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Old 20th September 2012, 10:40 PM   #1761
6L6 is offline 6L6  United States
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That speaker has good efficiency (for a 'normal' speaker) and a very smooth impedance curve. Any version will play them well.

So would a 'original' F5 .
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Old 20th September 2012, 11:03 PM   #1762
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Quote:
Originally Posted by beetle View Post
What do you think is the best? Low bias ~1-1.5A with 35V rails or high bias ~1.5-2A with 24V rails? Will bridge the F5t so the speakers will see double voltage any way. Will use 8 output devices per channel, F5 turbo V1. Will drive these speakers with it: Dynaudio Special Twenty-Five loudspeaker Measurements | Stereophile.com

Dissipation is already crazy with this.
that depends on what you want the amp to do.
the higher bias, the higher classA power. lower the rails, lower the power will be.
the best way. amp wise., is 2+A bias with +/-40V rails. but that will cost you in regard to cooling. so ask yourself. how much power do you need. you are the only one that can answer that.
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Old 20th September 2012, 11:11 PM   #1763
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Originally Posted by beetle View Post
What do you think is the best? Low bias ~1-1.5A with 35V rails or high bias ~1.5-2A with 24V rails? Will bridge the F5t so the speakers will see double voltage any way. Will use 8 output devices per channel, F5 turbo V1. Will drive these speakers with it: Dynaudio Special Twenty-Five loudspeaker Measurements | Stereophile.com

Dissipation is already crazy with this.
well. just had a quick look at those speakers. first no,no in regards to class A is the 4ohm nominel. sec is the 89db at 2W so 86db at 1W.
if you want this to play in class A a good way up. it demands alot.
say +/-45 rails and around 2.6A bias. will give you 50W class A at 4ohm. and a dissipation of 234W pr ch. + losses in PSU.
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Old 21st September 2012, 12:53 AM   #1764
a.wayne is offline a.wayne  United States
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Originally Posted by AudioSan View Post
that depends on what you want the amp to do.
the higher bias, the higher classA power. lower the rails, lower the power will be.
the best way. amp wise., is 2+A bias with +/-40V rails. but that will cost you in regard to cooling. so ask yourself. how much power do you need. you are the only one that can answer that.
Not much 400 @1 will work for me ....
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Old 21st September 2012, 01:12 AM   #1765
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wayne. 400W class A at 1ohm?
better call your plant to get them to turn up the juice
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Old 21st September 2012, 09:34 AM   #1766
a.wayne is offline a.wayne  United States
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wayne. 400W class A at 1ohm?
better call your plant to get them to turn up the juice
Nope 100 watts class-a @ 8 ohm works for me ..
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Old 21st September 2012, 09:43 AM   #1767
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hehe wayne thats possible you will need 2.6A bias then. and +/-40V rails or more
mine will run on +/-50-52V and bias as high as my sinks can handle 2.5-2.6A.
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Old 21st September 2012, 11:49 AM   #1768
beetle is offline beetle  Germany
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Originally Posted by AudioSan View Post
well. just had a quick look at those speakers. first no,no in regards to class A is the 4ohm nominel. sec is the 89db at 2W so 86db at 1W.
if you want this to play in class A a good way up. it demands alot.
say +/-45 rails and around 2.6A bias. will give you 50W class A at 4ohm. and a dissipation of 234W pr ch. + losses in PSU.
In this case you recomend one pair of output devices. I am planing to bridge the amp, so I have a different case here. So the voltage the speaker is seeing is double. Therefor twice the wattage. So I think lowering the rail voltage is no problem her. Or is it? I am going to bridge it to have symmetrical inputs. Or is there anything wrong with my consideration?

Why 2 output devices and not 4?

45V Rails with 2.6A bias will be quite a bitch to keep cool. With 8 output devices each channel allmost 1kw of heat.
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Old 21st September 2012, 11:57 AM   #1769
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so you planning on a balanced amp? then you can cut the rails in half
but then agein. on 4ohm speakers? thats 2ohm pr amp.
the bias i'm talking about is total bias for all pairs.
but to run this at any high class A power will give you a headake and a electric bill thats off the roof

Last edited by AudioSan; 21st September 2012 at 12:00 PM.
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Old 21st September 2012, 02:30 PM   #1770
beetle is offline beetle  Germany
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Bias is not summing up when bridged, as far as I understand. Disipation will be this per channel: 2 F5t*2A Bias*24V*8 Output devices = 384W or 576W with 3A Bias.

I am thinking about using one Modushop 5U 500 case per channel. They tell one sink can handle 0.2C°/W. There are 4 of them per chassis. 2 output devices per sink. Makes 96W to 144W disipation for each sink. 19.2 to 28.8°C above ambient in best case.

I think 100W per sink should conservatively spoken be possible. Then let's see if the sink can handle more heat.

What do you think?


Maybe my GF will be off to the moon when I tell her about the consumption. She is allready suspicious about my gear. Maybe I get rid of the power-on LEDs soon. She thinks there are to many of them. No LED, no consumption. solved.
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