Hi AL - you almost answer the question yourself. The F5 may not be sufficient for your speakers and music taste. But before you start building something else, I would suggest figuring out if your preamp has enough gain to get the full swing out of your F5.
My preamp has no gain, is a buffer B1. The Buffalo Dac (and legato) connected to B1 gives a maximum of 2V.
THE f5 + B1 goes well and sounds great. Only very few issues I have to turn the volume up to-7dB or-5db, almost 0 dB and full power of F5.
So I ask, what is the power developed by the F5 for 4 ohm speakers.
Speaker 8ohm 25W is the manual says.
THE f5 + B1 goes well and sounds great. Only very few issues I have to turn the volume up to-7dB or-5db, almost 0 dB and full power of F5.
So I ask, what is the power developed by the F5 for 4 ohm speakers.
Speaker 8ohm 25W is the manual says.
50 at 4
you need some gain in preamp
see thread about F5 dedicated preamps , with few from Juma
you need some gain in preamp
see thread about F5 dedicated preamps , with few from Juma
2Vac cannot drive the F5 to full power.
2Vac with 5 to 7dB of attenuation cannot drive the F5 to quarter of maximum power.
The F5 if built properly is a 50W into 4r0 amplifier, but @ 1/4power it is down to just 12.5W of maximum output.
2Vac with 5 to 7dB of attenuation cannot drive the F5 to quarter of maximum power.
The F5 if built properly is a 50W into 4r0 amplifier, but @ 1/4power it is down to just 12.5W of maximum output.
What type of Volts are those?
that is, 12.5 W.
I'm thinking of an amp with KT88 and studied whether PP 25W or SE 12W.
The output stage of the BII LEGATO DAC gives 2V peaks in the signal. This signal passes through a B1 with an attenuator for resistance:
http://www.diyaudio.com/forums/digi...itally-controlled-relay-volume-regulator.html
I listen to-15db or-11db. And only in some song came to -5db. That's enough power for me. Never hear 0DB.
So if I put the pot on 0dB, the F5 is taking 50W, but if I put in-6db gives me 12.5 W. Is that so?,
Thanks for the replies.
http://www.diyaudio.com/forums/digi...itally-controlled-relay-volume-regulator.html
I listen to-15db or-11db. And only in some song came to -5db. That's enough power for me. Never hear 0DB.
So if I put the pot on 0dB, the F5 is taking 50W, but if I put in-6db gives me 12.5 W. Is that so?,
Thanks for the replies.
The F5 with the standard 6X gain needs ~2.4Vac to reach clipping.
That 2.4Vac is ~3.3Vpk
2Vpk will take the F5 to ~60% of maximum output or about 9W of maximum output.
That 2.4Vac is ~3.3Vpk
2Vpk will take the F5 to ~60% of maximum output or about 9W of maximum output.
AndrewT excuse my ignorance, but the 60% of the maximum output for 4 ohms speakers (50W), is not 30W?
2Vpk as a proportion of 3.33Vpk is ~60%.
That leads to driving an F5 upto ~9W into 8r0. But not more.
Into 4r0 that would be <~18W
That leads to driving an F5 upto ~9W into 8r0. But not more.
Into 4r0 that would be <~18W
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Read what AndrewT says, his math is always spot on.
Don't be confused by the doubling of amplifier power into a 4 ohm speaker... Yes, the power is more, due to increased current, but the total system efficency/output will be the same because the 4ohm speakers have different sensitivity ratings -- 4ohm speakers are 2.83v/1M, 8 ohm speakers are 1W/1M. Effectively the 4ohm speakers are rated 3db more efficient than they really are... In reality they are 3db less efficient than a typical 8ohm speaker. And so the doubling of amplifier power into the 4ohm load makes up for the 3db loss in the efficiency rating, and everything works out the same.
That might not be the best explanation, but hopefully you get the idea.
Anyway, most people only use a few watts on a continuous basis - the peaks are much bigger, of course. But you might do 95% of your listening using 4-8W.
What you are experiencing now is that the biggest signal your source/preamp can throw at the amp is only able to get it to ~half it's output.
Don't be confused by the doubling of amplifier power into a 4 ohm speaker... Yes, the power is more, due to increased current, but the total system efficency/output will be the same because the 4ohm speakers have different sensitivity ratings -- 4ohm speakers are 2.83v/1M, 8 ohm speakers are 1W/1M. Effectively the 4ohm speakers are rated 3db more efficient than they really are... In reality they are 3db less efficient than a typical 8ohm speaker. And so the doubling of amplifier power into the 4ohm load makes up for the 3db loss in the efficiency rating, and everything works out the same.
That might not be the best explanation, but hopefully you get the idea.
Anyway, most people only use a few watts on a continuous basis - the peaks are much bigger, of course. But you might do 95% of your listening using 4-8W.
What you are experiencing now is that the biggest signal your source/preamp can throw at the amp is only able to get it to ~half it's output.
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I was wondering, is the F5 stable without any feedback? If so, has anyone tried listening to their F5 without any negative feedback? How did it sound?
Zero feedback? I don't know if it would be stable. However, you can reduce the total feedback by increasing the value (Commonly 220 ohm instead of 100 ohm as drawn) of the feedback resistors. (R5,6,7,8)
This also increases the input sensitivity, a welcome change.
Yes. My understanding of the F5 is that in it's 'normal' configuration it needs 4v input to swing full output. Are there any variables in this that I'm not aware of? You know how these things really work... I just build them. 🙂
You can do what I did. I was able to find a 12 VDC switching regulator chip, that I use to drop the F5 rail voltage to run protection boards and also VU meter circuitry.
As a switching regulator, it's very efficient--and therefore runs very cool. I didn't even need to heatsink them.
Just make certain you filter the regulator input/output (small chokes and caps will do it), to prevent any regulator switching noise from getting into the audio.