Music Reference RM9 MK II

0 Members and 1 Guest are viewing this topic. Read 4685 times.

dhunte21

  • Jr. Member
  • Posts: 34
Music Reference RM9 MK II
« on: 27 May 2011, 01:35 am »
Ok! So where do I begin, I was given this amp by a good friend who parted out several pieces of his equipment. Now first off this this is HEAVY!!!

I have a few questions, first off when I power the amp up I get a like a kind of a Bong noise from the transformers, is this normal. There is also a very low level hum from the trannies, you can also hear it through the speakers, I gets lower as I move the gain switch to low and louder as I move the gain switch to high. There is also a very little low level buzzing in the speakers, I realize that as I move my IC's away from the trannies it seems to get lower! Odd place to place the input jacks. what I did notice is that 3 of my 6922 tubes tested at 30 percent while one tested at 80 Percent. The tubes I would have to say are original due to the fact that they have RAM on them.

I am not new to tube amps as I have several, but this is my first Music Reference and I was wondering if this is normal with this type of unit. Also I take it there is no way to Bias each tube on individually. What is the best way to Bias this beast. I bias until the red light just begins to come on, is this on the low side?

Also I seems as though 4 tubs on one side were also replace due to the fact that 4 of the el34 has RAM on them and the other 4 don't. Any recommendations here, Plus I would love to use KT88 or KT66 tubes, is this possible?

Well I think I pretty much covered any concerns that I might have. Any help will be greatly appreciated.

Thanks in advance

Clio09

  • Industry Participant
  • Posts: 127
Re: Music Reference RM9 MK II
« Reply #1 on: 27 May 2011, 02:21 pm »
Congratulations on your acquisition of an RM-9 MkII. In regards to your noise issues I first want to say this is not normal and an exception with Roger's designs as building quiet amps is one of his specialties IMO. I have owned an RM-9, and currently own an RM-10 MkII and EM-7 v12, all of which were/are extremely quiet.

My guess is the tubes may be the culprit of some of the noise. How do the output tubes bias? Can you get the driver tubes to match using the pots on the amp? You mentioned some of the drivers tested better than others.

In any case I would recommend you get the amp re-tubed and only buy tubes from Roger. As for the amps inputs, they are positioned such that the transformers can cause some interference. Roger at one time recommended to me using shielded cables and showed me how to position them to reduce the potential for noise.

As for the transformer noise best to talk to Roger about that. Hope things work out for you with this amp. It is a very good amp that you should enjoy for many years.

Scottdazzle

  • Industry Participant
  • Posts: 1057
  • ModWright WyWires Daedalus Skogrand VPI Zesto
    • Vivahifi.com
Re: Music Reference RM9 MK II
« Reply #2 on: 27 May 2011, 06:31 pm »
dhunte21,

I had a similar noise problem with regard to interconnects when I had this model of amp.  Two things helped: 1. be sure to use shielded cables, and 2. find a way to keep them angled away from the transformer.

You should get new sets of matched tubes from RAM Labs.  After that, you should be able to tell if the amp has problems requiring a repair.  Good luck.  That's a fine amp.

Scott

rbwalt

Re: Music Reference RM9 MK II
« Reply #3 on: 27 May 2011, 10:35 pm »
i to had some noise problems with my MK2. mine use to make the same noise when i turned mine on. i had some transformer hum also. just the way it is. try to keep the interconnects away from the transformers if possible. on to the tubes: order up a complete new set of tubes from roger as he is simply the best at testing and grading of tubes. rogers favorite tube is the siemens nos el34. i would send the amp in to roger and have him go over it. one of the problems with the Rm9 series is that the driver tube sockets can work loose from the circuit board. this happens due guys who love tube rolling. also the bias setting pots are a problem on the amp. the have a very short rotation life and can get dirty along with the push buttons. stay with roger on this amp as he knows it from top to bottom. after all he designed  and built it.

i now have a RM9SE and it is dead quiet! enjoy it as i did with mine. i had mine for 11 yrs and had some siemens  nos el34's in it and they lasted for the 11 yrs!

rob.

dhunte21

  • Jr. Member
  • Posts: 34
Re: Music Reference RM9 MK II
« Reply #4 on: 27 May 2011, 11:17 pm »
Thanks for the input!! I did give the amp a once over and checked the trace on the board as well as looking at the solder joint on all tube sockets, all check out fine. The amp Bias well and holds the bias and balance quite well. I am to try 4 new 6922 tubes as the ones I had 3 seemed to check out poorly on my tube checker. I know that most tube amps trannies have slight hum, I will try to use some shielded IC's and see how they sound, but I really think that problem might lie with the tubes themselves.

