Discussion in 'Audio Hardware' started by Robin L, Aug 12, 2015.
Truth! But I was trying to be conservative.
Just to note a couple of differences. I have the older version:
If I up the volume on my receiver the background noise from the 42-2101 is barely audible. My cartridge is the Shure 97, high frequencies are less rolled off than with the other phono sections I've been using as of late. Looking at the photos you provided, I'd gather that the power supply is the biggest limiting factor on the unit's performance.
Just made a small adjustment, checked the noise level again—if I set playback level at a normal playback volume, there's no audible noise from the phono preamp at all. If level is set to the highest level I regularly play music, background noise is restricted to only a very faint hiss with no hum whatsoever. Of course, the 42-2101 might be slightly different than the "A" version and there is also the possibility that Dmckean's preamp isn't functioning as well as my pre-amp. But I would not call this a noisy pre-amp, have owned/used plenty of those in the past.
I was pointing it out more for the fact it wouldn't cost a lot to completely rebuild this thing with audio grade resistors and new caps or just completely build one from scratch if one wanted to. Doing that and running this thing on a proper regulated and filtered DC power supply would probably improve things further.
If yours is completely silent, I'll play around and see if I can get mine that way too. Maybe I introduced a grounding problem somehow or something.
Not exactly silent, but the self-noise is a lot lower than the power amp stage of most power amps I've heard. Haven't opened mine up [yet] but I would suspect the earlier iteration of this design had more space between the transformer and the amp stage. An argument in favor of wall warts for low-cost phono stages. My intent is to get another one of these pre-amps, make a gel-cell power supply.
I was able to track the noise down.
I quick installed a MM cartridge and the noise was a gone. Then I reinstalled the Denon and the SUT and the noise was back. So I tried my Graham Slee and the noise was gone again. I opened my SUT to check the ground and remembered this was the second thing I ever soldered way back 8 years ago and I did a pretty lousy job. So I quick re-flowed all the solder joints and completely redid three of them and put everything back together with the Realistic and no noise now. Very little anyway.
It's a little odd that the noise didn't show up in my three other phono stages and only the Realistic but it's all sorted out now and still sounds great.
Mine has the same orange drops and a older baby blue electrolytic caps.
I had been looking to replace my 2101a because I was getting a thump every time a major appliance kicked on. I haven't been happy with other pre-amps and from this thread and a thread on stereo.net, it looks like a battery modification will eliminate my issue and give me a good pre-amp. The price is right anyhow. I might try a wall-wart since my Bozak Maddison unit is of that configuration without thumping from my house AC. Has anyone else made this mod?
Mine JUST developed a very low hum in the left channel only. Im going to try the art dj pre ii next to see how it measures up.
I have one. Sound quality isn't jaw-dropping or anything, but it's not too bad, and the thing is absolutely dead silent. I use a beefy power supply from a pair of speakers, not the supplied wall wart.
Besides the occasional very low ac thump the Realistic 42-2101a also picks up thumps directly on its case or shelf it is sitting on. It's like a microphone. I isolated the unit and covered it with a wash cloth, problem solved. Its response is very good but I ain't happy.
I bought a Bozak Maddison CLK-PH8 pre-amp for $33 which has great specs and the AC thumps are gone but I get a greater 10 Hz noise pumping which I believe is cartridge resonance. I also see it to a lesser extent with the Realistic unit. The noise is greater on a Pioneer cartridge with a 2.5 mV output than it is on an Empire with 3.5 mV output. Sadly the Empire 400TC is bottoming out and clipping loud sections. If it's not one thing it's another. I'm looking for a new cartridge with 5 mV output to pull the signal even higher above the cartridge noise. Until then I'm using the Pioneer PC-400 and applying a high-passs filter with purer results.
Since the photo I took of my Realistic 42-2101a is at the top of this forum I thought I'd drop in.
For anyone who may be interested, here's the transfer function of the actual unit pictured, along with the plot for my receiver's phono preamp picked up at the tape out.
I put mine back in the system this weekend and gave it several days. It is very quiet and has a very lush midrange. I see why people like it.
You must have something different, this preamp plugs directly into the wall.
And unless he's using powered speakers, there's would be no power supply in a speaker either. Doesn't make sense. might require elaboration.
Just out of curiosity, anyone with one of these Rat Shack Phono Preamps also have, or have heard, the Lounge phono pre? Observations welcome.
I'm interested but not sure what the graph indicates.
It's a pair of frequency response graphs, one for the RS preamp and one for the preamp in an Onkyo receiver. Unfortunately I didn't gain match them at 1kHz, which would have made the graph easier to interpret, but you can see how the RS preamp's response peaks at 100Hz and falls off below that while the Onkyo receiver preamp peaks at 70Hz. As far as I know the RIAA curve should continue upward, with some gentle leveling out, down to 20Hz. The Onkyo receiver comes 30Hz closer to this goal than the RS preamp. In addition to that the RS falls off more steeply above 1kHz.
Using pink noise?
Using a sweep.
I recently swapped out this amp due to a small hum in one channel. In the description, I did a needledrop of the realistic vs. the art dj pre-ii amp, which you can download and listen.
Well, I found the original data so I gain matched them at 1kHz. The differences and similarities are more apparent. Turns out they are pretty similar above 1kHz.
So somewhere between 5.0 and 6.5mv is this preamp's limit. It makes some pretty horrible noises during hot cut passages with my Shure M55E installed.
I have an Empire 400 TC rated at 3.8 mV output at 1 kHz and I see source clipping from the Realistic Pre-amp. I wrote this off as a cartridge problem. I was also seeing a 10 Hz and 30 Hz buzz so I bought a Bozak Madisson CLK-PH8 Pre-Amp (nice specs for an inexpensive amp) and experienced the same results. I assumed the buzz was at the turntable. I then purchased the Ortofon 2M Red cartridge rated at 5.5 mV to boost the gain at the source hoping to solve the buzz but was ready to return it due to a clipping problem with it. I tracked down the source of clipping which I had thought was physical within the cartridges by recording a segment without pre-amp and the clipping was gone. Problem found. So I bought the Art DJ Pre-II amp because the gain can be controlled (at input) and the clipping indicator light is a big plus. This was also within my budget and the specs acceptable. Setting the gain at -2 on the Art DJ has fixed the problems. The Realistic amp did a good job with my older / original Pioneer cart rated at 2.5 mV. I guess the times have changed and my 1980 equipment needed upgrading for the newer cartridges.
So I ended up with: My Pioneer PL520 turntable, Ortofon 2M Red cartridge, Art DJ Pre-II pre-amp, into a Xonar DG sound card.
My ears are pleased, hope this helps.
So anyway the 2SC1327 is not an FET.
I just got this one and compares very favorable to my 42-2101a (Made in Japan) not the 42-2109 (Made in Korea)
1970 Realistic 42-2930 preamplifier
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