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McIntosh MA230 Setup

M

Marvin Braun

New Member
I Just bought a McIntosh MA230 at an estate sale for $500 and I’m a novice at setting up a vintage tube amp. I want to know if, after a tube test, is there's anything else I need to know about bias adjusting, matching sets of tubes, placement, or anything else prior to set up. Will it drive my JBL L100 speakers? Will any of these cages fit the amp?
http://shop.ebay.com/i.html?_nkw=Mc...6.m270.l1313&_odkw=McIntosh+MA+cage&_osacat=0
A friend will come over help me set it up, but he suggested I ask for any helpful suggestions before he comes quite a distance to help me. Any information you think would help will be greatly appreciated.
 
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I fixed an MA230 for a friend some years ago and loved the sound of that amp. If you don't have the manual, call or e-mail McIntosh and ask for a copy. Their customer support is outstanding, so I doubt you'll have any problem getting this information from them at no charge.

The MA230 combines a solid-state preamp with a tube power amp using 7591 output tubes. The tubes on each channel should be matched for transconductance, and it's very important to set the bias using the procedure in the manual. You'll need a DC voltmeter to do this job. Power tubes throw off quite a bit of heat, so be sure to place the amp where the airflow around it is adequate. The amp is conservatively rated at 30 Watts per channel, which is more than enough to bring your L100s to life.
 
Ma230

Dr. Tinear,
My friend suggested that I ask you these questions - "What would improperly adjusted bias's effect, or how could you tell if they are 'off'?" Also, "With a tube tester would we be able to tell if we had a matched quad?" Thanks.
Marvin Braun
 
I'll confess I'm not familiar in particular with the MA230, I'm just stating generalities.

If you set the bias according to the manual, you're most of the way there. Most testers test the tube, but the circuit is always the final arbiter.

So, in sequence you'd:
1. Test the tube and match as closely as possible
2. Bias in circuit.

The result of not doing that would likely be shortened tube life, and if way off, it might affect the sonics. The manual is your friend. Get one.
 
The MA 230 and an MR67 was my first Mac set up. Nice amp. I have also used mine as a stand alone tube amp, bypassing the SS pre. I used my MX110 as a pre. The bias doesn't have to be off by much for the sound to suffer. The 3d imaging will suffer. It would benefit from a restoration if it hasn't already had one. I still have to do mine, the only vintage piece which is still totally stock.
 
Confirming Destructor's comments: This amp is now into its 4th decade of life. The electrolytic cap are old, dried out and are a danger to further damaging the amp. The bias settings will not be worth much at this point since the voltages will be way off anyway.

I highly recommend a rebuild first if your friend wishes to use the amp safely and reliably for many years to come. See the many discussions about this and the MA-230 at the McIntosh forum here at AK.

Cheers,

David
 
1. the ma 230 has no tubecage only woodcase as option
2. u can messure bias there are 4 testingpoints on the chrome
positive in testpoint negative on - speaker must be set to 0,7 volt
3. enjoy sound:D
 
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