Hitachi HA-M1 Mini Integrated Amp

LBPete

Rolling Along
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Came across this little Hitachi Amp and tuner the other day. It's tiny 9" wide and 7 deep. That's a used pencil on top.

The big surprise was the inside, a big ass toroidal transformer and good size heat sinks. It uses some kind of power packs for the amps. Overall very well made. The case is steel but the face plates and back panels are plastic. The tuner assembly has aux phono and tape inputs. Judging by the LED power meters, it's from the late 70's or very early 80's

The DC offset on one channel is way high, 120mv or so. I tore it down to see if there were any adjustment trimmers but couldn't find any. I also don't see a protection relay.

Does anyone have any suggestions on how to get the offset in line?

- Pete
 

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I have always had a soft spot for that type of miniature system, though I've never had one. Of the ones I've seen pics of, that one sure looks to be the meatiest. Good luck on the offset.
 
Pretty neat little amp there. Looks like a pain to work on, I bet the first thing the service manual says is :"Remove transformer to access.........."
 
I have that same system at home. No I don't know how to adjust the DC offset though. :scratch2:
Hard to believe that two of these systems survived. I couldn't find anything on the web about them. Do you have any of the owner information?

As far as the transformer, it comes out pretty easily. It just has one bolt through its center. It only took 10 or 15 minutes to tear it down and put it back together.

I'm guessing the only way to correct the dc offset is to change the chip. The are pretty buried and I couldn't read the id numbers.

- Pete
 
Hitachi HA-M1/FT-M1 amp/tuner

I know this is an old thread,but believe it or not I also scored these two gems with the original HS-M1 MKII bookshelf speakers! They are odd,thick plastic,but the cabinets are 6.25" deep and they sound fantastic! I found them at a yard sale while buying some items from the gentleman for my daughter and I spied the little tykes sitting on his work bench.Unfortunately,though,he had thrown-away the matching cassette deck because it stopped working and he thought it was worthless.It also was missing it's original DIN cable,so I just used single strands of thick wire.Wow! this systems sounds clean! I have been looking for info on these babies for 2 years and finally something popped-up.I thought it was 20 wpc and was happy with that,but 40 wpc out of this little gem....INCREDIBLE!
Now if I can just find or have made,the correct DIN cable for it and maybe find the missing deck,I will be in heaven.I love this system!:banana:
 
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I have no real experience with this unit, but in general, amplifiers that have no pots to adjust bias are generally set through a closely match set of pre-drive transistors. This also assumes the resistors and zeners are also up to spec.

hummm... this assumes the unit uses transistors. This is late enough tht it could all be handled within the "power pack" module.
 
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I'd forgotten all about this old post. The unit uses a small IC amplifier chip for each channel. From what I was able to find out, they were developed for Car audio systems. The bias and offset are not adjustable. So the only recourse is to replace the chip. They are still available though.

Can you post pictures of the speakers? It would be nice to see more of the set.

- Pete
 
Hi


I have one of these units as well. Bought it about 8 years ago. I have the Tuner, Amp and the Acoustic Suspension 2 way speakers. It's a nice unit and will also operate on 12 volt (car or RV). The unit also has a microphone input with a separate mic volume control as well as a magnetic phono input.The bass speakers has a fair size magnet has the enclosure is line with felt-type acoustic insulation. I estimate the amplifier at about a true 15 watts RMS into 8 ohms per channel probably over about 40-20,000Hz at about 0.5% Harmonic and Intermodulation distortion. The speakers that come with the unit are 4 ohm units but the amp drives 8 ohm speakers without any problem.

My wife was using this unit with her Yamaha Digital Piano with a MIDI attached Yamaha Keyboard. The keyboard was running through the Hitachi driving a set of Kenwood 8 ohm speakers. The setup was really belting out the bass and drums pretty darn good. I now have this unit in my Den and am in fact listening to it now. The speakers that came with it are only suitable for very low level background music listening.
 
I finally rebuilt the original speakers and will try to post the pics of the system.I had forgotten about my post here.The integrated amp and tuner are still kicking butt in my garage!
 
