I have the rig together and working, but it's a step or two behind your changes. All the changes on the main board are up to date, with C2 = .068. The EQ board has R3 at the original value, 36K5. I mounted one of my 451C bodies that I had never used before, with an original Panasonic Shibata stylus with very few hours. Ran it for a couple of hours to break it in. Blue-tac on the nose, no other damping yet.
My (very initial) listening impression tells me it's too bright. And my measurements show a broad peak in the treble of 3 to 4 dB. Low end is flat to 30 Hz, so I'm not in a hurry to change C2 on the main board. I'm using a test record with spot frequencies, 30 is as low as it goes. I have not yet built the test jig, so I'm not measuring the preamp itself.
My next step is to move R3 towards the values you're using.
The cartridge/Preamp combo is considerably quieter than the quietest vinyl I've played so far.
My (very initial) listening impression tells me it's too bright. And my measurements show a broad peak in the treble of 3 to 4 dB. Low end is flat to 30 Hz, so I'm not in a hurry to change C2 on the main board. I'm using a test record with spot frequencies, 30 is as low as it goes. I have not yet built the test jig, so I'm not measuring the preamp itself.
My next step is to move R3 towards the values you're using.
The cartridge/Preamp combo is considerably quieter than the quietest vinyl I've played so far.
My initial impressions were the same, adding C2 shifts the boost in the lower midrange downwards slightly, and made a surprisingly big and completely unintuitive improvement, also matches my target curve better.
R3 IMO needs to be 56K or higher for satisfactory results, and here is where it gets a bit tricky - I'm at 68K and that might be just a bit more than optimum, but it's certainly closer. I've struggled a bit with LF behavior in these cartridges because it seems to be heavily influenced by arm mass and how well coupled to the arm the cartridge actually is.
I have stylus issues and am currently running a 465C because of the high mass of the tonearm in use, it's not a good match with the stylus I have, but that stylus sounds better than the others even so. (Boron cantilever, MR stylus)
I used pink noise on an STR test record the last time I tested EQ which was several iterations back, even then it seemed to be in an acceptable range although I was never happy with the subjective result. (within a +/-2.5dB range except at the top where it rolled off a bit excessively)
R3 IMO needs to be 56K or higher for satisfactory results, and here is where it gets a bit tricky - I'm at 68K and that might be just a bit more than optimum, but it's certainly closer. I've struggled a bit with LF behavior in these cartridges because it seems to be heavily influenced by arm mass and how well coupled to the arm the cartridge actually is.
I have stylus issues and am currently running a 465C because of the high mass of the tonearm in use, it's not a good match with the stylus I have, but that stylus sounds better than the others even so. (Boron cantilever, MR stylus)
I used pink noise on an STR test record the last time I tested EQ which was several iterations back, even then it seemed to be in an acceptable range although I was never happy with the subjective result. (within a +/-2.5dB range except at the top where it rolled off a bit excessively)
I searched the thread but could not find information on PCBs for the preamp. Are any still available to order or are gerber files available as well as a current BOM? Thanks in advance.
Unfortunately the boards are not currently available. If someone else is willing to set up and run an at cost GB and will also agree not to make the gerbers publicly available I would be willing to provide them and an updated BOM. The gerber files and BOM for the latest EQ are already here on the thread.
Kevin
Kevin
It's not pretty, but it does seem to work: sorbothane that is.. Specifically Isolate IT! 1/8" x 12" x 12" sheet - this stuff is really sticky, and more effective than the blue tack it replaced in damping some of the body resonances and cross talk.
The bodies of these cartridges are really a big weak spot...
The bodies of these cartridges are really a big weak spot...
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Hello. I am interested in building a new phono SG preamp for my EPC-450C-II and EPC-450C cartridge. The latest version is A2.5 plus the 8.1 equalization card?
I built a preamp version based on the LME49720NA CI, very simple. Does anyone here know? It would be interesting to talk about it.
I own the Panasonic SE-405 demodulator. After I changed all electrolytic capacitors and about 31 transistors, it was excellent!
I built a preamp version based on the LME49720NA CI, very simple. Does anyone here know? It would be interesting to talk about it.
I own the Panasonic SE-405 demodulator. After I changed all electrolytic capacitors and about 31 transistors, it was excellent!
