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Yamaha A-1 Vintage Amplifier Review

mhardy6647

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In 1983, I had a Yamaha that looked identical to this R700, but mine was 70wts a channel and this one is 50wts, so I have no idea what it actually was.
Sounds like the R-900.


1686362806422.png

source: https://www.hifiengine.com/hfe_downloads/index.php?yamaha/yamaha_r-900_brochure_en.pdf

I had a dump-find R-700 that had issues... although I still have a dump-find R-1000 that works properly (so far). The R-700/900/1000 models had some issues with inadequate heat-sinking on some components that rendered them quite failure prone, if memory serves. EDIT: I'll bet @restorer-john rememembers all of the gory details right off the top of his head! ;)


(R-1000 on the bottom)
 

Labjr

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By the late 70's Yamaha was using Sanyo STK monolithic amplifier modules in their receivers instead of discrete transistors. So they were cutting cost. IMO, none of them were anything special. And now, they're nearly impossible to repair when they fail. Can't get parts.
 

NoxMorbis

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Sounds like the R-900.


View attachment 291213
source: https://www.hifiengine.com/hfe_downloads/index.php?yamaha/yamaha_r-900_brochure_en.pdf

I had a dump-find R-700 that had issues... although I still have a dump-find R-1000 that works properly (so far). The R-700/900/1000 models had some issues with inadequate heat-sinking on some components that rendered them quite failure prone, if memory serves. EDIT: I'll bet @restorer-john rememembers all of the gory details right off the top of his head! ;)


(R-1000 on the bottom)
It was the 900! I remember it didn't have the frame the 700 has and was dark like the one you posted. And they 'boast' a -76dB THD. Crazy. The Aiyima 08 Pro is better than that, plus it's rated at THD+N. Amazing.
 

NoxMorbis

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By the late 70's Yamaha was using Sanyo STK monolithic amplifier modules in their receivers instead of discrete transistors. So they were cutting cost. IMO, none of them were anything special. And now, they're nearly impossible to repair when they fail. Can't get parts.
No way man. They said on the box they had "MOSFET" amplifiers! LOL Oh the marketing back then. :facepalm:
 

Mat

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I was thinking of getting one of these as an amp for my turntable and maybe later pairing it with a dedicated power amp down the road (and just using it for the phono/pre), but then saw this 1 page back

Also, there is no real pre-out with this amp. That "pre-out" comes directly from the main amp. That's why there is no separate input for the power amp I guess.

Is this bad? Not a real pre-out? Does this mean I should only use it as an integrated?
 

LancerFIN

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The specs Yamaha listed for A-1 pale in comparison to their M- and MX- lineup of power amplifiers.
So I am bit confused why people are getting excited by the A-1? Some M- and MX- models can be had for around the same price or slightly more.
On top of the performance they are some of the best looking vintage amps ever made.


I have MX-50. Which is entry level in this lineup.

css06o.jpg


Specs for M-80
52jrc7.jpg


Specs for MX-1000
4s4nh7.jpg


Yamaha-MX-1000-60250.JPG
 

Mat

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Can't comment on why it's better than the 80s stuff outside of build quality, but I did buy one and recently recapped it while cleaning some other stuff up so far (havent done the big caps yet). That said, it absolutely sings now vs. when I first picked it up.

Some thoughts...
I'm not sure the benefit to the DISC mode just yet, comparing it to Phono w/ Tone disabled is very hard to pick out what's shifting, if anything. Has anyone else had experience with it being beneficial? I tested with my headphones and while there was a difference, it was like switching DAC filters, and there was no wrong or consistent answer. DISC had slightly more crispness on the vocals but through the pre-amp I think it sounded more enjoyable. Blind testing and picking moments where I preferred the sound was pretty split and probably depends on the song. Eh...

I don't currently have a subwoofer to attach so using the tone controls and boosting the bass is very useful with my Klipsch RP-600Ms. While I love EQing and tone controls, the drawback is usually them being noisy and also boosting underlying noise. This thing is dead silent, it's almost unbelievable. To compare I also have a Yamaha C-4 pre-amp from the era (much more expensive) and their top of the line EQ from the 80s, and both have faults and add levels of (tolerable) noise. This flaw is easier to pick up with headphones, and I can say that when cranking the bass with tone enabled, I'm just not hearing any noise enter the signal. This vintage engineering really puts something like the Schiit Loki / Lokius to shame, especially since they market those units as being better than vintage despite being noisy as hell.

PXL_20230929_041706568.MP.jpg


Speaking of headphones...oh boy. While I have the C4 as a dedicated headphone amp, since it has a dedicated headphone amp built in, the A1 has the headphones built into the tone board and like most integrateds it's an afterthought. Interestingly, though, is just how quiet this thing is even with headphones. Usually its easy to pick up on junk noise with 300ohm headphones once things get moderately loud - even on my modern headphone amps I notice it with high enough gain, and especially with an EQ in the loop. What the A1 is doing here is nothing short of magical to me. I can crank the bass, and crank the volume to head-exploding levels and it's just eerily silent. The 1978 C4 has a dedicated HP board and has noise, the A1 doesn't - go figure. That being said, the A1 is too big, heavy, and hot to use as a headphone amp, but it's interesting to me nonetheless.

