[Coco] WTB Orchestra 90 cartridge

[RETRO Innovations]

On 8/1/2016 10:39 PM, Jayeson Lee-Steere wrote:
> Sure is an interesting topic.
>
> One point in the link shared earlier is that for decoupling caps, the
> distortion is scaled down according to the relative voltage drop across the
> cap. Using an oversized cap value will reduce the voltage drop and
> therefore the distortion. For this particular usage, I wouldn't be overly
> concerned about distortion from ceramic decoupling caps.
>
> However, the piezo effects are potentially huge. I just soldered a 10k
> resistor across a 1uF 1206 MLCC cap. Tapping that arrangement with tweezer
> points easily generated spikes approaching +-10v.  I'm interested in how
> NPO/low K cap types would go, but it seems easier to just use polyester and
> be done with it.
>
> I guess one other note is that the circuit has some low value caps to
> ground. They look to me to be for RF suppression and so I think should be
> ceramic. I'm pretty sure there are plenty of low K options available in
> those small values.
If you look at Zippster's pic of the unit, you can count 5 cans (1 power 
supply bypass and 4 audio) and 4 non ceramic caps (audio) alongside the 
ceramic decoupling caps.  So, at least Tandy felt they needed film for 
the RF suppression.

Jim