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Genera?
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ICL1P View Drop Down
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Points: 2341 		Post Options Post Options   Thanks (0) Thanks(0)   Quote ICL1P Quote  Post ReplyReply Direct Link To This Post Posted: 08 May 2017 at 7:57pm
I'm now building my second Genera and have encountered something I don't remember from last time.  I sent an email, but have not heard back from Graham or John yet, so, since it might be of interest to others as ignorant of electronics as I am, I thought I'd post the question to the wider forum audience.

My question is, have I correctly identified the correct capacitors?  The markings on the caps are not the same as on the project sheet component list or the kit parts list.  I'm pretty sure I've got it right, but would like to be reassured.

 project sheet component list Kit parts list Actual
C1A, C1B, C6A, C6B 100uF 25V 4 x 100uF 100V 4 x 100uF 63V
C2A, C2B 220pF 2 x 220pF 2 x 220pJ 100
C3A, C3B, C8A, C8B 4.7nF 4 x 4n7nF 4 x 4n7J 63
C4A, C4B, C5A, C5B 2.2nF 4 x 2n2F 4 x 2n2J 100
C7A, C7B 10uF 25V 2 x 10uF 100V 2 x 10uF 100V
C9 220uF 25V 1 x 220uF 100V 1 x 220uF 63V
C10, C14 1uF 2 x 1uF 2 x 1uK 1E7
C11, C13 470uF 35V 2 x 470uF 63V 2 x 470uF 63V
C12 22uF 35V 1 x 22uF 35V 1 x 22uF 35V


Edited by ICL1P - 08 May 2017 at 7:57pm
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Reflex M & ACCESSION M, CuSat50, Majestic DAC, a Proprius pair.
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Graham Slee View Drop Down
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Points: 16298 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 09 May 2017 at 2:59am
Sorry for not answering your email as promptly as I would have liked.

The list looks OK to me.

The different voltages between the project sheet and the kit part list come about because the project sheet gives the lowest safe to use voltages, whilst the kit uses the voltages I prefer to use. Where the actual is of a different voltage (63V) it is because the higher voltage wasn't in stock when we came to reorder, and so the next nearest voltage was chosen (substitution). Its OK to go higher (as we have), but going below the circuit minimum recommended voltages could result in a blown out capacitor.

Where it shows pf but the component reads pJ, the p is short for pf and the J stands for the tolerance, which is 5%. The last number here refers to its voltage rating.

The 1uF capacitor is likewise marked u for uF, and K for 10% tolerance. And the 1E7? Good question! But it's the right component.Wink
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ICL1P View Drop Down
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Points: 2341 		Post Options Post Options   Thanks (0) Thanks(0)   Quote ICL1P Quote  Post ReplyReply Direct Link To This Post Posted: 09 May 2017 at 7:29am
Many thanks Graham. My googling had explained some (voltage differences), but not all of it. I'll crack on with it. :-)
Ifor
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Reflex M & ACCESSION M, CuSat50, Majestic DAC, a Proprius pair.
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ICL1P View Drop Down
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Points: 2341 		Post Options Post Options   Thanks (0) Thanks(0)   Quote ICL1P Quote  Post ReplyReply Direct Link To This Post Posted: 13 May 2017 at 10:28am
My second Genera is successfully built and sounding really rather good from the off. Henry Mancini's Hatari.
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Points: 14 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Alasdair Quote  Post ReplyReply Direct Link To This Post Posted: 07 Jun 2017 at 8:26pm
Dear All,
My Genera has now given me several years of pleasure. The Paratrace stylus on my Denon DL103 cartridge is getting worn, so I have installed my old Rega RB100 cartridge. This is an interesting fixed stylus mm cartridge from the 1980s which has excellent tracking and amazing channel separation (over 40dB across the range) but a droopy treble (5dB down at 10kHz according to old reviews). Changing the Genera capacitors C5a and C5b from 2200pF to 1500pF lifted it a bit, so I thought I'd try disconnecting C5a and C5b completely. This lifted the treble some more and it now sounds rather good. Any comments/ suggestions?
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Points: 16298 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 07 Jun 2017 at 9:51pm
Do you have the specification for the cartridge? It's inductance might give us a clue.
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Points: 14 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Alasdair Quote  Post ReplyReply Direct Link To This Post Posted: 07 Jun 2017 at 10:20pm
Dear Graham,
Thanks for the quick reply - much appreciated. 
Rega never quoted an inductance for the RB100. I suspect that its design was probably related to the Goldring Epic, which was around at the same time, but I am sorry to say I don't know what the inductance of that was either - and it might not have been the same anyway. All I have to go on is that the HiFi Choice review at the time found that increasing input capacitance only had a small effect on the cartridge frequency response curve. 
That's why I thought I would try reducing C5a and C5b, as you had suggested this modification to give a little treble lift for someone who wanted to modify the equalisation for old Decca FFRR LPs. I am happy to trust my ears for deciding the adjustment as long as reducing or disconnecting C5a and C5b won't do any harm to the Genera. However any guidance you can offer about 'dos and don'ts' would be very welcome. 
Regards,
Alasdair
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