Here's a few pictures of the completed build. I have tested a few sine wave in unbalanced mode, from 10Hz to 120KHz with 1V and everything is clean. Square wave stays pretty sharp until a little over 20KHz but I'm guessing the power supply is probably the issue and using balanced signal it would be better also.
I also tested with some music on my test speaker (very cheap speaker). This week will be connected to my main system.
All the best!
Do
I also tested with some music on my test speaker (very cheap speaker). This week will be connected to my main system.
All the best!
Do
Do,
Maybe I should just copy and paste compliments from other posts on your build pics for various projects; would make writing the current post easier.
As usual, your latest build looks excellent - really well organized and executed., congratulations! Thank you for sharing the pics, and tell us more about the sound and synergy with your system once you get some listening done.
- Zia
Maybe I should just copy and paste compliments from other posts on your build pics for various projects; would make writing the current post easier.
As usual, your latest build looks excellent - really well organized and executed., congratulations! Thank you for sharing the pics, and tell us more about the sound and synergy with your system once you get some listening done.
- Zia
Hi Do,
good job! May I ask why you mounted one of the boards upside down and the other one not? Is it just for optical symmetry?
As far as I know, it is always better in terms of cooling efficiency to have the power devices next to the heatsink's bottom edge?!? I suspect the LM3886's at the left handed board will get hotter at the same load than the other ones.
Best regards!
good job! May I ask why you mounted one of the boards upside down and the other one not? Is it just for optical symmetry?
As far as I know, it is always better in terms of cooling efficiency to have the power devices next to the heatsink's bottom edge?!? I suspect the LM3886's at the left handed board will get hotter at the same load than the other ones.
Best regards!
Hi Kay Pirinha,
It was not done for visual but for keeping cabling distance as much as possible the same length. The position on the heatsink is not that trivial for a Class AB, B, since when the heatsink gets the heat spread after several minutes, they become the same temperature. There's not enough heat being dissipated through this amp with the size of the heatsink and it is spread in a good length on the heatsink. I would do different with a Class A amplifier.
All the best!
Do
It was not done for visual but for keeping cabling distance as much as possible the same length. The position on the heatsink is not that trivial for a Class AB, B, since when the heatsink gets the heat spread after several minutes, they become the same temperature. There's not enough heat being dissipated through this amp with the size of the heatsink and it is spread in a good length on the heatsink. I would do different with a Class A amplifier.
All the best!
Do
Thanks Tom and Chris for the compliments!
I will let you know as soon as the burn in period is done. I'm giving the amp 48 hours.
Chris,
I have these foam pads on Class A amplifier heatsinks for several years and so far they're still holding in place. One can always remove the foam and put in the 3M VHB instead.
All the best!
Do
I will let you know as soon as the burn in period is done. I'm giving the amp 48 hours.
Chris,
I have these foam pads on Class A amplifier heatsinks for several years and so far they're still holding in place. One can always remove the foam and put in the 3M VHB instead.
All the best!
Do
I'm shying away from the MegaFit connectors, actually. They're pretty expensive and often out of stock. I'm considering using JST VH-series instead. They're industry standard. They're not as beefy (10 A per pin) but one can just put multiple pins in parallel. They're nearly always in stock and if not, TE has a product that's a plug-n-play substitute.
Regardless of which connector type I settle on, I can certainly add it to the output of the Guardian boards.
Tom
Hi drpro,
Please see here
Modulus-686: 380W (4Ω); 220W (8Ω) Balanced Composite Power Amp with extremely low THD
Thanks
Do
Please see here
Modulus-686: 380W (4Ω); 220W (8Ω) Balanced Composite Power Amp with extremely low THD
Thanks
Do
I would expect the Connex SMPS800RE to provide plenty of power for driving the MOD686 to clipping, at least short term.
The supply is "rated" for "800 W" continuously, "1000 W" peak, and "1150 W" "short term". Now, I use quotes as the power "ratings" are music power. I.e. the supply is "rated" for operation with an 800 W Class D amp running at clipping with music signal having a 10 dB crest factor.
Specifying audio SMPSes in music power is sadly common. I thought we gave up those kinds of specs in the 1970ies, but I guess not.
I put certain terms in quotes as I haven't seen an actual data sheet for this supply. It would be nice to know the test conditions and such. The description available on Connex's website says the power numbers are with fan cooling. It's also mentioned that the supply will shut down once the heat sink reaches 90 ºC, which is nice.
The Modulus-686 draws about 750-800 W from the supply when driving a 4 Ω load to clipping. With a 10 dB crest factor, it should be able to run with music signal at clipping levels continuously if provided with adequate cooling.
In my experience, the Connex supplies will generally supply about 1/3 to 1/2.5 the specified power continuously. I.e. the "300 W" SMPS300RE will supply 100-120 W into a resistive load. It can handle a short-term load higher than that, but the RMS power needs to be within the 1/3 to 1/2.5 of rated power range.
Tom
The supply is "rated" for "800 W" continuously, "1000 W" peak, and "1150 W" "short term". Now, I use quotes as the power "ratings" are music power. I.e. the supply is "rated" for operation with an 800 W Class D amp running at clipping with music signal having a 10 dB crest factor.
Specifying audio SMPSes in music power is sadly common. I thought we gave up those kinds of specs in the 1970ies, but I guess not.
I put certain terms in quotes as I haven't seen an actual data sheet for this supply. It would be nice to know the test conditions and such. The description available on Connex's website says the power numbers are with fan cooling. It's also mentioned that the supply will shut down once the heat sink reaches 90 ºC, which is nice.
The Modulus-686 draws about 750-800 W from the supply when driving a 4 Ω load to clipping. With a 10 dB crest factor, it should be able to run with music signal at clipping levels continuously if provided with adequate cooling.
In my experience, the Connex supplies will generally supply about 1/3 to 1/2.5 the specified power continuously. I.e. the "300 W" SMPS300RE will supply 100-120 W into a resistive load. It can handle a short-term load higher than that, but the RMS power needs to be within the 1/3 to 1/2.5 of rated power range.
Tom
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Fabulous work Do!!
Your layout and attention to the fine details is top notch.
Congrats and ENJOY your newborn
Thanks Vunce!
Thanks Anand!
Funny enough, when you put the lid back on, no one can see anything but it's all in my head I guess! LOL