300b's for Kaiju

[drewh1]

Happy Holidays Bottleheads!

I have a heavily modded Stereomour and Crack, Now I want to build the Kaiju!  As I already have built and modified a couple of kits without issue, I plan on starting with all the high end stuff, Mundorf silver/oil output caps, teflon tube sockets, Goldpoint Volume control, and some other special goodies. Which leads me to wonder about tubes. I have JJ 2a3's in my Stereomour and enjoy them. I have the following questions for you experts and then would like some opinions on the best tubes, (knowing no one has actually built this amp yet?)

1. Mesh plate vs solid plate - I have heard great things about true mesh plate tubes, seems the only 300b with real mesh is the EML. 
2. Does changing the driver tube have more tonal impact than changing the output tubes?

what tube would you use (under $1000 a pair range, so I can't afford NOS)?

EML Mesh Plate
Sophia Princess
JJ 300b
Sophia Mesh Plate  (I understand this is a solid plate with little holes in it)
Shuguang Treasure

I am leaning towards the EML mesh as they seem to be highly regarded by many as long as they are used with the soft start.

Thanks in advance and sorry for kicking a dead horse!

drew.

[Paul Joppa]

Jac at EML advises accurate filament voltage, so I would get the regulated DC filament board if you get those tubes. He also advocates using a hum pot, which Kaiju has. I'd also go for a V-cap or other quality cap between the driver and the 300B (0.1uF/600v).

Sorry, I've done very few comparisons of 300Bs.

[drewh1]

Helpful information Paul - thanks. I am leaning towards the EML. Also thinking Mundorf silver/oil for the output caps.

[drewh1]

Hey Paul,

I noticed this information on another thread.

The other issue is that EML specifies +/-4% for filament voltage, but power line voltages can vary +/-10% (sometimes more outside the US). Never fear, we have ways to adjust that voltage if necessary. You might check your power line before you start the actual assembly.

My mains measure between 125 and 128 volts. About a 6% variation. Will this need to be regulated for the EML Mesh?

thanks,

[Paul Joppa]

...
My mains measure between 125 and 128 volts. About a 6% variation. Will this need to be regulated for the EML Mesh?

thanks,

Like the Stereomour II, Kaiju has excess filament voltage which is dropped by series resistors to get the desired voltage. These resistors can be modified to deal with out-of-bounds power line voltage. The DC option is regulated so it needs no adjustment.

[drewh1]

got it! thanks again for your quick response.

[Paul Birkeland]

teflon tube sockets, Goldpoint Volume control,

I consider teflon tube sockets to generally be a significant downgrade from what we provide.

The controls on the Kaiju are for channel matching and are not volume controls, so I would also consider this modification to be a bit of a downgrade also.

-PB

[drewh1]

Ok, I'll take your input, and appreciate saving any money that isn't well spent - so besides output caps and tubes, and DC filament, are there any other places you might consider worth upgrading.

However, one of the reasons I want the Goldpoint is because I have a remote servo motor volume control, sort of a must have for me.  So is not at all possible to use the goldpoint (even if it is a trade-off)?

[Paul Birkeland]

We have left considerable room for alternate parallel feed and interstage coupling capacitors.  I wouldn't mess around with anything else. 

A remote servo volume control would go well into a preamp...

[drewh1]

duh - I didn't do my homework!

Would a passive work? The Submissive?

[Paul Birkeland]

duh - I didn't do my homework!

Would a passive work? The Submissive?

It kind of depends on what you have, and to some degree what your sources are.

A passive control tends to have a lower input impedance, which can be a tougher load for your sources to drive, and also a higher output impedance than the average linestage would have.  Do you have a link to what you'd like to use?

-PB

[drewh1]

Hi Paul - My source is an Ayre DAC with 2 v rms output. I do not need source switching as everything goes through the DAC via USB. In fact I never wired the switch in my Stereomour.

I know this seems like sacrilege but can't I incorporate a simple 100 k ohm volume control into the amp chassis between the inputs? That would be preferable to an external unit. Apologies if I am being dense . . .

[Paul Birkeland]

I know this seems like sacrilege but can't I incorporate a simple 100 k ohm volume control into the amp chassis between the inputs? That would be preferable to an external unit. Apologies if I am being dense . . .

The layout of the Kaiju makes this nearly impossible.  You can put the control in its own box with a very short pair of cables to the Kaiju, that would work nicely, though it still depends a bit on the impedance of the control you have. 

[drewh1]

100 k ohm (same as Stereomour)

[Paul Birkeland]

I would build that into a Smash or a BeePre.  A 100K control isn't going to be that happy driving cables.

You may also be able to just use the volume control in your DAC, but YMMV.