McIntosh MC-30's, MX110 tube discussion. Perfect 6U8, 12AX7, tube? See post #43 for Steve's input.

Armstrong, it is isn't it?

Ron's comment is absolutely so true -- besides, every tube tester had their own spec's for each tube (which differed amounst all test set varieties/manufacturers; because at the time, there were no universal testing standard for a specific test, such as for Gm, etc.).

Bob

 

Hi , this is my first post here and when I stumble on to this thread, I was telling myself wow what an abundance of answers regarding my recently acquired MC225 and MX110 combo.
Appreciate if anyone has any experience regarding Zenith 6u8 as I have a pair on board the MX110. My unit sounded veiled and I'm wondering is it due to the tubes or should I take it for a recap and what which caps might I be looking at ? Any inputs is much appreciated .
Cheers.

 

I'd experiment with the first 12AX7 on the MC225 too, the brand of tube used here seems to make a big difference in Sound too.

 

Hi Steve , thanks for the tip . On the 12ax7 I have tried a 5751 that improves the tonality. I've also ordered some RCA 6u8 from the bay and will plug in to see if it improves before sending it to a tech for a total checkup.
By the way , what tubes would be good for the MC225. Currently I have on board a mixture of 7591 namely Fisher, Dynaco, and unknown brands cos the letterings have since faded.
Also, teles ecc83, rca clear tops 12au7 , unknown 12bh7.
Anyway thanks for the quick response. Much appreciated.

 

Soulster, I would really recommend you have your tech replace the old selenium rectifier in the power supply, which is essential for safety and longevity of the unit. Also, I would change the coupling caps, especially the old "bumble bees" to newer caps. Those old caps tend to not be up to spec now. AudioKarma is a great place for information about the MX110Z. A lot of Mac folks, including Terry Dewick, who works on these a lot, hang out there.

 

Hi fortherecord, will check on those areas and Steve thanks for the link.
Appreciate your directions . Cheers.

 

Hi Steve et al,

I'm using this as the primary guide to working with my new (to me) mx110z. If you've learned anything since then (other than the RCA 6U8, 6U8A discussing later in the thread) and have anything else to add, I'm all ears. Can't wait to dive into some tube rolling. This is my first experience in tube audio. I appreciate your work documenting some of this. Super helpful.

 

thanks man, once again, a helpful read for me...

 

Hi guys, I hope u guys don't mind me revisiting this thread.
I just picked up a Mx 110. It arrived last night actually.
After reading this thread i pulled it back out of the wood case and checked my tubes.
My 6U8's in V16/V17 are Philips(new ones i think) and the 12AX7 in V13/14/15 are actually 5751 which i have read are a lower gain tube.
These are 2 RCA jrc ones and one new Philips.

I was just wondering if i should pick up a couple RCA 6U8 and maybe a matching RCA 5751.
Would this improve the sound? Sounds pretty good to me now but this is my first tube amp as well.

Your thoughts or any help would be appreciated. Thanks.

 

I like GE 6EA8's (sub in for the 6U8A) in 16/17 - it's fuller and less glarey than the RCAs.
I like RCA 12AX7's (long grey plate are fine) in all other sections. Black plate longs are great but not necessary.
I totally didn't dig the Telefunken sound. I know that's heresy, but I didn't like it here.
Matter of fact. I gave up all my Telefunkens (12AX7) because I didn't like the sound of them...(this was with the Tannoy Monitor Gold 15")

 

6EA8 eh? I was just going to buy some 6u8's.....i will have to do a little research h on that one. thanks

 

It's a drop in.
Basically a GE 6U8A works the same and has the same sonic characteristic.

 

Yeah, Audio Classics, in the greater Binghamton, NY area, put 6EA8 tubes in to replace the 6U8 ones, and I thought they sounded better too. This could be one of those inner-circle Mac club tricks.

Experiment with the 12AX7 V3 position, this will give you more bang for the buck. The choice of tube there, I think makes a bigger difference. Both channels go through that gain stage tube.

 

Ok thank you. I have a pair of GE 6U8 on the way and a pair of 6EA8. Going to try them both and see what i prefer.
What position is the V3? I would like to see what i have there currently.
thanks for the suggestions.

 

Yep.
Modafferri did that to mine.
That's why I stuck with them and bought some more.

 

The postion numbers for the preamp section tubes are silk screened right next to each tube on the chrome chassis. There are 3 12AX7s, v1 and v2 are for the phono section, v3 is for the line stage along with the two 6U8s.

 

I am running a McIntosh MX-110Z and MC-240. When I play my Sota Turntable with a Shure V-15 Mxr the volume drop is significant vs my Denon 1910 CD/DVD player. Is there anything n particular I need to check or change? I was using the Outlaw 950 Preamp with a Music Fidelity VLPS phono amp into both the Outlaw 770 and MX-110Z and did not notice the difference to be as drastic. I have to turn the volume to about 2-3 o'clock to get listenable level with the turntable. Is it the difference in the MX-110Z phono section vs the VLPS

 

What tubes are in the phono section?
Are they 12AX7's?
Have you checked the volume pots that control each sections volume?

 

The MX110z is actually a pretty transparent preamp which from my experience betters the other preamps like the C22 or C11 in its phono stage. It also has more bass than those preamps, only the C20 can better it in that regard.

 

Audio technica AT120E s a great cartridge for that preamp. That cartridge's higher than average MM output seems to mate with the MC110z's phono stage very well

 

Anyone traveling or near the Binghamton, NY area owes it to themselves to visit Audio Classics and tour the MCIntosh Labs Factory. It's a gas!