Agreed about VCAs. They typically degrade the performance of the best
analog circuits by an order of magnitude (distortion, noise, bandwidth,
Maybe I'm the only one, but I would prefer to have a mono sum (with a fine
adjustment for L/R balance to minimize the noise floor) in addition to the
stereo outputs. I always print both stereo and mono. That way, the mono
track can often be used as-is, and if it turns out that there is an anomaly
someplace that only shows up in one of the two channels, it can be edited
from the stereo track into the mono file. I actually do the mono summing
in my DAW, but if I had the choice, it would prefer to do it analog.
That said, I tend to do more EQ tweaking digitally in post. Spending time
adjusting EQ during playback puts additional unnecessary wear on the disc.
On Sat, Apr 11, 2015 at 3:03 PM, Tom Fine <[log in to unmask]>
> Hi Corey:
> I'd be OK with analog/manual switches and knobs, but you'd have to go
> co$tly if you don't want them to wear out. Figure this thing is not a set
> and forget device, people will be fiddling with the controls every time
> they put on a disk. That's a lot of hard use in a production environment.
> Also, I agree with Richard and Paul, that's the way to go with outputs.
> Richard's suggestion is perfect, just throw a set of RCA-to-TS adapters in
> the box.
> I don't think I included balanced inputs on my list, I agree with your
> point about them. I forgot if it was in this context or another that I said
> just use Henry Matchboxes if it's that critical. The only circumstance I
> can think of where it would be super-critical like that would be if you
> were looping through something like an old Pultec that really wants to feed
> a 600-ohm balanced device.
> -- Tom
> ----- Original Message ----- From: "Corey Bailey" <[log in to unmask]
> To: <[log in to unmask]>
> Sent: Saturday, April 11, 2015 3:53 PM
> Subject: Re: [ARSCLIST] "Best of both worlds" disk preamplifier
> Hi Tom,
>> Thanks for bringing up this topic as I'm currently designing a
>> restoration phono preamp for my own use. I'm doing this simply because it's
>> been awhile since I've built anything electronic or done any board level
>> work and I feel the need to scratch that itch.
>> I'm basically going to build in everything on your wish list except for a
>> couple of things:
>> Unbalanced (phono) inputs only The only reason I can see for balanced
>> inputs is for a line input to the EQ sections (an outboard option I already
>> have). Besides, to do this requires more amplifier stages (even if unity
>> gain) and I want to keep the active stages to a minimum.
>> The outputs will be both balanced and unbalanced.
>> You wrote:
>> <SNIP>"What I'd like to see built and marketed is a disk preamplifier
>> that does the initial impedence and capacitance match with the cartridge
>> and the first stage of amplification, then offers bridged output off that
>> stage, goes on to do a passive EQ with all the turnover and rolloff
>> options, and then an output stage. So, a person could play a disk once
>> (efficient workflow), make a flat transfer to a separate digital file, and
>> do the EQ to the best of their expertise and taste -- so there is
>> immediately a usable/listenable copy for researchers, library clients,
>> online, reissue or whatever. The idea of making two passes doesn't fit
>> budget-constrained workflows, and many of us are not at all sold on digital
>> EQ (which also takes extra time and extra steps after playback, again
>> inefficient). The device I describe offers the best of both worlds -- you
>> get that flat transfer to archive and do whatever in the digital domain at
>> some later time, but you end up with a listenable/usable sound file at the
>> same time." <SNIP>
>> I plan on building my preamp as a dual-mono piece of gear with a coupling
>> switch that allows for an EQ'd and Flat transfer simultaneously (or any
>> combination thereof). Alternatively, it will have RIAA EQ options and be
>> able to be used as a stereo phono preamp.
>> By "passive EQ", I presume you mean an RC network in front of an
>> amplifier stage.
>> I'm still on the fence regarding impedance/capacitance matching for my
>> own use because I only use the usual "standard" cartridges. It's an easy
>> add-on though.
>> Regarding your "Dream Preamp" comments:
>> If you want to keep the end result as clean and as "esoteric" as possible
>> (which I plan to do), you avoid things like VCA's, relays and anything
>> digital or even CMOS. It's only going to be hand operated, gold contact
>> switches and minimal amplifier stages.
>> That said, I'd like to see more opinions and wish list features regarding
>> this thread.
>> Corey Bailey Audio Engineering
>> On 4/11/2015 5:46 AM, Tom Fine wrote:
>>> Does anyone know of any reviews of this unit similar to Gary Galo's
>>> testing of the KAB preamp? Maybe that's fodder for an ARSC Journal article
>>> -- a testing and features shootout between this unit, KAB, the LOC Preamp
>>> and the TDL Restoration preamp. Maybe throw in an old McIntosh or Marantz
>>> for comparison.
>>> One thing I'd love to see on my "dream preamp" would be a digital-logic
>>> control panel for the EQ, rather than rotary switches or pushbuttons. I'd
>>> prefer the audio to be confined to a PC board, where all the EQ components
>>> could be laid out with short signal paths, with routing done by little
>>> micro-relays or whatever they're using these days. And of course separate
>>> controls for turnover and rolloff.
>>> Calibrated precision output levels may be useful for some folks. I
>>> notice that the unit Parker distributes has VCA controlled outputs, which
>>> is a good idea. Using a digital-logic user interface could accomplish this
>>> with VCA's.
>>> -- Tom Fine
>>> ----- Original Message ----- From: "Parker Dinkins" <
>>> [log in to unmask]>
>>> To: <[log in to unmask]>
>>> Sent: Saturday, April 11, 2015 8:19 AM
>>> Subject: [ARSCLIST] "Best of both worlds" disk preamplifier
>>> Date: Fri, 10 Apr 2015 08:00:14 -0400
>>>>> From: Tom Fine <[log in to unmask]>
>>>>> Subject: "Best of both worlds" disk preamplifier
>>>> The device I describe offers the best
>>>>> of both worlds -- you get that flat transfer to archive and do
>>>>> whatever in the digital domain at
>>>>> some later time, but you end up with a listenable/usable sound file at
>>>>> the same time.
>>>> These preamplifiers have been available for some time:
>>>> Parker Dinkins
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