Compare: Modwright LS 36.5 & Audio Research LS26

You must replace the stock 6H30's with the 6H30 DR's! This is a no-brainer and will make a profound impact, especially in bass.

You must replace the stock 6H30's with the 6H30 DR's! This is a no-brainer and will make a profound impact, especially in bass.

Interesting. As I understand it the DR's are the military-spec'd version of the 6H30 - can you elaborate on the differences between the stock version? Is there a difference in materials and or construction of the tube, or are they just culled from stock 6H30's using higher standards of tolerances? Which amp(s) are you using? I'm using Quicksilver 300B SET mono amps in a relatively small-midsize room in nearfield. Do you have a good resource for DR's? I know Conus sells'em.

Vett93 asked...

"The Modwright LS 36.5 uses only one pair of 6H30s in the signal path. However, it has both single-ended and balanced inputs. How do you do that with just one pair of tubes?"

Rather than using a dual differential circuit the 36.5 uses two Electraprint step down transformers to produce the balanced outputs.

Colopilot:
Can you explain the differences between the standard dual differential ballanced circuit and the implimentation Dan
chose for the LS 36.5? Do other designers use the same approach?

Thanks,
Jim

"Can you explain the differences between the standard dual differential balanced circuit and the implementation Dan
chose for the LS 36.5? Do other designers use the same approach?"

Probably not well enough to do any good. LOL.

I just tried to write a nice, succinct explanation but, after rereading the several paragraphs a few times, I decided I was way out of my depth. In any case...

The 36.5 uses the Electraprint transformers as phase splitters to produce the balanced signal outputs. Using a dual differential circuit would have produced the same balanced output but then that would be a whole different beast of a pre, wouldn't it?

I'll assume Dan didn't want that for reasons of cost and complexity and purity of design etc...

But I'm guessing.

The reasons for having a transformer coupled output is pretty straight forward. You get a balanced output (for CMRR) and you get a lower output impedance for driving amps with low input impedances. Are there compromises to doing it this way? Probably, there are always compromises, but someone with more knowledge than I have needs to step in to explain what they might be.

As for others doing things this way, I assume it's the standard way to get a true balanced output from a SE circuit.

Would I could be more helpful...