[corndog71]

I recently finished building Bob Latino's ST120 which is a beefed up version of the Dynaco ST70 but geared for KT88/6550/KT120.  It has a three-tube, low gain driver section made for the 12BH7.  While Bob is partial to the classic Dynaco chassis I opted for my own layout and chassis.  The main reason I got a bigger box was because I wanted to use Clarity Cap TC series 700V film power supply caps.  They worked so well in my modded ST35 along with RAM tubes I had to use them in the ST120 kit.

While I wanted to get all RAM tubes I also live on a budget and in case I made any mistakes I needed a cheaper set of tubes for testing.  So I got some 6550's from Upscale audio.  I had a few 12AU7's on hand to try in the driver section.   At first I tried an ElectroHarmonix feeding a pair of NOS RCA cleartops.  Then I remembered I had a newish Genalex 12AU7 and threw that into the voltage gain stage.  It was better but overall the sound still seemed a bit diffuse.

Then my RAM 12BH7's arrived and I put those in.  They immediately seemed better but it wasn't until a few nights later when I could relax and really listen that I found them to sound amazing!  Soundstage width and depth is the best I've ever had in my rig!  I had no idea driver tubes could make such a difference.  I still want Roger's KT120's but I have to save up for them.  For now it sounds pretty damn great and Roger's tubes once again have blown me away.



And a shot of the guts for those that care.

[Roger A. Modjeski]

Thanks for the compliment on the RAM tubes. I checked Upscale's price and we to charge a bit more ($25) per tube. However I personally test all the tubes these days and do a lot of weeding out, sometimes whole batches go back due to too much grid leakage or poor cathodes (low emission and high sensitivity to filament voltage). I doubt Upscale does this.

[WireNut]

Heard that. When I get ready to re-tube my Sonic Frontiers SFL-2 preamp (soon) I'll be seeking out Roger. Never purchased from RAM before but with what I've been hearing about how good Roger checks his tubes I need that kind of service. My left channel always seems louder then the right in my preamp. I think its because the two tubes used in the gain positions don't provide the same gain even tho they are both Siemens.

 I have about 7-9 Siemens 6922 tubes, some came with my preamp, and two of them I bought about a year ago. But now they are all mixed up and I don't know which ones are good and which ones are crap. Wonder if Roger could test them all for me for a fee and find a few good ones that match for gain and noise
 
 The first four tubes I'd like to replace in my SFL-2 preamp are used in the non-critical positions. I believe they are used as cathode followers and don't provide any gain. Problems is I'm not sure what to buy for those positions or how much I really need to spend on tubes in those locations 

Hopefully Roger will read this and give some recommendations.

Here's a photo. The tubes used can be 6922 or 6DJ8's. Mixing both types is not a problem as long as they are matched pairs.
Looking at the tubes from front to rear, the front 4 tubes are the non-critical tube locations and don't need to be mega-buck tubes.
The next two tubes are the most critical locations and provide the gain which need to be the best sounding tubes in the preamp.
Lastly, the two tubes at the rear of the unit (behind the gain tubes) are important and should probably be very good sounding but not as critical as the two gain tubes.