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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. 

buellrider97
mulveling's avatar
mulveling
1,963 posts
 

Popping/scratchy sounds on engaging the bias switches, and triode/ultra mode (I generally prefer ultralinear and leave it there), are normal. They’re loud & clear on 96dB Tannoys, but not anwhere near danger or concern for tweeters. It’s also typical on shutoff, though it shouldn’t be too intensely loud.

The hum on one side that dissipates over time is odd, I haven’t encountered that one before! Worth asking Rogue about. Definitely call ’em up to chat! Though there’s absolutely nothing here that’s too concerning to me - I’d have taken those amps to town and back by now lol.

The years in storage doesn’t concern me too much either - there’s nothing in these amps that has proven unstable or problematic, excepting any 2000s era EH KT88 - which were before the M180’s time anyways (M150's got hit by this). I’ve had one Tung-Sol KT120 lose vaccum in storage - its getter flash turns chalky white so it’s easy to spot those.

buellrider97 OP
419 posts
 

@mulveling  @audphile1 ​@jafox , we’ll here’s the latest. Got involved with helping my elderly mother and missed my window to call Rogue. However I added a streamer and a dac/pre combo that’s single ended from a headphone system. The amps had some hum, but it’s budget single ended stuff. Anyway played some music and when I cranked it up the right side had a garbled background sound that sounded like static and a dying transistor ( just my description). Switched sides on input, then switched sides on speakers , it’s definitely the amp. Also with it all hooked together, I noticed a slight ground loop issue. When I muted the source and turned off the good amp , there was a mild pop from the bad amp. I’m wondering if there might be something failing in the power supply filter that causes noise but the amp still functions. Also I went to Rogue’s website for the owners Manuel and there’s only the M-150. The 180, does not have the ground loop switch like the 150. Also I tried the 4 ohm tap and when I powered one on it sounded dead. I immediately shut it off as not to cook a tranny. Another reason to need a Manuel , are both sets of terminals connected? Anyway I’ll try Rogue tomorrow, but again, any input is appreciated. Cheers, Mike B. 

buellrider97 OP
419 posts
 

    Todays update. First off thanks for your guidance, second they’re going to Rogue for either repair or possibly a Dark Upgrade. Bill at Rogue spent 30 minutes on the phone with me while the tech listened. The amp in question went into a nasty screeching oscillating that scared everyone. They also recommended using Pirate Ship for shipping fees. Thanks to all, Mike B. 

jafox
1,466 posts
 

@buellrider97 Happy to hear of your communications with Rogue.  They got back to me quickly for the three times I had questions on the Apollos.

As for paying for the Dark upgrade, compare the cost of updating your amps to Dark vs. selling your amps once they are running well, and seek a good deal on a used pair of Dark.  Here is one example, from a dealer no less.  Notice the Make Offer option.

https://www.audiogon.com/listings/lisba80c-rogue-audio-m-180-dark-monoblock-amplifiers-black-very-good-condition-tube

buellrider97 OP
419 posts
 

@jafox , Good morning, I appreciate your idea. The bad amp definitely needs repair. I had it at best playing but with an underlying distortion that sounded like a bad driver tube. But it’s more than that because when I swapped out tubes and restarted it, the amp went bonkers and started screeching and popping at about 90 db. It scared my dogs it was so bad. It happened 3 times, 2 of which I was on speaker phone with Rogue’s staff. A ballpark figure to fix it ( guesstimate ) is about $500. A Dark upgrade would negate the repair charge and run me $2500. As great minds think alike I’ll get the Dark upgrade. Since the amps were free, it pencils out better than the ones you suggested. Plus mine are silver and match my system and excluding the current issue are in excellent condition. Cheers , Mike. 

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