Thanks for all the input.

rbwalt

Re: Music Reference RM9 MK II
« Reply #5 on: 28 May 2011, 01:58 pm »
just remember the driver tubes are not interchangeable.you can not put tubes that are for V1 into V2. V2 tubes do not have to be as highly graded as V1 tubes. get your tubes from roger as he matches them much better than others. as far as your tube checker goes it will not be able to test the tubes parameters as well as rogers  can.

rob.

dhunte21

  • Jr. Member
  • Posts: 34
Re: Music Reference RM9 MK II
« Reply #6 on: 28 May 2011, 11:18 pm »
Ok, ok, ok, now you totally threw me off, on my RM9-MKII the amp uses 4 6922 tubes, now which would be considered V1 and V2. It take it that V1 will be the two front sockets and V2 will be the 2 rear sockets. Now why is it that the tubes can not be interchanged, aren't they pretty much the same tubes, ie plate, heater values?

I just need a little bit more understand of the amp. Granted its my first Music Reference, and I'm trying somewhat to understand the construction. What is V1 and V2 are they Input Stages? And if so why the change in tolerance in the 6922 tubes?

Things that make you go Hum!!

rbwalt

Re: Music Reference RM9 MK II
« Reply #7 on: 29 May 2011, 02:20 pm »
yes v1's are the front tubes. if you get matched tubes for V1 and V2 the tube grade and specs for V2 are not as critical as V1. as such they should not be switched. go to music reference/ram labs and read up on tube matching and you will see what i mean. no one tests and grades tubes like roger does.

rob.

dhunte21

  • Jr. Member
  • Posts: 34
Re: Music Reference RM9 MK II
« Reply #8 on: 31 May 2011, 03:57 pm »
Thanks Gentlemen for all your input, I will take it under my wing. I will be changing out those bad tubes, and purchasing some new ones from Roger. Now as far as the output tubes, they all are original Rams, I did test them and they tested good.

Can I use KT88, or KT66 tubes with this amp without doing any damage? I have an 8 NOS KT88 G.E.C that was given to me by one of my good friends. He's not a tube guy, they were his dads and he had no use for them.  I have never heard of them, anyone have any idea if there are any good. The said made in England.

Thanks in advance.

Ericus Rex

Re: Music Reference RM9 MK II
« Reply #9 on: 31 May 2011, 06:48 pm »
You can use EL34, 6CA7, 6L6, KT66, KT77, 6550, KT88 (have I forgotten any?).  You'd just need to change the bias for the different tubes.  I think Roger is recommending 30mA for the first four listed and 40mA for the others.  I've had the EL34s, KT66s and KT88s in mine.  I preferred the KT88s.  The only catch with using your GECs is that this amp must have matched-gm quads.  If your tubes aren't matched for gm then DON'T install them, you'd end up burning out the ones that do most of the work.  And at their current prices you don't want to burn out any of those!

hoppy08520

  • Jr. Member
  • Posts: 21
Re: Music Reference RM9 MK II
« Reply #10 on: 31 May 2011, 07:25 pm »
OP, it may take you a little while, but I'd recommend scanning through some of the posts in this forum as there have been quite a few threads where people compare the various tube options for the RM-9.

I've read almost all the threads on that topic because I was in your shoes asking the same question, and at this risk of mischaracterizing the overall theme I've picked up from these threads, here's my summary of the collective wisdom (so to speak):

  • I think people generally prefer the EL34 for this amp, but there are also some who like the KT88 or the 6550.
  • I'm not an authority, but I've picked up a general feeling that RM designed the RM-9 around the EL34, so even if it works very well with other tubes, something about the design is optimized for the EL34.
  • A lot of what people say about these tube types in the RM-9 is similar to how people characterize these tubes in general, for any amp. So if you read in a general forum where someone says, "The 6550 tube sounds << zzz >> to me", you'll read the same things said about that tube in the RM-9.

