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Realistic 42-2101/42-2101-a Phono Preamps

Discussion in 'Audio Hardware' started by Robin L, Aug 12, 2015.

  1. Robin L

    Robin L Musical Omnivore Thread Starter

    Location:
    Fresno, California
    Looks like the screws that hold the outer case work of the pre-amp are on the sides:

    [​IMG]

    [​IMG]
     
  2. jupiterboy

    jupiterboy Forum Residue

    Location:
    Buffalo, NY
    Mines been modified. Sounds pretty nice. A little grain. A little puffy in the bass. If you have fat RCA connectors, they may not work so well with the recessed RCA jacks.
     
  3. djohannesen

    djohannesen Member

    Location:
    Olympia
    Tried screws on side of case, but the case did not come apart when removed.
     
  4. Robin L

    Robin L Musical Omnivore Thread Starter

    Location:
    Fresno, California
    Are there screws on the bottom? And can the wire be spliced from the outside?
     
  5. djohannesen

    djohannesen Member

    Location:
    Olympia
    Oops, case was just very tightly wedged on. Looks like it will be easy to replace the cord.
     
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  6. George Blair

    George Blair Senior Member

    Location:
    Portland, OR
    This unit has been breaking in now for a couple weeks. I upgraded to matching Audioquest interconnects from Project Debut Carbon - Realistic Phono Stage - Yamaha S-501 Amp, and played a bunch of records. I was about ready to switch back to the Cambridge 540-p, as the sound was bright and weak in the bass, but I also was hearing improved clarity and soundstage so I stuck with it. Suddenly everything came together, the brightness relaxed, bass improved, focused clarity & soundstage - in short records sounded better than before. How much of this is due to the new cables, or the Realistic I'm not sure, but I'm keeping it.
     
    Robin L likes this.
  7. Robin L

    Robin L Musical Omnivore Thread Starter

    Location:
    Fresno, California
    I've been using some unshielded cable out from the Realistic unit, a DIY pair I made 20 years ago. Made from continuous-cast copper crystal, silver-clad Van den Hull interconnect. The Realistic pre does take a few weeks to break in. I'd bet the Realistic unit has better resolution than the Cambridge Audio unit.
     
  8. Slack

    Slack Forum Resident

    I am guessing that these Realistic phono stages might not suit budget systems as well as some of the smoother but less revealing op amp based ones [like the Cambridge Audios].
    To my thinking they are just neutral and clear sounding .
    I sold my tricked up EAR 834P because I found that the Realistic sounded just as good.Not the warmth of the EAR but I think more accurate and just as musically engaging in its own way.Not that the EAR was bad.Those two have been by far the best phono stages I have tried and there have been plenty.
     
    Robin L likes this.
  9. George Blair

    George Blair Senior Member

    Location:
    Portland, OR
    Yes, resolution is very present. Remarkable really, considering the thing is a cheap metal box.
     
    Robin L likes this.
  10. ARCCJ

    ARCCJ Forum Resident

    Location:
    US
    I owned this when it was a new preamp--not very good at all as frequencies are restricted to 15,000Hz on the top end and either 30 or 50Hz on the bottom, and also 'slurred' a lot of the highs as well, kind of like sibilance. (I would have to find an old Radio Shack catalog to get those specs.) Mid-fi at best and it was a big jump in quality when I moved up to an integrated amp. These were used to adapt newer turntables to old equipment like consoles which already sounded mediocre, and had auxiliary inputs but no phono inputs.
     
    doctor fuse likes this.
  11. Bolero

    Bolero Senior Member

    Location:
    North America
    has anyone hot-rodded these to get better quality components inside, or tweaked the circuit?
     
  12. action pact

    action pact Music Omnivore

    I bought one of those Realistics for $20 off Craig's List a few years ago. It sounds surprisingly nice for a cheap old preamp.
     
  13. Robin L

    Robin L Musical Omnivore Thread Starter

    Location:
    Fresno, California
    Not my experience at all. Having three receivers I used as phono pre-amps, including a Harman Kardon 660 and a Kenwood 9600, the Radio Shack 42-2101 does a better job in all respects, in particular as regards lack of added sibilance. Perhaps it simply did not work in your system.
     
  14. dmckean

    dmckean Forum Resident

    Location:
    San Diego, CA, USA
    Specs are right here and it'd definitely be easy to build something better with modern JFETs.

    Stereo Pre-Amplifier
    (420-2101A) Specifications Faxback Doc. # 40137


    Sensitivity (for 200 mV output at 1 kHz, 50 K Ohms)
    Phono............................................................... 2.5 mV

    Output Level, 50 K Ohms Phono, 3 mV Input........................... 240 mV

    Maximum Output Level at 1 kHz........................................ 6.0 V

    Input Overload Level (for 1% THD) Phono............................. 100 mV

    Signal to Noise Ratio Phono, 3 mV input.............................. 55 dB

    Frequency Response.................................. +/3 dB: 30 - 15,000 Hz

    RIAA Equaliztion................................................... +/-2 dB

    THD at 200 mV Output.................................................. 0.5%

    Stereo Separation at 1 kHz........................................... 50 dB

    Impedance
    Inputs............................................................ 55 KOhms
    Outputs........................................................... 50 KOhms

    Power Requirements..................... 120 volts AC, 60 Hz, 1.5 Watts Max.

