WTB: turntable phono preamp (RIAA)
Fred
requirements. (They seem to be 20 at Maplin and ~15 on e-BAY)
http://www.maplin.co.uk/module.aspx?moduleno=28732
http://cgi.ebay.co.uk/New-Turntable-Phono-Pre-amp-RIAA-Transfer-Vinyl-to-CD_W0QQitemZ300378385188QQcmdZViewItemQQptZUK_AudioTVElectronics_HomeAudioHiFi_Amplifiers?hash=item45eff26b24
After 35 years of faithful service, I've decided to retire the old
Pioneer SX-680 tuner amp (a classic) and use one of these mini combo
units.
It has line in and out, but not with phono equalisation, etc. so a bit
of jiggerypokery is needed to use the turntable. (Actually the
turntable has a 12V DC supply inside and I considered making one, but
then decided the effort was not justified.)
Get in touch at (fix this in the obvious manner):
snoop-dot-dog99 at en-tee-el-world-dot-komm
Fred
>Don't expect too much with a S/N ratio of (only) "better than 50dB". A
>good separates amp will be in the high 70s or better.
>
>The quality of the power supply be a significant factor to bear in
>mind.
Interesting. I expect these ~20 pound units are simply one of the
reference designs using just a quad, FET input, low noise op-amp.
That's what I was planning before deciding my time was worth more.
Thanks.
The Natural Philosopher
> On Sat, 02 Jan 2010 11:57:13 GMT, Fred <nob...@nowhere.com> wrote:
>
>>> Don't expect too much with a S/N ratio of (only) "better than 50dB". A
>>> good separates amp will be in the high 70s or better.
I am fairly sure that thermal noise limits you to around 68dB weighted,
with a 2mv input.
Best I could ever get was that, connected to a very low source
impedance(300ohm) genny. A typical MM pickup is of course of complex
impedance, round the 2k level 'where it counts'
Of course you can fudge those figures by using a higher reference input
voltage. From a much lower source impedance. But it doesn't affect what
you get in practice.
Its pretty hard to ge a master tape that's better anyway, as microphones
and suchlike have a thermal noise of their own.
>>>
>>> The quality of the power supply be a significant factor to bear in
>>> mind.
>> Interesting. I expect these ~20 pound units are simply one of the
>> reference designs using just a quad, FET input, low noise op-amp.
>> That's what I was planning before deciding my time was worth more.
>> Thanks.
>
> They probably are similar, but good design (including layout) is
> important when dealing with low-level signals.
>
Screening is the only real issue. Its no big deal to make a good preamp,
as long as its not connected to a power amp. A simple shunt feedback FET
opamp will net you around 60dB SNR and very low distortion: To get lower
noise you need a bipolar input stage and series feedback though. BC109
or equivalent will immediately put you into the 65-68dB bracket.
Batteries are good..no earth loops!
> For the small outlay I'd say it's probably still worth giving it a go
> - you can always flog it on eBay if you don't like it. It may depend
> on your source material :-)
>
> If you get one and the PSU is poor you could try running it from a
> stack of AA cells.
Jules
> After 35 years of faithful service, I've decided to retire the old
> Pioneer SX-680 tuner amp (a classic)
Oh heck, I had one of those - it was simply lovely. Also a SX-626 and a
SA-510 amp. The sad thing is, I really don't remember what I did with the
former two (the SX-626 was fished, working perfectly, out of a farm skip).
I've still got (I hope, I left it in my parents' garage) the SA-510. I've
got some more recent Pioneer stuff too, but it's just not the same somehow!
I can't comment on the sound quality (although they suited me fine - had
a couple of big Wharfedales for noise and small B+Ws for quieter times),
but I just loved the 'UI' design on the old Pioneer stuff. I always had
the impression that they spent an R+D fortune on getting the instrument
lighting *just right* ;-)
You're making me want to go out and spend money...
cheers
Jules
Duncan Wood
<t...@invalid.invalid> wrote:
> Mark wrote:
>> On Sat, 02 Jan 2010 11:57:13 GMT, Fred <nob...@nowhere.com> wrote:
>>
>>>> Don't expect too much with a S/N ratio of (only) "better than 50dB". A
>>>> good separates amp will be in the high 70s or better.
>
> I am fairly sure that thermal noise limits you to around 68dB weighted,
> with a 2mv input.
>
> Best I could ever get was that, connected to a very low source
> impedance(300ohm) genny. A typical MM pickup is of course of complex
> impedance, round the 2k level 'where it counts'
>
Thermal noise is sqrt(4KTdFR), so about it's about that
> Of course you can fudge those figures by using a higher reference input
> voltage. From a much lower source impedance. But it doesn't affect what
> you get in practice.
>
> Its pretty hard to ge a master tape that's better anyway, as microphones
> and suchlike have a thermal noise of their own.
>
>
Large diaphragm mics get you into the low to mid 80s, 150 Ohms & the
output levels higher, the distortion normally gets you 1st nowadays.
Fred
Sorry, I had a typo in there.
It was only 25+ years of faithful service.
Superb audio.
Good FM tuner.
Crap AM tuner.
Until an expert advised me the fix, it slightly interfered with
shortwave reception due to an inherent high frequency instability in
the audio power amp ICs.
I also have the matching tape deck CT-F500 - kinda average, but OK.
Cheers.
Jules
> Sorry, I had a typo in there.
> It was only 25+ years of faithful service.
>
> Superb audio.
> Good FM tuner.
> Crap AM tuner.
> Until an expert advised me the fix, it slightly interfered with
> shortwave reception due to an inherent high frequency instability in
> the audio power amp ICs.
They seem to be sitting at about $100 - $120 this side of the Pond, and
about $30 shipping. Maybe I can get lucky and find a broken one for cheap
that I can fix. Lots of second-hand stores in this area, too, so trawling
them might get me a bargain...
I had a Sony tuner (ST-A3L, IIRC, after some Googling) which always seemed
reasonable, but it was some oddball width that just didn't go with
anything else that I had so I got rid of it eventually (possibly to a
cam.misc inhabitant).
> I also have the matching tape deck CT-F500 - kinda average, but OK.
I can't remember all the tape decks I had now. I know I had* a JVC KD-A7
which was a pretty nice unit (and some newer Kenwood thing - the less said
about that one the better)
* I might still have it. Nasty feeling I got rid of it when I got the
Kenwood though, which would be a real shame. It's all in storage at my
folks' place, so I can't simply look and see :-) (although I'm curious
about it and the SA-510 now, so maybe I'll see if my dad can check)
Oh, I still have a much newer (but still over 20 years old now) Pioneer A-717
amp, but it just never sounded as nice somehow as the SA-510 (and it's all
a bit too black and plastic-like! :-)
cheers
Jules