Looking for advise regarding Rogue M180’s
Last week a friend gifted me a pair of Rogue M180’s. They were sold as 180’s and I received them from the original owner. Im guessing them to be 10-12 years old. They were used when first purchased for about 5 years sparingly. Since then they have resided on a flat dolly in a spare bedroom. The amps still have the original Phillips ECG 5751 and 5814A’s installed. The original EH KT 90’s are loose in a box with an octet of low hour Gold Lion KT-77’s . Years back when in use the owner contacted Rogue and stated they were too powerful for his room size and speaker selection. Rogue responded by recommending the GL KT77’s and suggesting that he could also lower the bias from 40ma to 30ma. I was provided the supporting emails dated September 2019. Here is my situation followed by my questions. I currently have a low power single ended system with Zu speakers. Second, the owner stated one might have a hum, but was not sure. He’s on his second complete system since and has a room full of gear he’s lost interest in and his memory is vague. Also back then he had power issues with his provider and stated they installed a new transformer on the street. So my questions are first, checking for any hum. My intent is to take a single amp and connect one JBL 4312 to it. Install the KT77’s, plug it in and listen for a hum and bias the tubes. Do I need the input open or shorted ? Or something else ? Second, the 12AX7’s being replaced by the 5751. I see there’s a mu of 70 Vs 100 with the 12AX7. Does that effect the overall output power of the amp or just change tone and distortion? FWIT I have 6-7 pairs of NOS Telefunken 12AU7’s but zero 12AX7’s. My intent is to check for hum without causing any damage. If a hum exists, I’ll ship to Rogue. In the short term if I’m successful, I’ll test drive with my existing Rogue RP-1, the JBL 4312A’s that are mint and the 26” Sound Anchor stands I have with them. And I’d like to get some Telefunkens to put in the 12AX7 positions. After that, there’s a pristine Rogue Hera that’s been inspected and re tubed by Rogue that I’ll ask to purchase before I start looking for speakers worthy of the pairing. Also I emailed Rogue for support a week ago and have not received a response. Thanks in advance for any feedback and my apologies for grammatical spaghetti, but I’m limited to an IPhone. Cheers , Mike B.
Make sure all the tubes are seated. Plug the amps in and connect them to your jbl speakers. Power them on with no signal flowing thru. Let them warm up for 30-45min and adjust bias. Leave them on and see how the bias holds. If no noise try them out. As to Rogue support…just call them. My experience with these guys is very positive. I dealt with Nick and Mark there when I had RP1 and ST100. Good sounding electronics. Best of luck. |
First off - WOW, nice gift!! The og owner’s claim that the M180 was "too powerful" is a bit odd, and Rogue’s response to them was equally odd. These amps have a very high gain, and that is the main issue when paired to high efficiency speakers. Compounding this - Rogue doesn’t make the quietest tube gear. Yeah - hums and tub hisses are quite common with high sensitivity speakers. If it’s not noticeable from your seating position then don’t worry about it. I’ve long said Rogue should use a 2nd reference system with high efficiency sepakers, so they can hear some of these issues. That said, Rogue can still make some great sounding and high-value tube gear. It’s perfectly fine to turn on the amp with input open / unconnected. Just make sure it’s hooked up to a speaker - DON’T turn a tube amp on without a load connected to its binding posts. Also don’t connect or disconnect its inputs while it’s on. The 5751 sub is a good choice for a couple reasons: 1. they have a different sound quality than 12AX7, with more precise imaging at the expense of image size. 2. they have a lower gain by about 1-2dB, which will help in your case. You can also sub 12AY7 and lose another dB or 2 of gain. The KT77 sub (and bias adjustment) is fine, but not strictly necessary. The EH KT90 tubes sound a little bright and lean / dry through mids, so you might well prefer GL KT77. An RP-1 is not anywhere near the performance level of those M180. The Hera is one of my favorite preamps ever - but it’s got a very high gain, so you’ll probaly be cutting its gain knob all the way down. And you’ll still probably be hearing some tube-rush "hisss" through your high sensitivity speakers - even from your sitting position. You’ll also hear that trademark "pting-tashhhhhh" sound of its 6H30 tubes when they’re disturbed (mute / unmute). But past that, I think it should be an amazing sounding combo! I preferred Hera to their current flagship RP-9. The RP-9’s sound reminded me a lot of those EH KT90 - not bad, but not my thing. |
@audphile1 , Thank you for your input, your experience with a vast amount of gear and your straightforward recommendations are always appreciated. @mulveling , I was hopeful you’d respond and save me sending a PM. I’ve long read your advice and admired your equipment. Your knowledge of tube gear including Rogue is greatly appreciated. Your comments on small tube sound characteristics has been invaluable to me. I was concerned about the input being open Vs closed by means of a shorted input connector. Having read online I noted in guitar amp forums it was stated to short the input when checking for hum. As I’m planning on using the JBL’s, I’m not too concerned with the noise I get with high dB speakers like my Zu and Klipsch. I also didn’t realize the the Hera had such a high amount of gain and that would explain the original owners complaints of too much power. FWIT the original owner was formerly a dealer that changed careers and went into estate law. I know he carried Rogue, Modwright, Acoustic Zen, and Dali. He once loaned me a Modwright KWI 200. After the Rogue gear he had a full quiver of Bryston with Dali stand mounts and JL Fathom subs. His current system is Macintosh and B&W’s. His room is treated with GIK items. I couldn’t live with those B&W’s, the tweeters are deadly. |
