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

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

  1. Classic Car Guy

    Classic Car Guy Analog Recording to the Next Level

    Location:
    Northwest, USA
    Here's the picture. Sorry my experience in turntable is ground zero.
    Well not necessarily. Lets just say I messed up so many 33's and 45's that's why I went to cassette world with no regrets.

    [​IMG]
     
    DRM likes this.
  2. R. Totale

    R. Totale The Voice of Reason

    Say what? If it meets RIAA specs, surface noise in the audible range will be no more evident in a topology where RIAA compensation is done in feedback than it would be with any other circuit design.
     
  3. Phil Thien

    Phil Thien Forum Resident

    Location:
    Milwaukee, WI
    I'm talking about pops and tics, which can be accentuated by phono stages employing RIAA in the feedback loop.

    You can google "riaa feedback accentuate pops tics" and find more.
     
    cmarti likes this.
  4. Classic Car Guy

    Classic Car Guy Analog Recording to the Next Level

    Location:
    Northwest, USA
    @Phil Thien
    I kind of miss the old school way like asking some like yourself and working my way from there. Honestly I talked to a lot of people that knows a lot but how come they're changing their equipments more often like changing wives and the last thing I always hear is this is it? Lol...
    I been using the same cassettes since the 80's and recorded thousands of music and enjoyed it. I don't need to ask anyone else but just you.
     
    DRM likes this.
  5. R. Totale

    R. Totale The Voice of Reason

    Not doing too well with your suggested googling. Perhaps your can point me to somewhere where this theory is explained, other than someone just saying it is so. I do see someone posting a curve without RIAA EQ and saying pops and clicks might be accentuated there, which makes sense as the higher frequencies in the signal were not attenuated as they would be once RIAA was applied. But if the pops and clicks are in the audible range, what would make them improperly louder than the musical signals surrounding them at the same frequencies only when the EQ is applied in the feedback loop rather than when the same EQ is applied passively? If the two preamps (passive and feedback) have the same input to outputs transfer function across the audible range (necessary if they are both in spec) why would they be different only for audible clicks at the output of one of them?
     
  6. Davey

    Davey NP: Broadcast ~ Haha Sound (on repeat, as usual)

    Location:
    SF Bay Area, USA
    It's mainly about stability and overload in feedback amplifiers when handling impulse-type signals, and can be exacerbated in the NF type equalizers when compared to CR types. It's one of the reasons some of us migrate to no feedback tube circuits in phono preamps with CR equalization, just that sense of naturalness. Ralph Karsten of Atma-Sphere made a nice post around here on the subject, well it was on a few subjects, but somewhat related, and he had a section on this issue (his company is dedicated to making some very fine zero feedback tube amps and preamps, so may be a little biased on the subject :)) ... Proper Cartridge Loading Can Make a Big Difference


    BTW, a relatively inexpensive zero feedback solid state phono preamp is the old Creek OBH-8 from the late 90s, you can find them pretty cheap on the used market. The SE version is even better, they moved to JFET inputs, and a bigger power supply, along with some other changes, though harder to find these days. It's become somewhat of a cult classic in modern times, there are even circuit boards and parts kits to build your own now on ebay. The newer MK2 model is something entirely different, they have moved to a high feedback opamp design.
     
    Last edited: Aug 18, 2020
  7. Classic Car Guy

    Classic Car Guy Analog Recording to the Next Level

    Location:
    Northwest, USA
    I was able to pickup one today and seems like its in good shape like almost new. I guess you can recondition that unit along the way with some parts that are almost next to nothing.
     
  8. jcwlow

    jcwlow New Member

    Location:
    Malaysia
    Hi guys,

    On the back of the many rave reviews on the net, I purchased a stock 2109 off the bay recently and was thinking of a recap and a swap out of the resistors in R03 and R04 (originally 68k) for 56k metal film resistors.

    However after having a quick view of the 2109 board I noticed that the caps in C01,C02, C07,C08, C09 and C10 have different values and sizes for the 2101 in the diagram and pictures that I've seen here in this thread and others :
    2101 2109
    C01, C02 4.7uf, 25v 4.7uf, 50v
    C07, C08 10uf, 35v 4.7uf, 50v
    C09,C10 47uf, 25v 4.7uf, 25v

    My gut feeling tells me that I should just recap premised on the equivalent values of the stock caps in the 2109 but at the same time I'm wondering if I should recap based on 2101 values for fun or maybe that's just a bad idea and a waste of money? Space on the 2109 board also looks a whole lot tighter than on the 2101 board so maybe this explains the smaller caps in C07,C08, C09 and C10 for the 2109.

    Haven't had the time to check all the other values of the other parts on the 2109 board but other than the different sized caps in the 2101 and generally more space on the board the layout of the 2109 looks the same to me as the 2101 (as pictured here) .

    Anyway this thread has been really informative and helpful, thanks.
     
