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Old 6th September 2007, 07:56 AM   #1121
lykkedk is offline lykkedk  Denmark
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Bridged option for 2x F4 MonoBlock's ???

Hi all, i am in for listning to my F4 right away. So i have this quistion :

If i bridge the F4, what will actually happend ? lower distortion, and nothing more, ofcause the capacity of currency will double, but voltagesving stays the same ? I will stay at the same listning level right ?.
I simply can't understand why the distortion will be lowered, could someone explain ?

I will just short the input and output and give it a try later, but i like to know what happens CAN SOMETHING go wrong here ??? ...

Jesper.
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Old 6th September 2007, 08:26 AM   #1122
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When bridging you must drive one F4 with an inverted signal related to the other F4, e.g. any balanced preamp does just that.
The load - that is, the loudspeaker - will be connected between "hot" on both F4s (normally the RED binding post).
The output transistor of each F4 will still have the same current capacity. No increase in current capacity. But as the two F4s swing in different direction, the output voltage is doubled.
So the "U" in that formula P=U^2/2R is doubled.

If you do not have a balanced output preamplifier you can use
1. an audio transformer
2. an op amp configured in the inverting configuration

Regds
Rolv-Karsten
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Old 6th September 2007, 08:32 AM   #1123
lykkedk is offline lykkedk  Denmark
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Quote:
When bridging you must drive one F4 with an inverted signal related to the other F4, e.g. any balanced preamp does just that.
I am not sure, that you are right here. I have two F4 monoblock's, and will bridge one for LEFT, and the other for RIGHT. The pre i have, has only singleended out at the moment..

Jesper.
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Old 6th September 2007, 08:38 AM   #1124
cviller is offline cviller  Denmark
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Quote:
Originally posted by lykkedk


I am not sure, that you are right here. I have two F4 monoblock's, and will bridge one for LEFT, and the other for RIGHT. The pre i have, has only singleended out at the moment..

Jesper.

I guess the setup you are refering to is to simply run the two channels of each "box" in parallel as monoblocks. With that you'll most likely get the ability to drive lower impedance, but besides that I doubt you'll get much improvement. I guess you can get better performance in this aspect simply by turning up the current (provideded you have sufficient heatsinking and psu capability).
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Old 6th September 2007, 08:56 AM   #1125
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Running the output stages of F4s in parallell is something completly different than balanced mode.
This will surely give more juice for difficult loads like old Quads (but NP said it sounded good on these already, or was that the F3?) Instead of parallelling F4s one could make a F4 with more output transistors, but of course there's a limit to that (driving their gates) which NP probably can inform us about.

If I was going the F4 route I would first listen carefuly if one plain F4 circuit per speaker would do. If more swing is needed I would bridge F4s. A >20 V swing balanced preamp would then be needed. Look to www.passlabs.com or for DIY follow the Curl BlowTorch thread or look to Erno (www.borbelyaudio.com).

RK
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Old 6th September 2007, 09:05 AM   #1126
lykkedk is offline lykkedk  Denmark
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Hey... CViller... having a good time out there ?

Quote:
I guess the setup you are refering to is to simply run the two channels of each "box" in parallel as monoblocks. With that you'll most likely get the ability to drive lower impedance, but besides that I doubt you'll get much improvement. I guess you can get better performance in this aspect simply by turning up the current (provideded you have sufficient heatsinking and psu capability).
Well, that was my bellive too, I guess i will have to wait to get more out off them, until i have made some balanced out of whatever pre it might be Good then, the sound is amazing anyway. This is my first class A project till now, and i am really glad with the sound. What 'really' suprised me, was that there is absolutely no hum at all, not even from my pearl-phonostage (i used to have a little hum here)... Well it has been very excitited to make them... I guess the weekend will be in for hour's of listning !!!

Jesper.
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Old 6th September 2007, 09:05 AM   #1127
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parallel operation doubles the damping factor, for some that may be beneficial.

You think the Blowtorch can swing 40 volts peak to peak ?
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Old 6th September 2007, 09:30 AM   #1128
lykkedk is offline lykkedk  Denmark
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Posted by R.K.Rønningstad :

Quote:
If you do not have a balanced output preamplifier you can use
1. an audio transformer
2. an op amp configured in the inverting configuration
Might be a quick sollution with an audio-transformer, how does that work ??? Just for temporary use...

Jesper.
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Old 6th September 2007, 09:36 AM   #1129
Magura is offline Magura  Denmark
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Maybe a quick mock up of a BOSOZ?

Magura
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Old 6th September 2007, 09:38 AM   #1130
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Quote:
Originally posted by jacco vermeulen
parallel operation doubles the damping factor, for some that may be beneficial.

You think the Blowtorch can swing 40 volts peak to peak ?

Yes, I do, or else I would not have proposed it

That infinite BlowTorch (BT) reverse engineering thread has revealed it has balanced outputs and runs off cirka +/- 24 Volt rails.
So me thinks the hot pin on ts XLR output swings to almost +24 Volts while the cold XLR pin swings down to -24 Volts simultaneously, so between hot and cold more than 40 Volts of undistorted music appears!!!
Remember the hot pin of the XLR is connected to one F4 input and the cold one to the other F4 input. So these swings between the 24 Volts rails of the BT. The F4 runs off 22 Volt rails, so this should be a nice fit. The BT should possibly be able to even overload the F4.
So put the BT and the F4 in the same chassis boyz, and get the worlds best integrated amp!

RK
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