Anyone know about phono preamps?
Inkblot
Posts: 26,889 Forum Member
✭✭✭
Yeas ago I bought a Linn Classik tuner/amp/CD system with a Pro-ject turntable, Ortofon cartridge and Pro-ject The Phono Box preamp. I've never been bowled over by the sound quality on LPs, though it can sound excellent on CD and FM. Recently I replaced the stylus and yesterday tried out a 180g vinyl album and it sounded quite unimpressive and "shut in", plus the volume needed to be cranked up a lot compared with other sources.
Since the volume is low my thinking is that the most likely weak link is the daft-named The Phono Box preamp. The cartridge is an OM520 II which I'm sure is a moving magnet so should not need a moving coil level preamp. Is there a good, preferably inexpensive, preamp that might reveal more of what's on the discs and improve the volume?
Since the volume is low my thinking is that the most likely weak link is the daft-named The Phono Box preamp. The cartridge is an OM520 II which I'm sure is a moving magnet so should not need a moving coil level preamp. Is there a good, preferably inexpensive, preamp that might reveal more of what's on the discs and improve the volume?
0
Comments
Why is the preamp there?, doesn't your amp have one built-in?.
But as Winston has said, LP's don't sound anywhere near as good as a CD - but some people prefer their inferior quality.
No. Don't know why as Linn used to be a big name in turntables, but the Classik only has Aux and tape inputs.
As to the quality, my main concern is that the volume is low as this suggests the preamp isn't up to the job. With the volume cranked up but no record playing there's no noticeable hum or hiss so it's not an earthing problem as far as I can tell.
Has it worked OK previously?, if so does it have batteries inside, and do they need replacing?.
It runs off an AC adaptor.
I've found what I think is the correct spec for the preamp I have and it says that the gain is 32dB. Many of the preamps currently on the market have a gain of 39 or 40dB. Would that make a difference to the perceived loudness of the phono source when compared with, say, CD?
This one sounds like it may be suitable: http://www.amazon.co.uk/UK-version-Pre-amplifier-turntables/dp/B005ES0KJY/ref=sr_1_3?ie=UTF8&qid=1387816425&sr=8-3&keywords=phono+preamp
Yes that looks like it might be a good one. Not sure what their policy is on returns if you're not happy with the item. Guess I'd have to ask.
You'd have to pay the return postage (unless the unit was faulty) and the 551p would have to be in perfect condition.
http://www.which.co.uk/consumer-rights/regulation/distance-selling-regulations
How can it "not be for for purpose"? - it's a phono preamp, unless it's faulty (which would be EXTREMELY unlikely), then it's got to be "fit for purpose" - unless RS sold it you on the basis it would do something else (such as work as a microphone preamp) when it's obviously not "fit for purpose".
"Fit for purpose" doesn't cover free trials, or your own mistake in buying the wrong thing, or buying something you didn't need.
See http://www.richersounds.com/information/returns
They do that - I've had cause to return stuff for what I thought was a churlish reason; they accepted it no questions asked. You might even find that they can guide you to what you need, avoiding the need for a return.
Edit - just noticed that link refers to online purchases. The same policy applies to goods bought in the shop.
I was hoping someone could advise on the gain question, though. Would a cartridge with 3mv output sound much louder through the Cambridge (39dB gain) than through my existing preamp (32dB gain)?
Yes, a bit, but 3mV is fairly low output for a moving magnet design. One would expect the average moving magnet cartridge to produce around 5mV.
Gain figures are pretty meaningless, particularly as phono preamps aren't flat devices (they give massive bass boost and treble cut).
But as far as gain figures go, 3dB is considered the minimum change you can actually notice.
As Gomez mentioned, it could be the cartridge that's faulty - which is far more likely than the preamp.
* Sigh *
Do we have to reduce the discussion to this level every time vinyl is mentioned on this forum?
Whilst CD has the potential to to have a vastly superior dynamic range than vinyl, the widely reported Loudness war often negates that advantage when dynamic range compression is used to increase the loudness of a CD.
In such instances a correctly mastered vinyl album can often sound far superior to its CD equivalent, hence the resurgence of vinyl.
However back to the OP.
Moving Coil and Moving Magnet cartridges have different output levels so the correct Phono Pre-amp has to be used. Many, like the one I have, has inputs for both types. However many manufacturers produce a high-level output MC cartridge which can be used with the MM input on a Phono Pre-amp.
As has already been mentioned, the Cambridge Audio 551p gets consistently good write-ups for a MM only Pre-amp.
It could still be too quiet for example despite working as intended. Thus not fit for the users needs.
I got the 3mV figure from an Ortofon pdf so I think it's correct.
The cartridge was supplied with the Pro-ject turntable, and the Pro-ject preamp was recommended by the dealer (Sevenoaks, but probably over 10 years ago). I should really have done a bit more research before buying it but they had a package deal on offer and the system sounded good when demonstrated with CDs.
There's a difference between "not fit for purpose" and "not fit for the users needs"
If it's too quiet, then there's a fault elsewhere - as there very probably is anyway - it would be VERY, VERY unusual (and EXTREMELY unlikely) for a phono preamp to go faulty (and even more so for both channels to go faulty at the same time).
The OP mentioned it's fed from a PSU, perhaps the PSU is faulty? - external PSU's commonly fail over time, particularly the cheap made in China ones (usually cheap caps).
Sorry, but complete nonsense
Buying something exactly right for the purpose it's sold expecting it to 'magically' repair a fault elsewhere in the system doesn't make it fall under the term "unfit for purpose".
Generally all preamps are similar gain, just as all pickups (of the same type) offer similar outputs. The actual specified output of the PU is really of VERY little use, and is pretty well meaningless.
There were (in the very distant past) special PU's occasionally, which had extremely high output levels (in excess of 1V), but they were crystal ones, specially made to feed single valve amplifiers. Normal two valve amplifiers used normal level crystal/ceramic PU's, with outputs in the 100mV's region.
It's a pity he's not local, I've got a PU preamp he could try.
It's streets ahead of the Pro-ject preamp. Maybe it's the higher gain, because I don't need to turn the amp up as far; whatever the reason, there's a more natural sound, particularly to the bass, and it draws one in and feels more involving. It's difficult to explain - and clearly some don't accept that vinyl can sound good - but it's like the band is tighter, or perhaps funkier and less metronomic.
So thanks for the suggestions but in the end a new phono stage worked wonders.