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GSP Preamp

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Graham Slee View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 29 Apr 2016 at 1:20pm
As Bob was wondering what is happening to the preamp (see Designing a Rega Rim Drive topic) I can announce that I now have three sample cases for the remote control.

One in particular stands out as being stylish enough and more importantly workable. However, it only takes 2 x AA cells which limits the power supply to 3 volts.

This causes a further problem as the encoder works down to 2.4 volts but has the steering diodes (which select the right switch) in series with it. Therefore the minimum supply is 3 volts because diodes drop 0.6 volts and 2.4 + 0.6 = 3. With me so far?

Therefore it will only work on fresh batteries which is a bit of a sod. And it won't work at all using rechargeables.

One way around this is to use a type of diode called a Schottky which has a smaller voltage drop and if one can be found that gets it down to 0.2 volts, then battery life will be considerably extended - but it still won't work with rechargable batteries because they are 1.2 volts, not the 1.5 volts each that will be required.

If machined out (something that John C shook is head at) it could take an E-cell (PP3 to us Brits) and then it would last "forever" (or seem that way). But machining adds cost and is a lot of messing about.

Oh what fun designing stuff is Cool

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Post Options Post Options   Thanks (0) Thanks(0)   Quote morris_minor Quote  Post ReplyReply Direct Link To This Post Posted: 29 Apr 2016 at 2:19pm
Thanks for the update, Graham! Smile
Bob

Majestic DAC/pre-amp
Accession MC/Enigma, Accession MM, Reflex M, Elevator EXP, Era Gold V
Solo ULDE, Novo, Lautus USB and digital, Libran balanced, CuSat50
2 x Proprius + Spatia/Spatia Links
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Paul H Quote  Post ReplyReply Direct Link To This Post Posted: 29 Apr 2016 at 9:50pm
If it were easy it would be boring and you'd get no sense of achievement. That's what I tell myself when things get frustratingly difficult to sort :)

Edited by Paul H - 29 Apr 2016 at 9:51pm
ProJect 1Xpression Carbon UKX w/ Ortofon 2M Black; Arcam Alpha 7 CD player; Graham Slee Revelation M pre; Denon PMA 355UK amp; Epos K1 speakers; Blue Jeans LC-1 interconnects. Room: 2.9m x 3.1m.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 16 May 2016 at 9:16pm
Before designing the preamp circuit for real, the power supply has to be sorted out.

It is here that I'm thinking of making a special PSU1 which outputs +/-24 volts and 30V (nom.). If successsful it can also be used as a 48V phantom supply for microphones, finding use in pro-audio.

In fact the circuit is drawn up, it just requires prototyping.

After that, the preamp circuit can be designed.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gijo1977 Quote  Post ReplyReply Direct Link To This Post Posted: 05 Dec 2017 at 1:45am
Graham,

This thread seems to have run pretty cold now for 12 months or so. Have there been any updates or progress towards a pre? I am interested in the Proprius, however I would need to also find myself a good preamp to deal with them and the source material (Phono and CD).

I was considering a passive pre, but then found this thread and my interest was sparked :)

Thanks for any updates

Dan
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tg [RIP] Quote  Post ReplyReply Direct Link To This Post Posted: 05 Dec 2017 at 5:32am
Daniel,
if you only need one analogue input you might be shocked by how well the majestic DAC performs as a preamp.
Tony G
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gijo1977 Quote  Post ReplyReply Direct Link To This Post Posted: 05 Dec 2017 at 5:53am
Tony,

I am actually scared how well it will perform ;) I cant really afford a Majestic on top of the Proprius, should I head in that direction.

I will inevitably be contacting Keith for a loaner I guess, but I was hoping to find a good step into separates without having to get that Majestic.

Any recommendations for a good vintage or passive pre would also be taken ;)

Dan
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