Chienmortbb Posted July 11, 2022 Author Share Posted July 11, 2022 (edited) There is a blog called the slow diyer where a chap up north (Scandinavia not Hotton) tells the story of his slow audio builds. Compared to me he is a formula one car, however: I tested the Kilowatt today with speakers and music. It is quite impressive with the 8" Ramsa cabinets I keep at home. I have to be careful as they are only rated at 80 watts RMS although I suspect Ramsa were a little more conservative with their ratings that most modern speaker companies. I only had it wired as a stereo amp but it gives me confidence to go forward with it. It seems to run quite cool, it was warm but no more than that. What most people forget is that the heat from a class D amp does not change too much as the power goes up and with the ambient temp so high it was a fair test. That being said, I will fit temperature controlled fans as the amps have a linear voltage output that corresponds to the heatsink temperature. That makes it easy to add fan cooling. I now need to work out the best place for the fans. The noise is not an issue as the amp is for PA use not as a bass amp (if you see a bass pre-amp wanted ad tell the mods and get me banned) but the fans will only come on if the amp is hot and they will be run at lower voltages than specified so the noise should be minimal. Next is to finish the front panel (escutcheon) design and get it made. I am getting it made without anodizing as it is cheaper and I may well change the design later. I also need to build the auxiliary power regulators for the level meters and DSP. Edited July 11, 2022 by Chienmortbb 4 Quote Link to comment Share on other sites More sharing options...
stewblack Posted July 11, 2022 Share Posted July 11, 2022 A fascinating read. Thank you for sharing. Quote Link to comment Share on other sites More sharing options...
tauzero Posted July 11, 2022 Share Posted July 11, 2022 I realise that it's a bit late to be asking this, but couldn't you have achieved the inversion required for bridging by reversing In+ and In- on the inputs on one side? Alternatively, by using a decent quality op-amp as a unity gain inverter? Quote Link to comment Share on other sites More sharing options...
Geek99 Posted July 11, 2022 Share Posted July 11, 2022 That whooshing sound is not a misbehaving transistor, it is due to all of this going right over my head 1 Quote Link to comment Share on other sites More sharing options...
Chienmortbb Posted July 12, 2022 Author Share Posted July 12, 2022 7 hours ago, tauzero said: I realise that it's a bit late to be asking this, but couldn't you have achieved the inversion required for bridging by reversing In+ and In- on the inputs on one side? Alternatively, by using a decent quality op-amp as a unity gain inverter? Yes I could have used either method but as the modules have a balanced input, I was going to just reverse the XLR hot and cold cable on the B channel via the slide switch. 1 Quote Link to comment Share on other sites More sharing options...
Chienmortbb Posted July 12, 2022 Author Share Posted July 12, 2022 7 hours ago, Geek99 said: That whooshing sound is not a misbehaving transistor, it is due to all of this going right over my head Do you mean my last post or all of it? Quote Link to comment Share on other sites More sharing options...
Chienmortbb Posted July 12, 2022 Author Share Posted July 12, 2022 (edited) 11 hours ago, Chienmortbb said: It is quite impressive with the 8" Ramsa cabinets I keep at home. I have to be careful as they are only rated at 80 watts RMS although I suspect Ramsa were a little more conservative with their ratings that most modern speaker companies. To explain a bit more. These old Ramsa WS-A80 speakers are passive and rated at 80 watts RMS but are 20 years or more old. They were conservatively rated. However the amps are capable of well over 300 watts into 8 ohms. So I had to be careful. Add the fact that I was in a shed and that I value my ears... 11 hours ago, Chienmortbb said: I only had it wired as a stereo amp but it gives me confidence to go forward with it. It seems to run quite cool, it was warm but no more than that. So the A input was fed from the Main L output from my mixer and the B input was fed from the R output of my mixer. Despite the outside temperature being close to 30 degrees C, after half an hour the sides of the amp case were only warm to the touch. I will do some proper temperature measurements soon but as a rule of thumb, 30-40 degrees is warm 50-60 is hot but 60 is just about OK to touch without burning. 70 degrees is too hot to keep your fingers on. Based on this, I guess the temperature was under 40 degrees. 