Hi Myles,
That NTC installed at star gnd is really not necessary, the amp boards and psu boards have NTC’s already. Try disconnecting the amp board ground to chassis connection. The psu ground to chassis for each channel should be all thats needed.
I can’t help but think the small psu for the SSR protection boards is throwing a monkey wrench into the clean ground?? You could also try leaving all your wiring as is and bypass the small psu and SSR protection boards. Connect the speaker outs (+)directly to the amp board and gnd(-) to psu ground. When doing this make sure you disconnect the AC from the SSR psu.
I know, more work created for ya. But you’ll get this bump in road ironed out for a dead quiet FH9HVX 😉
That NTC installed at star gnd is really not necessary, the amp boards and psu boards have NTC’s already. Try disconnecting the amp board ground to chassis connection. The psu ground to chassis for each channel should be all thats needed.
I can’t help but think the small psu for the SSR protection boards is throwing a monkey wrench into the clean ground?? You could also try leaving all your wiring as is and bypass the small psu and SSR protection boards. Connect the speaker outs (+)directly to the amp board and gnd(-) to psu ground. When doing this make sure you disconnect the AC from the SSR psu.
I know, more work created for ya. But you’ll get this bump in road ironed out for a dead quiet FH9HVX 😉
Does BD139 have to be on the n channel? In my build I am planning on using heatsinks down each side.... conventionally, with the MOSFETs on short flying leads. I had planned on having both n channel devices on one side and the p on the other and a BD139 on each side also. It suits Prasi 2 channel layout better. Or should I swap things about?
In my case, I omitted the thermistors on the two boards and used a single one on the Prasi supplied power supply board, which provided a convenient star ground point. This of course is very specific to my build since I used a single supply. With a dual mono PS setup, putting the
thermistors on the amp boards makes perfect sense.
Hi All!
Been following this amplifier for a while - own XRK's FH9HVX board- and it's about time to start asking questions and planning a build.
My first question revolves efficiency and power, which might need some context to justify: I have high efficient speakers (modified DIYSG Fusion 12 Tempests - 97-98db/w) and run them from a Class-D TPA3255 amp for TV and VERY passive listening- but the sound makes me feel uneasy when I more intentionally listen. Does not happen with my Adcom 535 or Dynaco/VTA ST70. That said, I love sipping power from the wall for pocketbook and planet- one reasons I went high efficiency in the first place.
I am interested in making this amp lower power, maybe 20 watts, and utilizing a SMPS for the highest efficiency delivery so I can keep the amp running for extended periods, while still keeping bias fairly high (110-150mA?) to keep the compression driver smooth and first 3/4 watt in Class A. Ideally!
Is it possible to run this amp at +/- 24V or something in the ballpark? A dual Mean Well LRS-100 perhaps? Do these transistors/ components not operate effectively at such low voltage? What considerations would I need to make around this platform for low power / higher efficiency? Is there another Class AB amp I should be looking at instead? I'm starting here because I've heard such great things about this amp, and appreciate the contributions of XRK / Vunce / JPS64 / Apex / Prasi (and so on!) to the forum.
Thanks for the help on question 1, in advance!
Been following this amplifier for a while - own XRK's FH9HVX board- and it's about time to start asking questions and planning a build.
My first question revolves efficiency and power, which might need some context to justify: I have high efficient speakers (modified DIYSG Fusion 12 Tempests - 97-98db/w) and run them from a Class-D TPA3255 amp for TV and VERY passive listening- but the sound makes me feel uneasy when I more intentionally listen. Does not happen with my Adcom 535 or Dynaco/VTA ST70. That said, I love sipping power from the wall for pocketbook and planet- one reasons I went high efficiency in the first place.
I am interested in making this amp lower power, maybe 20 watts, and utilizing a SMPS for the highest efficiency delivery so I can keep the amp running for extended periods, while still keeping bias fairly high (110-150mA?) to keep the compression driver smooth and first 3/4 watt in Class A. Ideally!
Is it possible to run this amp at +/- 24V or something in the ballpark? A dual Mean Well LRS-100 perhaps? Do these transistors/ components not operate effectively at such low voltage? What considerations would I need to make around this platform for low power / higher efficiency? Is there another Class AB amp I should be looking at instead? I'm starting here because I've heard such great things about this amp, and appreciate the contributions of XRK / Vunce / JPS64 / Apex / Prasi (and so on!) to the forum.
Thanks for the help on question 1, in advance!
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Hi r66cort,
I am actually using my FH9HVX for TV audio right now. It’s using less than 29W from the wall. I don’t know how much more efficient you can get than that for a Class AB with potential for 100W@8ohm??
I think “scaling down” psu requirements is more appropriate for class A amps that run full throttle all the time.
I would recommend building the FH9HVX as intended, it’s a wonderful amp.
I am actually using my FH9HVX for TV audio right now. It’s using less than 29W from the wall. I don’t know how much more efficient you can get than that for a Class AB with potential for 100W@8ohm??
I think “scaling down” psu requirements is more appropriate for class A amps that run full throttle all the time.
I would recommend building the FH9HVX as intended, it’s a wonderful amp.
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Thank you, Vunce! This is very helpful, and point well taken. A touch under 29 watts is pretty solid, indeed! Was this taken while playing music, or at idle?
Can you please remind me where you landed for your current FH9HVX power supply system? Are you using a dual mono linear PS? Post #175 showed you tried 28 / 32/ and 34V trafos - what voltage did you land on? 200/300/400 VA? Using All Cee's or CRC? I know at one point you enjoyed the Abletec with additional filtering, but had issues with the Cresnet? Was that ever resolved? Just trying to get a sense of your system, process, and how that relates to the numbers and your enjoyment of the amp.
