[tomchr]

Quote:

Do you know if the 300B can be interchanged with a 2a3? 

 
Not without a few component substitutions. See the "Output Tube Options" section of my DG 300B site. The operating point for a 2A3 is quite different from that of a 300B.
 
~Tom

 

[Tjj226 Angel]

Quote:

 
Not without a few component substitutions. See the "Output Tube Options" section of my DG 300B site. The operating point for a 2A3 is quite different from that of a 300B.
 
~Tom

 
Gotcha. 
 
I am trying to study up on designs like these. Next summer I hope to design a 300b mono block myself and try to throw as many western electric parts at it as possible. 
 
One big question I do have is the use of polarized capacitors. A friend of mine designs amps, and he bends over backwards to avoid using polarized caps in his designs so that he can use paper in oil capacitors. 
 
Were polar caps just unavoidable in your build, or did you use them for a greater purpose? 

 

[tomchr]

Quote:

I am trying to study up on designs like these. Next summer I hope to design a 300b mono block myself and try to throw as many western electric parts at it as possible. 
 
One big question I do have is the use of polarized capacitors. A friend of mine designs amps, and he bends over backwards to avoid using polarized caps in his designs so that he can use paper in oil capacitors. 
 
Were polar caps just unavoidable in your build, or did you use them for a greater purpose? 

 
Good luck with your design. The 300B is a very challenging tube to drive. My DG 300B is the pinnacle of about three years of research, design, simulation, and experimentation. I outline some of the challenges on my website.
 
I tend to approach design with an engineering mindset, hence, I specify components that will work well in a given application. I try to avoid capacitors in the signal path, but if I have to use a capacitor in the signal path, I use one with polypropylene dielectric. Polypropylene has very low dielectric absorption and low voltage coefficient, hence, these caps are basically sonically transparent. 
I use electrolytic caps in places that are out of the signal path - or where the non-idealities of electrolytics don't impact the circuit performance, but where a high capacitance/volume ratio is handy. The power supply is a good example of such an application.
 
Feel free to have a different opinion or choose different tradeoffs in your design. That's what DIY is about...
 
~Tom

 

[tomchr]

You can also find a bunch of my design musings here:
 
DeathTrap400™ : : A Pretty Damn Good 300B Amp
300B (and other DHT) Biasing Options
 
~Tom

 

[sceleratus]

Ya know what sux?  I'm on an island with my DG 300B.  There's nobody to compare "notes" with.
Somebody, please build one.  You will be rewarded. 

I Promise. 

 

[tomchr]

"On An Island". David Gilmore. Great album!
 
Oh... Not what you meant. I agree. Build them amps. Let us know what you think.
 
~Tom

 

[nelamvr6]

Quote:

Ya know what sux?  I'm on an island with my DG 300B.  There's nobody to compare "notes" with.
Somebody, please build one.  You will be rewarded. 

I Promise. 

 
 
Why don't you build one for me?  How much for one in mahogany? 

 

[NoPants]

what was the all in cost of the build if you dont mind me throwing it out there without examining the thread in detail? im curious to drive my k1000 with these but i think the opt boards and tubes are already north of 1k right? i wouldnt build this for someone for less than 3k, all things considered

 

[sceleratus]

Quote:

what was the all in cost of the build if you dont mind me throwing it out there without examining the thread in detail? im curious to drive my k1000 with these but i think the opt boards and tubes are already north of 1k right? i wouldnt build this for someone for less than 3k, all things considered

 
Here's almost the "all in" costs.  I posted it many pages back.
The cabinet doubled the cost and I upgraded to some handmade resistors and fancy caps.  Plus changing to a balanced interface added the cost of a 4 deck stepped attenuator.  I'm waiting on that and yes the valves.
 
Not for the faint of heart.
 

 

[Fearless1]

Quote:

 

Absolutely beautiful! I had no clue of the size until I saw it next to that piece of Schiit. 

 

[sceleratus]

Quote:

Absolutely beautiful! I had no clue of the size until I saw it next to that piece of Schiit. 

The mini LCD's are nice too.

 

[sceleratus]

Oh..... "Thank you" !

 

[tomchr]

I think it is possible to squeeze in below $1k, with only a slight reduction in sound quality. If you forego the differential input (no Jensen transformers), use output transformers from Edcor (their CXSE series is quite good bang for the buck), and machine your own chassis components, you'll land at about $1k.
 
That said, if you're spending that kind of money why not go the extra mile and make it truly high-end as sceleratus has done. Not counting the chassis parts, it's 'only' $400 more... And note that sceleratus did find that using differential inputs did improve the sound quality (that's why I built the circuit that way). What's $400 in the HiFi world anyway. And oatmeal really is quite nutritious. The family will love it!
 
It's a high-end amp. This has been confirmed by the many comments on it from the LA meet. A lot of people really liked it and posted rave reviews.
 
~Tom

 

[holland]

Quote:

Ya know what sux?  I'm on an island with my DG 300B.  There's nobody to compare "notes" with.
Somebody, please build one.  You will be rewarded. 

I Promise. 

 
I'm thinking about it, but it'll be pretty far back in the queue of things to do.  I'm also thinking about ways to make it more "useful" to me.  That is a headphone and speaker amp.  Custom wound transformers for sure with various taps and auto-switching circuitry for headphones and speakers, with multiple taps for headphone Z.  However, I'm not sure I want to change the plate load too much on the output tube, especially since headphones vary so much in impedance the load will change by default.  That brings up problems with gain, unfortunately.
 
So, still thinking, maybe a 2014 project.

 

[sceleratus]

Quote:

 
I'm thinking about it, but it'll be pretty far back in the queue of things to do.  I'm also thinking about ways to make it more "useful" to me.  That is a headphone and speaker amp.  Custom wound transformers for sure with various taps and auto-switching circuitry for headphones and speakers, with multiple taps for headphone Z.  However, I'm not sure I want to change the plate load too much on the output tube, especially since headphones vary so much in impedance the load will change by default.  That brings up problems with gain, unfortunately.
 
So, still thinking, maybe a 2014 project.

Wow.
You are the guy to pull it off.
 
Yup.
Jack at Electro-Print wound these for Audeze LCD2's.  50 ohm I think.
Jack can do Anything and although I have no experience with other OPT's I am glad I had him make them.
Very Old School.