F5 Turbo is posted

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Got the multi-meter just now, and the 120Hz track measured 9.5V (volume setting for large scale orchestral music). I am using a 100W rms into 8 ohms power amp now (Meridian), so I guess it is just barely enough, and I will probably need to build the v3 in this case.
 
Sorry 9.5 before or after X 4 mutiply ?

If 9.5 is after multiply F5 can go to about 2 volts of rails (not going to get in to the RMS bit as I alwayse get that wrong)
So wakyBKaky about 14 V peack

As long you get enoug current to sustain speakers there you be fine.

Does not have to be class A all the way. and 14 V / 4 homs = 3.5 A
3.5 / 2 = 1.75 A bias to stay class A

If this is 9.5 volts with signal at -12 dB then multiply by 4 that give you max voltagge you ask your amp to produce you going to need rails at over 55 V
and big sinks and fans and traffos and 2 dudes to carry the thing V3 OH yeah
 
Sorry for not being precise, 9.5 volts is before X4 multiply.

The prospects of building huge monoblocks is a bit too daunting for me. So I am wondering about either of the following:

1) Use v2 boards, and build a v2 with 32V rails.
With this option, the amp will not be able to give me the maximum voltage that I would like, on large orchestral music. What would it sound like when a 40V swing is needed but the amplifier is only capable of 32 during peaks of large orchestral music?

2) Use P-5c-2V20 boards available from the store, and build a v1 with 45V rails, but keep the bias within the range of 1A-2A, depending on the heatsinks that I can get. This option would give me enough voltage. I will just have to find a way to mount the diodes.

Would appreciate if you can give some comments on the following:

1. Which option would you recommend?
2. Would option 2 sound better than option 1?
 
Sorry for not being precise, 9.5 volts is before X4 multiply.

WOW that is going to be a big one

9.5 x 4 is 38 V RMS

That is realy a lot.
Considering that F5 clips at about 2 volts from suply rails.
32 V rails will not be near enough and it will clip

45 V is much better proposition.

As Papa recommend no more than 50 W dissipation for the big mosfets (TO247?) you need to bias at 1A

with 1A and 4 mosfets you get 200W dissipation on sink.

You wont need Class A all the way but I would consider going balanced and build mono bloks.

No point wasting money on trafos and the rest if you can't get the heath sinks.
 
Sorry for not being precise, 9.5 volts is before X4 multiply.

The prospects of building huge monoblocks is a bit too daunting for me. So I am wondering about either of the following:

1) Use v2 boards, and build a v2 with 32V rails.
With this option, the amp will not be able to give me the maximum voltage that I would like, on large orchestral music. What would it sound like when a 40V swing is needed but the amplifier is only capable of 32 during peaks of large orchestral music?

2) Use P-5c-2V20 boards available from the store, and build a v1 with 45V rails, but keep the bias within the range of 1A-2A, depending on the heatsinks that I can get. This option would give me enough voltage. I will just have to find a way to mount the diodes.

Would appreciate if you can give some comments on the following:

1. Which option would you recommend?
2. Would option 2 sound better than option 1?

What speakers are you using ......?
 
Thanks Bksabath for the advice, I will really need to think about balanced monoblocks, like you said, no point wasting money on the trafos.....

Hi a. wayne,

Strange enough, the speakers are small, b&w nautilus 805D, but my volume was set at 3 o'clock position for large scale orchestral music. Perhaps because they are very dynamic and the average level is low.
 
@jacco : good news :)

actually I'm having 2 pcs talema 2x25V 300VA for my gainclone, it's on sale now. I'm thinking to upgrade it into 500VA that will give more space in the future. I read somewhere in the articles saying that for power amplifier it's suggested to use carbon instead of metal, metal is for something beyond power amplifier like preamp,dac,cdp. IMHO & CMIIW
 
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WOW that is going to be a big one

9.5 x 4 is 38 V RMS

That is realy a lot.
Considering that F5 clips at about 2 volts from suply rails.
32 V rails will not be near enough and it will clip

45 V is much better proposition.

As Papa recommend no more than 50 W dissipation for the big mosfets (TO247?) you need to bias at 1A

with 1A and 4 mosfets you get 200W dissipation on sink.

You wont need Class A all the way but I would consider going balanced and build mono bloks.

No point wasting money on trafos and the rest if you can't get the heath sinks.
So I am again getting lost on this. If the recommended bias is .3-4v per FET, don't when we blast in a signal to it, we are going to cross that bias line and run class B once the diodes are conducting? Doesn't this mean that when this happens, a lot of energy is going to the speaker, and not the heatsink? (although not 100 percent efficiency) So it may sound better at that level (1A per device), but my assumption is that with V2/V3, this is not recommended.
I assume I don't have the right facts.
 
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Sorry Tea Bag
what is the problem?

All I am saiing is that if one runs 50 W worth of bias one one mosfet one need sink good enoug to dissipate 200 W worth of heath
4 times 50 = 200 yess?

Not getting in to what bias you seting with the V drop across your resistors.

And that as one side conducts more the other conduct less or what so ever

Just stating that if one run max recommended 50W dissipation on 4 mosfets....

And in Cliu post of 2 weeks ago it looks like he has a big need for loads of Juce with the Nautilus

And another thing Papa said that the mosfets sound beter at higher bias
 
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BKsabath,
Dont disagree with the math, I just don't understand the goal of running 1A across the FET.
Maybe there is math that I am not aware of at play.
I just think biasing high goes against Papa's following comments from F5T article.

"We see that these devices will slowly start conducting at voltages just above the idle voltage across the 0.5 ohm Source resistors. It will be necessary to heat sink these diodes, remembering that their case is electrically connected.
The point at which the diodes conduct is temperature dependent, so you will want to set the bias so that it makes a nice transition above the bias point and doesn't run away when the amplifier gets hot.
If you are competent, fearless and also own a fire extinguisher, you can find this point. Just run the amplifier into a reasonably low impedance until it gets good and hot – as hot as you plan to let it get - ever. Then adjust the bias to a point below where the idle current starts to really take off. You should find that this point is around 0.4 volts across the 1 ohm resistors. If you are a fraidy-cat, then just set it at 0.3 volts, and conservatively fuse the AC line."

With this said, doesn't that stress the heatsink and FETs less during idle at least? Assuming big blast are periodic, I think we can get away with less here.
 
Not any particular goal
As Papa said they sound better at higher Bias

I most certanly hope that there is no math involved as I am scared of it.

Another way to pluck the Duck is to find the point at wich the diodes (taking in acount the themperaturedependency of those) start conducting and then select the resistor value to give the required V drop at wanted Bias.
reducing the value of the resistors will acieve tuning of the Vdrop across them to siut the diodes.

I think Papa like this bit of lateral thinking the figures it gave us for the V drops accros that resistor value and those diodes.

Tweaking the resistors will make you free

And another thing may be worth investigating such as a different diode, possibly a 2 pin one or a comon anode type as I don't like the way the boards turn op with the current diode type (I am in no way refering to the "published" design but to my own)

Eventualy I will mount mosfets (pins from under the boards) stiking out flat and diodes will be on opposite side in contact with sinks and keep them at the same more or less constant themperature.

This give me the oportunity to use the top for the power rails and speakers out buss bars.

Yess big blast are periodic (I hope to get the Diodes in Turbo mode only when I am plaiing 1812 or having a party) and all depends on the kind of musick one play and how ungry the speakers are.

By the way Did you try Pano test?

For Cliu set up and the voltage he normaly stated he uses this will certanly be more often than not so it looks like he would be advantageous to run the mosfets at the maximum 50 watts dissipation Papa reccomend.
 
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