Any info on what the Smash upgrade will comprise of?

[Cleet]

I guessing C4S and read somewheres a high/low attenuator setup. Anything on the power supply? Are we keeping the 0D3?

I kind of like the big 0D3 with it's funky colored glow so I hope it stays.

And the million dollar question, how do I get on the list of the folks who get it first? 
Thanks
Cleet.

 

[Paul Birkeland]

Josh and I finished up the manual shoot last week, and I'd expect a product page to be forthcoming shortly. 

For the Smash-up, the plate load resistors are replaced with C4S active current sources.  This modification alone provides superior power supply noise rejection, lower distortion from the nearly horizontal load line, and increased gain.  Based on not having to use a resistive plate load, we also were able to bump up the bias on the 4P1L to allow for more incoming signal voltage before the onset of grid current.

In the power supply, the 0D3 is dropped so that we can install a dual mono hybrid shunt regulator, which uses a 6SN7. 

-PB

 

[corndog71]

Could a 12AU7 be substituted for the 6SN7?

 

[Paul Birkeland]

Yes, a 12AU7 could be substituted.

In the upgrade instructions, there isn't actually any need to remove the octal socket, as so few connections are made to it with the 0D3, so it stays put. 

Switching to a 12AU7 would require a socket, hole shrinker, and adjusting which components go where.

-PB

 

[Cleet]

In the power supply, the 0D3 is dropped so that we can install a dual mono hybrid shunt regulator, which uses a 6SN7. 

-PB

Paul, is the dual-mono setup needed for implimenting C4S?

I'd love to keep the 0D3 both for aesthetics (love the lights man! )and the fact that I had used MUR860's for the rectifying bridge which (to my ear at least) did add a smidgen of smoothness especially at the tops.

Can I get a copy of the revised circuit so I can have a look at the changes on the PS side?

Thanks
Cleet

 

[Paul Birkeland]

The circuit is part of the kit, and is included with the manual.

There isn't really enough current available in the stock power supply setup to run the C4S boards and the 0D3.  You'd really want to replace the 1K 25W resistor with a 50mA C4S, and the thermal load on that setup would require a massive heatsink. (Just look at how massive that resistor is in the first place!)

-PB

 

[Cleet]

Paul

I'm trying to find out how the dual mono part is implemented. Does the smash-up require a second hi voltage rectifiying bridge, or do you split the B+ into duals downstream from the bridge?

As I mentioned, I did "my own thing" on the bridge and am reluctant to undo it again. 

thanks
Paul

 

[Paul Birkeland]

The raw power supply is left alone, then split at the high voltage regulator.

 

[Doc B]

I think it might be a little bit premature to discuss a redesign before we have even delivered the first run of the product. Maybe once the kit is in the field we could take these kinds of questions up.

 

[corndog71]

The only reason I asked about the 12AU7 is that it's easier for me to get better grade tubes that have been selected for a purpose such as this.  I've had a hard time finding decent 6SN7s in the past and the good ones tend to cost a lot.

 

[mcandmar]

That is a valid point as 6SN7's can be pricy, but there is also the Russian 6H8C which is cheap as chips

 

[Paul Birkeland]

The only reason I asked about the 12AU7 is that it's easier for me to get better grade tubes that have been selected for a purpose such as this.  I've had a hard time finding decent 6SN7s in the past and the good ones tend to cost a lot.

The 6SN7 is in the power supply, I wouldn't be too worried about using a high end tube here.

-PB