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Modifying a Coincident Dynamo Mk1

Hello all,

Have been modifying my Coincident Dynamo Mk1 for some time and I could use a helping hand from more experienced users.

If I understood correctly, looking at the image attached the 2 Epcos 22uf/500v are the filter caps which come after the rectifier (in my case the 5AR4) and these have to take into the account the rating of the tube and capacitance limit which is 60uf?

If my ramblings prove to be true can this position be improved on with better caps and/or a slightly larger caps?

Looking at the, what I think to be the power supply cap, which is a 470uf/500v, would there be a benefit in putting a larger cap without causing other issues? For instance the Mk2 Dynamo has much bigger caps in that position but I suppose the transformers are different as well. Id be looking to get more bass and mid bass and some readings say this is the place which can yield some results.

I have done several modifications already with mixed results so if anyone is interested I can share the details but Im trying to learn more about the positions and parts and their relative role. Any ideas and suggestions are welcome.

Link to insides below.

Thanks in advance!

https://ibb.co/JqW6JDb

P.S. For some reason the picture did not want to upload via the insert photo, sorry for the link.

neverlast

Showing 7 responses by imhififan

imhififan's avatar
imhififan
2,218 posts
 

Link to insides below.

https://ibb.co/JqW6JDb

 

 

 

imhififan's avatar
imhififan
2,218 posts
 

I would leave the rectifier caps alone.

+1.

To improve sound quality, my suggestion is change the volume control pot to a stepped attenuator like a Gold point, Khozmo or even a Eizz from Aliexpress.

 

imhififan's avatar
imhififan
2,218 posts
 

No experience with Audio Note basic pot, TKD is good but expensive. If you are not using the volume control and always set it to maximum, my suggestion is to use a resistor to ground instead of the volume control potentiometer.

 

imhififan's avatar
imhififan
2,218 posts
 

The easiest way to bypass the volume pot is to move the two yellow wires from the center lug to the lugs for the blue and brown wires respectively.

It will eliminate any noise caused by dirt buildup on the wiper.

 

imhififan's avatar
imhififan
2,218 posts
 

https://ibb.co/dBt4DhT

imhififan's avatar
imhififan
2,218 posts
 

If I understand their voltage ratings add up and the uF rating in this case is only half of the first caps value, being 11uF correct?

Two identical capacitors connected in series will double the voltage rating and halve the capacitance value.

Two identical capacitors connected in parallel will have the same voltage rating and double the capacitance.

As can be seen from the picture, these two 22uF 500V capacitors are connected in parallel, so the effective capacitance is 22+22=44uF.

 

 

imhififan's avatar
imhififan
2,218 posts
 

https://ibb.co/R7YJVdg

I can't tell from the picture above whether the two 47uF 400V capacitors are connected in parallel or in series.

I could be wrong, but it looks like the two large 1000uF 315V capacitors are in series with a 100KΩ balancing resistor across them. If so, the voltage would be doubled, but the capacitance would be halved to 500uF, not much more than the MK1.

I hope someone with MK2 can confirm it.

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