Thank you again for your help. Much appreciated!
Can you please remind me where you landed for your current FH9HVX power supply system? Are you using a dual mono linear PS? Post #175 showed you tried 28 / 32/ and 34V trafos - what voltage did you land on? 200/300/400 VA? Using All Cee's or CRC? I know at one point you enjoyed the Abletec with additional filtering, but had issues with the Cresnet? Was that ever resolved? Just trying to get a sense of your system, process, and how that relates to the numbers and your enjoyment of the amp.
Thank you again for your help. Much appreciated!
Looking foreward to getting my fh9 built. Just got an ACA done and I'm really impressed . I don't know if they're comparable, but seeing as they use similar output devices.... maybe a little . I use irfp140n in the ACA .
For my FH9 I'm going with a 32vac trafo for a little under 50vdc
For my FH9 I'm going with a 32vac trafo for a little under 50vdc
Very cool, jimk04! Sounds like a nice sweet-spot. Are you thinking dual mono?
I hear great things about the ACA. Looking at building an ACA mini myself - push pull for a little more efficiency in Class A. Only issue is the heat, live voltage on the heatsinks, and my 10 month old. Current solution is "holding," but...
I hear great things about the ACA. Looking at building an ACA mini myself - push pull for a little more efficiency in Class A. Only issue is the heat, live voltage on the heatsinks, and my 10 month old. Current solution is "holding," but...
Great Setup! I’d say you have a few months before the “fence” becomes a guardrail for a walking toddler, LOL!!
The FH9HVX was playing at low/moderate volume driving 90dB 8ohm speakers during the meter reading in the above picture.
I haven’t popped the lid in quite a while, I’ll take a peek and gather some info….
The FH9HVX was playing at low/moderate volume driving 90dB 8ohm speakers during the meter reading in the above picture.
I haven’t popped the lid in quite a while, I’ll take a peek and gather some info….
Ha! Thanks, Vunce! Yes, I expect the "fence" will need some buttressing in the coming months. A whole new level of DIY - protecting your other projects!
Appreciate you popping the top of the FH9HVX!
Appreciate you popping the top of the FH9HVX!
Not quite no, I have the Prasi compact stereo layout PCBs. So 2 channels one on board. Fed from one PSU.
So it isn't optimum but what I might do is build another stereo board, fed from another PSU, and then I have 4 channels and I can bi-amp the L and R channels then. One stereo board per speaker.
Just seeing you built the RACAM! Now coming here to find you're planning a (effectively) dual mono bi-amped FH9!? Slightly jealous 😛
Don't be too jealous....I've been building the fh9 for ever,! This stereo board is very tight soldering wise and it took me a while to get all the parts together. Hopefully will hear it sometime soon. Too many audio projects....too little spare time!
Topless FH9HVX!
Single 500va trafo with dual 32v-0-32v center tapped secondaries. Each channel gets its own Compact CRC psu board that was designed by DIYA member Prasi. Mine are set up for straight CC operation, jumpers were installed in the R positions. This combo yields +/-42V rails and bias current is set to 160mA. Heatsinks are barely warm after all day/night operation, perfect summer amp 🙂
Single 500va trafo with dual 32v-0-32v center tapped secondaries. Each channel gets its own Compact CRC psu board that was designed by DIYA member Prasi. Mine are set up for straight CC operation, jumpers were installed in the R positions. This combo yields +/-42V rails and bias current is set to 160mA. Heatsinks are barely warm after all day/night operation, perfect summer amp 🙂
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Thanks Jim! These psu boards enabled the use of this center tapped trafo for essentially a dual mono power supply in a very compact chassis.
VERY nice, Vunce. Kudos. What is that compact chassis from? You have some great finds for donor chassis.
Vunce, your FH9 is a BRICK! Compact, dense, and cool - especially with the heatsinks having a slight curvature a la Hafler DH-220. Thank you for taking the time to investigate the PS and share a photo. VERY helpful!
I assume Prasi's CRC PS boards are smaller than the All Cee's, and it also looks like you have 60,000uf per channel in your dual PS arrangement, if I'm reading correctly? I'll save you from the wide eyes emoji, but that's pretty wicked. Is the plate between the trafo and PS boards purely for structure, or to also mitigate magnetism issues?
I am considering using a Dynaco stereo120 chassis as the base for my build (already own) - with a pair of "really big heatsinks." Maybe I can get sneaky and integrate 2 PS boards as well. I also noticed XRK did a point-to-point PS capacitor arrangement for his Griddle Amp not dissimilar to the old Dynaco's. Has anyone attempted, or have references/links to, building something like this for all caps? (You can also tell me it's too much work and not worth my time. Ha)
Thank you all again for your help and input.
I assume Prasi's CRC PS boards are smaller than the All Cee's, and it also looks like you have 60,000uf per channel in your dual PS arrangement, if I'm reading correctly? I'll save you from the wide eyes emoji, but that's pretty wicked. Is the plate between the trafo and PS boards purely for structure, or to also mitigate magnetism issues?
I am considering using a Dynaco stereo120 chassis as the base for my build (already own) - with a pair of "really big heatsinks." Maybe I can get sneaky and integrate 2 PS boards as well. I also noticed XRK did a point-to-point PS capacitor arrangement for his Griddle Amp not dissimilar to the old Dynaco's. Has anyone attempted, or have references/links to, building something like this for all caps? (You can also tell me it's too much work and not worth my time. Ha)
Thank you all again for your help and input.