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

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

  1. Phil Thien

    Phil Thien Forum Resident

    Location:
    Milwaukee, WI
    Thank you for your help.

    Did you catch that I mentioned that this unit has undergone a parts upgrade that I ordered on eBay? So not stock, and I'm not sure if some of the component values were altered. Perhaps that could explain the 3k hump that is missing? If you have any interest, I can likely find the instructions that accompanied the parts kit and see if I can find substitutions.

    On the power supply issue, I think I may just cut the power cord to maybe 6" or so and then use a short single-receptacle extension cord. Checks all the boxes, cheap (my favorite box).
     
  2. Phil Thien

    Phil Thien Forum Resident

    Location:
    Milwaukee, WI
    I missed that, it sounds very interesting to me, please somehow keep me in the "loop."

    I listened for a while with the 30k loading, which is essentially flat, and it sounds very good. It also sounds good (more like fun?) without being loaded down, that smile puts a smile on your face.

    I was surprised to see that I didn't effect any substantial changes in the bass with the parallel resistors, I thought you had mentioned that loading it down would effect the bass/subsonic?

    Again I appreciate everyone's help.
     
  3. harby

    harby Forum Resident

    Location:
    Portland, OR, USA
    If you just want a short cord and not a noise improvement, then yea, pull it back into the enclosure and chop off and re-solder.

    There's one "upgrade" selling on eBay. Cleverly turned away the cap values in the picture. However, think I see 11k resistors, which would be crazy random happenstance, since I published this response-flattening mod including that value two years ago (with even more resistor changes though) (original schematic first):


    [​IMG]
    [​IMG]
    (4.9 is a typo, makes no difference vs 4.7)

    Today, the mod re-analyzed with my current inverse RIAA.
    With a VM540 sim, and only 70p for cabling and 100p internal, the high frequency peak:
    [​IMG]
    Why a +/- 0.1dB Sutherland is only nice on paper...
     
  4. Phil Thien

    Phil Thien Forum Resident

    Location:
    Milwaukee, WI
    @harby, I checked the instructions that accompanied the 42-2109 kit, they say "First, replace the capacitors. The capacitors in this kit are the exact same capacitance (uf) ratings as the originals, and the voltages are the same or higher. They are much higher-quality, but are smaller because of advances in electronics design."

    In the meantime, I finally got my $12 (I think, eBay purchase) TC-750 quieted. I found a thread at Superbestaudiofriends.org (I know, I know) that provide some guidance on improvements. Unfortunately, it appears some of the posts are by people that really don't know much more than I. So in the end, I ended-up reversing some of the changes. The unit now powers from the same linear power supply that runs the turntable motor.

    An interesting thing to me, is that I did pull the approx. 220pf load capacitors in the TC-750 and so my capacitance is whatever is contributed by the circuit, and my cables (cables approx. 155pf), and I still have a substantial peak. I guess either the capacitance from the circuit is substantial or that is just the way it is. I can lower resistance and tame that peak, I just wanted to see what I was starting with.

    I am pleased to have less bass hump and be able to see how changes to my arm effect the low-frequency performance of the arm.

    Also somewhat interesting, is that the TC-750's output is approx. 2db higher than the 42-2109. I've adjusted the curves so they overlay, but the TC-750 is certainly louder.

    Perhaps we can start a TC-750 thread, and you can help with RIAA improvements if you ever have the time, I know you are busy and maybe the idea doesn't even seem that interesting to you.

    I do have one of the 24vdc regulated adapters on the way, I plan to try that on this TC-750. What sort of advantage may I see in running these sorts of discrete circuits with 24v instead of 12?

    [​IMG]
     
  5. harby

    harby Forum Resident

    Location:
    Portland, OR, USA
    Connecting 24V to the TC-750 will bring back a "bass hump". It will also blow up the 18V power filter capacitors.

    [​IMG]
    Above response shows just 155pF total load - on an AT 460mH/800 ohm(you don't say what model).


    More voltage gives more headroom, here the output of +20dB over 5mV RMS input at 1kHz. 12v (brown) clips.
    [​IMG]
     
    Ingenieur and Phil Thien like this.
  6. Phil Thien

    Phil Thien Forum Resident

    Location:
    Milwaukee, WI
    Again, thank you for all your help.

    I've removed the 18v power filtering capacitors, in anticipation of using a 24v supply.

    A 1.25db hump may actually flatten the bass a little, it seems like it is slightly rolled off now. I'm hoping for flatter, not enhanced as in the Realistic.

    I guess I'm going to find out.
     
