Author Topic: Clavinet E7 "Hiss Mods" - Opinions  (Read 177 times)

Offline ilcaccillo

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Clavinet E7 "Hiss Mods" - Opinions
« on: January 11, 2020, 05:53:07 PM »
Hello,
I'm servicing a Clavinet E7 at the moment.

I would like to ask you opinions on the Hiss mods described in this video from Vintagevibe:

https://www.youtube.com/watch?v=47ZnyzLW2Hk

It recommends soldering 2 extra capacitors.
One 100pf between Base and collector of the input transistor and one 470pf between base and collector of the output transistor.

Here is a schematic with the mods in red:



It removes the Hiss and some people like it, but there's also opinions that it kills the tone of the clavinet since it forms a Low Pass Filter.

What are your opinions on this?

Thank you so much

« Last Edit: January 12, 2020, 01:44:36 PM by ilcaccillo »

Offline OZDOC

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Re: Clavinet E7 "Hiss Mods" - Opinions
« Reply #1 on: January 12, 2020, 12:07:14 AM »
I've not tried those mods. As you'd be aware, you can temporarily pop those capacitors in the circuit using alligator clips and decide whether you (or your customer) like the results. And you can explore variations of the values. But it seems to me that, if it's hiss rather than brightness that you're chasing, then thinking about low-noise transistor substitutes might be worth experimenting with.
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Offline ilcaccillo

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Re: Clavinet E7 "Hiss Mods" - Opinions
« Reply #2 on: January 12, 2020, 01:43:46 PM »
I already replaced low-noise transistor substitutes might be worth experimenting with.

I already replaced the BC550C input transistor for a MPSA18 selected for higher gain.
But anyway the BC550C is already a low noise transistor

Offline Jenzz

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Re: Clavinet E7 "Hiss Mods" - Opinions
« Reply #3 on: January 12, 2020, 02:23:54 PM »
Hi .-)

BC550C and MPSA18 differ only 1 dB regarding noise, but sometimes it is worth a try.

The additional caps reduce the hiss, but also cut treble, so this mod is a matter of personal taste.

I allways change the 1 meg resistor to a metalfilm type, the 8,2.pF ceramic to a 10pF Mica and the 100uF across the supply to an low ESR type.

Jenzz

Offline ilcaccillo

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Re: Clavinet E7 "Hiss Mods" - Opinions
« Reply #4 on: January 12, 2020, 03:11:53 PM »
Hi .-)

BC550C and MPSA18 differ only 1 dB regarding noise, but sometimes it is worth a try.

The additional caps reduce the hiss, but also cut treble, so this mod is a matter of personal taste.

I allways change the 1 meg resistor to a metalfilm type, the 8,2.pF ceramic to a 10pF Mica and the 100uF across the supply to an low ESR type.

Replaced all the tantalum for a Panasonic low ESR Electrolytic and the Ceramic in the tone circuit for a COG of the same value.



Hi Jenzz,
thank you so much for the reply.

I replaced all the resistors in the audio signal path for Metal Film, the 1 Mega was included

The 8,2.pF ceramic I replaced it for a COG capacitor of the same value

The 100uf filter cap, I replaced it for a 330uf Panasonic 105 degrees low ESR.

I guess I will have to do a sound test with or without the additional caps to check if the treble reduction impacts a positive or negative outcome for our taste.

Thank you so much