As far as normal music listening goes I'm very impressed so far. My current/previous amp for vinyl is a restored Marantz 2225 and its a night and day difference both in quality and headroom. Even using my Bifrost 2 into the AUX I was able to tell it was my Bifrost 2's sound signature, whereas on the Marantz there was nothing special going on (basically bottlenecking the DAC).

Contemplating what to do about the 18,000uf filter caps right now, and still want to clean & re-thermal the transistors in this. New LEDs should be here this week as well. :D
 

AnalogSteph

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I'm not sure the benefit to the DISC mode just yet, comparing it to Phono w/ Tone disabled is very hard to pick out what's shifting, if anything. Has anyone else had experience with it being beneficial?
I mean, it's just an input selector + tone amp bypass, so if all the contacts involved are in good shape the differences should in fact be negligible.
Speaking of headphones...oh boy. While I have the C4 as a dedicated headphone amp, since it has a dedicated headphone amp built in, the A1 has the headphones built into the tone board and like most integrateds it's an afterthought. Interestingly, though, is just how quiet this thing is even with headphones. Usually its easy to pick up on junk noise with 300ohm headphones once things get moderately loud - even on my modern headphone amps I notice it with high enough gain, and especially with an EQ in the loop. What the A1 is doing here is nothing short of magical to me. I can crank the bass, and crank the volume to head-exploding levels and it's just eerily silent. The 1978 C4 has a dedicated HP board and has noise, the A1 doesn't - go figure.
The C4 headphone amp stage is a bit... odd. It has a crapton of gain for some reason.
c4-hpa.png

1 + 10k/150, that's almost 37 dB! And that's following the entire preamp! One thing's for certain, you want to keep the HP LEVEL waaay down at all times. And then a whopping 330 ohm output impedance. That thing could use some reengineering efforts. I can give it a shot if there is any interest. It's a bit tricky since you have to modify the compensation, get the DC balance right and not get into any trouble with the input bootstrapping, plus reducing bias circuit distortion.

With some guesstimates regarding input transistor noise, I'm getting 66 µV of output noise (-83.6 dBV) over a 20 kHz bandwidth. Given that a 300 ohm only sees less than half that, the end result should be about 30 µV (-90ish dBV). While not great, that should not normally be audible in ~103 dB/V Sennheisers.

Try setting HP level on the C-4 such that normal volume is reached at about 11 o'clock on the main volume dial. Still noisy? It should not be.

BTW, the A-1 does not have "the headphones built into the tone board", it is in fact the customary dropper resistor (330 ohm 2 W, apparently) following the power amplifier. And specified residual noise (DISC mode) is in fact just slightly lower than the C-4 at 50 µV. A 112 dB SNR (TONE off) is very respectable in any case, the C-4 scores only 106 dB.
 
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Mat

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I mean, it's just an input selector + tone amp bypass, so if all the contacts involved are in good shape the differences should in fact be negligible.

The C4 headphone amp stage is a bit... odd. It has a crapton of gain for some reason.
View attachment 316463
1 + 10k/150, that's almost 37 dB! And that's following the entire preamp! One thing's for certain, you want to keep the HP LEVEL waaay down at all times. And then a whopping 330 ohm output impedance. That thing could use some reengineering efforts. I can give it a shot if there is any interest. It's a bit tricky since you have to modify the compensation, get the DC balance right and not get into any trouble with the input bootstrapping, plus reducing bias circuit distortion.

With some guesstimates regarding input transistor noise, I'm getting 66 µV of output noise (-83.6 dBV) over a 20 kHz bandwidth. Given that a 300 ohm only sees less than half that, the end result should be about 30 µV (-90ish dBV). While not great, that should not normally be audible in ~103 dB/V Sennheisers.

Try setting HP level on the C-4 such that normal volume is reached at about 11 o'clock on the main volume dial. Still noisy? It should not be.

Maybe the high gain design is because it relies on the volume/trim to make it compatible with other impedances? Personally I like to have the the HP volume high, around 7-8, and knock down the overall volume with the main volume. Just the result of trial and error until I was happy. It's incredibly noisy over 9/10 on the hp volume, like it ramps up in the final two notches.

Noise isnt an issue when the 2 volumes are staged adequately, I'm just making a comparison to the A1 going full throttle being silent while the C4 (or any of my other vintage amps for that matter) can't go past 3/10 main volume without noise creeping in and up usually.

BTW, the A-1 does not have "the headphones built into the tone board", it is in fact the customary dropper resistor (330 ohm 2 W, apparently) following the power amplifier. And specified residual noise (DISC mode) is in fact just slightly lower than the C-4 at 50 µV. A 112 dB SNR (TONE off) is very respectable in any case, the C-4 scores only 106 dB.
I guess I just meant the jack itself is on the tone board, nothing special - as you said, customary dropper style
 
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