First Watt F5

For the three and more legged things
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Nick
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#16

Post by Nick »

I got the PCB's and transistors from diyAudio folk. Peter Daniels I think for PCB's. Very easy build. Hardest part was tapping the holes in the heat sink, but that's because my M3 taps are made from play-dough.
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#17

Post by Mike H »

I've had that problem!
 
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#18

Post by pre65 »

I have had real problems tapping into soft alloys, but the high spec dural (or HE30) I use is normally not too bad.

If it's not a critical application, or needing to be done up really tight, I sometimes use a gnats bigger drill (and lubricate the tap with fairy spit. :lol:)
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#19

Post by Nick »

Not much choice for nats bigger with M3 though.
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#20

Post by IslandPink »

I've just marked out the M3 hole positions for Mosfets on my heatsinks.
I've decided to contract-out the drilling and tapping to my mate Len who reckons he can do this properly . I'm pretty sure he can do it better than me .
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#21

Post by Andrew »

I'm really tempted to have a go at this amp....ho hum too much to do, not enough time. be good to test it on a pair of Quad 63s....
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#22

Post by steve s »

Paul Barker wrote:. It is really nice. Obviously much better at bass than a low power valve amp.
Nick says he has been listening to it at home quite happily.
i would be suprised if it was really any better in the bass than a low powered valve amp with decent valves in it paul ?


i was very suprised at the sound of Eds amps.. they where impressive
on a sound per £ they are much better value..

when tapping alloy.. use parafin as a cutting lube otherwise it will tear
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#23

Post by ed »

Paul Barker wrote: Obviously much better at bass than a low power valve amp.
in post 4 I made reference to the F5 and F4 being similar, it was post 750 here that I was referring to:

http://www.diyaudio.com/forums/pass-lab ... er-75.html

what I meant to say is I didn't want to risk £100 and a weeks work to find that I'd already got the same amp, If you see what I mean.

If they are the same, and I guess Nick might be the best judge cos he's heard both, then I can say that I've got a low wattage valve amp that equals the bass. My experience is that the speakers make more than a profound difference to the end result, I think due to the DFs involved. The F5 has twice the DF of the F4, and also twice the noise, so again the speakers will tell the tale. I developed a back horn(pipi) which the F4 couldn't play with at all due to DF, so I'm pretty certain it's a big factor.

the truth is out there......just gotta find the money to nail it down
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#24

Post by brig001 »

ed wrote:I developed a back horn(pipi) which the F4 couldn't play with at all due to DF, so I'm pretty certain it's a big factor.

the truth is out there......just gotta find the money to nail it down
I agree about DF. I took my ported speakers to Colin's (Toppsy) and they were extremely bass heavy on a valve amp (can't remember which one), but fine on my 1 Watt class A and a NAD solid state amp. When I looked on WinISD, and set an output impedance of 8 ohms - probably somewhere near, there is a 7dB peak in the output at around 80Hz. drop below 1 ohm, and it's gone.

My speakers are flat to around 40Hz, so any boost in bass is undesirable, so they are only really suited to solid state amplification, if the bass output of a speaker is falling below 100Hz, an increase in bass from low DF is desirable, so bring on the valves.

Just my simple take on this and contains sweeping generalisations, but I think the principle is right.

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#25

Post by Mike H »

Nick wrote:Not much choice for nats bigger with M3 though.
Even imperial doesn't help, you need something like a 7/64th's :lol:

Or a 3 and a half 32nd's....


 
 
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#26

Post by Nick »

If they are the same, and I guess Nick might be the best judge cos he's heard both, then I can say that I've got a low wattage valve amp that equals the bass. My experience is that the speakers make more than a profound difference to the end result, I think due to the DFs involved. The F5 has twice the DF of the F4, and also twice the noise, so again the speakers will tell the tale. I developed a back horn(pipi) which the F4 couldn't play with at all due to DF, so I'm pretty certain it's a big factor.
Well, its hard to say, the F4 is a buffer, so most of what you hear is the character of the gain stage before it. Other than that, yes I think they are very similar. And yes the f5 has more noise, but again, something needs to add a extra 15dB of gain to the F4 to make them equal. So the noise will increase in that situation. In both cases, the noise is lower than most if not all valve amps.
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#27

Post by Paul Barker »

I don't hear any noise. We haven't got folk who stick their ear into speakers have we?
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#28

Post by Nick »

The numbers on Nelson Pass's site lists the various amps vital statistics, and the noise of the F4 is 50µV the F5 100µV. But both are lower than we need to worry about I suggest. 100µV and 25w is a 102dB S/N ratio

Not that I think Ed is saying it is.
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#29

Post by ed »

Nick wrote:The numbers on Nelson Pass's site lists the various amps vital statistics, and the noise of the F4 is 50µV the F5 100µV. But both are lower than we need to worry about I suggest. 100µV and 25w is a 102dB S/N ratio

Not that I think Ed is saying it is.

I was just pointing out the differences in spec in order to cover all the bases when discussing whether the two amps might be the same or similar. Noise might have nothing to do with overall sound but DF certainly seems to.

its funny how 4 or 5 years ago I was defending the first watt amps against all comers, narrowly avoiding the ducking stool. Now I seem to be defending the humble SE valve amp against the first watts....

watts going on?
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#30

Post by Nick »

F F F F Fashon (turn to the left)

:-)

Using the right tool for the right job, thats my take. I think I remember liking your first F2 Ed, though that my be me altering my memory to sute :-)
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