[Coco] WTB Orchestra 90 cartridge

[Zippster]

Researching this a little more, there are NPO dielectric ceramics that
would seem to be suitable for audio path applications in this value range as well.

Point well taken though.

- Ed


> On Aug 1, 2016, at 3:04 AM, Jayeson Lee-Steere <cocolistemail at titaniumstudios.com> wrote:
> 
> 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
>>>> 
>>>