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Preamp for my MC30 pair, a Sensi needed.

Discussion in 'McIntosh Audio' started by zenarrrow, Apr 18, 2018.

  1. TSmith8605

    TSmith8605 Senile Member Subscriber

    Messages:
    778
    Location:
    Sunnyvale, CA
    Dynaco equipment was designed to provide decent, credible sound quality at the lowest possible price. As such, the build quality and cosmetic are sacrificed as are features. McIntosh is designed with the opposite approach of providing best sound, best build quality, most features and so a much higher price.

    The gain controls on the MC30s are a nice-to-have feature. That the ST 70 does not have this feature is one of the ways they kept the price lower. A competent tech could easily install gain controls in an ST 70 if you want the feature added.

    Don't overthink the clear-path thing. The gain control is just a variable resistor and is not going to add appreciable noise or distortion to the signal. In fact, the signal path in the MC30 uses four small tubes per channel verses just one small tube per channel in the ST70 and so is a much more complex signal path and yet the MC30 clearly delivers much better sound and lower noise.
     
    zenarrrow likes this.

     

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  2. zenarrrow

    zenarrrow AK Subscriber Subscriber

    Messages:
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    Location:
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    Thank you. From now on I am all ears, an empty page to soak up knowledge. You guys all have years and years on what I know. So I may ask silly questions, but remember I do appreciate it very much all the answers and patient you all have showed me.
     
  3. zenarrrow

    zenarrrow AK Subscriber Subscriber

    Messages:
    740
    Location:
    Wyoming USA
    Well at many attempt at types of tweaks. Fiddling with the tone controls. Placing felt in front of the horns etc, speaker placement etc.
    I have come to the conclusion, that for one I don't like having to adjust the tone controls at the beginning of every listening session.

    Don't know if it's the MC30s or the MC30s with the Altec Lansing model 14 horns.

    When I hook my ST-70 back in with the MX110Z everything is precisely accurate.

    So, a conclusion , MC30'S with the Pas 2 Bright. MC30'S with the MX110Z bright. Pas 2 with ST-70 I notice what I never noticed before a lot of back ground white noise(?).

    But with the mx110z MC30'S and my Altecs, a pretty darn good combo.

    Maybe the 30's bring out more of the brightness in the Altecs.

    One thing I am unable to try is different speakers in the mix. Except a pair of Altec 890 Bolero's. Which don't do my system justice on any level.

    Maybe I should save my money and send the 30's into someone who can address my issue with an open mind, with my concerns with my current gear.

    Any suggestions with speakers for a mx110z MC30 setup? As this the only option I haven't tried to adjust.

    Thanks Joe
     
  4. mnmmt

    mnmmt AK Subscriber Subscriber

    Messages:
    152
    Location:
    Minnesota
    Speakers would be my guess as to where the issue lies. Horns make my ears ache. I use modern tannoy dual concentric speakers and love them (they are a quasi horn with the wave guide tweeter, but make my ears happy). Any Tannoy will work well with McIntosh.
     
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  5. zenarrrow

    zenarrrow AK Subscriber Subscriber

    Messages:
    740
    Location:
    Wyoming USA
    Yeah, just weird that the ST-70 doesn't reflect this issue, maybe because the MC30's are so much more detail...?
    As I have stated at times the combo is super musical, almost unreal in how they sound. Just been narrowing down the possible culprits. This will be my new goal
    - as the first response - has to be of interest to you.

    I would hate to send them (mc30's) off and have them come back the same. And they might just well come back just the same. Thank you very much.
     
  6. zenarrrow

    zenarrrow AK Subscriber Subscriber

    Messages:
    740
    Location:
    Wyoming USA
    Are you speaking of these roughly?
    https://www.ebay.com/itm/TANNOY-Rev...558414&hash=item1ca022c33d:g:nxYAAOSwHLNZWsuu

    Some of the Vintage ones seem to be pretty expensive.
     

     

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  7. mnmmt

    mnmmt AK Subscriber Subscriber

    Messages:
    152
    Location:
    Minnesota
    I have the saturn s8, which is a prior version of the xt8f, which get excellent reviews. The problem may not be with the mc30s, but with the st70. If it hasnt been restored, it may just be dull sounding. I have a bunch of old receivers i have restored, and a lot of them sounded wooly and rolled off on the top end before restoration. It may just be that old caps in the st70 counteract the bright tweeters?
     
