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.

 

[drewh1]

Hi Paul - BTW, I really appreciate you spending this much time on this issue. I am really trying to keep my system simple. unfortunately my DAC has been made with the same philosophy and does not have a volume control. I would prefer to build an external passive volume control since I do not need additional gain or source switching. If you could tell me the input impedance of the Kaiju, I'll figure out what I need to use and build it into a separate box. I can use my servo on any Goldpoint and can build one to match the necessary impedance. I am able to keep the interconnects very short so that shouldn't be a big issue. 

thanks again for your time with this.

 

[Paul Birkeland]

Your DAC has a heroically low output impedance (something like 70 Ohms), and the Kaiju has 100K input impedance.

A passive control that was in the 10-15K range between the two should work well. 

If you need long cabling anywhere in the chain, I would recommend having it between your DAC and whatever is feeding the DAC, which would allow for the DAC itself, level control, and amplifier all to be fairly close together.

-PB

 

[drewh1]

thanks Paul!  I also may have found a solution that takes out any additional circuitry in the signal path. I can control the volume digitally with J-River. Should have no impact on quality at all. I have been playing with it with my Stereomour. I just have to find a convenient way to access it remotely. So I have options. Anyway, I am now super excited about building this amp and can't wait to start ordering (after the first of the year!)

Really glad you guys do what you do. Happy New Year.

 

[jdm]

drewh1

I am using dual 10K mono Goldpoint ladder type attenuators between an Ayre QB9 and Paramount 300B amps (original version with 12at7) with no problems. Interconnects are 2 feet long from dac to attenuators and 3 feet from attenuators to amps.

Jim 

 

[drewh1]

Great to know Jim - thanks.  I am going to go with Goldpoint so I can attach my servo motor to it. I have my DAC and amp located next to each so I can get away with very short interconnects.

I am interested in the digital volume with J-River, but am reading conflicting reports about quality impacts. imagine that in the audiophile world

BTW, I just got the DSD upgrade. I had the old 96k version. It really is worth the money, takes the QB-9 DAC to a whole new level. Not a subtle improvement, and way cheaper than buying a new DAC. Highly recommend it.