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first-time tube DIY project...phono preamp
first-time tube DIY project...phono preamp
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Old 31st August 2005, 05:42 PM   #1
jim_vt is offline jim_vt  United States
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Default first-time tube DIY project...phono preamp

Hey all...

Planning to buy my first turntable, a Music Hall MMF-5 (w00t!)

Need a phono preamp for it; thinking I could build one myself since it looks fairly straightforward. Does anyone have any good plans for a tube phono preamp?

Thanks in advance
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Old 31st August 2005, 07:29 PM   #2
EC8010 is offline EC8010  United Kingdom
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I don't want to put you off, but you should be aware that a phono pre-amp is the hardest of valve projects to make successfully. Part of the art is in the design, but a lot is in the construction. It's very easy to make one that hums...
The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...
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Old 31st August 2005, 07:55 PM   #3
karma is offline karma  Canada
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yes i have made 2 in the past that hum really nice
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Old 31st August 2005, 07:56 PM   #4
KevinTams is offline KevinTams  United Kingdom
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I would take seriously the advice from EC8010, it took me 3 attempts to make mine completely quiet. The work and aggro was definitely worth it though

THe big thread above has a huge amount of detailed info on how to build the KYW valve el cheapo and the psu to go with it and how to design the psu and how to correctly wire the grounds. If you're serious you will need to read several of the posts very carefully to extract the most information.
My input is fed from a transformer which ups the voltage from a very low output mc cartridge and is quiet enought that I cannot hear it more than 2 feet away on full volume.

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Old 31st August 2005, 11:34 PM   #5
Eli Duttman is offline Eli Duttman  United States
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What do you use for a line stage? Many phono stage designs need to be combined with a linestage that has some gain. In order to use a MM cart. and a "unity" gain line stage, the phono stage will have to provide 50 dB. of net gain and 55 dB. net is indicated with a HOMC cart.

A Bottlehead Seduction kit is reasonably foolproof, but even fully tricked out with CCS loading, 40 dB. net gain is all it delivers. So, a Seduction needs to be combined with a line stage that has gain.
Bottlehead Corp.

There are techniques using resistive voltage dividers that allow high O/P sources, like CDPs, to comfortably work with a line stage that has gain.

Mull over all the information provided by those who have responded. Don't spend any cash without some CAREFUL reflection.
Eli D.
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Old 1st September 2005, 12:30 AM   #6
mach1 is offline mach1  Australia
Join Date: Sep 2004
Location: Brisvegas
I can thoroughly recommend Kurt Strain's 6ER5/6GK5 phono pre. Use a ground bus, tube shields and keep construction compact.

If you want to save on construction costs you can use the 2 or 3 volt versions of these tubes which cost peanuts (RCAs are very good). You can also use IXYS IXCP10M45S based CCS' instead of the C4S specified.

Hope this helps
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Old 1st September 2005, 12:44 AM   #7
cerrem is offline cerrem  United States
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Although I agree with all the previous advice 100%....
I would say GO FOR IT......
Hey, so you will make some mistakes and maybe pull out a few hairs and curse ...possibly waste some money...But in the end you will be better off...cause you will have gained knowledge the old fashion way...learn by doing.... Heck you may be a future contributor to post such as these and provide others with usefull info you figured out on your own....It won't happen over night...Just keep chip'n away and the phono stage will keep improving...
If it were one advice to tell a first time phono stage builder, I would say to focus on the quality of the B+ and the grounding scheme......

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