Hi Gianluca, thanks to you and Stuart for your work! As I asked you last time, will this holes pattern be available for the 4U heatsinks?
Thank you,
Gaetano.
Yes, disparity in the driver is concerning. I ran your scenario with the driver NPN hfe=130 and PNP hfe=210 in sim. I saw 20kHz .000103% THD with the drivers matched and 20kHz .000109% THD for your situation. Needless to say but the distortion was hardly affected. The current mirror and the TMC feedback really throw the distortion into the mud. The current mirror is the most important to match along with it's emitter resistors.
The 2sc5171/2sa1930 trade SOA for speed, because of this I don't recommend them as drivers for 4ohm use greater than 50V rails.
Jeremy
I have a question Gianluca. If someone orders one of your chassis/heatsink off the diyAudio Store, they will still have to let you know somehow to use the Wolverine drill template. I bring this up as what is the best way to go about this? Order the chassis off your website instead and not the diyAudio Store?
Jeremy
Hi Jeremy,
Sure, you can place your order on the DiyAudioStore and add 2x https://diyaudiostore.com/collectio.../products/drilling-and-tapping-40mm-heatsinks to your cart together with your chassis/heatsinks only.
Just make sure you write in the customization description something on the line of "holes for the Wolverine board" so once my colleague sees that she will assign the order to me.
EU members can order directly from our website and add 2x https://modushop.biz/site/index.php?route=product/product&product_id=490 (more than 20 holes) to complete their order
Sure, you can place your order on the DiyAudioStore and add 2x https://diyaudiostore.com/collectio.../products/drilling-and-tapping-40mm-heatsinks to your cart together with your chassis/heatsinks only.
Just make sure you write in the customization description something on the line of "holes for the Wolverine board" so once my colleague sees that she will assign the order to me.
EU members can order directly from our website and add 2x https://modushop.biz/site/index.php?route=product/product&product_id=490 (more than 20 holes) to complete their order
Gianluca,
So everyone knows... Stuart sent you drill locations for 3U, 4U, 5U, for both 300m and 400mm deep chassis options. Correct me if I'm wrong.
Jeremy
A Jedi:
See post #1454, in response to my inquiry as to whether a 3U 300mm Dissipante chassis would be adequate. After laying out my design, it became apparent that more space was needed to house everything I want to put into the amp. See Post #1464 as a follow-up.
Regards,
Scott
So my understanding is that the 3U 400 is adequate for both heat and space requirements although it may necessitate mounting the boards perpendicular. Is this correct?
I ran some dissapation numbers for 4 ohms driving a reactive load with 10dB peak to average music. Here are the max rail voltages using standard rectified and filtered power supply with about 10% sag under load. You can do more on the smaller chassis but you'll have to put a fan on the sinks.
Here is a good rule of thumb
3U 40x120x400mm ~50V rails
4U 40x165x400mm ~60V rails
5U 40x210x400mm ~70V rails
Jeremy
A Jedi. Don't worry. 3U400mm will be enough. I bet you'r not planing on pushing full power +10db peaks at 4 ohm for hours and hours and hours when running 3 pair outputs at +/-60Vdc. In the real world, i run my Honey Badger at 70mA bias pr outputfet. on 4U300mm sinks (internal sinks) at +/-57-60Vdc The sinks never exeed 50C. A 3U400mm sink has more capasity then a 4U300mm. and your sinks will be external.
Yes, my recommendations were for heavy use as I don't know who is the light user or heavy user so It's better to default more conservative.
If you're building a multi-channel home theater amp that would be considered light use and you could get away with less heatsink.
Jeremy
I for one use the same amps for HT and for music duty. So no. And one can realy push the amps in HT use also. But average low(ish) frequency output will be lower.
But for the use that you made your calculation, even 50V rails and 4ohm load will kill the amp over time.
But for the use that you made your calculation, even 50V rails and 4ohm load will kill the amp over time.
4 ohm loads shouldn't kill the amp, if it does there's inadequate cooling and you should have gone with the bigger heatsinks and/or fan cooling to begin with. Junction temperature determines reliability.
Jeremy
Jeremy
It's a lot more to it then cooling. SOA, Outputstage capacity, railvoltage and load. Clipping becomes an isue when driven like your calculations.
you can try driving a 3 pair 150W BJT output at +/-70V with 4ohm load (that dips into 3ohm) as hard as hard gets continuously for 8 hours. I bet it will not survive even if you cool it with liquid nitrogen.
you can try driving a 3 pair 150W BJT output at +/-70V with 4ohm load (that dips into 3ohm) as hard as hard gets continuously for 8 hours. I bet it will not survive even if you cool it with liquid nitrogen.
Yes, with a 3 pair output stage not just any transistor will work on 70V rails. These plots show the temperature derated SOA(per transistor) with a heatsink temperature of 60°C per driving 4 ohms at 45° phase angle (which means the real part of the load is 2.83 ohms and the reactive part is 2.83 ohms) using 3 pair. These plots also take into account the rails sagging by 10% which would be the equivalent of a 1200VA transformer for two channels. This is why we made a 4 pair option, so more than a select few transistors can run on 70V rails.
Jeremy
Jeremy
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