No problem. I used 984-ATS-PCB1070. https://www.mouser.com/ProductDetai...%2BwC%2BxZA==&countrycode=US¤cycode=USD
If someone need output mosfets for FH9HVX amp, I have a pair of FQA46N15 and FQA36P15 mosfets. PM for details.
Greetings everyone!
After almost 18 months of enjoying my FH9HVX amplifier, I noticed recently that the left channel was only about half as loud as the right channel. after removing other components from the system one by one to rule them out as the problem I ended up with just an old mp3 player feeding the amp directly and the problem remained. The sound from the left side is not bad, just half as loud so first I did a check of all connections and found nothing visibly wrong. Then I measured voltages at the pins of the N and P mosfets and compared them to the right side with respect to ground. The P voltages were spot on left and right but the N voltages showed the following discrepancies. Left side; Gate 3.7v, Drain 52v and Source 21.5mv. Right side; Gate 3.6v, Drain 51.9v, and Source 35mv, a difference of 13.5mv on the source pins. I should note that I set the bias at 26mv two days ago.
What else should I be looking at?
This amp has become my main listening amp and I prefer it to my HK receiver and literally every other amp I've built! it runs 8-10 hours a day, every day and until now the performance has been outstanding!
For some reason I cannot currently transfer pics from my phone to my pc which I'm using to write this but could probably do it from the phone to the forum if pics are requested.
Jim
After almost 18 months of enjoying my FH9HVX amplifier, I noticed recently that the left channel was only about half as loud as the right channel. after removing other components from the system one by one to rule them out as the problem I ended up with just an old mp3 player feeding the amp directly and the problem remained. The sound from the left side is not bad, just half as loud so first I did a check of all connections and found nothing visibly wrong. Then I measured voltages at the pins of the N and P mosfets and compared them to the right side with respect to ground. The P voltages were spot on left and right but the N voltages showed the following discrepancies. Left side; Gate 3.7v, Drain 52v and Source 21.5mv. Right side; Gate 3.6v, Drain 51.9v, and Source 35mv, a difference of 13.5mv on the source pins. I should note that I set the bias at 26mv two days ago.
What else should I be looking at?
This amp has become my main listening amp and I prefer it to my HK receiver and literally every other amp I've built! it runs 8-10 hours a day, every day and until now the performance has been outstanding!
For some reason I cannot currently transfer pics from my phone to my pc which I'm using to write this but could probably do it from the phone to the forum if pics are requested.
Jim
Glad you like the FH9HVX!
It sounds like the output stage is working fine (because the source is mV so DC setpoints are good). If something is off here, you have massive DC offset or the output is very distorted.
A few things to debug problem.
1. swap your input left/right does the softness change or stay the same?
2. check your signal cables for loose connection, frayed wire etc.
3. Check your amp’s solder joints around the input stage. Input coupling cap, etc. If you made amp using quick disconnect output stage you can remove the amp in 5 minutes. Retouch solder joints around input. It sounds like a cold solder joint that got worse with time.
Good luck!
It sounds like the output stage is working fine (because the source is mV so DC setpoints are good). If something is off here, you have massive DC offset or the output is very distorted.
A few things to debug problem.
1. swap your input left/right does the softness change or stay the same?
2. check your signal cables for loose connection, frayed wire etc.
3. Check your amp’s solder joints around the input stage. Input coupling cap, etc. If you made amp using quick disconnect output stage you can remove the amp in 5 minutes. Retouch solder joints around input. It sounds like a cold solder joint that got worse with time.
Good luck!
legis31, I had a similar problem just awhile ago. I found it to be a loose molex connection on the amp board input. I could move the female part a bit and the sound would increase, I take my finger off and it goes back to faint volume. I changed the tin connectors and reinstalled the connection, the problem was solved. I hope your's is this easy to solve.
MM
MM
X,
Thanks for the quick response. After checking the solder joints on the board & finding nothing, I replaced the input wires only to arrive at intermittent sound instead of reduced volume so I wriggled the wires and the sound returned. Hmmmm... It seems I have an internally defective rca jack and not a cold solder joint. I never had one fail before so it's possible that when I first soldered it I may have overheated the jack's center lug or maybe it was just defective all along. Just touching the interconnect to it caused intermittent sound so I changed that with a new rca cable and had the same problem. I'll swap out the jack later on today. None of my interconnects fit snugly on it either but are tight on the other channel. Sloppy tolerances maybe.
I'm going to install an SFP in the amp at the same time, too since the backordered parts for it finally arrived.
Thanks again!
Jim
Thanks for the quick response. After checking the solder joints on the board & finding nothing, I replaced the input wires only to arrive at intermittent sound instead of reduced volume so I wriggled the wires and the sound returned. Hmmmm... It seems I have an internally defective rca jack and not a cold solder joint. I never had one fail before so it's possible that when I first soldered it I may have overheated the jack's center lug or maybe it was just defective all along. Just touching the interconnect to it caused intermittent sound so I changed that with a new rca cable and had the same problem. I'll swap out the jack later on today. None of my interconnects fit snugly on it either but are tight on the other channel. Sloppy tolerances maybe.
I'm going to install an SFP in the amp at the same time, too since the backordered parts for it finally arrived.
Thanks again!
Jim
I’m glad it is a simple faulty connector.
Reminds me of a story. I pulled my hair out for over a week because when I looked at the amp signal on Oscope it was distorted like amp was struggling with clipping. But when I listened to the amp it sounded fine. Turned out I had an RG-174 BNC cable that was internally shorted (probably from being stepped on). So the cable was shorting out the amp’s output!
Reminds me of a story. I pulled my hair out for over a week because when I looked at the amp signal on Oscope it was distorted like amp was struggling with clipping. But when I listened to the amp it sounded fine. Turned out I had an RG-174 BNC cable that was internally shorted (probably from being stepped on). So the cable was shorting out the amp’s output!
Hi X, boards arrived in Aus.
Mouser parts arrived, and what they didn't have, I have ordered from Element 14... .
10f/rs225 Speakers are going great on the LM3875, but definitely looking forward to this amp to really drive them!
Cheers.
Nik
Mouser parts arrived, and what they didn't have, I have ordered from Element 14... .
10f/rs225 Speakers are going great on the LM3875, but definitely looking forward to this amp to really drive them!
Cheers.
Nik
Got the boards today, thank you!
Now I’m curious if any of the you guys built this amp with other than the bom specified inductors . Any cheaper replacements?
I was thinking to wind my own 15ga inductor.
Now I’m curious if any of the you guys built this amp with other than the bom specified inductors . Any cheaper replacements?
I was thinking to wind my own 15ga inductor.
As long as it is close a 1.0uH to 1.5uH and at least 30A with low sub 10mohm DCR and pads that fit the slot cutouts for soldering. I could not find anything low enough for 2923. VER or AGP series?
See the second part of this post https://www.diyaudio.com/community/...w-class-ab-for-lean-times.353512/post-7084429