Also, you might want to buy the manual (http://www.tubeaudiostore.com/rm9maricoled.html) for the RM-9 because it might answer some of your more technical questions and it has the schematic.

Good luck and enjoy the amp.

Roger A. Modjeski

Re: Music Reference RM9 MK II
« Reply #11 on: 4 Jun 2011, 05:45 pm »
Thanks to all for helping out this new owner. You are doing a fine job!! I'm still sorting things out in my new home/lab. There is still a lot to do.  Make sure he knows about testing the amp with shorting plugs to determine how quiet the amp itself can be. This is the ONLY way to eliminate cable and preamp noise.

wilsynet

  • Full Member
  • Posts: 1201
Re: Music Reference RM9 MK II
« Reply #12 on: 4 Jun 2011, 06:03 pm »
I have an 8 NOS KT88 G.E.C that was given to me by one of my good friends. He's not a tube guy, they were his dads and he had no use for them.  I have never heard of them, anyone have any idea if there are any good. The said made in England.

My understanding is that the GEC KT88 and KT66 are legendary.

dhunte21

  • Jr. Member
  • Posts: 34
Re: Music Reference RM9 MK II
« Reply #13 on: 16 Jun 2011, 03:29 am »
OK! So today I had a big surprise, I got some matched 6922, and installed them, the amp was almost dead quiet. The only problem is when I am trying to balance the two sides and I depress the button there is quite a loud pop in my speakers.

The Left side balance quite well, but what I have noticed is that i have to depress the button quite hard on the right side and it seem as though when I did that the Bias light flickers and blow the fuse on one of the tubes. Now what can the problem be. But on playing the amp I have not problems at all.
Can someone tell me the purpose of the balance control and how critical is it.

Thanks

rbwalt

Re: Music Reference RM9 MK II
« Reply #14 on: 16 Jun 2011, 02:01 pm »
remember that the pots for balancing the driver tubes have a very short rotation life( about 100 turns). now the push botton's  can get dirty. try spraying some contact cleaner down into the button and move it around the best you can. this will help clean the contacts. also make sure that the driver tubes are seated properly. i know this sounds silly but do it anyways. on the rm9's the driver tube sockets are soldered to the main board. they can become lose if the fellow that had it prior to you did allot of tube rolling. if you still have problems giver roger a call or e-mail him about it and he will give you the skinny on it. i would only get roger's advice on it. after all he designed it and built it. if you wondering how i know all of this i had a rm9mk2 that did the same thing. i ended up sending back to roger for a complete going over. the new amps have much better pots with longer rotational life. i had mine for 11 yrs. i also had some NOS EL34's siemens  in it for those 11 yrs without any problems. i now have a RM9SE.

good luck and happy listening to a classic amp!

r.

rbwalt

Re: Music Reference RM9 MK II
« Reply #15 on: 17 Jun 2011, 10:15 pm »
when balancing the driver tubes it is fine if you get a loud pop( bias is way off) when you push in the button. push it in and then turn the bias pot while pushing the button in and out until you get no pop or very little. that's it.

r.

Roger A. Modjeski

Re: Music Reference RM9 MK II
« Reply #16 on: 21 Sep 2011, 09:09 pm »
OK! So today I had a big surprise, I got some matched 6922, and installed them, the amp was almost dead quiet. The only problem is when I am trying to balance the two sides and I depress the button there is quite a loud pop in my speakers.

The Left side balance quite well, but what I have noticed is that i have to depress the button quite hard on the right side and it seem as though when I did that the Bias light flickers and blow the fuse on one of the tubes. Now what can the problem be. But on playing the amp I have not problems at all.
Can someone tell me the purpose of the balance control and how critical is it.

Thanks


Matched 6922s? Matched for what? The first driver tube for an RM-9 needs to have its SECTIONS matched for DC within 3 volts at the operating point in the RM-9. None of the tube matchers out there know how to do DC matching. RM-9 drivers properly matched are available at tubeaudiostore.com under driver tubes.

The pop you hear when you press the balance button will diminish and disappear when the driver is properly balanced. The louder the pop the more out of balance is the driver. You can actually fine tune the balance by listening to the pop and ignoring the light.

rbwalt

Re: Music Reference RM9 MK II
« Reply #17 on: 22 Sep 2011, 01:13 pm »
 that's how i use to balance my RM9MK2 drivers. just listen to the pop sound.



R.