Personal comparisons of valves suggested for DRD

[Paul Barker]

Jack in his first article on 300b DRD suggests 6n1p similarities found to E88cc parallel or 6aq8 similarites to ECc85 I’m planning D3a.

Anyway ECc85 and Russian version both have too high ri of 9k7, even parallel they are a poor choice because of the inductive load affecting the gain. But they are the outright winner on low input capacitance. If it were only one parameter that matters ecc85 is a star. The e88 cc and 6n1p are close in ri even after paralleling, and no worse than D3a ref. Capacitance. So a parallel e88cc of which I have a ton is viable.

But because gain matters when you are limited in anode volts (the nature of direct coupling) gain matters dominantly.

So I’m still with the D3a on the matter. At 57 mu the ecc85 is nearest to 77 but the stumbling block is almost 5k ri parallel.

Its clear D3 a is winner. But then the sound nature of the input valve driver contributes more to sound than the output valve according to many over the years.

I’m just going to have to hope it sounds great. I’ve never heard it in this position at home. Though I couldnt fault an amp Mark used it up front of. So I guess its a good gamble.

BUT the EL38 se I made sounds great and uses e88cc. I also know Morgan likes it.

I’ll just have to wait and see if all the versions output valves utilising D3a going forward are lacking sound quality because.

Another present obstacle is out of the 20 odd hammond 56C’s I have only found two so far. Ho hum.

First amp for DRD is 6em7 so 1 will be ok to learn from.

[Paul Barker]

http://vinylsavor.blogspot.com/2012/12/ ... h-d3a.html

Well I’ve found a few fans, and one of them uses it to drive a el34, the rest are all phono stage most 600 ohm lcr fans. But one just a normal phono stage.

So I’ll press on with D3a.