  9. jcwlow

    jcwlow New Member

    Location:
    Malaysia
    Sorry the table didnt turn out right in my post... It was supposed to be something like this

    Model 42-2101/ 42- 2109
    C01, C02 = 4.7uf, 25v / 4.7uf, 50v
    C07, C08 = 10uf, 35v / 4.7uf, 50v
    C09,C10 = 47uf, 25v / 4.7uf, 25v
     
  10. harby

    harby Forum Resident

    Location:
    Portland, OR, USA
    Diagram again, (apparently Imgur deletes anonymously posted images after a while...) C22 on original schematic is a resistor.

    [​IMG]

    A higher voltage rated capacitor doesn't change the specification, it just increases the safety factor and perhaps lifespan. In small values of modern caps, high voltage rating is the entry level.

    A lower capacitance value is almost always a less expensive component, likely the driving factor for these changes. C07 mainly changes the highpass, but all the components work together, along with the transistors (which changed in later models) to shape characteristics.


    The simulated circuit hand-tweaked with different values (some requiring series or parallel components) to get the frequency response as flat as possible, with highest symmetric linear output, with similar modern high-gain BJT transistors (r25 is the input dummy load):

    [​IMG]
    (stock response would be wiggles from -38dB to -40dB, not +/- 0.1dB)
     
  11. jcwlow

    jcwlow New Member

    Location:
    Malaysia
    Thanks for the lucid explanation and mod schematic, Harby. It certainly helps a noob like me.

    Should be able to try and replicate this in a 2109. Visually the layout looks the same as the 2101.

    Anyway, the stock 2109 sounds great except that the bass sometimes distorts when played loud - I'll try a quick resistor change to 56k at R03/04 to see if this goes away otherwise I'll have to look at the other changes.
     
  12. nerdorama

    nerdorama Active Member

    Location:
    Eastern WA
    New member to this forum. I have an old Realistic phono that I bought in the 70's. It is model 42-2930. It's in a small metal can with the jacks on either side. I haven't traced the circuit but the transistors are different that any that I've seen in this thread. They are marked B175, which I assume is 2SB175 and consequently a germanium PNP type. Anyone used one of these.
    Thanks,
    John
     
    cmarti likes this.
  13. cmarti

    cmarti Forum Resident

    That's an old one indeed, I own the same one but badged under a different name brand. It hums so maybe I should replace the capacitors to see if that helps.
     
  14. Classic Car Guy

    Classic Car Guy Analog Recording to the Next Level

    Location:
    Northwest, USA
    I was able to record almost 55-c90 tapes using this phono preamp. The tone is magical. My recordings sound just like an LP. Love it.
     
  15. harby

    harby Forum Resident

    Location:
    Portland, OR, USA
    Looks like Amir at ASR finally put this box on an analyzer.

    Conclusion: Noisy power supply, as one might expect; distortion as listed on the spec sheet. Built-in smile EQ.

    [​IMG]


    Response mirrors my simulation, depicted below at the same pixel scale (giving validation to the mods a few posts ago to flatten the response)
    [​IMG]

    You can see in the bode plot above, another much flatter green line. That's a custom tweaked version of the preamp in the Realistic SA-102 mini-receiver - a better way of using four transistors, here, refined from post #167 with better specs (by putting aside practicalities such as sub filtering and RF filtering, and cranking up supply voltage...)

    [​IMG]

    We can also ask the 102mod to go nearly rail-to-rail, while the 2101a clips (now to build it someday):
    [​IMG]
    (In fairness, though, with its internal +/- 2.5v supply, an Art DJ Pre II can't get anywhere near either Realistic's levels)
     
  16. Phil Thien

    Phil Thien Forum Resident

    Location:
    Milwaukee, WI
    I used one of these for a while, it handily beat all the current low-cost options on the market.

    I don't think I'd consider +/- 1.25db much of a smile, I read somewhere the other day that the RIAA spec allows for 2db of variance.

    I did purchase a kit with new transistors, caps, and resistors on eBay and modify mine.

    The Mofi StudioPhono still kills it.
     
    patient_ot likes this.
  17. Classic Car Guy

    Classic Car Guy Analog Recording to the Next Level

    Location:
    Northwest, USA
    Mine was already good. but just make it run smooth with a piece of mind, I added a phase capacitor and made the unit 3 prong. Its probably not a $750.00 preamp.
    I use unit on recording and I'm very happy with it.
     
  18. lazydawg58

    lazydawg58 Know enough to know how much I don't know

    Location:
    Lillington NC
    This has been a very interesting read so far, (about half way through the thread) though I'm not nearly as technically savvy as most of you here. I occasionally pick up receivers at estate sales (pre-pandemic), junk shops, yards sales and see if I can get them up and running without too much cost or effort. But the old vintage equipment from the 60s and 70s are appearing less and less, or commands a much higher price than just a while back. What I do see more and more often are 1990s-2010s receivers coming from surround sound TV systems. Of course most of those don't have phono inputs so I tend to just walk right past them. But then I realized that a simple phono pre-amp going into an aux input is a simple work around. These "multi-media systems" I'm not that sure of quality wise but they often seem to push a lot of wpc. So I ended up getting a 42-2109 pre amp for $30 on ebay to see what I could do with a couple these receivers. Please note I'm not really looking for anything approaching audiophile quality, just good consumer level or "Mid-Fi" fun. So my questions.
    1. I know the 42 2101 was assembled in Japan and the 2109 in Korea. Other than that what is the difference between the two?
    2. When were these new on the market? 70s? 80? both?
    3. Are there reasons why using these surround sound receivers coupled with pre-amps like the Realistic 42s as power sources isn't a good idea?
     
