Kaiju - Quiet amp using very efficient speakers? Hum resolvements? [resolved]

[Natural Sound]

Nice clean build, Chris. Let us know how you like the DC conversion after you've had some time to evaluate the differences.

[Paul Birkeland]

When you get past 110dB efficiency, you can install the DC filament supply board and rewire the output transformers for a lower secondary impedance.

The hum reduction from rewiring the output transformers is not as drastic as adding the DC filament supply, but you will also get a reduction in tube self-noise in the process at the expense of making less power (which you don't need with speakers that efficient).

-PB

[fritzthecat]

When you get past 110dB efficiency, you can install the DC filament supply board and rewire the output transformers for a lower secondary impedance.

The hum reduction from rewiring the output transformers is not as drastic as adding the DC filament supply, but you will also get a reduction in tube self-noise in the process at the expense of making less power (which you don't need with speakers that efficient).

-PB

I installed the DC filament supply board yesterday but it got late so I decided to check it today. I wired the output transformers for 16 Ohms as this is the impedance of my midrange drivers the Kaiju is thought to drive. So this means I might rewire them for 8 Ohms or 4 Ohms? Or even 2 Ohms? What should I try? Power is not an issue anyway - with these speakers I can easily blow myself out of the room...;o)

[Paul Birkeland]

Go for 2 Ohms.  Your speakers need just a tiny drip of power to blow your eardrums out, so shedding gain/power is quite desirable.

[fritzthecat]

thank you - so I went exactly in the wrong direction. I guess for the JBL slot tweeters it is the same. I am planning to implement some Stage Accompany Ribbon Tweeters - as they are among the best I have ever heard.

Using several binding posts would it be possible to get several options regarding OT wiring? Or is that a stupid idea? Maybe because of additional metal and wiring attached to the OTs?

BTW: almost no more hum after installing Filament upgrade! I'm amazed!

[Paul Birkeland]

Using several binding posts would it be possible to get several options regarding OT wiring? Or is that a stupid idea? Maybe because of additional metal and wiring attached to the OTs?

There are a couple of ways to wind the secondary of an output transformer.  The low cost option is to wind a single winding and just tap it at 4, 8, and 16 Ohms.  This allows for three impedance taps on three separate binding posts, but you leave a lot of unused copper on the secondary when you use the 4 and 8 Ohm taps, which impairs coupling between the primary and secondary . 

Our transformers require a little more effort to rewire for different taps, as the secondaries are wired in lower impedance sections to  improve coupling between primary and secondary at all impedances, and therefore impedance switching is more complicated than just adding binding posts. 

[fritzthecat]

I didn't know that as the few tube kits I built so far all are the other less sophisticated types. Thank you very much!