  7. Phil Thien

    Phil Thien Forum Resident

    Location:
    Milwaukee, WI
    I've been powering the TC-750 from the same Pyramid 12vdc linear regulated power supply that drives my turntable's motor. I just snipped the cable off the low-end linear (but unregulated) AC adapter that accompanied the TC-750, and wired that to the binding posts on the Pyramid.

    Yesterday I received the 24vdc adapter (the Jameco one mentioned) and figured I'd check my HiFi News pink noise track with both the Jameco 24vdc and the Pyramid 12vdc.

    Not much to see, actually, the curves overlay fairly nicely. No real bass hump coming from the 24vdc as was expected based on comments from @harby. I do note that having read quite a few discussions on these, the component values don't necessarily match schematics, and the unit I'm using is the TC-750LC, which has a variable output (more on that below). So @harby is at a disadvantage in making projections.

    Anyhow, here is the 24vdc vs. the 12vdc:

    [​IMG]

    I had read in a thread some time ago, don't remember where, that the variable output on these actually alters the response curve along with the output level. So I tried testing for this by recording the same pink noise track at both the 75% output level as well as 100% output levels. REW (the software I'm using) allows me to shift curves up/down so I can overlay curves at different amplitudes. So I did that here, and found the 75% results in a more even high-frequency output, almost as if I've modified the loading lower. I'll play with this some more in the future, as I can give-up gain at the phono stage, I have plenty of gain further down the chain.

    So here is that curve...

    [​IMG]
     
    Ingenieur and JohnO like this.
  8. Slack

    Slack Forum Resident

    It would be nice to see this thread return to topic.
     
    Music Please and quicksrt like this.
  9. Phil Thien

    Phil Thien Forum Resident

    Location:
    Milwaukee, WI
    In what way exactly?

    No talk of the TC-750? It is the kissing cousin of the 42-210x, and there have been lots of other preamps/receivers discussed?

    No attempt at objective data/measurements/comparisons?
     
    patient_ot likes this.
  10. Phil Thien

    Phil Thien Forum Resident

    Location:
    Milwaukee, WI
    So @harby, I was able to go back and do some better measurements of the 24v vs. 12v on the TC-750 and was able to see the slight boost in the LF as you indicated.

    Do you have any ideas on flattening the slight rise in HF starting around 15k on the TC-750? I don't know if a similar RIAA EQ change can be made, as you made for the 42-2101a.

    Sorta academic because I can't hear it anyhow, but if it can be flatter, I'd give it a shot.
     
    Ingenieur likes this.
  11. Phil Thien

    Phil Thien Forum Resident

    Location:
    Milwaukee, WI
    Can the 42-2101a/42-2109 use a higher voltage power supply, provided the capacitor ratings are high enough?

    I read somewhere that the transistors are rated for considerably higher voltage.

    Someone mentioned to me they have a 30v linear/regulated supply they can provide, no real markings on it but it was removed from an insanely expensive industrial scanner.
     
  12. Music Please

    Music Please Active Member

    Location:
    Sepulveda Pass, CA

    Agreed,

    Was very much enjoying reading this thread up to about page 8. Would love it if we could get back on topic of just the Realistic 42-2101/42-2101a and talk about it's refinement, how it sounds, comparisons and any nice mods that other members have done to make it sound nicer without changing a lot of its architecture or turning it into a frankenstein (although remote locating a small linear power supply or battery for it would be an easy & benefitting mod).
    I was particularly interested in keithv 's posts about the boards he was making for himself and how was the end result? (albeit, its been a long while since his last posts).
    These stock phono preamp seems to be standing up to the competition over time and still going strong. Would love to hear more about it from other members.

    Also, for the ease and convenience; I wonder how an Acopian 28EB30 or 28EB15 (28v) linear PS would sound with the 42-2101a? Fairly easy to pick up reasonably a used one on eBay and small sized (relative). It's still needs a box for protection. These USA made ones are known to having really good ripple measurement (for the price & size) and actual ripple is typically much better than stated in the spec's.
     
  13. Music Please

    Music Please Active Member

    Location:
    Sepulveda Pass, CA
    Also just wanted to ask, has anyone compared the 42-2101A to the stock battery powered version Realistic 42-2111 ?
     
  14. MCM_Fan

    MCM_Fan Senior Member

    Location:
    Oregon
    Thinking about picking up a 42-2101A for my niece. I recently found a Dual CS 607 with a pretty decent Ortofon cartridge (ULM 55E) for her at a thrift store. I did a clean, lube and adjust on the turntable and replaced the damaged interconnects and ground wire. I am currently running it in my system using the DIY CNC phono stage I built a couple years ago and it sounds pretty decent.

    She has a pair of powered speakers and just needs an inexpensive phono preamp to go between the turntable and speakers.

