Edcor GXSE-5-15k or WSM 15k:600. Recommendations for preamp output?

swimtoview said:

Hi Ian,

Great to hear from you and thanks so much for the info!  I'm trying to get settled on all my build projects, and I've about decided to do a couple RCA builds for a more colored tube pre and probably 4 of your Classic design for a more linear set of tube pre's.  Does this sound like a good way to go?  It's a long term project, but I'm hoping to have most of the gear in my studio built by me in the end.  Your tube mixer with the Helios makeup gain eq's will be the centerpiece for sure.

Thanks again -

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swimtoview said:

Hi Ian,

Great to hear from you and thanks so much for the info!  I'm trying to get settled on all my build projects, and I've about decided to do a couple RCA builds for a more colored tube pre and probably 4 of your Classic design for a more linear set of tube pre's.  Does this sound like a good way to go?  It's a long term project, but I'm hoping to have most of the gear in my studio built by me in the end.  Your tube mixer with the Helios makeup gain eq's will be the centerpiece for sure.

Thanks again -

Hi, RCA OP-6 with all that gain makes no sense this days because you would be amplifying and attenuating all the time, even with ribbons. It is quite difficult one to build because material isn't that easy to get, cost is high with probably custom choke, psu has to be very good, etc.  From RCA something like BA-2 is very easy and sound excellent on many sources. Cinemag has quite a few transformers for output, they are cheaper than Sowters and perform very well. I prefer their 50/50 core. If it is not on website they are very nice to talk to and always check schematics before giving recommendations. There are a few other RCAs, BC-3C console's preamps can have quite high gain, but ~50dB from BA-2  is enough for almost any situation we encountered...
Ian's Classic would be much, much easier and cheaper. It is also good learning experience because of all information shared about it. And as Ian said, you could do SRPP or Mu Follower, depending on your drive needs. Most people don't need to drive 600 ohms, 10k or more is typical today. Iirc, either output configuration could be built and compared on same pcb.
It seems like both configurations would work without output transformer which is interesting thing to try. I really like EMRR's WE-141A/Gates SA-70 mash-up, output is cathode follower which doesn't need output transformer. Cheap, easy,  good sounding build with enough drive too. Iirc EMRR used OT anyway, probably to get some more drive. I'm not sure if it is really needed.

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AusTex64 said:

If you're going for the "RCA sound", consider using a UTC A-10 or similar for the input transformer. I feel the Jensen is a bit sterile in this application. If you were going for "pristine and clean" the Jensen might be a better choice.

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My3gger said:

I have one vintage US transformer very similar in specifications to A-10, could be pretty much the same thing and sound. Seems like it doesn't have early 1% THD like Jensen at about -2dBU/20Hz. Is this your observation too? A-10 like transformer works more like Cinemag CMMI-10C, although later seems cleaner at lower levels, a bit like Jensen. I also like it because of 50 ohm tap, similar to V72 input.

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