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Old 12th September 2012, 06:11 AM   #11
dazed2 is offline dazed2  Canada
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vdi - I thought about it but when I built the original F5 I bought two trafo's for the hell of it so I have one in use and the other one to use for another F5. going V1 turbo would mean getting more trafos.

bear - yes I read and re-read your meaning I think you are right.

Having said that, I went back to AndrewT's suggestion and looked up NYCone and JBL4435's balanced build and from my understanding I would have to lift R1 and R2 and cross them with the other board and I should be close....
I guess I may have to change R11 and R12 to 22R as well .
Since in my build I took out the protection circuit I think that would be it..?

Perhaps in this configuration it would be true balanced and it wouldn't see the speaker load as half impedance?
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Old 12th September 2012, 09:56 AM   #12
AndrewT is offline AndrewT  Scotland
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bridged and balanced apply double the voltage to the speaker cf. a single version of the amplifier.
That doubled voltage necessarily requires a doubled current being fed to the speaker.
As far as the amplifier is concerned, it thinks and feels like each single half of the balanced/bridged amplifier is driving a load that is half the impedance of the actual load that is fitted between the outputs.

Each half of a balanced amplifier has to be designed to drive that half impedance load. Then one combines the two halves into an integrated pair of "balanced amplifiers". The balanced amplifier potentially offers much greater quality advantages over a pair of bridged amplifiers that started life as unbalanced.

If you don't believe this, then read the F5x more thoroughly. The supply voltage is substantially reduced. The bias current is substantially increased. These two changes were implemented specifically to allow the amplifier to drive the effectively halved load impedance.

The balanced version of the F5t achieves similar by increasing the output stage pairs cf. the original F5.
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Old 12th September 2012, 02:27 PM   #13
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the quality advantages may or may not translate into audible benefits, since the even order harmonics tend to cancel, and this is one of the "benefits" of the F5 (the even harmonics)...

I think this is one possibility...

Otoh, I always liked the early Jim Bongiorno SUMO amps, they were "bridged" amps internally. Maybe you could say balanced.

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Old 23rd September 2012, 02:50 PM   #14
dazed2 is offline dazed2  Canada
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Alright, so perhaps it is not as "simple" as I thought it may be.

Ok, so I tried the amp in its current form with a much higher sensitivity speaker (about 98db) and yes it is very good, and useable close to concert level volumes. I'm almost happy, if not for the fact that they cost about $7K to build

So having read NP's F5T write up, what would adding just the MUR3020W diode in parallel to the source resistor do in the regular F5? As long as I use anything other than the Toshiba MOSFET's (fairchilds, IRFP etc) this should allow peak currents to close to 20A. This should mean I would be better equipped to control big drivers?
This seems like a generally easy thing to do, in an existing setup.
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Old 23rd September 2012, 10:22 PM   #15
flg is offline flg  United States
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$7k? The speakers? Certianley not an F5!
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Old 23rd September 2012, 10:30 PM   #16
Zen Mod is offline Zen Mod  Serbia
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7K for speakers to build ?

gimme a break

whatever it is , it is certainly in scam of the century category
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Old 23rd September 2012, 11:10 PM   #17
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Ill do it for 2k, keep 1k and you still save 4k. Everybody wins. Just dont tell stefanoo.
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Old 23rd September 2012, 11:12 PM   #18
Zen Mod is offline Zen Mod  Serbia
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well , I prefer to have just one idiot around , and that's me
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Old 23rd September 2012, 11:45 PM   #19
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Old 24th September 2012, 12:50 AM   #20
dazed2 is offline dazed2  Canada
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Why not 6-7K?
Here is what they look like
TAD TH4001 clone project
They were TAD clones
If someone can build and get the parts for less... I'm all ears!

PS I was wrong... I guess its about 95dB. But man did the combo sing!

Last edited by dazed2; 24th September 2012 at 12:57 AM.
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