F5 Turbo Builders Thread

[Rush]

Originally Posted by buzzforb

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

[buzzforb]

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.

[buzzforb]

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?

[AudioSan]

the 4" will be the best

[Rush]

Originally Posted by buzzforb

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.

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

[Rush]

Originally Posted by buzzforb

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?

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

[buzzforb]

Originally Posted by AudioSan

the 4" will be the best

meaning the 4" thick flat bar?

Originally Posted by Rush

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 agree all around. Drop the diodes, use 4 fets, bias each at .5A or more, and use .22R resistor.

[AudioSan]

the 4" wide 1/2" thick will do the job.

[a.wayne]

I would agree with this assumption ....

Originally Posted by Rush

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

[anilva]

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.