11 hours ago, Chienmortbb said: That being said, I will fit temperature controlled fans as the amps have a linear voltage output that corresponds to the heatsink temperature. That makes it easy to add fan cooling. I now need to work out the best place for the fans. The noise is not an issue as the amp is for PA use not as a bass amp (if you see a bass pre-amp wanted ad tell the mods and get me banned) but the fans will only come on if the amp is hot and they will be run at lower voltages than specified so the noise should be minimal. A word about fans. Many bassists hate fans but there are pros and cons. According to Rod Elliott of the Audio Pages https://www.sound-au.com/heatsinks.htm#s18 fans have to blow not suck. Section 18 of the article details Rod's conclusions on fans. I must admit that I cannot find the source but I have it in my mind that a fan cooled heatsink can remove 4 times as much heat as one passively cooled just by a heatsink if placed correctly in relation to the heatsink, I have done some experimentation myself with fans and the noise. Again if you read Rod Elliott's article, he says that the turbulence caused by the fan is what helps the cooling. Of cause turbulence means noise BUT I found that most of the noise is caused by vibration. Sadly the metal used on most amps is a great sounding board and makes the noise problem worse. I have managed to reduce the noise on fans on some amps using rubber mountings from AKASA and you can get low noise fans from companies such as Noctua. The Noctua Fans are well made but to get the lowest noise you have to use an adapter that reduces the speed, probably by reducing the voltage applied to the fan. Ho Noctua do take care to reduce vibrational noise as far as possible but you pay for this extra and the fancy packaging. I have tried Gelid low noise fans and found that apart from the white fan blades, they give no advantage over traditional fans. To reduce noise you have to have rubber mountings and/or run the fans at a lower voltage and hence a lower speed. This of course reduces the cooling efficiency of the fan. Edited July 12, 2022 by Chienmortbb 2 Quote Link to comment Share on other sites More sharing options...
Chienmortbb Posted July 12, 2022 Author Share Posted July 12, 2022 There are issues with the enclosure I am using with regard to heat dissipation. If you look at the side panels, you will see that the extrusions are horizontal rather than vertical and I don't want to put fans on the outside. So fans must be inside but inside the panels and heatslugs of the amp modules are smooth. The question is, do I attach heatsinks inside to create something that a fan can work on, or would a fan just blowing air through the case help? Rod's article suggests not. Extra heatsinking will add weight and although the whole thing is not heavy, the enclosure alone already weighs 2Kg.It also does need a small amount of extra circuitry to drive the fans so I have to decide whether the extra weight and mechanical and electrical complexity are worth it. 1 Quote Link to comment Share on other sites More sharing options...
Geek99 Posted July 12, 2022 Share Posted July 12, 2022 9 hours ago, Chienmortbb said: Do you mean my last post or all of it? Any of it 1 Quote Link to comment Share on other sites More sharing options...
itu Posted July 12, 2022 Share Posted July 12, 2022 Have you been thinking about transportation? If you want to put the amp to a case, is the ventilation still functional and valid? My Glockenklang has good fans, but when I put it to a 2U case, I needed to use every millimeter to enable ventilation to reach even adequate level. I used several spacers. Now the fans aren't screaming at high speed all the time. If you want to make an uneducated trial, you could try to use smoke to see, how the air is circulating. I know it may be more or less an experiment. But if there are dead corners somewhere, you may be able to see them. Use PC or any other clear plastics on top of the unit. Quote Link to comment Share on other sites More sharing options...
JapanAxe Posted July 12, 2022 Share Posted July 12, 2022 57 minutes ago, itu said: ... If you want to make an uneducated trial, you could try to use smoke to see, how the air is circulating. I know it may be more or less an experiment. But if there are dead corners somewhere, you may be able to see them. Use PC or any other clear plastics on top of the unit. I think the @Chienmortbb is hoping there won't be smoke 2 Quote Link to comment Share on other sites More sharing options...
nekomatic Posted July 12, 2022 Share Posted July 12, 2022 10 hours ago, Chienmortbb said: Extra heatsinking will add weight and although the whole thing is not heavy, the enclosure alone already weighs 2Kg.It also does need a small amount of extra circuitry to drive the fans so I have to decide whether the extra weight and mechanical and electrical complexity are worth it. You could have a look at CPU heatsinks which tend to use thin copper fins rather than thick extruded aluminium ones? Might have to do a bit of bodging, but they’re not expensive on eBay Quote Link to comment Share on other sites More sharing options...
