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Genera Modification for 78's

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GregR View Drop Down
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    Posted: 01 Jul 2020 at 10:58pm
Hello All,
In my ever narrowing quest to find something older than myself, I have recently become interested in 78 record playback.
I have already rebuilt a P******t Debut III. I have setup a shim system for the tone arm to adjust VTA, and rewired the tonearm. I am using an Audio-Technica M95sp. P******t makes a custom pulley for 78's and I had a custom belt made by Origin Live. My strobe light indicated it's spinning exactly at 78, which means Pro-Jects' speed controller should be helpful.
I'm using an old Sony receiver, I could do better.
Does there exist or is it possible to mod the Genera kit to be more like the Jazz Club, which is outside my budget?
Ideally I imagine the signal path as:
"Stereo" output from the M95sp
"Stereo" EQ and MM gain
Center channel tap from a Dolby Pro Logic encoder
Headphone or speaker amp.
Thank you,
Greg Ritacco
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Fatmangolf View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 02 Jul 2020 at 8:53pm
You should already be able to connect the VM95SP to the Genera input and I assume you already are doing so. You could fit a mono switch inside the Genera but the effect will be similar to using the centre channel output from a DPL processor feeding a single channel amp and centre speaker. Adding a mono switch is a DIY job you could probably do if you have already built a Genera, so...

When you say "more like the Jazz Club" Greg, do you mean adding switchable equalisation?

Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GregR Quote  Post ReplyReply Direct Link To This Post Posted: 02 Jul 2020 at 9:27pm
Hi Jon,
Excuse the confusion, yes I was wondering if it's possible to have a switch select curves like the Jazz Club.
I can't use my Genera because I hard wired in MC transformers. Also, it's too nice. I'm in "experimenter" mode with this project, so I will need another one I can cut on.
Some 78 fans add a switch to their preamp to select right only, left only or both channels using a "stereo" cartridge like the M95sp. They say usually one channel is quieter than the other, but my listening tests suggest otherwise.
I read on the web (so you know it's true :) about using an old pro logic encoder. The idea is that the encoder will send the majority of noise to the left and right channels and the common signal, the music, to the center channel. Mostly. The center channel output is split and sent to the amp.
Thank you for taking the time to consider this.
-Greg
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 02 Jul 2020 at 9:55pm
Ah, I see what you are doing with the DPL centre being split. Years ago I found a fair bit of the vinyl noise is out of phase and goes to the surround speakers which can be turned down or unplugged. Your solution of feeding another amp with only the centre channel signal has the same effect. More recently I tried series wiring the left and right sides of the cartridge, on my mono LP's I concluded that using a mono switch is much easier.

Yes in theory you could alter some of the capacitor values in the phono circuit to get different EQ, a shallower rolloff than the standard RIAA. The Genera kit booklet or the long and very good educational thread about its development is on this website, either would probably give some clues. But I know enough to realise the values are found by trial and error, and the sound will change due to phase changes.

Back to the 78's. I had a Revolution M before I got an Assession M. The former has pretty versatile EQ covering 78's and my recollection is that the treble reduction on those was not as great as RIAA or Decca.

Now for some modern hi-fi heresy. Greg, does your AV processor have tone controls? If so just use them at your preferred settings for the record you are listening to.



Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote GregR Quote  Post ReplyReply Direct Link To This Post Posted: 06 Jul 2020 at 6:30pm
Hi Jon,
I will probably go the tone control route if I can not successfully modify my Genera. Since my 78 playback system would not be called high end anyway, I will be using an old DPL unit, why not tone controls to fine tune the EQ?
And while this thread is focused on EQ, I am starting to think adjusting TT speed on a per disc basis will make as big a difference as tone adjustment would.
Having said that though, it's a happy surprise to hear how much music did get recorded onto a 78.
If you would like I could report back my findings with the DPL.
Greg
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Post Options Post Options   Thanks (0) Thanks(0)   Quote patientot Quote  Post ReplyReply Direct Link To This Post Posted: 06 Jul 2020 at 6:39pm
IIRC the Revelation and Jazz Club include circuitry not on the regular G.S. preamps, which would include the DAK Genera. If you were to attempt to DIY switches and alternative EQ settings, my guess is you would need a secondary circuit board and a larger enclosure for the Genera. All this would be a considerable amount of work for a potentially sub-optimal result. If you really think you need a Jazz Club my recommendation would be to save up for one or look for one used. You may be able to buy a used Jazz Club for a favorable price from a GS owner that upgraded to something else. 

My 2 cents...
SL-1200 MK7 (modified) + Reflex M + PSU-1 used with AT150-40ML, AT VM95ML, Stanton 680mkII + Ogura, and Shure M35X cartridges.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote GregR Quote  Post ReplyReply Direct Link To This Post Posted: 07 Jul 2020 at 1:27am
Mr 2 Cents,
That is a good suggestion. With me it's a process.
Step 1, quiet down the discs as much as possible.
Step 2, be able to vary the speed in a reproducible way.
Step 3, fine tune the EQ.
Step4, improve the overall sound, such as purchase a Jazz Club.

Previous to Jon's suggestion I have read and re-read the Genera docs. To mod the Genera with any chance of success I think I would need a sweep generator, reverse RIAA circuit, and a 'scope, probably way more money than a Jazz Club. And I agree, my results would not be as good as a Jazz Club.
-Greg
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