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ARSCLIST  April 2007

ARSCLIST April 2007

Subject:

Re: (dream) restoration phono preamp opinions wanted

From:

Eric Jacobs <[log in to unmask]>

Reply-To:

[log in to unmask]

Date:

Wed, 4 Apr 2007 19:52:47 -0700

Content-Type:

text/plain

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text/plain (242 lines)

Thanks, John, for the succinct summary of my questions.

I might opine a bit, but I really wanted to hear what others had
to say first.  But I can lead the opinion poll to stir up the pot...

1.  Modern phono preamps with adjustable EQ: Everything I use and
    have tested is sonically challenged, or inaccurate, or lacks
    flexibility, or is very clumsy to use (ie. DIY plug-ins which
    require you to open the case up and fiddle with inserting Rs
    and Cs into the motherboard).  The most accurate RIAA EQ
    among the field is +/-0.5 dB, unless you put the Boulder 2008
    ($32,500) into the mix, which has +/-0.1 dB accuracy and each
    individual EQ costs $1,000.  Among the preamps I use and own
    are the Elberg MD-12, Millennia Media LPE-2, and Boulder 1010
    (RIAA only).  I've tested the KAB Souvenir.

2.  EQ in hardware (analog) versus software (digital): In short,
    if you use a graphic or parametric software EQ, you get kind
    of close, but you're still off by a few dB in some bands
    (parametric), and really doesn't quite sound right to my ear
    (too many filters perhaps with a graphic equalizer).  The
    difference between analog and digital EQ are not subtle.

    With one exception: the AnalogEQ VPI (plug-in) for the Cube-Tec
    Audiocube (64-bit floating point audio processing up to 192 kHz).
    They get it right, and the results are nearly indistinguishable
    from an analog EQ.  However, a complete Cube-Tec Audiocube
    workstation with appropriate plug-ins for restoration work will
    set you back at least $10k or more.  In my mind, the Cube-Tec
    software is worth it (I use an Audiocube daily, and am pleased
    with it).  The AnalogEQ allows you to set slope, turnovers, and
    roll-offs, as well as shelving and low/high-pass just as you
    would with an analog phono equalizer.

3.  Tube vs solid-state: A poorly designed tube preamp will indeed
    have non-linearities that can be described as euphonic (or
    consonant, if you will).  A well-designed tube preamp will be no
    less accurate than a solid-state design.  However, the tube design
    may have some advantages, primarily that they have wider bandwidth
    than transistors - significantly so, measured in 1-2 orders of
    magnitude.  I think that the transient response from a good tube
    design may be more accurate than most transistor-based designs.
    This transient response shows up in the stereo image.  In the case
    of the tube-v-transistor tests that I ran, the tube-based preamp
    imaging placed instruments more realistically both laterally as
    well as front-back.  That's my working hypothesis at the moment.

4.  How many of you use your mono/stereo switch on your phono preamp
    when doing transfer or remastering work?  Just curious...  I
    rarely use mine.


Eric Jacobs

The Audio Archive
tel: 408.221.2128
fax: 408.549.9867
mailto:[log in to unmask]





-----Original Message-----
From: Association for Recorded Sound Discussion List
[mailto:[log in to unmask]]On Behalf Of John Ross
Sent: Wednesday, April 04, 2007 4:43 PM
To: [log in to unmask]
Subject: Re: [ARSCLIST] (dream) restoration phono preamp opinions wanted


This whole discussion is a side issue. Eric Jacobs asked about EQ
settings on phono preamps and I replied by describing the two tube
preamps I use on pre-RIAA discs. I mentioned that the McIntosh C-8
requires an external power supply because that adds to the cost of
acquiring and using a C-8.

Somehow, people became focused on power supplies rather than
adjustable turnover and rolloff, which was the original issue. Can we
accept that yes, a tube power supply might hum, but that hum can be
eliminated in software?

As far as I'm concerned, the more interesting questions are the ones
that Eric asked: First, are there modern preamps that offer correct
and accurate EQ adjustments for 78s and pre-RIAA LPs? Second, what
are the relative merits of adding EQ in hardware versus software? And
finally, does the difference between tube and solid state preamps
matter when making archival copies of old discs?

