TRL Dude or Joule 150 MKII for Major Pre Upgrade

Grannyring, I have an extra transformer since I went from a two-channel transformer box (both L and R channels in one box) to mono transformers (two boxes) when I moved my monoblocks further apart (although they are now closer together again). The balanced cables out of the transformers should be no more than 1M long. The ones I use are about 2 feet long. To use the one-box version, your monoblocs must be reasonably close together.

I had offered to let another member try the transformers. Since he is not having the buzz issue and I do not think he needs/wants to try the transformers right now, maybe you would like to try them and see if they help. This would be interesting information for me too, because then I would learn whether a single-ended Dude might work for me.

My plan earlier this week was to try the single-ended (SE) Dude that was up for sale on this site and if I liked it to go ahead and order a balanced Dude while continuing to use the SE Dude. I planned to use the SE version for the 3 months it takes TRL to make these and then sell it after I received my new balanced Dude. I declined to buy the SE Dude after my research indicated the 5K ohms output impedance may not work with the transformers. However, Almarg is correct, I do not believe I spoke with Bill Whitlock when I called Jensen last week.

Almarg, I know Ralph's preamps are fully balanced and would work properly with my set-up. While I respect Ralph and his company immensely, I just didn't care for the sound of the Atma-Sphere preamp that I owned some years ago. It was a tricked out MP-3 with teflon, regulated power, and Caddocks. I am aware of an Atma-Sphere preamp for sale now that is called an MLS-1 Linestage, which is apparently a one-box precurser to the MP-1. I know it is old because it has the yellow board they used early on. This pre was apparently at Atma-Sphere recently where it received; new filter caps, HV regulated power supplies, fast rectifiers, the latest 3.1 version volume attenuator, main power transformer, and state of the art copper CuTF V-Cap coupling caps, as well as a full cleaning of all controls and input/output connections. The price is reasonable but I have no idea where something like that would fall between the MP-3 and MP-1. It would have to offer something above the MP-3 I owned for me to consider trying it.

Grannyring, your issue doesn't seem to me to be a ground loop issue, as it occurs even when the preamp is unplugged from the AC outlet (and with no source components connected). Therefore I'm not at all certain that a Jensen transformer would solve the problem, which I'm frankly out of ideas on.

For anyone else who may be able to contribute ideas on Grannyring's issue, it was discussed here. Note that multiple sets of interconnect cables were tried, as well as both the Dude and Lightspeed preamps. Yet the problem goes away when the inputs to the amp are disconnected, and the problem did not occur until the previous speakers, which were electrostatics, were replaced with passive speakers.

Best regards,
-- Al

My Dude works fine with my low gain power amp. But when it was used with a pair of high gain tube monoblocks, I could hear some humming noises. So I got rid of the ground loop by floating the signal ground from the AC ground at the power amp, but keeping the chassis connected to the AC ground for safety. It has been quiet since then.

Vett93 , please help me understand what you did? I am not understanding your fix? Are you saying you simply used a cheater plug on the amp? If so, tried that also.Thanks

Mitch2, thanks much for the offer. I want to try what Vett93 is saying and I may take you up on your offer.

Al, you may be right or I may have a ground issue that is induced between gear thru the ic's .....don't know. I have another system I may place the amp into today to see what happens.

Back to the OP, the Joule will likely be easier to find here used (if that is your intent) than the Dude, simply because more have been made over a longer period of time. There is an LA 150 MkII for sale here now. I owned that preamp and it would be a huge upgrade over the Rotel. You would also have the option to upgrade it to the Signature Edition [LA-150 MkII SE] version in the future for $1,750. In addition to a very nice appearance, the Joule offers a couple of neat features that can have practical applications such as selectable output impedance of 400 and 1200 ohms, and selectable gain from 0 to 11 dB. The 6350 tubes used are no longer made but Joule has thousands for when you need more, and they are also available in other places...here is something I found about those tubes:

6350: This tube was mainly manufactured for IBM and other computers in the late 1950s to mid 1960s. Sylvania and GE blackplates are considered the best of all with this tube. It has a mu or gain factor of 18 so is very close to the 12AU7. These were made to tight specs and carefully quality checked, since replacement in a computer of the day was difficult and costly, and the tubes were expected to operate 24-7. These make impressive upgrades to the standard 12AU7!