  19. MLutthans

    MLutthans That's my spaghetti, Chewbacca! Staff

    Didn't rejected Shure mic capsules wind up in Realistic microphones? Any chance something similar was going on here? Sure looks Shure-ish to me (like a cut-down M64), but that may be mere coincidence, or intentional look-alike construction.
     
  20. McLover

    McLover Senior Member

    Location:
    Athens, Tennessee
    I think Japanese built Shure M64 copycat build. Which fit the price tag.
     
    MLutthans likes this.
  21. old45s

    old45s MP3 FREE ZONE

    Location:
    SYDNEY, AUSTRALIA
    I've been using an old REALISTIC DJ Mixer for the past 20 years as a pre amp. It did the job well however after upgrading my cartridge to a Bronze I thought I'd better buy a proper phono preamp.
    I've ordered a Shiit Mani... still waiting for it. It's on a slow boat from the US West Coast.
     
    lazydawg58 likes this.
  22. Phil Thien

    Phil Thien Forum Resident

    Location:
    Milwaukee, WI
    I was wondering whether the substantial roll-off above 15k I was getting with my pink noise test records was due to the Parks Budgie phono preamp. The documentation indicated the RIAA was +/- .5db from 20-20k I think, but I wondered.

    So I grabbed an old 42-2109 I have (upgraded with a parts kit I got on eBay) and plugged that in and measured using the Hi-Fi News pink noise tracks (this is the Producer's Cut version of the album, apparently the pink noise and sweep tracks were improved on this version).

    Anyway, results below.

    Actually not as bad as I had figured it would be, these are sort of nice for "vintager" jazz.

    Questions to the brains here.

    (1) I occasionally like to swap phono stages around. Due to my equipment rack, the rather long 120v AC cord on this is a PITA. The schematic shows a 10v transformer, can I simply remove that and the cord, install a DC jack where the cord now enters, and use an AC-AC 10v wall wart? Would a 9v wall wart likely work? 10vac wall warts are "around," 9vac wall warts are plentiful. Having a disconnect on the back of the unit would be helpful.

    (2) I wouldn't mind taming that HF peak by paralleling some input resistors. But @harby (I think) mentioned that the input resistor is part of the RIAA filtering (if I understand that correctly) and lowering that value may in fact alter the bass?

    (2a) Instead of #2, I could remove the 100pf input caps and (if necessary) increase my cable capacitance slightly. Interestingly, if I plug the values used here into PhonoLCR (cartridge = 490mh/780-ohms, 185pf capacitance and 50k resistance loading) the predicted resonance frequency is 16.8k, very close to the peak seen here.

    (3) I sure would like to find a phono stage with a very flat response, a subsonic filter that can be disabled via a switch, a mono switch, very high overload #'s, and the ability to change (internally) the input capacitance and resistance via capacitors and resistors in sockets. I imagine I could have a Darlington made with sockets, or order it w/ those positions unpopulated and add my own sockets. The units with subsonic and mono switches are already getting kinda pricey though, for this DIY guy.


    [​IMG]
     
  23. jupiterboy

    jupiterboy Forum Residue

    Location:
    Buffalo, NY
    I hear you, I've got a rumble filter and a mono switch and the wires going everywhere are obscene.

    Try some loading plugs and set the resistance to 38K and try a measurement. That is commonly a favored choice for these AT carts and the one where I've had the best luck.
     
  24. Phil Thien

    Phil Thien Forum Resident

    Location:
    Milwaukee, WI
    Yep, I'll give it a shot.

    I did another test w/ a different cabling configuration, so here is a pic of that (below).

    I think these preamps have a natural lift, and so does my cartridge. Someone in this thread or another indicated using loading resistors effected the bass, I guess I'm going to find out.

    [​IMG]
     
  25. Davey

    Davey NP: Broadcast ~ Haha Sound (on repeat, as usual)

    Location:
    SF Bay Area, USA
    Yea, you really need a little reverse RIAA circuit to just look at the preamp as a baseline without cable and cartridge effects, pretty simple if you have some parts boxes on hand, or can just buy one for about $20 ... or you can do it in software and use some impedance conditioning on your source ...


    [​IMG]

    Reverse RIAA


    Are you plotting live from the record, or do you plot from a file? What software are you using to generate the plots?
     
    Last edited: Oct 29, 2021
    JohnO and patient_ot like this.

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