    First question: the specs for the ULM 55E list the output voltage as > 0.7mV. That's pretty high. Would it be high enough to cause clipping with the 42-2101A? If so, is there a different decent, but inexpensive, phono stage that has a higher overload margin?

    Second question: If the 42-2101A is compatible with the Ortofon cartridge, I'd like to at least replace the 40+ year old electrolytic caps before sending it to her (she's on the opposite coast from me). This will be her first turntable and we are operating on a minimal budget (which is why I thought of the 42-201A). While I have the soldering iron out, is it worth the few extra dollars to purchase one of these part replacement kits from eBay ($14.99 + $4.00 shipping), or should I just pick up the replacement electrolytics from Mouser and call it good?
     
  15. Phil Thien

    Phil Thien Forum Resident

    Location:
    Milwaukee, WI
    That is .7mv @ 1cm/sec, which is 3.5mv @ 5cm/sec (the more conventional spec these days). That should be fine, you should be safe up to about 7mv @ 5cm/sec., maybe a little more I think.

    I've done that upgrade kit. It evens out the HF response, it is inexpensive and I think worth it.
     
    MCM_Fan likes this.
  16. harby

    harby Forum Resident

    Location:
    Portland, OR, USA
    This phono pre can easily output 3V RMS or more. Post #215 I make it clip.

    The transistors look like eBay knock-off specials. Real On Semi KSC1845FTA have three lines of text like seen in this listing. Also, looks like the code, if can be relied on, is lower "F" gain 300-600, while you'd be better with "E" 400-800, or a BC549C where the part number includes the gain.

    They don't actually include any RIAA capacitors, where 1% is best. Under 5% would be good at the 100nF on the input, affecting bass, where this kit has 10%.

    I'd measure the problem before you look for a solution.
     
    MCM_Fan likes this.
  17. MCM_Fan

    MCM_Fan Senior Member

    Location:
    Oregon
    Thanks for the input. I don't have measurement capability. This will be my niece's first turntable set up, and since I am on the opposite coast and won't be on hand to help her out I'm just looking to make sure the 42-2101A is reliable and dependable, any improvement in sound quality is an added benefit.

    With that in mind, do you have any specific recommendations? I don't mind ordering the parts myself through Digikey or Mouser.
     
  18. harby

    harby Forum Resident

    Location:
    Portland, OR, USA
    If you must frustrate yourself with soldering, it's probably going to be easier to get one of the Motronix clones and stick it in a box with two output RCAs for the same price as a "mod kit" for a 40 year old preamp (except they are now charging "Israel" $17 shipping for a $1 China speedpak). You can use an external linear power supply instead of humming transformer in the box.
    [​IMG]

    Or they have them as kit form if you want to measure the tolerances of components you got or solder in your own upgrades, a spooky resemblance to the Realistic SA-102 mod circuit I posted a while back:
    [​IMG]
     
  19. MCM_Fan

    MCM_Fan Senior Member

    Location:
    Oregon
    Thanks, but with Est. Delivery Tue, May 10 - Thu, Jun 2 for the Motronix clone PCB, I'd rather just send her the unmodified 42-2101A so she can start spinning records.
     
  20. harby

    harby Forum Resident

    Location:
    Portland, OR, USA
    Or if she has a computer, an ART USB Phono Plus to not only listen via a stereo or its headphone jack, but also to record phono and line sources.
     
  21. MCM_Fan

    MCM_Fan Senior Member

    Location:
    Oregon
    I had an Art DJ PreII a couple years ago, but sold it on my local craigslist when I upgraded. Wish I still had it, it would be perfect for her beginner's vinyl set up.
     
  22. Sounds_Good

    Sounds_Good Active Member

    Location:
    CA, USA
    Hi
    does anyone have any suggestions on how to reduce the load capacitance of this Realistic preamp ? What parts or capacitors would need to be changed to do that ?
    Seems its a bit high (300-400pf) and I want bring down to ~200pf.
    Thanks.
     
  23. Phil Thien

    Phil Thien Forum Resident

    Location:
    Milwaukee, WI
    Are you talking about the 42-2101/42-2109? The input capacitance is 100pf, there are two 1o0pf caps (one for each channel) that you can remove.
     
  24. Sounds_Good

    Sounds_Good Active Member

    Location:
    CA, USA
    2101. It does not have those parallel caps at input, thats why I was not quite sure and had to ask how to reduce capacitance in that case.
    Didnt realize 2109 was significantly different.
     
  25. Phil Thien

    Phil Thien Forum Resident

    Location:
    Milwaukee, WI
    You sure it doesn't have the caps? If not sure, post a pic of the component side of your board.
     

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