Finished one of the amp and test fitted inside my mono bloc cabinets 
The amp is running hot and making my Troels to sing in one channel and USSA-5 on the other. Hopefully in the next couple of weeks should finish the second channel too and hear the stereo. Made some good use of DIY skills and the JLH1969 L type profile aluminium plates for this and it does make life easier but too tight inside the case with the VU meter. Auto bias comes to pretty stable 285mV with the offset hovering around 0.00mV. Offset drifts a bit with temperature changes but very very stable and the amp gets hot within 15-20 mins of playback. i could place fingers for few seconds so going by Papa's temperature check seems like around 500C.
Few pics of my build and thanks to everyone providing valuable inputs and especially Papa for the mosfets
The amp is running hot and making my Troels to sing in one channel and USSA-5 on the other. Hopefully in the next couple of weeks should finish the second channel too and hear the stereo. Made some good use of DIY skills and the JLH1969 L type profile aluminium plates for this and it does make life easier but too tight inside the case with the VU meter. Auto bias comes to pretty stable 285mV with the offset hovering around 0.00mV. Offset drifts a bit with temperature changes but very very stable and the amp gets hot within 15-20 mins of playback. i could place fingers for few seconds so going by Papa's temperature check seems like around 500C.
Few pics of my build and thanks to everyone providing valuable inputs and especially Papa for the mosfets
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Thanks guys, Gyuri for your perfect timing on the jfets mounting made life easier it was picture perfect with the bias and offset and I never build any amp so far being so precise. Rock stable bias and offset around 0mV.
Oh yes already with single channel I am mesmerized its making the Jantzen woofer to shake which I never saw it moving that much air paired with the dual mono USSPA preamp and 1862 R-2R dac as source
Need to play for 2-3 hrs continuously to check the heat dissipation on the heat sinks which are like 300/150/50mm aluminium nice profile.
Looking for tricks to cheat the XLR/RCA single ended usage and avoid any kind of toggle switch. As toggle switch not sure if it induces some sort of noise being signal carrying. I do have Soekris 1021 balanced DAC so want to try that as a direct source for balanced and check as never I have heard a balanced setup so far.
Oh yes already with single channel I am mesmerized its making the Jantzen woofer to shake which I never saw it moving that much air paired with the dual mono USSPA preamp and 1862 R-2R dac as source
Need to play for 2-3 hrs continuously to check the heat dissipation on the heat sinks which are like 300/150/50mm aluminium nice profile.
Looking for tricks to cheat the XLR/RCA single ended usage and avoid any kind of toggle switch. As toggle switch not sure if it induces some sort of noise being signal carrying. I do have Soekris 1021 balanced DAC so want to try that as a direct source for balanced and check as never I have heard a balanced setup so far.
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One update is that the single channel is now doing the duty and I am enjoying the sound it produces. But after an hour of play on my 300/150/50mm sized heat sinks its running very hot like I could put my fingers on the heat sink for 8-10 seconds but the L type profile is extremely hot like I cannot put the finger even for a second. Is this normal or do I need to be worried about the size of the heat sinks? I am half way into my second channel build and the only reason to use custom cabinet is because of those beautiful big sized VU meters
If you built it with Semisouth, I would try and get more efficient heat transfer from the mosfets to the heatsink and get the device temperatures down. Do you have access to more of these 'L' brackets? Is it possible to add a second one - flipped upside down and attached under the other one to double the flange thickness and heat transfer to the heatsink?
It looks like you are already using thermal compound between the bracket and the heatsink too. Have you measured the temperature anywhere or are you able to?
Beautiful cases and your work is nice and tidy! Well done!
It looks like you are already using thermal compound between the bracket and the heatsink too. Have you measured the temperature anywhere or are you able to?
Beautiful cases and your work is nice and tidy! Well done!
I'm with Jeff, butI can tell you if you can't touch the sink for 3-4 seconds it's too hot. I wouldn't run it until I had some known readings.
If you get a laser tester, you should know they vary by rotating them on the axis to the sink/chip you are testing. You can get some low readings turn it 20 degrees and it jumps. What I'm saying is shoot it from multipal angles when checking for temps.
If you get a laser tester, you should know they vary by rotating them on the axis to the sink/chip you are testing. You can get some low readings turn it 20 degrees and it jumps. What I'm saying is shoot it from multipal angles when checking for temps.
Thanks guys I do not have any IR gun but let me check.
To further specify I can put my fingers on the heat sink fins for like 10 seconds or more usually after an hour of play. But once I switch off and test by putting the fingers near the L profile aluminium plate where the mosfets sit they are extremely hot and cannot place more than 1-2 seconds.
This seems to run very hot when compared to my USSA-5 class A amp where I have used 300/150/83mm sized heat sinks again mono blocs. May be I underestimated the heat by getting this custom made cabinet. Lets see if I can measure the heat.
