From: unruh on 31 Jan 2010 16:04
On 2010-01-31, Tony Houghton <h(a)realh.co.uk> wrote:
> In <uoug37-gad.ln1(a)neptune.markhobley.yi.org>,
> Mark Hobley <markhobley(a)hotpop.donottypethisbit.com> wrote:
>> The line out would not usually clip, unless the input level is too high to
>> start with. You may get away with using the cassette player input rather than
>> the record player input on the back of the amp.
> I think the tape etc inputs would be too far the other way ie the level
> would be too low to use a reasonably wide range in the ADC (ie samples
> would only use a few of the available bits and have the effective
> resolution of, say 8-bit, instead of 16-bit). Besides, RIAA has
> additional bias to compensate for the medium's frequency response.
??? all tape drives have internal preamps to bring them up to line-in
Records are all recorded with strong bass cut and treble boost.
The former is to make sure that the bass on the tracks does not make
huge excursions, while the latter is to ensure that that the high
frequency surface noise does not drown out the music. The phono output
must therefor have the inverse filter applied-- bass boosted and treble
decreased. The phone input on an amplifier has that filter in the amp.
If his record player has a preamp, then that filter is in the player
itself and you MUST NOT feed that into a phono input on any amp. (you
will get very strong bass and non-existant treble.)
The other inputs-- tape, CD,... are all with no frequency shaping, and
roughly "line in" amplitude.
From: Martin Gregorie on 31 Jan 2010 16:09
On Sun, 31 Jan 2010 19:08:08 +0000, Mark Hobley wrote:
> Or you may also think about a USB turntable too :) I'd love to know if
> they are any good.
I think that depends how good your ears are. Mine are pretty bad due to
25,000 miles in a Landrover, close exposure to screaming model engines
and one or two rock concerts. However, due to once building a good hifi
amp and then several iterations of finding and dealing with hum and
distortion I ended up trained as a hypercritical listener - my ability to
hear distortion and be annoyed by it still persists.
I have my doubts about USB turntables, ranging from mechanical noise
(using a light turntable in a direct drive motor is a recipe for rumble)
through the arm and cartridge quality and, depending on the circuit
layout chances that digital hash from the output stages can appear as
noise added to the input via the PSU.
I have a feeling that a good used turntable from eBay plus a U-record or
equivalent would give a better result but ymmv
martin@ | Martin Gregorie
gregorie. | Essex, UK
From: unruh on 31 Jan 2010 16:35
On 2010-01-31, Martin Gregorie <martin(a)address-in-sig.invalid> wrote:
> On Sun, 31 Jan 2010 10:08:02 +0000, Mark Hobley wrote:
>> Out of interest. What record player are you using? Do you have the
>> record player connected via a sound card, If so do you have a pre-amp in
>> between? or do you have one of those record players that connect via
> I started off with an ION U-record 'external sound card', i.e. an A->D
> converter, that connects to my laptop (running F10) via a USB port. I'm
> using Audacity to create WAV files and (currently) Brasero to convert
> these into audio CDs. I rapidly learnt that, while its easy to record
> each vinyl side as a single track, the resulting 2 track CD is almost
> useless unless you want to play right through every time because its a
> real pain to find individual tracks - much worse than a casette tape.
Use gcdmaster to take that single track and split it into tracks.
There is also a program whose name I forget (I think it is gramaphone)
which is supposed to find periods of silence and make tracks with those
silences as the markers. It works sometimes. It works not at all if the
tracks run into each other.
> BTW, although the U-record is a fairly cheap & cheerful device, it does
> have a decent Burr-Brown AD converter, accepts both MC and line level
> input and lets you control its gain. It has no analogue outputs. It
> doesn't add any noise or distortion that I can hear.
It could be fine. Try
for a program to test out your soundcard, although if you have no analog
output from the card it will not work
Distortion can be subtle.
> My stereo system is quite old, consisting of Garrard 301 deck with an SME
> arm and Shure V15 cartridge driving a Quad 33/303 amp and Celestion
that means that the phono deck has no built in amplifier. So you have
to run it through at least the preamp of your Quad. Note that it should
have a volume control on that preamp.
Reading about the Urecord, it probably has an RIAA filter on it already
The turntable output is very low level, I am not sure what problem you
> Ditton 44 speakers. It has other sound sources too: a Quad FM3 tuner,
> Nakamichi BX-125 tape deck, Sony CDP338 CD player and (recently added) a
> Roku Soundbridge internet radio tuner.
> I soon realised that simply plugging the record deck into the U-Record
> was pretty limiting in terms of audio sources, so things got rearranged.
That is a disaster, since the phono deck has no RIAA equalisation and
the sound coming out will be very very bass shy and treable heavy.
> I added a QED 2-way tape switch to the mix. The Naka and the U-record are
> connected to it as tape decks and its third connection goes into the Quad
> 33 preamp's tape socket. The result is that I can record to CD via the U-
> record from all the other audio sources including the Naka and the Naka
> can record from all sources except, obviously, the U-record which has no
> analogue outputs.
From: Mark Hobley on 31 Jan 2010 18:08
Tony Houghton <h(a)realh.co.uk> wrote:
> I think the tape etc inputs would be too far the other way ie the level
> would be too low to use a reasonably wide range in the ADC
Right that is interesting. There is sometimes pre-amplification on the
turntable input to account for the low output from a magnetic pickup. That
is why I suggested the tape input which would skip the pre-amp, because a
cassette deck would have already amplified the signal to a sufficient volume.
It depends on the input impedance of the sound card. It it is purely
resistive, then you are right. A 2K ioe 10K reisistor in series would
I have not tried this, but I was thinking of an in series for attenuation and
a parallel across the lines to retain the impedance. Maybe you need a couple
of isolation capacitors too, but these are probably not necessary. You could
probably get away with a "twist the wires together and apply electrical tape"
job if you wanted to test this.
What do you reckon? 2.5V output for 150 ohms input?
(I made that up btw, so don't go on my figures).
Linux User: #370818 http://markhobley.yi.org/
From: Tony Houghton on 31 Jan 2010 18:54
Mark Hobley <markhobley(a)hotpop.donottypethisbit.com> wrote:
> It depends on the input impedance of the sound card. It it is purely
> resistive, then you are right. A 2K ioe 10K reisistor in series would
> provide attenuation.
> I have not tried this, but I was thinking of an in series for attenuation and
> a parallel across the lines to retain the impedance. Maybe you need a couple
> of isolation capacitors too, but these are probably not necessary. You could
> probably get away with a "twist the wires together and apply electrical tape"
> job if you wanted to test this.
> What do you reckon? 2.5V output for 150 ohms input?
> (I made that up btw, so don't go on my figures).
When I was having a similar discussion in uk.comp.homebuilt someone
posted a link for calculating resistor values for a couple of simple
TH * http://www.realh.co.uk