Mac 1500 Transistor Upgrade

I have a McIntosh Mac1500 receiver, and I've read that the transistors in the preamp can be upgraded to improve the sound quality significantly. Most of these transistors are type 2N3391A, according to the manual. They are mounted in sockets, making them very easy to remove. I was wondering if anyone has performed this upgrade or has any information about it. I'm not sure if the original transistors were of low quality or if the assumption is that they wear heavily over time. Would be interested to hear about that as well. Primarily, I was hoping someone could point me toward a particular make/manufacturer of 2N3391A that would offer the best sound quality. Thanks in advance.

 

I don't know where you read this, but I am skeptical. Have you asked McIntosh themselves whether such an upgrade is worthwhile?

 

If it works correctly, leave it alone.

 

I read this here: McIntosh MAC 1500 | Classic Receivers

 

Want a McIntosh receiver, skip the MAC 1500, get a MAC 1700, a MAC 1900 without impedance switch, or a MAC 4100. More reliable all 3, all 3 sound better and have enough power to drive reasonable speakers.

 

I'll chime in here. I too have a 1500, and I'm interested in the upgrade as well.
I noticed someone on "Reverb" had sold one with the upgrade:
"McIntosh MAC 1500 hybrid tube receiver, restored & stunning | Scott's Boutique | Reverb "
And after reaching out to him about info, this was his reply:

Hi, Aaron. The MAC 1500 service manual lists the part numbers
for transistors. I looked them up, sent them to the McIntosh guys. This was
the reply:

"Part# 13200400 has been replaced by part# 13225400. Part# 13200200 has
also been replaced by part# 13225400. They are $1.00 each. I have them in
stock. We have A $10.00 minimum order."
I ended up ordering 14 for my tech. Good luck."

I ended up getting in touch with the parts guys at Mcintosh labs, and ordered 20 of the transistors at 1 dollar each.
He told me they were the same transistors they use in all their amps.

I can't give you any comparison about quality, as the amp is currently being serviced, and was dead when I acquired it,
But My thoughts are that it must be an improvement, as the amp was made at the onset of transistor tech, and the upgrades are from the factory and up to the same standards. In any case, this is how you would go about getting the upgrade parts. Good luck man!

 

I know this is an old comment, but I just came across it. I CANNOT begin to agree with this. I have had the 1500, 1700 and borrowed a 1900. The 1500 is, by far, the better unit. It is also the most dear . . . For a reason. It’s tubed output and driver stages are top quality. I have not heard a 4100. Though I have seen one. No thanks!

In any event, I too have wondered about the transistor upgrade, but never bothered with it. The 1500 swam laps around my other vintage amplifiers as is. I regret selling it more than any other piece of equipment I have ever owned, save (perhaps) a Naim Nait 2.

 

If McIntosh Laboratory Service and parts departments approve the new transistors in their own units. I call that a safe recommendation and one which could be done with confidence. Go for it. They know and support their older equipment quite well.

 

I still prefer a pair of MC 30 power amplifiers (for tubes) but really like the MC 2505-2 power amp better or the MC 2105 best yet, and the MX 110 Z chassis tuner/preamplifier to the MAC 1500. For a hybrid unit. And I really don't like the tuner in the MAC 4100 very well . I like the MAC 1700 and pre impedance switch MAC 1900 very well. MAC 1500 for me is also a bit too underpowered for my needs. MAC 1900 handles any reasonable speaker I need to drive which fits in my home.

I say this as someone who has owned a MA 5100, 2 MA 6100 (early version I currently own, and the last version with impedance switch which was my first McIntosh amp). I have also owned the MAC 1900, and the MC 2505-2 coupled with the MX 114 FM tuner-preamplifier. So I have wide experience with McIntosh equipment.

 

That is good to hear - my 1900 doesn't have the impedance switch and I always thought I was missing out.

 

Why is the pre impedance switch 1900 better?

 

I found the pre-impedance switch versions more reliable, and better behaved. And less likely to have been ran hard as used equipment into reactive 4 ohm loads which dipped to 2.7 ohms. The switch was put there to satisfy the Federal Trade Commission pre-conditioning rules for power ratings.

 

Thanks for the reply. From your answer it appears you’ve owned a number of 1900s with and w/o the switch. Is that correct? Just wonder what your sample size is to make that claim.

I’ve owned one of each. My first one was with the impedance switch. That was in the early ‘00s. I never had any issues with it and it sounded great. I very recently re-acquired one w/o the switch and a fairly low serial #.
This 1900 also sounds lovely. But frankly with the passage of time I’d be hard pressed to say that’s it’s any better or worse than the previous unit I had.

I actually recall discourse and claims, but might be wrong, that the ones with the switch were more highly regarded.

 

My sample size is 2 of the sister MA 6100 integrated amplifiers, my current one without. One MAC 1900 personal unit with. My physical medicine and rehabilitation doctor's MAC 1900 with (I refurbished this one for her), and two announcers MAC 1900 receivers (one with, one without the impedance switch). I've had all the above units on my bench.

 

Having owned and used all 3 1x series MAC receivers, I do have some experience......

My preference is for the 1500, followed by the 1900 then 1700. The 1500 sounds like a modern Fisher 500c. Tube warmth but a degree of precision that the 500c lacks. The SS preamp is the weak point of this design. The amp stage sounds like a cousin of the 225, but definitely a step back. The 1900 is a 2nd generation SS design and sounds better for it, along with adequate power. The 1700 is the step child....SS pre and amp stage, with a simplified tube tuner section. Early SS design that just sounds mediocre.

I reviewed contemporary lab tests of the 1500. I was impressed by the test results. Full power was available across the freq spectrum, and the FR was basically flat from 20-20khz with excellent square wave results. Most tube amps of the era had FR rolloff at low frequencies, and square waves that exhibited both ringing and overshoot. Over the years I have learned that some test results are directly related to sonic character. You can hear the quality of the amp section in the 1500 compared to other tube designs.