2. amps-preamps
  3. 190559-99185

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
neverlast OP
15 posts
 

Regarding the volume control, I had the chance to hear it can have a dramatic effect in the amp. I have read about these attenuators and they get good reviews the only problem is they are either very expensive or too large to fit, or both. Does anyone have any experience with the Audio Note basic 100k pot or TKD pots?

imhififan's avatar
imhififan
2,217 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.

 

neverlast OP
15 posts
 

Removing the pot was my idea when I got the amp but at the time when I asked Israel he told me to just use the pot wide open. Although I sometimes adjust the pot to a lower setting its open or almost open most of the time as I use a preamp.

If you could show an example of how this could be done I would be very interested to try it.

imhififan's avatar
imhififan
2,217 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.

 

paul_lindemann's avatar
paul_lindemann
51 posts
 

Just my opinion, but Israel Blume tried dozens of Caps and values prior to deciding on the best match.

I have modified a few power amplifiers, with assistance from Robert Hovland.  Bob had an excellent comment that has stayed with me to this day.  He said that it is almost never the best Capacitor, Resistor, wiring Etc. that produces the best sound, rather it is the synergy between the circuit and components that usually will sound best. 

Of course, asking Israel, may be a good way to go.

More to discover