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SuSy dynahi v2

Kevin Gilmore's higher-powered version of the dynalo

Re: SuSy dynahi v2

Postby DEFL » June 8th, 2015, 1:05 am

Very easy if you have desoldering gun (e.g. Hakko 808 or FR-300). Heatsink will rest in its place, no need to remove it.
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Re: SuSy dynahi v2

Postby jmc » June 8th, 2015, 3:46 am

mloutfie wrote:Yeah that's what I think. my other board is fine. I changed the 500ohm resistor to 680ohm to reduce the bias as low as 75mV looks like I have to switch it back to 500 Ohm because I can only raise the bias to 400mV now.

Man this is hard.... compared to making tube amp like bottlehead crack this is a whole different level.


If you are using the onboard heatsinks with the MJE15030/15031 the bias point is 375mV or .375V. Kevin reduced the current because of the smaller heatsinks. .75V should be for offboard oversized heatsinks only.

If you want to raise the bias you need to change the 2 50ohm resistors near the input and output terminal blocks to 75 or 100ohm.
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Re: SuSy dynahi v2

Postby mloutfie » June 8th, 2015, 4:55 am

jmc wrote:
mloutfie wrote:Yeah that's what I think. my other board is fine. I changed the 500ohm resistor to 680ohm to reduce the bias as low as 75mV looks like I have to switch it back to 500 Ohm because I can only raise the bias to 400mV now.

Man this is hard.... compared to making tube amp like bottlehead crack this is a whole different level.


If you are using the onboard heatsinks with the MJE15030/15031 the bias point is 375mV or .375V. Kevin reduced the current because of the smaller heatsinks. .75V should be for offboard oversized heatsinks only.

If you want to raise the bias you need to change the 2 50ohm resistors near the input and output terminal blocks to 75 or 100ohm.


Really? Do you have a link? I haven't seen 375mV mentioned as dynahi bias for onboard version. I think the reason my bias stop at 400mV is because I have replaced the 500ohm next to the biasing pot in to 680ohm.

I was going to set it back to 500ohm to be able to increase bias. But I will read up again because if 375mv is enough I can use what I have installed
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Re: SuSy dynahi v2

Postby jmc » June 8th, 2015, 5:49 am

I don't have a link but this is what Kevin told me (by PM):

"The onboard dynahi is trimmed for lower power because of the onboard heatsinks.
If you wanted to crank the bias, you have to change the 2 x 50 ohm resistors near the input
and output jacks to 75 or 100 ohms."

I am almost sure the onboard heatsinks can´t handle 0.75V for a long time. The maximum voltage I used with the onboard heatsinks was 0.5V and everything was really hot, and it was an open build without enclosure.
I finally biased my boards at 0.35V and never looked back.
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Re: SuSy dynahi v2

Postby mloutfie » June 8th, 2015, 5:59 am

Thanksforthat.what heatsinkdid you use? I've got 2.5"installed
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Re: SuSy dynahi v2

Postby jmc » June 8th, 2015, 6:11 am

I also used 2.5".
I can't remember where I read about the 0.375V anymore, maybe I'm confusing something but I am pretty sure you can't go up to 0.75V on those boards without risking damaging the output transistors.
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Re: SuSy dynahi v2

Postby mloutfie » June 8th, 2015, 6:20 am

the output resistor does get hot even with 400mV. so I guess you've been using they susy dynahi with 375mV and running good?
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Re: SuSy dynahi v2

Postby jmc » June 8th, 2015, 6:28 am

I don't have it anymore, I sold it, but yes, it is still running good and sounding great
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Re: SuSy dynahi v2

Postby DEFL » June 8th, 2015, 8:46 am

Schematic of version with on board heatsink and off board heatsink are same, so Kevin didn't change anything.
I'm using version with on board heatsinks with standard resistors value and easily dialed bias to 0.75V.
I left it switched on for 6 hours and everything was OK.
Note I used 1.5' tall heatsinks (gonna change to 2.5' later).
Yes, it was very hot. But it isn't supposed to run cool.

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Re: SuSy dynahi v2

Postby jmc » June 8th, 2015, 10:51 am

R23 and R34 are 100r on the schematics but the onboard version has 50r on the silkscreen. Kevin Gilmore says to always follow the silkscreen because it's the latest version of their amps.
Of course it's supposed to run hot but I think there's hot and too hot.
Anyway I guess the best thing to do would be to ask KG why can't you get the bias up. It's what I did and he told me to lower the bias.

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