Geek99 Posted July 14, 2022 Share Posted July 14, 2022 I would actually like to be able to do this kind of thing; you know, just spin off a valve amp like I’m making toast #deepenvy Quote Link to comment Share on other sites More sharing options...
Chienmortbb Posted July 14, 2022 Author Share Posted July 14, 2022 On 12/07/2022 at 22:05, JapanAxe said: I think the @Chienmortbb is hoping there won't be smoke No but it is a good point. Smoke (without fire or exploding semiconductors) is often used to check airflow in various industries. Quote Link to comment Share on other sites More sharing options...
Chienmortbb Posted July 14, 2022 Author Share Posted July 14, 2022 On 12/07/2022 at 23:58, nekomatic said: You could have a look at CPU heatsinks which tend to use thin copper fins rather than thick extruded aluminium ones? Might have to do a bit of bodging, but they’re not expensive on eBay I have been looking at those. More later. Quote Link to comment Share on other sites More sharing options...
Chienmortbb Posted July 25, 2022 Author Share Posted July 25, 2022 If there is one thing for sure it is that we often do not learn from our mistakes. Anyone that followed my After Eighty build will remember that I blew the onboard auxiliary voltage fuses. Well I did it again on one of the modules, and on these the aux voltage also supplies the IRS2092 class D controller IC. So it looked dead but with help from Connex I found the problem and fixed it. So next thing is to put fuses in the Aux supply lines then carry on with the build. 1 Quote Link to comment Share on other sites More sharing options...
Chienmortbb Posted September 9, 2022 Author Share Posted September 9, 2022 A little progress. I have installed a perforated aluminium platform under the amps and have worked out where to put the junction board, I have also installed two 60mm fans, aimed directly at the heatsinks but also pushing some air under the PCBs. The idea for that is to add cooling to the IRS2092 controller chip mounted underneath. The fans mean I will have to re route the output cables to the speakons. The fans are attached to the perforated aluminium using two cable ties at the bottom and it seems quite secure at the moment. The fans are slightly angled. This is so that the air goes towards the front and the top vent. The junction board is designed to tidy up the wiring so expect to see a member of sockets and maybe a few other components there soon-ish. I am still thinking about how to control the fans. 2 Quote Link to comment Share on other sites More sharing options...
JapanAxe Posted September 10, 2022 Share Posted September 10, 2022 9 hours ago, Chienmortbb said: A little progress. I have installed a perforated aluminium platform under the amps and have worked out where to put the junction board, I have also installed two 60mm fans, aimed directly at the heatsinks but also pushing some air under the PCBs. The idea for that is to add cooling to the IRS2092 controller chip mounted underneath. The fans mean I will have to re route the output cables to the speakons. The fans are attached to the perforated aluminium using two cable ties at the bottom and it seems quite secure at the moment. The fans are slightly angled. This is so that the air goes towards the front and the top vent. The junction board is designed to tidy up the wiring so expect to see a member of sockets and maybe a few other components there soon-ish. I am still thinking about how to control the fans. What’s the perf board for? Quote Link to comment Share on other sites More sharing options...
Chienmortbb Posted September 10, 2022 Author Share Posted September 10, 2022 2 hours ago, JapanAxe said: What’s the perf board for? I was wondering that. No, seriously, it will be the place where the interconnecting cables will terminate. So the multiway connectors from the amps will be terminated there to allow them to be split into 2/3 way connectors to do to the DSP, input/output XLRs and Aux power from the amps. I might put the low voltage regulators on there too, but I do have some separate regulator PCBs that I might use. That is the next job, the layout of that perf board, should not be too difficult. I also need to think whether I need to use the other features such as Shut Down or Mute Out (Mute mode=5V Run mode=-5V) Basically an indication that the amp is in protect mode. Temperature feedback (Maybe use to turn on the fans?) Mute (Pull-Down = Mute, left open or 5V Run). Is this needed on a power amp for PA use? Incidently, as I have to run mains from the back to the front, the perforated aluminium will act as a shield keeping any radiated mains interference away from the audio signal and Aux power lines. I need to place the DSP board. That will attach to the front panel. Of course, the front panel design is still a work in progress.😃 3 Quote Link to comment Share on other sites More sharing options...
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