To further specify I can put my fingers on the heat sink fins for like 10 seconds or more usually after an hour of play. But once I switch off and test by putting the fingers near the L profile aluminium plate where the mosfets sit they are extremely hot and cannot place more than 1-2 seconds.
This seems to run very hot when compared to my USSA-5 class A amp where I have used 300/150/83mm sized heat sinks again mono blocs. May be I underestimated the heat by getting this custom made cabinet. Lets see if I can measure the heat.
Run it up with the cover on and then open and check it, both on the chip and right around it on the sink, you also have that L bracket, so soak it and check the chips, the L and then the sink close to where the transfer is made.
These amps will actually be hotter when they are not driving speakers. No load means the sink has to burn off all the energy instead of sharing with the speaker.
You may be fine, let the numbers tell ya and let us know. I always over sink, or over cool actively. If I crank up the cooling on my AN Monos, they will run just over room temp. lol
JT
These amps will actually be hotter when they are not driving speakers. No load means the sink has to burn off all the energy instead of sharing with the speaker.
You may be fine, let the numbers tell ya and let us know. I always over sink, or over cool actively. If I crank up the cooling on my AN Monos, they will run just over room temp. lol
JT
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Till I get hold of some sort of heat measurement like IR gun, I thought of another idea to put some low noise PC fans using a 5v mobile charger. It seems to run the amp a bit cooler as after 1-2 hrs the sinks are hot to the touch but I can place my fingers for a longer time. I also ran the amp this time lid closed and checked the finger test after an hour of play and it seems to run a bit less hotter compared to earlier.
But definitely realising that the 300/150/50mm heat sinks are a bit undersized for J2 I love this VU meter custom cabinet and I am yet to connect the VU meter to check its movement
But definitely realising that the 300/150/50mm heat sinks are a bit undersized for J2
I love this VU meter custom cabinet and I am yet to connect the VU meter to check its movement
Active cooling can help or even replace those large sinks. I did the AN with active and no external sinks they run cool and you can use smaller boxes. I think there are pics of it in the Pass picture thread.
Good call on getting some cooling on there until you know for sure if you instead on using it.
I've been mulling over the idea to run one submerged in like fishtank style. Seperate part for fish and the other for non conductive coolant. If I run it hot enough I can even cook fish while listening. lol
Good call on getting some cooling on there until you know for sure if you instead on using it.
I've been mulling over the idea to run one submerged in like fishtank style. Seperate part for fish and the other for non conductive coolant. If I run it hot enough I can even cook fish while listening. lol
That's a lovely looking monoblock chassis. However it looks to me like there are no cooling vents/holes in the bottom plate. Because the output devices and the angle holding the output devices are dumping a lot of heat into the interior of the chassis, good ventilation of the interior would help reduce the temperatures that you are experiencing.
I suggest drilling some large holes in the bottom plate and also adding some holes to the top plate. Replacing the existing chassis feet with taller feet to allow better air flow would also be a plus.
I suggest drilling some large holes in the bottom plate and also adding some holes to the top plate. Replacing the existing chassis feet with taller feet to allow better air flow would also be a plus.
Lol, good idea and innovative of cooking fish
Thanks Ben Mah for the compliment, yes that is a custom mono blocs designed and got from Aliexpess. The top plate does have nice wide ventilation holes but only towards the backside starting from the middle. I did try twisting both sides to see which mosfet is dissipating more heat but its actually almost the same. Yes you are right about the bottom plate there are no holes, I will try and drill some holes especially right below the PCB side so that there is good amount of cool air circulation from below and I am using the 1" sized rubber bushes as feet for increasing the height of the cabinet. Another issue is also the only place I am allowed to put my stuff is inside the TV shelves with windows and I always keep the windows open while playing
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I don’t like that L-profile. Too thin and too many holes reducing the contact surface. Maybe there should also be more screws clamping the profile tightly to the sink.
I suggest mounting the transistors+pcb straight to the heat sink, making sure that the relevant heat sink areas are totally smooth.
Plus plenty of holes in the bottom and top covers, and high feet, as suggested already.
I suggest mounting the transistors+pcb straight to the heat sink, making sure that the relevant heat sink areas are totally smooth.
Plus plenty of holes in the bottom and top covers, and high feet, as suggested already.
Hmm yes repurposing the JLH69 L profile plates here but I made sure to put around 6 screws on the plates and no air gap between the sink and plate as a think layer of heat seek compound without overlaying more than required.
Those plates make mounting easier and one of the reason to use as I usually do mounting directly on the heat sinks in all my builds except the VFET where Papa provided the custom L profile for the VFETs. I am going to try and mount the second channel directly on the heat sink. Now only concern is to remove this L profile need to remove the mosfets and TO-220 resistors desolder and put them on the heat sink directly