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retrofiting a Dolby circuit to a Tape deck
retrofiting a Dolby circuit to a Tape deck
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Old 6th November 2017, 12:10 PM   #1
armarra1 is offline armarra1  Australia
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Default retrofiting a Dolby circuit to a Tape deck

Hi,
Is it possible to swap out a dolby NR circuit for another to gain access to a dolby S noise reduction capability from another unit that's broken elsewhere but dolby works.

rationale:
I simply haven't found any tape changer decks that have dolby S.

I realise it would not be a simple task, but would it be possible to remove the dolby S or audio section from a dolby S deck and retro fit that into a tape changer deck ?

perhaps it can be done in another way.. but I'd think that the dolby circuitry is localised on the tape deck somewhere.
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Old 6th November 2017, 01:06 PM   #2
adason is offline adason  United States
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Everything is possible, but what you describe would likely be lots of work and painstaking adjustments. Without extensive measurements, result may not justify the effort.

Here is my suggestion. If you are not stuck with dolby S, you can use Nikko external dolby system for cassette players. I used to have it, it works well. You simply disengage internal dolby on the deck, and only use external unit. It has nice blue fluorescent display.
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Old 6th November 2017, 07:30 PM   #3
russc is offline russc  England
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I just had to Google that.
I'd never heard of a tape changer deck!
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Old 9th November 2017, 06:45 AM   #4
armarra1 is offline armarra1  Australia
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Default it thinks it is a....

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Originally Posted by russc View Post
I just had to Google that.
I'd never heard of a tape changer deck!
yep... here is a comedic take on the identity crisis for the tape changer.

https://www.google.com.au/url?sa=t&r...RB18MuSrbKxRJ0

mine arrives next few days.
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Old 9th November 2017, 06:49 AM   #5
armarra1 is offline armarra1  Australia
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Quote:
Originally Posted by adason View Post
Everything is possible, but what you describe would likely be lots of work and painstaking adjustments. Without extensive measurements, result may not justify the effort.

Here is my suggestion. If you are not stuck with dolby S, you can use Nikko external dolby system for cassette players. I used to have it, it works well. You simply disengage internal dolby on the deck, and only use external unit. It has nice blue fluorescent display.
I hear you, but if the donor deck is also a pioneer of similar vintage, odds are that the mechanism to play is the same, so either replace that in one piece or plug in the one there to the donor board. or have them both connected to the play head... I'll work out something.

the benefits of the CT-W703RS would match well with the CT-M6R which I already have coming.

I'm also thinking that if the play mechanism is standard, then the better quality components needed for dolby S would be worth swapping into the rather ordinary CT-M6R.... pipe dreams maybe but time will tell.
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Old 26th December 2017, 09:42 PM   #6
Johnny2Bad is offline Johnny2Bad  Canada
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You can just build a standalone version, run it [tape out] > [encoder] > [deck] for recording and from the [deck] > [decoder] > [tape in] on playback. That way all you need to worry about is the correct voltage power supply, which you should be able to measure.

Alternately, depending on what you mean by "doesn't work but works" you can just power up the non-working deck and insert it where [encoder] and [decoder] are in the above chain. Easy peasy.
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Last edited by Johnny2Bad; 26th December 2017 at 09:45 PM.
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Old 28th December 2017, 02:40 AM   #7
armarra1 is offline armarra1  Australia
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Originally Posted by Johnny2Bad View Post
You can just build a standalone version, run it [tape out] > [encoder] > [deck] for recording and from the [deck] > [decoder] > [tape in] on playback. That way all you need to worry about is the correct voltage power supply, which you should be able to measure.

Alternately, depending on what you mean by "doesn't work but works" you can just power up the non-working deck and insert it where [encoder] and [decoder] are in the above chain. Easy peasy.
I have noticed that the Dolby s donor deck also has flex system that brightens up the sound of cassettes with poor frequency response. On top of that the donor deck has automatic bias, level and equalisation adjustments so I'm trying to meld the two decks such that the ribbon cable that carries the auto tape type and loafed a indicators connects between the two.
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Old 6th January 2018, 04:24 PM   #8
Johnny2Bad is offline Johnny2Bad  Canada
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Auto Bias is unlikely to work on a daughter deck; it usually records a test tone to the tape, reads that tone and adjusts the bias. You might be able to use a manual bias, then you're just sending the test tone(s) to the daughter deck and manually adjusting the meters.
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Old 6th January 2018, 08:15 PM   #9
armarra1 is offline armarra1  Australia
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Originally Posted by Johnny2Bad View Post
Auto Bias is unlikely to work on a daughter deck; it usually records a test tone to the tape, reads that tone and adjusts the bias. You might be able to use a manual bias, then you're just sending the test tone(s) to the daughter deck and manually adjusting the meters.
Thanks for your response.

Yes I think it's a difficult project but in theory I'm trying to use the tape loading features of one deck with the audio features of the other incl auto bias, so once the tape is loaded the other takes over the control.
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Old 6th January 2018, 08:21 PM   #10
armarra1 is offline armarra1  Australia
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Originally Posted by armarra1 View Post
Thanks for your response.

Yes I think it's a difficult project but in theory I'm trying to use the tape loading features of one deck with the audio features of the other incl auto bias, so once the tape is loaded the other takes over the control.
The test tones are 400hz and 8000hz I think, yes I know but they're part of the features once the tape is loaded aren't they.

If I can somehow marry the tape select and load of one with the audio(playback/rec/biasauto/flex/S-dolby) of the other I'd be set. Easy in concept much harder in implementation. Got the service manual of both.
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