[shk]

I am a newbie to this forum, but not to the rm9, (original owner of #51) which I have enjoyed for many years. I have made few changes to my system until recently. I replaced my preamp with a passive attenuator (Lightspeed) to very good effect. I pored over this forum and the relevant ones from AudiogonN to help with my decision and am grateful for all the good advice I garnered. Learning a bit about impedance matching, gain and sensitivity helped me make some good decisions, but I have been puzzled by the information on this forum about connecting my speakers (Merlin Signature 3+). I have plenty of gain (rarely get my volume knob past 9 o'clock on the lightspeed or my old preamp) and found Roger's advice about light loading attractive and very clear: use the lowest tap that provides sufficient volume to get less distortion, longer tube life etc. When I try this (4 ohm tap into my 8 ohm speaker) my system sounds dull, loosing dynamics and mid range sweetness on vocals. I also tried using the 2 ohm (instead of 0) and 8 ohm tap to similar effect. Perhaps my speakers are in some way atypical or my understanding is flawed. Can anyone speak to this.

Thanks

[Ericus Rex]

That's interesting about using the 2 ohm tap for negative connection.  When you do this and use the 8 ohm tap for positive do you then get a nominal 6 ohm tap?

Did you try different feedback settings while you were light loading?  You may recapture some of that magic with another setting.

If you find you like the sound of your sys best using the 0/8 ohm taps don't sweat it.  You'll still get thousands of hours out of your tubes and not even notice the higher distortion.

Good luck and welcome to AC!

[rbwalt]

      wow you have a old pair of bobby's 3+'s!  the merlins are going to sound best on the 8 ohm tap.  i used the 8 ohm tap on my old rm9mk2 to drive my merlin VSM's and i use that tap on my RM9se to drive the merlin MXM's. my sound is to say fantastic. tube life? well i got 11 yrs out of NOS siemens el34's on my old amp. have the same on my SE. if your amp has the gain/ damping selector switch leave at the medium setting. 

hope this helps some.

ps. i might have had a hand in building your 3+'s.         

[shk]

I'm not sure about the math on the 2-8 connection - the impulse came from a suggestion Roger made to another poster elsewhere in this forum. I would like to understand this better. I continue to enjoy experimenting. The system is very transparent (changes are noticeable and different recordings are affected in different ways). Suggestions and insights are very welcome.

Oops, I just saw rbWalt's post while I was typing. I guess that confirms my impressions so far, but experimenting is still fun.

Thanks

[rbwalt]

remember so many little things add or take away from what you are hearing or want to hear. what tubes are you using in the RM9? power cords, speaker wire, interconnects all play a part though small they all add up. what kind of platform is the amp sitting on? is it sitting on the rubber feet that came with it. getting it off its rubber feet will make a difference. it will open and smooth things out. music will be more dynamic with better sound staging, layering etc.


have fun!

ps.  proper  isolation of components plays a big part and i think is widely overlooked or poorly understood.

[Ralph]

I have the Martin-Logan Sequels (hybrid electrostatics) whose minimum impedance is 2 ohms, so I use that tap on the RM-9. I find that I get the best tonal balance and transparency by using medium gain; low gain does result in a certain thinness in the sound, probably because of overdamping. But Roger is definitely correct in maintaining that using the lowest possible output impedance tap results in the best sound.

[shk]

I am finding myself partial to the 2-8 connection on many recordings, but the standard 8 ohm tap on others. Can someone explain the effective output impedance of the 2-8 connection?

Thanks

[rbwalt]

bet the amp has a hard time driving those ELS's to a reasonable level. must eat tubes.

[rbwalt]

bob at merlin says the 3 + 's sound better on a 8 ohm tap.

[shk]

Say hello to Bobby. He probably won't remember me, but he sold me the 3+'s at Paul Heath's shop in Rochester, back in the day. I agree the speakers sound better off the 8 ohm tap than the 4 ohm tap, but I'm wondering if you guys ever tried the 2-8 connection. Using that with the medium feedback setting is doing some very nice things at my house.

Thanks, Steve Kurtz

[rbwalt]

will do Steve. you must be a rochestarian then. sad to say that poor Paul passed away a few months ago. boy that was a long time ago when you bought them. glad to hear that they are still sounding well for you. what tubes are you using in the amp? boy maybe we can get you into a pair of VSM's someday.

rob.

[Ralph]

bet the amp has a hard time driving those ELS's to a reasonable level. must eat tubes.

Actually, I get excellent SPL at that setting.

[rbwalt]

good. glad it works well for you though the amp was not designed to drive difficult loads. enter the rm200 or the rm9se both amps are able to drive low impedance speakers with much greater ease without pushing the output tubes into distress and thus shorter tube life.


enjoy!