My vintage McIntosh MX-110 preamp surprised me today. Follow up post #61!

Interesting, mine definitely looks like the second one, TR290.

 

I've never seen the 2nd version, always see the shorter tube.

 

I've always heard the RCA blackplate was THE 6U8 to use here.

 

The RCA could well be. But I haven't heard anyone try the ECF802. And all the other 80 series Telefunkens are monsters. The frame grid ECC803s were famous for having SILLY ruggedness and service life, and very neutral sound. I gathered up a few of the Tesla copies for use in guitar amps, but have never put them in yet, since I am not really going to play much until I get back into a detached house again.

ccm

 

All I know about Teles is they come with smooth or ribbed plates. My MX110 came with the 2 Tele ECF802s in it when I first bought it, The RCA tubes are better sounding. I left the 3 Tele ECC803s in place as those are the best version of the 12AX7 I've had in vintage McIntosh gear. They sound mushy in modern tube gear though, including the C2300.

 

VERY cool, fortherecord! That's great that you have heard the ECF802 AND the RCA. Now I feel better about the RCAs.

Three Tele ECC803s would practically be worth the cost of the preamp these days! You scored.

How would you describe the sound of the 802s, and what the RCAs do that is better?

Lastly, have you tried the ECF82 Siemens that Steve mentioned he enjoyed in that other thread he recently bumped?

ccm

 

The RCAs just seem to have better all around definition in their sound than the Teles, granted the Teles I have are well used and pulls.

 

I have had my MX110-Z since 1967 and am always thankful it made me a music lover. The synergy with MC-30's is a very special one.

I have tried the phono stage in the past, but lats time mine was a bit noisy so I use my EAR 834P now but might go back the in the 110 again. Any other comments on the phono would be welcome from Steve or anyone else.

I also run my modern music server into it and enjoy that very much. Anyone think the Aux in or Tape in sounds better than the other ?

Is there also something about the unit sounding better with Loudness on or is it me ?

Anyone still making wooden cases btw ?

 

I'm just peachy to know that I own and use the same piece as SH
Steve, I admire and think it important for a mastering engineer to still "listen" and be a music lover. I once met a mastering guy who said he could not remember the last time he simply listened to anything. I ran.

 

Excellent!
I am looking for one and without success. Will keep looking...it's the only one within my budget.

 

Envious here.

I'll go thru my notes this evening & see what I used for the 6U8.

Best

Bob

 

What do people have a preference for, the earlier MX110z with shiny gold face plate or the later brushed gold one?

 

Anyone you could get would be my guess.

 

They're not exactly cheap now.

 

This is true.

 

The working one I linked earlier sold for only 1225 on ebay.

That's pretty affordable.

ccm

 

Sort of a home version of an "aural exciter"?

 

Experimenting with 6GH8s should be cheap - I picked up a sleeve of NOS RCAs for $25 to use with boards I picked up for my Dynakit MK IV amps. The 6GH8 is similar to the 7199s that Dyna used, but have a different pinout that requires a few wires to be rerouted. 7199s prices have gotten steep, so it's good to know there are cheaper options available.

 

Wow, long time since I've been over here to Steve's site.

CAtching up, I've had MX-110s off and on since the mid-70s. The latest one came to me in 2003 or so from my step-mother-in-law. It also came along with an MC-225 with the original sales receipt from 1963. It, along with another MX-110 were fully restored some years ago, including new dial glass from Radio Daze.

As has been discussed, 2 of the three triodes inside the 6D10 are used as a buffer circuit for both of the phono inputs, the tape head input and the Aux input. Yes, it is the same configuration as found in those stand-alone Tube Buffers you see marketed to 'soften' the sound.

The Tape Monitor, however, does indeed bypass this input and goes straight to the 12AX7 that's part of the Bass/Treble control circuit. The 6U8s, being dual triodes themselves, are configured in a cascode arrangement. Essentially, you can look at this tube as being a single operating device but with dual triodes inside it.

One cool trick you can do with the MX-110 is to use it as a tube buffer alone by feeding your audio signal into the Aux input then take feed the Tape Out into whatever else you want to drive. This uses only the 6D10 as a standalone cathode-follower buffer. In this way, you can then determine what effect the 6D10 has on the sonic character and even do 6D10 tube rolling without having to figure out the rest of the preamp's characteristics.

BTW, I'd strongly recommend anyone who wishes to tube roll an MX-110 preamp to have the power supply fully rebuilt, all the inter-stage coupling capacitors and that all operating voltages in each stage be within spec. If this isn't done, all you'll be doing is hearing tired parts interacting with different tubes.

IIRC, there were 3 versions of MX-110 with the majority of the production of what is known as the Z series, from the letter found in the serial number. The last 2 series had a 6D10 used but the application varied slightly. Also, there were a small number of factory service bulletins issued on the MX-110 some relating to additional adjustment controls for the Magic Eye tuning indicator, the replacement of the final 2 I/F cans due to slight performance improvements and, most significantly, the replacement of ceramic coupling caps for the then-new film caps around the 6D10 for popping noises when switching the Input Selector due to DC leakage in those caps.

McIntosh made production changes as the product flowed down the assembly line. Service Bulletins were issued when those changes were made.

Cheers,

David

 

David:

I recognize you from the AudioKarma McIntosh forum. You helped me a few years ago when I was rebuilding my MX-110. It's still going strong, so it must have been great advice!

See Steve Hoffman's post #61 in this thread. This is the way he was using his MX-110 to add some magic to his system.

This is one of the things you recommended to me. Replacing the ceramic capacitors in the signal path made a big improvement in sound quality.

Wes

 

Hi Wes,

I do remember our online and offline conversations. Glad the MX-110 is doing well for you. I still have mine although it is just sitting right now. This thread certainly gets me motivated to reinsert it inline, though.

I see Steve's post about doing just what I suggested - should have read through the whole thread, n'est pas?

Cheers,

David