John Ross

At  4/4/2007 02:35 PM, you wrote:
>This whole discussion is a little bit off. A power supply for a tube
>preamp is easily built or obtained, and these days you can really
>clean up the DC and send DC to the filaments to beat hum as low as
>possible (usually inaudible unless there's something else wrong
>inside the preamp or it was never a great design). For instance,
>PowerOne used to make regulated supplies all the way up to 200VDC
>for a half amp or so, plenty for a preamp. And they make plenty of
>12V or 5V adjustable to 6VDC supplies of different amps for the
>filaments. If the supply needs more than 200V, you can always find
>an old Lambda tube supply on eBay for south of a hundred bucks.
>Those things were built like tanks and rarely need anything except a
>new rectifier tube.
>
>-- Tom Fine
>
>----- Original Message ----- From: "John Ross" <[log in to unmask]>
>To: <[log in to unmask]>
>Sent: Wednesday, April 04, 2007 2:57 PM
>Subject: Re: [ARSCLIST] (dream) restoration phono preamp opinions wanted
>
>
>>Powering C-8s is not a problem for me -- I own four (count them,
>>4!) Mac 20W-2 power amplifiers that do the job just fine. And they
>>too have a hum adjustment pot.
>>
>>Just offhand, I'm guessing that finding a D-8A power supply today
>>(or a D-8, which would also work) would be far more difficult than
>>finding a C-8 preamp. I found a couple online, in the $300 price range.
>>
>>John Ross
>>
>>At  4/4/2007 11:27 AM, you wrote:
>>>Hi John,
>>>
>>>Just FYI, Mcintosh built an external power supply called an D-8A
>>>that will run the c-4 or c-8 beautifully.It has a hum balance pot that
>>>is effective in minimising hum. Note minimising !!
>>>
>>>Hope this is usefull. Or buy the parts and build one yourself. Nothing
>>>special.
>>>
>>>Bob Hodge
>>>
>>> >>> [log in to unmask] 4/4/2007 1:20 PM >>>
>>>I've been working some from mono LPs to master to CD.  In my experience,
>>>accurate recording/playback eq is imprecise at best, and, quite
frequently,
>>>imaginary.  Further eq is always needed.
>>>
>>>I've encountered a specific situation where I've had three issues
>>>of a Period LP, all mastered before 1959, each with its own
>>>eq.  One was early, probably Columbia, c. 1951, for which I used
>>>the LP setting. Another, mastered by RCA with the type in 1954 in
>>>small block letters and numbers, used NAB,  a third, using the
>>>same RCA matrix number but handwritten, fell in the cracks
>>>somewhere. I used RIAA and adjusted a whole lot with an equalizer.
>>>
>>>Tube equipment has hum- it's genetic!  It should be removed during
>>>the restoration process.  If you prefer your finished audio with
>>>tube sound, ok.
>>>But don't plead accuracy.  You are deliberately including non-musical
noise.
>>>
>>>In short- you know the answer.  Listening.
>>>
>>>Steve Smolian
>>>
>>>
>>>----- Original Message -----
>>>From: "John Ross" <[log in to unmask]>
>>>To: <[log in to unmask]>
>>>Sent: Wednesday, April 04, 2007 12:31 PM
>>>Subject: Re: [ARSCLIST] (dream) restoration phono preamp opinions
>>>wanted
>>>
>>>
>>> > At  4/3/2007 10:24 PM, EricJ wrote:
>>> >>When it comes to phono preamps that are capable of
>>> >>historical EQs, I was wondering...
>>> >>
>>> >>1.  How many people use anything but RIAA, NAB, and FLAT
>>> >>     EQs for digital transfers when doing preservation work?
>>> >
>>> > For 78s and pre-RIAA LPs, I generally use a tube-era preamp that has
>>>
>>> > front-panel adjustments for Turnover and Rolloff. A McIntosh C-8 is
>>> > particularly flexible, but it requires an early Mac power amplifier as
a
>>> > power supply. I also like my Scott 121-C, with the Dynaural Noise
>>> > Reduction function. I wouldn't use the noise reduction for
preservation,
>>> > but it's nice for casual listening. Of course, any tube equipment of
that
>>> > vintage almost certainly needs to be re-capped before you would want
to
>>> > use it for serious work.
>>> >
>>> >
>>> >>2.  Is the ability to reproduce a wide range of EQs on the phono
preamp
>>> >>important, or do you apply the final EQ in the DAW using digital
filters?
>>> >
>>> > I think either approach is acceptable, as long as the EQ is correct.
>>> >
>>> >>3.  Do you use an analog processor in conjunction with your DAW to
apply
>>> >>EQ later to a FLAT digital transfer (ie. an analog processor loop)?
>>> >
>>> > No.
>>> >
>>> >>4.  How often do you run into the situation where your phono preamp
>>> >>doesn't have the EQ you want?  It gets close, but not quite
>>> what you want.
>>> >
>>> > That is not an issue with either the Scott or the McIntosh preamps.
>>> >
>>> >>8.  If the phono preamp has accurate EQ(s), is quiet, and has low
>>> >>distortion, does anyone prefer tube versus solid-state electronics?
Does
>>> >>this matter?
>>> >
>>> > Obviously, I'm partial to tubes, but for RIAA  EQ, I also use
solid-state
>>> > (including a McIntosh C-24, a Stanton 310 and some other
>>> broadcast preamps
>>> > with balanced outputs
>>> >
>>> >
>>> >>9.  Do you use a custom-built phono preamp or a commercial phono
preamp?
>>> >
>>> > They're all commercial devices.
>>> >
>>> >
>>> >>And if there's a phono preamp that supports historical EQs that you
>>> >>really absolutely love, let me know, because maybe I should be buying
>>> >>instead of building.
>>> >
>>> > As I said earlier, I like both the Mac C-8 and the Scott 121-C.
>>> > Unfortunately, both are subject to the demands of the loony
collectors'
>>> > market, so the prices are out of line with their value as playback
tools.
>>> > You can find relatively inexpensive C-8s, but they're useless without
an
>>> > expensive MC-30 or 20W-2 amplifier to supply power to the tubes.
>>> >
>>> > John Ross

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