Should the switching diodes be on same heatsink
I have gone through the thread and did not get a conclusive answer. Should I mount the MUR3020W switching diodes used in F5T v2 and v3 on the same heatsinks as the Fairchild outputs or can I mount them on separate smaller independent heatsinks. Buzzforb picture shows independent heatsinks.
Any experiences? Thanks in advance.
I have gone through the thread and did not get a conclusive answer. Should I mount the MUR3020W switching diodes used in F5T v2 and v3 on the same heatsinks as the Fairchild outputs or can I mount them on separate smaller independent heatsinks. Buzzforb picture shows independent heatsinks.
Any experiences? Thanks in advance.
Buzz,
Have you listened to your F5T without the diodes installed?
I was wondering if they do anything at all until they "turn on" sonically?
I have low power need (bi-amping a smallish speaker (Snell E2)) and although I built one channel with diodes on the main heatsink, I doubt I will actually pull enough current to fully turn them on.
I know you experiment a lot and when I have the time to finish the other channel of my F5T - V2 I will try this and eliminate the diodes altogether, turning it into a V1 like the one Nelson built in the article.
I will also try smaller Rs sense I am only paralleling 2 output transistors.
Rush
I dont reallt pull enough juice either. That being said, you are accomplishing something similar when your drop down the Rs value, because you eliminate the Vdrop that occurs in proportion to that value. Because they are in parallel with Rs, the transistion is not immediate but gradual. This is something that eluded me mentally. If you consider this fact, how you build your F5T determines whether or not you will "hear" them. If you want to hear them, then use a single pair and push it hard vs multiples, whcih will rarely get pushed hard enough for their use. All this is said based on semi efficient speakers. Folks with big multiways are going to be in that region more than I, considering i have a FR crossed to a 12" woofer.
FWIW, my two pair version driving my 12" woofers in parallel, rarely pushed them hard, and that was listening to TRON soundtrack at thumper levels. It really is a beautiful setup for higher power needs, but most on this forum are crazy enough to bias their amps into Class A all the way, in which case it is moot.
All this assumes that you dont think that a 200W amp sounds better than a 50W amp driving the a set of 90dB speakers.
FWIW, my two pair version driving my 12" woofers in parallel, rarely pushed them hard, and that was listening to TRON soundtrack at thumper levels. It really is a beautiful setup for higher power needs, but most on this forum are crazy enough to bias their amps into Class A all the way, in which case it is moot.
All this assumes that you dont think that a 200W amp sounds better than a 50W amp driving the a set of 90dB speakers.
I do think a 200W amp sounds better than a 50W amp pushing a 90db speaker, not because of the watts, because of the power supply and number of output devises. So if we build our 50W amp with the current capability of a larger amp, not the higher voltage rails, then they should sound the same given all else equal, IMHO.
Rush
Then why not go with V3, biasing the outputs at .5A across 1ohm Rs. You get more devices, higher DF, more stable temps on individual fets. Basically choices made by Nelson in XA.5 series. Or go V3 on dual monoblocks, maintaining 1A bias and gaining in all other respects. PSU is simple and size is matter of choice. Nelson does 90mF per rail, I believe. Beauty of F5T is scalability. Simple amp with very simple path to more power. You probably have a very good idea of what to do based on out conversations. FWIW, I do believe the 2 pair F5T sounds better than the F5.
Anybody who can help with this question?
In mating two larger heat sink together to form one larger sink, which would be a better implementation for heat dissipation?
Heatsinks being used will be 10.08 version from Heatsink USA. I have two options for heatspreader. One is large piece of L aluminum with 2" flange that is 1" thick and a 4" flange that is 1/2" thick. The 1/2" thick section would be tied to the heatsinks and the overall length would be about 12-14" on a heatsink that is about 18" long after being cut down.
The other option is a big piece of 2" thick aluminum 4" x 12-14".
What do you think?
In mating two larger heat sink together to form one larger sink, which would be a better implementation for heat dissipation?
Heatsinks being used will be 10.08 version from Heatsink USA. I have two options for heatspreader. One is large piece of L aluminum with 2" flange that is 1" thick and a 4" flange that is 1/2" thick. The 1/2" thick section would be tied to the heatsinks and the overall length would be about 12-14" on a heatsink that is about 18" long after being cut down.
The other option is a big piece of 2" thick aluminum 4" x 12-14".
What do you think?
The reason why would be, number of devises per channel (I bought the V2 boards and am committed to stereo amps) and Rs of 1 ohm. I am thinking Rs should be the lowest you can get away with. Also I am old and the weight of working on and moving a V3 is more than I am willing to bare. Compromises everywhere.
Rush
I'll bet you can get the heatsinks welded together for less than $100. The issues would be smoothing the welded area. A surface grinder would be nice, but a large file and a DA sander with 60/120/240 grit sand paper would do it. Or you could notch your heat spreader at the joint if it remained proud.
I say this, with the same problem and I have not done this. I even own a mig welder with aluminum capability (and a DA). We should ask Heatsink USA what aluminum they used, so the proper weld rod can be chosen.
Rush
the 4" will be the best
meaning the 4" thick flat bar?
I agree all around. Drop the diodes, use 4 fets, bias each at .5A or more, and use .22R resistor.
Regarding heatsinking for Switching diodes
I have asked a question earlier on heatsinking of the switching diodes MUR 3020WT at the outputs of F5T V2.
I did get a reply of keeping the heatsink separate from the heatsink of the output devices. OK. Can I run a simple aluminium flat tying the 8 MURs on each side as a heatsink. How much heat should I expect? I am using Teabag's boards.
TIA.
I have asked a question earlier on heatsinking of the switching diodes MUR 3020WT at the outputs of F5T V2.
I did get a reply of keeping the heatsink separate from the heatsink of the output devices. OK. Can I run a simple aluminium flat tying the 8 MURs on each side as a heatsink. How much heat should I expect? I am using Teabag's boards.
TIA.