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Old 5th April 2010, 11:23 PM   #7681
Renron is offline Renron  United States
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No aversion here, I prefer it! Aikido 6sn7.
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Old 5th April 2010, 11:24 PM   #7682
tinitus is offline tinitus  Europe
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Quote:
Originally Posted by a.wayne View Post
What is the aversion to running a pre-amp with the F5 ?
I suppose none
Tho being a buffer, B1 is a preamp too, right

But if you have speakers with a bit "pronounced" top, you might be in luck that a passive attenuator rolls off the top a bit, if using longer interconnects
A tube pre with higher output impedance might do that too
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Old 6th April 2010, 12:16 AM   #7683
a.wayne is offline a.wayne  United States
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I have never heard a system that didn't benefit from a pre-amp , wouldn't leave home without one ...


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Old 6th April 2010, 12:42 AM   #7684
labjr is offline labjr  United States
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Some sources have have sufficient gain and output impedence built-in and don't need any additional preamp or buffer.
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Old 6th April 2010, 12:52 AM   #7685
cviller is offline cviller  Denmark
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But a preamp with gain will sound louder, which is appealing until you turn down to the level you had before...
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Old 6th April 2010, 01:12 AM   #7686
a.wayne is offline a.wayne  United States
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Quote:
Originally Posted by cviller View Post
But a preamp with gain will sound louder, which is appealing until you turn down to the level you had before...
Christian,

When using your boards , shouldn't there be more gain than standard F5? There are a few questions on your F5 blog in need of some attn.......

regards,

Last edited by a.wayne; 6th April 2010 at 01:14 AM.
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Old 6th April 2010, 01:18 AM   #7687
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Thanks to member Tea-bag, jazz, Cviller, A.wayne, Renron, and everyone that helped me along the way, I know have an operating amp! warming her up as we speak, and will fine tune in about 45 more minutes!

Thanks again guys- without your help I'd be going insane trying to figure it out. Don't get me wrong though-in the meantime I've learned so much more than if it would've went smoothly (take the good with the bad, ha)
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Last edited by acold7dusta; 6th April 2010 at 01:24 AM.
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Old 6th April 2010, 01:52 AM   #7688
cjkpkg is offline cjkpkg  United States
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Update:

I FINISHED the F5...I am now running an Antek 600VA 18V toroid. The PSU caps are 4X33,000uF. Rail voltage is 23.9V on both sides.

I am running at 755mV for a bias of 1.61A - 800 was a little too warm. DC output is less than 10.

I am gaining much respect for the F5. At first I was disappointed with the gain but with the incremental improvements in the PSU and burn in time are turning this into a very respectable amp.

I broke down and ordered a B1 board and matched jfets from passdiy. It will be interesting to see how this combination works. I complain of gain issues but honestly I NEVER listen to music that loud.

Once I get the B1 built the next step may likely be some larger uber-efficient speakers for the living room. Unfortunately I am relegated to bookshelves. BIB's are not an option at this time.

Looking at the Fostex FE167s maybe...drivers need to be <$100.
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Old 10th April 2010, 01:11 AM   #7689
cjkpkg is offline cjkpkg  United States
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getting some more time with the F5...been listening to XM jazz and XM chill line out to a homemade preamp - the UCP referenced in the chipamp forums. The speakers are diy Fonkens with fostex FE127E drivers eNabl'd(self).

I will post opinions when I complete the B1 build.
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Old 10th April 2010, 01:18 AM   #7690
kp93300 is offline kp93300  Malaysia
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Default DC offset of about 5 v !--help needed

I have been enjoying the F5 for the past 3 months.
Of late I notice that one channel has a high dc offset of 5 V and I am unable to trim it to below 4 V.
I can adjust the bias easily. I normally use .55V across the 0R 47 at R12 due to my small heatsink. .
After warming up for 45 minutes, I can adjust the dc offset to below 10 mv.
I have changed a new set of mosfet but problem persisted.
The other channel shared the same power supply and works well.
The thermister has been checked and Ok.
I need help to know where to troubleshoot.

thanks in advance .

kp93300
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