My ACF pre.

pre65 · Post by **pre65** » Thu Aug 29, 2013 2:45 pm

I've made a start on MY ACF pre amp.

I'd cut a bit of MDF to suit, but have changed direction a bit now. The original mains transformer I'd chosen is not really up to the job, so I've resurrected another PSU (from a past pre project) that can be used as choke input, and am (at this very moment) trying to move everything closer together to make room for the ACF bits.

Photo to follow if I'm successful.

pre65 · Post by **pre65** » Thu Aug 29, 2013 5:18 pm

Space is blooming tight on the base, I keep looking, and moving things around and then go away for a while. When I go back I try something else.

It's getting close now, so hopefully by close of play tonight I will have a layout that works.

Dave the bass · Post by **Dave the bass** » Thu Aug 29, 2013 8:08 pm

Shoddy!

DTB

pre65 · Post by **pre65** » Thu Aug 29, 2013 8:09 pm

I think it's sorted. Just need to screw everything down now.

The power supply is horrendously over specified, but there you are.

The eagle eyed will spot all the controls are at the back, saves wire.

simon · Post by **simon** » Thu Aug 29, 2013 10:41 pm

Blimey Philip! Even I think that's an awful lot of bits for such a simple circuit. Well done!

andrew Ivimey · Post by **andrew Ivimey** » Thu Aug 29, 2013 10:52 pm

It'll never work you know!

Cressy Snr · Post by **Cressy Snr** » Thu Aug 29, 2013 10:54 pm

Overkill power supplies rule baby!

pre65 · Post by **pre65** » Thu Aug 29, 2013 10:57 pm

andrew Ivimey wrote:It'll never work you know!

Have faith dear boy.

David says of his ACF pre -- "vocal articulation to die for "

So it's got to be worth a try, n'est-ce pas ?

pre65 · Post by **pre65** » Thu Aug 29, 2013 10:58 pm

SteveTheShadow wrote:Overkill power supplies rule baby!

If the results are positive next step could be a regulated PSU.

IslandPink · Post by **IslandPink** » Thu Aug 29, 2013 11:29 pm

pre65 wrote:The eagle eyed will spot all the controls are at the back, saves wire

Just make sure you have to reach over the HT cap to turn it off before bedtime - that's a proper man's breadboard

David · Post by **David** » Fri Aug 30, 2013 7:44 pm

David says of his ACF pre -- "vocal articulation to die for "

So it's got to be worth a try, n'est-ce pas ?[/quote]

Yep, I even started liking music I hadn't previously liked, the vocals /mids were that good...........

David

brig001 · Post by **brig001** » Sat Aug 31, 2013 11:04 am

Crikey Philip, that power supply is bigger than my power supply, my preamp, active crossover and power amps all put together. Hope it all goes to plan and keep up the good work.

Brian.
PS. Do you have any furniture left? That looks like part of a dining table to me

pre65 · Post by **pre65** » Sat Aug 31, 2013 11:21 am

brig001 wrote: PS. Do you have any furniture left? That looks like part of a dining table to me

Well Brian, since the wife died (7 years now) my house has become more like a workshop and warehouse.

BUT, at least I'm happy to do what I enjoy.

andrew Ivimey · Post by **andrew Ivimey** » Sat Aug 31, 2013 12:10 pm

ummmmmmmmmmm the input phonos have a long way to go through transformer territory to get to the valves. (I imagine the outputs will be at the back of the board.) Might not this signal journey be challenged a smidge more than necessary to keep out noise and artefact?

pre65 · Post by **pre65** » Sat Aug 31, 2013 12:12 pm

I've got the HT part of the PSU about finished now.

I need to work out the total current ACF will need with 2 X 6SN7 so I can sort out a test resistor.

Any ideas ?

As the top half cathode feeds the bottom half anode is there only one lot of current per valve ? If so I suppose 20ma ( 10ma per valve) would do for testing ?

audio-talk

My ACF pre.

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