    Size.......................................... 50 (H) x 90 (W) x 120 (D) mm

    (km-06/20/1997)
     
  15. Robin L

    Robin L Musical Omnivore Thread Starter

    Location:
    Fresno, California
    Kinda underlines the difference between measured and subjective performance to me. Playing my well-worn copy copy of Van Morrison's "Band and Street Choir" LP I hear less distortion on the inner track of side 1—I'll Be Your Lover Too—than on anything I've owned over the last twenty years. Can someone make a better J-Fet based phono pre from scratch? Doubtless. Would they be willing to send me one for $43, shipping included? I doubt it. Besides that, tell me what a finished J-Fet based phono pre would cost these days. Richard Schram of Parasound remarked that " A Vendetta today would cost over $8,000 if it could be built at all – there are no FET’s made today that are as quiet as the ones used in the original". And the John Curl designed, op-amp based Parasound JC-3 goes for around $3000. My question would be how the 42-2101 compares to modern gear in the $100 to $800 range. Feedback on this thread so far indicates that the cheap Realistic phono pre is competitive.
     
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  16. Adam9

    Adam9 Senior Member

    Location:
    Toronto
    I'm currently using a Realistic 42-2109 phono preamp which looks identical to the 42-2101a. I have no complaints.
    Thanks for this thread as I never even paid attention to what model my preamp was. Now I can update my profile.
     
  17. dmckean

    dmckean Forum Resident

    Location:
    San Diego, CA, USA
    I didn't mean to imply that these can't sound good and I'm sure they do. It wouldn't surprise me in the least if simple passive FET based circuits turn out to be giant killers. I'd love to see to see circuit diagrams for them.
     
    Robin L likes this.
  18. Robin L

    Robin L Musical Omnivore Thread Starter

    Location:
    Fresno, California
    Here's the schematic for those potentially interested:

    [​IMG]
     
  19. George Blair

    George Blair Senior Member

    Location:
    Portland, OR
    Can someone explain why an FET would be prohibitively expensive today?
     
  20. Robin L

    Robin L Musical Omnivore Thread Starter

    Location:
    Fresno, California
    It's like any other abandoned technology—The kind of low noise J-FETs that would elevate the level of performance to "Vendetta" standards are simply not being manufactured these days. However, I kinda doubt there's pricy parts in anything badged "Realistic". My guess is that a FET based moving magnet preamp could be cost effective in today's market. John Curl's concern was for the lowest possible noise floor for the Vendetta, enabling his phono pre to work directly coupled to the lowest output moving coil cartridges, skipping the transformer. But moving magnet phono preamps don't need as clean of a noise floor to sound good. The self-noise of the vinyl, no matter how good, would always be a greater factor than the self-noise of the preamp in a situation involving a typical high-output moving magnet cartridge.

    I've got my turntable system as dialed in as it's about to get with the gadgets I've got now. But I'd love to get a Realistic 42-2101a and use gel-cells as the power supply. As it is right now, self-noise is limited to a hash-y "rush" at a very low level, but the sonic characteristic of that "rush" describes the "grain" of the pre-amp's sound. I suspect that ditching the cheap power supply for battery power would elevate sound a couple of notches, tighten the bass and reduce the inherent grain.
     
    George Blair likes this.
  21. dmckean

    dmckean Forum Resident

    Location:
    San Diego, CA, USA
    I went ahead and picked one up. It's been in my system since Friday and I've spun quite a bit of vinyl. I'm using it with my KAB Technics 1200, Zu modified Denon 103R and a DIY Cinemag 1254 stepup transformer. My thoughts (in no order):

    It's a little noisy for a solid state preamp, I'm used to dead quiet when I put my ear up to the speakers and don't get that here.
    The presentation is very revealing and there's a silence during quiet passages and between tracks that I also get with my Croft preamp.
    It has great bass, it's tight and not bloated at all. A lot of cheap pre-amps get this really wrong.
    The highs are rolled off, no doubt about it.
    As you can see in my pictures below, the resistors are not the audio grade metal film type. This is probably the source of both the roll off and the noise but it could also be how the power is handled.
    The input resistance is 55k and I had the wire a 32k resistor in parallel to get the Denon sounding right.
    It does an especially great job with banjo, brass and baritone voices.


    [​IMG]SAM_0374 by dmckean44
    [​IMG]SAM_0373 by dmckean44
    [​IMG]SAM_0377 by dmckean44
     
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  22. dmckean

    dmckean Forum Resident

    Location:
    San Diego, CA, USA
    Missed this when it was posted. It's a pretty simple circuit for sure. You could build a nice DIY version for I'm guessing $100.
     
  23. action pact

    action pact Music Omnivore

    Could this be due in part to the age of the unit?

    That explains why my M97xE sounded unusually open and airy with my Realistic pre! (Many prefer that cartridge loaded at 62k instead of the usual 47k.)
     
    Robin L likes this.
  24. action pact

    action pact Music Omnivore

    I don't know much about this kind of stuff, but if a DIY version would cost around $100, that indicates that a factory-made new one of this quality would be, what, $200-$300 retail? That's pretty good for a preamp that I paid $20 for a few years ago! I should plug it in again and have another listen.
     
    Robin L likes this.
  25. Slack

    Slack Forum Resident

    Yes but a lot of components that might cost $100 to DIY sell for thousands of dollars.
     
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