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Old 3rd September 2012, 05:45 PM   #401
a.wayne is offline a.wayne  United States
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Is this the 4pr version Buzz...?
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Old 3rd September 2012, 05:59 PM   #402
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You mean the monoblocks. Yes and no. I am going to try a 4 pair version at half bias and a 4 pair version at full bias. The full bias version will go in the monoblock chassis. Sorry guys, but I am so behind. Just found out today got to leave town on business for the week.
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Old 16th September 2012, 03:22 AM   #403
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Default 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.
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Old 16th September 2012, 10:11 AM   #404
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Seperate but tied together.
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Old 16th September 2012, 11:36 AM   #405
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at least with high bias. if one run it on low bias, then it may be best to have them on the main sink. so that they start conducting earlier.
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Old 16th September 2012, 12:06 PM   #406
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Good point AudioSan.
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Old 16th September 2012, 01:54 PM   #407
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Quote:
Originally Posted by buzzforb View Post
Seperate but tied together.
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.

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Old 16th September 2012, 02:08 PM   #408
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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.
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Old 16th September 2012, 02:11 PM   #409
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Quote:
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....

All this assumes that you dont think that a 200W amp sounds better than a 50W amp driving the a set of 90dB speakers.
you forgot smiley :
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Old 16th September 2012, 02:18 PM   #410
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