Hi.
I live in Brazil, I must be alone in this world Panasonic Strain Gauges.
I built a preamp for cartridge strain gauges, based on a LME49720NA CI, very simple. But the result did not please me very much. I thought your project was fantastic and I want to build one, but I'm a beginner in the DIY environment, so if possible I need all the details (additional details) and I think about sending the project to a company to manufacture the PCB for me, but I need the archive. Could you please help me by providing all this additional material?
Thanks
I live in Brazil, I must be alone in this world Panasonic Strain Gauges.
I built a preamp for cartridge strain gauges, based on a LME49720NA CI, very simple. But the result did not please me very much. I thought your project was fantastic and I want to build one, but I'm a beginner in the DIY environment, so if possible I need all the details (additional details) and I think about sending the project to a company to manufacture the PCB for me, but I need the archive. Could you please help me by providing all this additional material?
Thanks
I would like the file in Gerber format for PCB fabrication. Please, if it is possible to do this, I would be very grateful.
Please, I would like to get pictures of the pre amplifier assembly. This will help me a lot. Thanks
I know it's late, the party looks like it's over! But if it's possible in the future, I'm interested in the latest version of PCB boards.
Well, i'm back to this forum after so many years.
About 13 years ago I published online a version of a super simple Strain Gauge preamp. Alas, maybe too simple.
Now i need to read the 35 pages. I'm very excited other members (kevinkr) have done a new design. Still got some EPC-450CII NOS cartriges to try.
About 13 years ago I published online a version of a super simple Strain Gauge preamp. Alas, maybe too simple.
Now i need to read the 35 pages. I'm very excited other members (kevinkr) have done a new design. Still got some EPC-450CII NOS cartriges to try.
Hi Flavio,
If you do build the design detailed here please be sure to find the last EQ I posted as it is by far the best.
You are fortunate to have spare cartridges, I am down to just one which I repaired some time ago (broken internal wire) and am quite careful with. It sounds very good compared even to my LOMC based set up. (I have one of Dave Slagle's boron cantilever, line contact styli on the 451C)
I've no plans for any further development activities on the strain gauge phono pre-amp for anyone still following.
If you do build the design detailed here please be sure to find the last EQ I posted as it is by far the best.
You are fortunate to have spare cartridges, I am down to just one which I repaired some time ago (broken internal wire) and am quite careful with. It sounds very good compared even to my LOMC based set up. (I have one of Dave Slagle's boron cantilever, line contact styli on the 451C)
I've no plans for any further development activities on the strain gauge phono pre-amp for anyone still following.
Hi @kevinkr
The fact that you have found a suitable EQ is by itself a major leap forward in the DIY community. I'll make sure to take a look when I have enough time.
I'll need to say that one of the EPC-45CII i had was a bit faulty in the sense that it had more mechanical resonances (it resonated with any pop/click on the record surface), the other two were just fine. And i still have two that are NOS, not opened yet.
Perhaps QC wasn't that good. Which is strange because Technics often has perfect QC.
The fact that you have found a suitable EQ is by itself a major leap forward in the DIY community. I'll make sure to take a look when I have enough time.
I'll need to say that one of the EPC-45CII i had was a bit faulty in the sense that it had more mechanical resonances (it resonated with any pop/click on the record surface), the other two were just fine. And i still have two that are NOS, not opened yet.
Perhaps QC wasn't that good. Which is strange because Technics often has perfect QC.
Bear in mind these cartridges were made nearly 50 years ago, and over time things shrink, etc. This was also a comparatively cheap cartridge at the time.
The very last EQ was a substantial improvement over all previous iterations. I still use for the little use the set up gets these days. I have another TT with Mutech Hayabusa on it which I use more, the SG sounds better in general on most material. 95% or more of my listening is now digital via roon ready streamer functionality in my MiniDSP SHD. My system isn't really analog anymore except for a few sources and the power amps - everything else is done in the digital domain.
The very last EQ was a substantial improvement over all previous iterations. I still use for the little use the set up gets these days. I have another TT with Mutech Hayabusa on it which I use more, the SG sounds better in general on most material. 95% or more of my listening is now digital via roon ready streamer functionality in my MiniDSP SHD. My system isn't really analog anymore except for a few sources and the power amps - everything else is done in the digital domain.