Great gift ! hopefully they are fine, if not i know of a great tech in Orange county, just finished hotrod of RM-9 and a big SS Accuphase for friends.
One other word ; Mullard
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.
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@buellrider97 My last set of Apollo monos (I had the og verison first, before Darks) had a minor hum on one side, into 96dB Tannoys. It was minor enough at seating position to ignore. As someone else mentioned, once the music starts it's gone and that's often good enough for me. I'd say there's a higher incidence of Rogue gear having little stray hums here and there, but frankly the hum and/or hiss is going to rear its head at some point when exploring tube gear, no matter the brand(s). Rogue tube gear generally gets you lots of gain and killer dynamics, bass, and slam - at some expense to noise floor and a "drier" midrange than most tube gear. I said to test w/ inputs open, and that's always worked for me. I don't find shorting necessary; it should be quiet enough even open, at the amp level (nothing downstream to further amplify stray RF/EMI pickups). But it would be fine to test inputs shorted too, if you choose. Yes, the modern KT90 has the EH label, not Tung-Sol. Rogue never shipped the older Ei KT90 tubes - they used EH KT88 back in the 2000's before they started getting some REALLY bad batches from Russia and switched to KT90 which were fine (the EH KT88 issues have long since been resolved - nice tube). I'm generally a big fan of Tung-Sol KT120, but Rogue's big tube monos seem to benefit more from the GL KT88's sweet midrange (and KT88 in general). I often prefer KT120 in VAC amps, but usually KT88 in Rogue. You just have to try for yourself - these Rogue amps facilitate quite a range of power tubes with their per-tube bias trimpots - I LOVE this feature! Again, great "score", and what a great friend - enjoy! Try to give the Hera a listen. It's not for everyone, but will always be one of my top favorite preamps, and I think it's a killer combined with M180 or Apollos. |
@buellrider97 - I goofed. No idea why I entered KT90 tubes above. The Apollos came with 12 KT120 TungSol tubes . I saw a tube site a couple weeks ago with a great sale on KT88's. But I thought I'd enjoy the Apollos for awhile before I look to compare other power tubes. Find a preamp with the sound you like rather than worry if it is balanced or not. And the IC that you use between the preamp and the M180s will greatly determine whether you hear the amps' capabilities or not. |
@tomic601 Hi, thanks for the input. I have the factory packaging and if a repair is needed I’ll ship to them. That being said , I really enjoyed your system pictures. You have some cool collectibles. I love your Mac amps and the other retro gear. Nice mount, it doesn’t look like a Rainbow, may I ask what it is ? I float tube fly fish at Lake Almanor in the fall. I’ve fished Monterey Bay my whole life, and currently pursue Tuna from San Diego. One last question, do you fly ? My son in law flew a Rhino at LAS Lemoore. Now he’s a T-45 instructor in Florida. Between fishing, hunting, target shooting and motorcycles I’m lagging on audio gear. Father Time is catching up with me and I have a lot more time for listening to music. Regards, Mike B. |
@mulveling @jafox Well I have them both powered up. The inputs are open and they’re biased at 40ma and holding steady. They are absolutely dead quiet. However I have encountered an issue. The first amp was great, no hum, and no popping. The bias was at zero for all four tubes so I set it at 30, let it sit for another 30 minutes and set at 40. When I flipped any of the four meter switches or the Triode/ Ultra linear switch, it was quiet. After an hour I hit the off button and it quietly shut down. However on the second amp it started with a very slight hum that went away. The 4 bias switches caused the amp to make a popping sound as did the Triode/ Ultra Linear switch. After about an hour the hum went away and only 2 of the bias switches cause a popping sound. When I pushed the off button it made a moderately loud pop and shut down. I came back after letting them cool and started both of them again. Both dead quiet, bias good. But I still get a static sounding pop from two bias switches on one side, the same sound when I flip the Triode/ Ultra Linear switch either way. And the pop upon shutdown. I’m leaving them powered on overnight. After all, they’ve been unused for 6-7 years. Tomorrow I’ll call Rogue as they never responded to my email. I want to get their thoughts before I add a source. I’ll post my findings. Regards, Mike B. |
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