apex AX-14 | TGM-10 | TDA7265 | LM4780 (Last in line)...maybe
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Old 10th February 2019, 09:23 AM   #385
yourownbuzz is offline yourownbuzz  Australia
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well with arrow you can pay by paypal avoiding intl txn fee, otherwise can look into something like a 28degrees credit card which has no intl fees.
rs do sometimes ship from the UK though which ends up taking about a week or a week and a bit, but for next day delivery items they really do next day courier it!
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Old 10th February 2019, 11:09 AM   #386
xrk971 is offline xrk971  United States
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Simple High Performance DC Coupled Class A HPA with sub PPM THD
Sounds like you are making great progress, Avtech!

The main amp is straightforward - I have built several and they fired right up. Just make sure you don’t put a PNP where there should be a NPN and you will be fine.
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Old 10th February 2019, 11:43 AM   #387
avtech23 is offline avtech23  Australia
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Simple High Performance DC Coupled Class A HPA with sub PPM THD
Thanks X. I'll also try not to let any of those little SMD critters escape!

I ended up mounting the voltage regulators onto a remote bracket as the orientation of one of the reg PCBs wasn't compatible with the vertical back to back heatsink arrangement. Otherwise, everything has fit together real nicely.
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The ever growing project list.. :NAP140 Clone, NAD 3020i & 3225PE, JLH1969, TDA2050, Fender 5F2A Princeton, NE5532 Preamp | : VSQC Phunk Style, Retro 50W | Filmosound 601 | SHPA | : Apex AX-14 | TGM-10 | TDA7265 | LM4780 (Last in line)...maybe
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