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DIY KT88 SEUL

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I'd like to advice You to change two shunt /big and small, that IMO is not good idea, they are with different structure/ caps in cathode of KT88 to one big with the same nominal, but with hi quality, like Black Gate, Elna. Result will be better in scene of sound.
 
Dear Juonito,

If you get even a little bit of hum try mounting your choke 90 degrees turned.Both your power tranny and filter choke are oriented in the same plane. Rotating the choke by 90 degrees will lessen the psu hum if any is induced in this orientation.
Cut a piece of thick carpet and keep the amp on it because your feet(the bolt heads) do not have any rubber cushion under.
Thats bad for the tubes as the vibrations will jerk them too much.

Very beautiful amplifier I should say.

Srian.
 
Hum is well in order. No audible hum. I put quite a lot effort on layout of all components and especially on grounding (black and copper wires). Layout is very symmetric, power source components in th centre of the layout.

Actullay I have thin black carpet pieces under the legs (can be seen in figure), but I can put other thicker ones under them.
 
One more thing. You have twisted the filament wiring very nicely. That's because it carries AC. The speaker wires also carry AC of similar power.

Since your amplifier is very beautiful may be one of your friends will request you to build one for him, or some one may have all ready decided to copy your layout. (I would have done so if I had time).

In that case try my suggestions regarding the orientation of the choke and twisting the speaker wires. I have seen this in professional amps. May be the difference would be seen if high sensitivity speakers are used or the output waveform observed in a scope or distortion analyzer.

After all she would have both beauty and brains.

Srian.
 
Twisting the speaker wires is a good hint. I will do that.

Orientation of choke is IMO not clear how it is best. I decided to orient both the choke and PT 90 degrees specifically compared to output transformers. That must also be taken into consideation. Moreover, turning is not easy since I have so much stuff in the centre of the layout. I made the layout very symmetric and power supply wires as short as possible. I should dismantle much and the result is not sure. But thanks, this is worth of consideration, too. In the next construct I maybe try that and analyse hum by measurements.
 
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5AR4 now in use. More dynamics and bass maybe still better !
Surprisingly tight bass in KT88 SEUL. Middles and highs fabulous.

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Hi thanks for your response. I grounded the shield on of the 6ej7 on my build. Does the shield need to be grounded or no?It sounds pretty nice. I have a lil bit if hum that I need to take care. I can only hear it about 6 inches from my 100db altecs. The amplifier sounds good so im happy. How did you ground your amp?

Thanks
 

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KT88 SEUL

Hi,

Grounding is difficult to explain shortly. Main thing was that I decided to have one point where I grounded everything. You can see it in the figure. It is the ground point of 47uF capacitor in the middle of the device. It is important that all components are grounded only from one point. For example cable shields only from one end. One important thing was also that I made a layout where component are radially situated.

I managed very well, I can not hear any hum at distance of about two inches from the speaker drivers.


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