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Phono Preamp Pt2: MC

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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: 16 May 2019 at 7:51am
The use of a 1n or 470p polystyrene for C4 will reduce the ultrasonic garbage which MC's are so handy in reproducing. Which of these two values to choose? Easy! Adjust to taste!

If you don't have a MJE243 perhaps you have a BD131? The use of a medium power transistor saves three small signal transistors!

Obviously you don't get this sort of info from the wannabe sites.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DogBox Quote  Post ReplyReply Direct Link To This Post Posted: 21 May 2019 at 4:38am
Originally posted by Graham Slee Graham Slee wrote:


Obviously you don't get this sort of info from the wannabe sites.
 

ThankYou so very much Graham! I am sorry that I have come across as annoying, senseless and an idiot. 
I "do" wish I could make sense of it all and I "should" have come back here to read replies instead of going off in that tangent I am so inclined (funny? inclined, tangent, angle??) to do. 

Maybe my medication has got me too zonked to make sense of the simple things I will never learn anything more taxing. I'm sick of having chronic pain. I'd much rather be doing something productive. [Which doesn't involve annoying people] 

Should have quit while I still had some tolerance afforded me. I come back here because I know YOU do the best electronics. I was singing your praise to someone just starting out in Hi-Fi who hadn't yet heard of Graham Slee Products... 

Hopefully I may be able to take part on this forum without you saying: "Oh Grief! Not HIM again!!!" I shall print out these pages for reference and see if I can't put together that circuit you SO KINDLY  put up. 

I am hoping to hear something better in my ears with MC cartridges than the infernal ringing that haunts my sleep. 

Y'never know, tomorrow might be a better day and I won't wake up at all and the sun can shine without me. 
Now, where's that Breadboard... 

DogBox Cry  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 21 May 2019 at 7:14am
Chronic pain! Medication! Been there! Misdiagnosis - turned out to be bladder failure! Only took them several years before my body finally gave them a clue... good job it did!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DogBox Quote  Post ReplyReply Direct Link To This Post Posted: 26 May 2019 at 3:56am
I wish it was misdiagnosis but it is Misalignment of lower back vertebra..and chronic arthritis thrown in. 
The two sizes of cap for C4 seem quite large in difference.. And I don't have any friendly Bats to check how good the Ultrasonics are..? Will it benefit also a bit further down the Richter scale? 
Will have to stock up on some more caps I see.. Polystyrene are a bit special - aren't they? 
Kind Regards,
DogBox 
[Steve]
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 26 May 2019 at 10:08am
C4 is a compensation capacitor and you don't hear the frequencies the suggested values turnover at.

I will repeat the word don't, not for your benefit, but for the benefit of skim readers who presuppose I haven't a clue (like in a recent review) Wink

Understanding what's going on in a circuit is nothing magical or groundbreaking, actually it's a pain, and quite a boring one at that. But distortions arise and a clever looking circuit often fails to impress due to a missed understanding.

We're all learning (except some know-all's) and it's nice now and then to get another take on how things work.

I have recently been reading Morgan Jones' Valve Amplifiers book, in particular related to this, the section on phono preamps, and the particular problem with MC's of their extended frequency response, which includes collecting all the "ground-up" ultrasonic gunge frequencies, which due to the CV response of the cartridge, will cause the collector's voltage swing to be larger than at signal frequencis.

If you remember, I said the single simple transistor will not produce much distortion because it isn't swinging much voltage, but distortion here is proportional to signal swing, so the "gunge" we don't hear can be sufficiently higher to produce ultrasonic harmonics which can heterodyne (mix) into the audible band and produce "new" and unmusical signals.

Anyone who followed my long MC 'rant' will remember me going on about heterodyning, and I welcome finding that another designer (of good repute) thinks on similar lines (Morgan Jones).

As for capacitor type, you could choose polypropylene, but some brands might not be suited, and polystyrene is possibly the 'safest' option outside my control.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DogBox Quote  Post ReplyReply Direct Link To This Post Posted: 26 May 2019 at 12:34pm
Thanks! Graham!!! Your Help is gratefully received. Does: LCR COMPONENTS ring any Bells? That's what our Farnell (element14) stocked..? 
Hopefully they're ok as I bought a few other values while I was at it... probably spent too much by jumping ahead..[something that I try and stop my mum from doing!Embarrassed
I DO have some reading to catch up on! Wow! With ICL1P's reference about you and valves [Don't tell me how it turned out - I love a 'who dunnit'!! and your All About The PreAmp...whew! 
That you bring them up again...could...could this...could this be "another plunge"? This time where the water is warmer..? Hope So! Cool Off to do my Homework..

DogBox
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Graham Slee Quote  Post ReplyReply Direct Link To This Post Posted: 26 May 2019 at 2:53pm
LCR are OK. Made in Wales (the one nearer me...)
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