Panasonic SE-405 schematic needed

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jason12

Member
Joined
Jan 27, 2009
Messages
17
Hi,

Just got Panasonic SE-405 demodulator. Does anyone have schematic for it, please? I saw an older thread with links. However links do not work anymore.

Thanks
 
I have a copy of a copy of the schematic. Please send me a PM if you would like a copy of this.

Vinylguy4
 
Thanks for posting the schematics.

I was thinking of getting an SE-405 and noticed from a picture on that auction site that there seem to be four trimpots on the bottom of the decoder with a label saying that the settings are specifically for the accompanying cartridge and need resetting for other cartridges (instructions in manual).

Does this mean that you need the special test record and instructions that originally came with the unit to match it to your particular cartridge, otherwise the unit's pretty much useless?

Another question, maybe a shot in the dark for something who knows. From the schematics it appears that one of the things the MM/semiconductor switch does is select between an RIAA filter (for normal cartridges) and another RC filter (R423, C419, etc). I was under the perhaps false impression that the Panasonic semiconductor cartridges had a basically flat response and didn't need any RIAA or other filtering. Perhaps it does need some sort of non-RIAA filter? Anyone have a clue? Thanks for any help.
 
Yes, you may have to adjust those four pots on the bottom but you don't need any one particular CD-4 record to do it. Most of them were all about the same and you can use any one of them.

I have a JVC record and a Harmon-Kardon and get similar results with either one.

The carrier level isn't all that critical and the only other thing to do is to adjust the separation pots for minimum output from the back channels with the correct track playing. I had no problem at all when I did my SE-405 and haven't had to readjust it at all even when changing cartridges. It is a very nice sounding unit; sounding pretty much like any good regular stereo component.

I like the Harmon record because there is a guy announcing the different tracks so it's easy to use.

As far as the input for a semiconductor cartridge, since there is a DC level on the lines (to power the semiconductor elements in the cartridge), there needs to be isolation capacitors in the inputs to keep the DC out. Of course, I'm just speaking from general knowledge of these things and I don't know exactly how they do it in the demodulators but I would assume that's pretty much what they're doing.

The response of the semiconductor cartridge would actually have to be the inverse of the RIAA curve if it doesn't need any equalization because what it picks up from the grooves has been RIAA altered. Again, I don't really know exactly what's going on there.

Doug
 
Thanks for the explanation of adjusting the demodulator pots; I see there is another thread in this forum on how to do this with any CD-4 disc.

The instruction sheet for the EPC-451 says "...the frequency response characteristics of this cartridge is equalized for RIAA recording curve in itself. Therefore it does not require the equalizer..." which suggests that no equalization of any kind is needed. Also, I see no evidence of any equalization for semiconductor cartridges in Lou Dorren's demodulator schematic. Also, a quote from Soundsmith, who offer a very expensive preamp for strain gauge cartridges:
"No "RIAA" filter circuitry is required or used in our preamp - just one ULTRA clean gain stage ... The Strain Gauge is a "displacement" device......which automatically compansates for the RIAA EQ"

However, I believe that the Panasonic and similar semiconductor cartridges' response to a record is not truly flat and does need some kind of equalization, witness this review of Soundsmith's preamp from dagogo.com:

"The strain gauge... doesn’t require the RIAA playback equalization. However, when a record is cut, it is recorded with the RIAA preemphasis curve and there are two “knees” (turnover and rolloff frequency points) that cause a dip and a peak to occur when not using the RIAA playback curve. Peter [of Soundsmith] has finally, FINALLY, fixed the issue. It’s one of the reasons the strain gauge hasn’t been my main cartridge—the funny frequency response."

I have also seen a published frequency response curve (in International Audio Review) for one of Sao Win's strain gauge cartridges (based on the same technology as the Panasonic) which shows a horrible looking midrange dip and high frequency peak (almost looks like an inverse RIAA response;)).

The reason I'm pointing all this out is that I hope to correct for any frequency response issues in these Panasonic cartridges, I'm just not sure how, without spending about $10,000 on a Soundsmith preamp.:mad:@: I'm wondering if the Panasonic SE-405 does this kind of correction.
 
Hmm so Peter oF soundsmith found a way to get a better response curve out of his new system? I'd love to know what he did. I heard his strainguage cart a while ago, couple years. And it is the best sounding cart i've ever heard. Can only imagine that it sounds even better. Anyway he has always been a proponent that the strainguages didn't need any eq because of the way they worked almost mirrored the RIAA? I guess almost isn't enuf for some ears. I dont know if the soundsmith preamp is even compatible with the panasonics cart. I believe they are different strainguage tech. Maybe Lou Dorren would know something about this as he is developing his new demod and supposedly it will also work with the panasonic strainguages.
 
Hmm so Peter oF soundsmith found a way to get a better response curve out of his new system? I'd love to know what he did.... I dont know if the soundsmith preamp is even compatible with the panasonics cart. I believe they are different strainguage tech. Maybe Lou Dorren would know something about this as he is developing his new demod and supposedly it will also work with the panasonic strainguages.

I believe that Soundsmith's strain gauge cartridges are the same technology as the Panasonic semiconductors (and also Sao Win's), here is a quote from Soundsmith's website:
"two tiny silicon beams sense the cantilever position, and change electrical resistance"
That is exactly how the Panasonic cartridge works. Actually, Peter has stated that he used to make and sell a preamp for the Panasonic cartridge, when they were still available. I'm sure that the Soundsmith cartridge has greatly improved on the cantilever and stylus, which is kind of cheap on the Panasonic. I don't know if the cartridges have the same frequency response, so the equalization might not be exactly compatible. Soundsmith's website has no information on the equalization, probably to keep it proprietary, but there is some information on the dagogo site:
http://www.dagogo.com/Events/2009CES/Coverage-XI.html
All I could glean from this is that the equalization is done with "shunt circuits", which seems to imply passive networks.

I too hope that Lou Dorren can provide some information on this, but he doesn't seem to have posted much recently, probably very busy getting his demodulator out.
 
I'll concede that they are both strain guages, I just was under the impression that Peters new cart was using a newer more advanced SG part. I wasn't sure it would be compatible but maybe from the Pre amps perspective they are the same functionally? I hope so. lol, I'd do it the opposite than you It would be cool to buy one of his carts to use with an old se 405 especially if we could find out about these shunt networks? Would be a cool mod to the se 405. I bet someone knows enough about the RIAA circuit and the SG carts to know what to do to create a shunt EQ. Fixing the sub bass issues that the article mentions should be easy too. Wish I was a phono stage expert lol.
 
Any chance of getting a copy of the schematic, the mediafire link appears to be empty.
Would be much appreciated.

Regards
James
captsnooze<at>iinet<dot>net<dot>au
 
Hello,

I hate to ask you, but could you please post the schematic again. This seems to be the only place on earth were you can find it. :)

Thank you
Ed
 
Thank you James, but unfortunately the service manual does not include the schematic, which is pretty strange.

Anyone out there with the schematic?

Thanks
Ed
 
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