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  8. zenarrrow

    zenarrrow AK Subscriber Subscriber

    Messages:
    740
    Location:
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    I will have to take a gander at my ST-70. I bought it restored a few years back. So I do not believe it is out of spec.
     
  9. zenarrrow

    zenarrrow AK Subscriber Subscriber

    Messages:
    740
    Location:
    Wyoming USA
    So, still battling the shrillness with my MC30's. Well just resigned until I can get them to someone to look at. I opened the bottom of the cover and looked around a little. I noticed between the output tubes the there are a pair of capacitors, on one amp they are wired in one way and the other they are backward..? They are both wired into the same pins on the tube socket.
    20180529_181357.jpeg 20180529_181349.jpeg


    Also, on one amp one of the large caps on the 11 pin is cracked. I have taken pictures and was wondering if you guys would take a look and see what you think. The black cap on the right, you can see a crack going all the way through. Not sure if this would cause anything, but I am just not sure. Thanks guys.
    20180529_181617(1).jpeg
     

    Attached Files:

  10. mnmmt

    mnmmt AK Subscriber Subscriber

    Messages:
    152
    Location:
    Minnesota
    I think those things in the first two photos are resistors, though I have never seen ones like those before. Those striped black capacitors are known as bumblebees. They are toast in my opinion and I would replace them ASAP. The cracked case indicates to me that moisture is in there, making them noisy at best, and likely to catastrophically fail at worst. Whether they are a cause of the shrill sound or not, I don't know, but I am immediately suspect of the "restoration" involved when an obviously corrupted cap was left in.
     
    zenarrrow likes this.
  11. zenarrrow

    zenarrrow AK Subscriber Subscriber

    Messages:
    740
    Location:
    Wyoming USA
    Yeah, I asked the seller if he had any ideas, nary a response from him. Maybe I will take them to a place in Salt Lake City I just found out about today.
    As far as restoration goes on these, does the more one does the more it takes away from the true McIntosh sound and feel ? Just Curious, Joe
     

     

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  12. BillWojo

    BillWojo AK Subscriber Subscriber

    Messages:
    2,712
    Location:
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    That's why I recommend a full restore on these golden oldies.
    Do you still have time to pursue a remedy with the seller?
    Replacing out of spec components on a 50 year old amp while leaving in anything that tested good is asking for trouble in my opinion. It may have sat for the last 20 years and now that it is up and running again the old parts are being stressed beyond the breaking point.
    My suggestion? Get a price for rebuild kits from Jim McShane and a quote from a good tech for the labor to properly rebuild these and get some money back from the seller. I think PayPal gives you several months to file a claim.
    These amps should blow away your ST70 in every way.
    Keep us posted.

    BillWojo
     
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  13. zenarrrow

    zenarrrow AK Subscriber Subscriber

    Messages:
    740
    Location:
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    So would you recommend a full restore? All caps and resistors?
     
  14. Bill Ferris

    Bill Ferris Super Member

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    1,667
    Location:
    NE. FL.
     
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  15. BillWojo

    BillWojo AK Subscriber Subscriber

    Messages:
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    Location:
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    I would if these are going to be keepers. Look at it as an investment that you get to enjoy. They only built so many of these and I doubt will ever build them again.

    BillWojo
     
  16. zenarrrow

    zenarrrow AK Subscriber Subscriber

    Messages:
    740
    Location:
    Wyoming USA
    I am going to keep them, I have no desire to sell them.
    I was just curious if restoring them fully replacing the caps resistors etc will take away the "mcintosh" sound. I want to keep it original to the best I can. But of course no good if caps are leaking or resistors not working properly.
    So yeah, just answered my own question.
     

     

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  17. BillWojo

    BillWojo AK Subscriber Subscriber

    Messages:
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    Location:
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    I would get parts kits from someone like Jim McShane, he will use high quality parts and select the appropriate types so it will be as close as can be. It doesn't look like the tech that did the work on your amps did that.
    Some folks want to keep 50 year old parts in a amp so they can keep the "sound". What I want to know is the "sound" the sound of an original factory fresh amp or the sound of worn and aging parts.

    BillWojo
     
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  18. BillWojo

    BillWojo AK Subscriber Subscriber

    Messages:
    2,712
    Location:
    Burlington, NJ
    So how are you making out with the amps?

    BillWojo
     

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