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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. 

128x128buellrider97
hiend2's avatar
hiend2
456 posts
 

Did you send in the 180's for dark upgrade

buellrider97's avatar
buellrider97 OP
431 posts
 

Good evening gentlemen, here’s the latest on the M-180’s. I sent them both to Rogue with a memo to repair/ upgrade/ retube/ return. That’s a lotta R’s 😆. Anyway I received a call yesterday and they were repaired. The one that malfunctioned had a bad resistor in the circuit that carries the signal from the 12AX7, hence one side of the tube wasn’t in play most of the time. This explains why it had a lower volume and a slightly distorted sound. Rogue also replaced the bridge rectifiers in both units and said they were working, but tired. They said that’s a common long term maintenance issue in their amps. Unfortunately a written request for upgrades was not sufficient to do the Dark upgrades. So I verified the dark upgrades and some new power tubes. So I’m back in the queue with an expected completion about 10 more days and then a week traveling home. In retrospect the amps popped when I first fired them up every time I hit the triode switch and turned them off. After a few days of experimenting with them this subsided. I think it was partially due to the weak rectifiers. Rogue also stated that the inner part of one chassis was tweaked from one being dropped on its side while boxed during transport. Apparently being bolted to the board while boxed only minimizes chassis damage. They were also adamant against buying any Russian power tubes that are currently produced. They said the failure rate is astronomical. They are being retuned with Psvane KT-88’s which is ok for now and gives me some stock tubes to set aside.  I’ll post when I receive them and try them out. Regards, Mike B. 

mulveling's avatar
mulveling
2,043 posts
 

@buellrider97 

Awesome, glad they're gettng the care they deserve, though the extra delay for upgrade is annoying. 

So my initial "everything will probably be fine" advice was completely wrong. Sorry about that. The bridge rectifiers in tube amps can take a lot of heat, so that makes sense. The other resistor being bad is an oddball but it happens. 

That's concerning about the current Russian tubes - I know they had serious issues circa late 2000s with EH KT88. Then smooth sailing (relatively) for a while with EH KT90 and TS KT120. Hadn't heard about the latest issues yet, but I guess it's not too surprising. It's a shame because Gold Lion KT88 were becoming the popular favorite for their sonic match to Rogue amps. 

I've never trusted Psvane power tubes (lots of isues with past KT120 attempts etc) but times do change!

How's your Hera?? Love mine. It shares duty with a $30K VAC Master in my 2 systems. I would say the ARC Ref 6, 3SE phono, Hera and Athena are all great examples of the "6H30 sound". Rogue's current flagship RP-9 did not sound like 6H30, to me, despite using these tubes. 

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