[Coco] WTB Orchestra 90 cartridge

[Jayeson Lee-Steere]

Quick follow up: it seems that small (5mm pitch) 0.1uF and 1uF polyester
caps have more options/are cheaper than bipolar electrolytics anyway.

On Mon, Aug 1, 2016 at 3:44 PM, Jayeson Lee-Steere <
cocolistemail at titaniumstudios.com> wrote:

> On audio, there are a lot of options about which caps are appropriate for
> audio, but all references I have seen say that ceramics are not an
> appropriate choice in the audio path. Given their strong piezoelectric
> properties, it is not clear to me what are appropriate uses for the
> recently available, high value MLCC ceramic caps. Too bad, because they are
> smaller and less costly than tantalum.
>
> This reference on audio caps seems fairly balanced:
> http://sound.westhost.com/articles/capacitors.htm
>
> Film capacitors are the thing to use where practical. It would seem some
> film types are better than others, but for this use, polyester would be
> more than sufficient. That is probably what the small value caps are in the
> original Orch 90. Next down the line are electrolytics, which are
> apparently fine for audio coupling if an appropriately large value is used.
>
> Jayeson
>
>
> On Mon, Aug 1, 2016 at 12:50 PM, Zippster <zippster278 at gmail.com> wrote:
>
>> Hi Jim,
>>
>> Responses in-line…
>>
>> PCBs should arrive tomorrow, so hopefully we’ll find out how they work
>> later this week.
>>
>> - Ed
>>
>>
>> > On Jul 31, 2016, at 11:06 PM, RETRO Innovations <go4retro at go4retro.com>
>> wrote:
>> > A couple questions:
>> >
>> > * Looking at the schematic of the orch 90, it looks like 3 of the caps
>> >   are non polarized electrolytic.
>>
>> I don’t want to open mine either, but I believe you are correct.
>>
>> > On your redesign, it looks like
>> >   you swapped out for ceramic or something similar.
>>
>> Yes, I used just plain ceramics, which I suspect will be just fine here,
>> but hey
>> that’s what prototypes are for.  :)
>>
>> > Was there some
>> >   reason why Tandy used the non polarized (I had not heard of them
>> >   before perusing the schematic)
>>
>> I can’t think of one.
>>
>> > * The r2r ladder.  I assume the original resistor networks were 1/8W
>> >   or 1/4W Did you go with 1/4W or 1/8W on the surface mount
>> >   replacements?  Or, did you go with something smaller?
>>
>> Bourns isolated resistor arrays.  Rated  .16 W per resistor, so somewhere
>> in-between.
>>
>> >
>> >
>> > I hate to open my sealed cart up, or I could probably answer part of
>> the second question.  Anyone have hires pics of an open cart?
>>
>> There’s a pic in the folder here, but not very high resolution.
>> <https://drive.google.com/open?id=0B1sgl615FlGnLWk1akpheXhCcWs <
>> https://drive.google.com/open?id=0B1sgl615FlGnLWk1akpheXhCcWs>>
>>
>> >
>> >
>> > Jim
>> >
>>
>>
>> --
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>>
>
>