Hard to believe that two of these systems survived. I couldn't find anything on the web about them. Do you have any of the owner information?

Three. I've got one, paired up with some Infinitesimal 4's and an Infinity subwoofer. Made for a killer office system, replaced with an Aiwa system (the silver faced 22 series) and some Infinitesimal I's.

bs
 
I know this an old thread but I thought you might like to see this beauty I found on the auction sites...
 

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Yes,I spotted that entire system on Ebay a while ago and the seller had some interesting info about it being a professional travel system.It makes sense as it does have multi-voltage capability,mic input with its own mix volume and I could see it being used as a small PA amp.Mine cranks my Speaker Labs bookshelfs and even briefly powered my Technis A21 towers AND still sounded clean!
 
I have the tuner,integrated amp and matching speakers(which I upgraded the woofers)and they still sound and work great!
 
Add me to the list of HA-M1/FT-M1 owners!

Discovered this system a few weeks ago on Lloyd Naftolin's "Seventies Stereo" blog, and immediately knew I had to have it. After Googling turned up nothing for sale, and eBay gave me a listing completed two miserable days prior, I stumbled upon a set on Innovative Audio's site.

It cost me $125 plus shipping from Canada to the US, but as of today the little Hitachi components are in my possession, and they're worth every dollar I spent. I have them powering a pair of Yamaha NX-E300 bookshelf speakers I got on eBay for a pretty good price last summer, which is a pretty decent match IMO, the Yamahas are 6 ohm with a nominal input power of 40w.

Having used the Yamahas with a modern Sony receiver before, I'm pretty confident that the Hitachi system sounds better. It looks nice, too. If I didn't know any better I'd say it were from the mid 90s, not late 70s. I especially like the LED level meters, probably because I work with pro audio systems and am used to seeing level meters.

This is my first time buying vintage gear, but not my first experience with it. I have a Realistic QTA-770 with 4 Mach One 4024s that was given to me by my grandmother several years after my grandfather died. Unfortunately my grandmother did some damage to one of the rear output channels by cranking the volume up the whole way a few times, so I can't run it at its full power (2x60w) in Stereomax without some distortion, I'm stuck in 2x25w stereo. In any case, that system exposed me to the quality and value of vintage stereo gear.

Why the QTA-770 story? Well, I'm 18 and headed to college in the fall, and want some sort of stereo for my dorm. The Realistic setup is a bit too large (actually a lot too large) for a dorm, so I had to think small. My original plan was to get the matching Yamaha receiver for my speakers, but then the vintage option came into play, and here I am with the Hitachi system. :music:
 

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Anyone else with this amp/tuner combo have a dead 5th tuning LED? Haven't seen it turn on for me once yet whilst going through stations testing the tuner. I'd open it up and have a look myself, but I'm waiting till the 30 day warranty period is over before I break the warranty label. Not that I expect these to quit on me. Very well built components.
 
Does anyone know where I can find a service manual for this set or the wiring diagram for the DIN connector?

Thanks

Kurt
KG6KMJ
 
Does anyone know where I can find a service manual for this set or the wiring diagram for the DIN connector?

Go to this page.

The 3rd line under the preview starts like this:
This file is downloadable free of charge. ...processing

After some time (perhaps minutes), it becomes:
This file is downloadable free of charge: Get Manual

Click on "get manual".

As for the offset discussed here-before, complete recap of electrolytics may solve the issue, as there are so many of theme used in feedback and compensation loops, that a small DC leakage current may cause a DC offset.
 
I just picked up one of these mini-systems as well. The FM section was begging for an alignment, and it cleaned up VERY well. Much better than I expected! It's not very selective with only 3 gangs and only one ceramic in the IF, but when left to it's devices it grabs an uncluttered station very cleanly. Excellent distortion and separation are possible

The amp has one channel with ~200mV offset, and I am little worried that there doesn't seem to be a protection relay. I do not get any "plop" noise through the speakers at power on/off though, so something is going right.
 
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