Technics SE-A5 Introduction & Description

Technics SE-A5 Stereo DC Power Amplifier

This is my collection of Technics SE-A5 stereo power amplifiers!  I have 3 units so far, two being standard SE-A5 and the third is an SE-A5 MK2. The standard ones are 120 watts RMS per channel and the MK2 is 150 Concentrated Power Blockwatts per channel and all have a vast reserve of power to give a real punch to the sound.  As you can see, they have beautiful full width illuminated VU meters that can be seen clear across the room with no trouble and the design has remained at the top of the Technics line for more than a 35 years.  There is a real big solid power transformer that is very quiet and the power capacitors are mounted in a block in the center of the main power amp board. Technics call this the Concentrated Power Block or CPB.  It's close to the output transistors sure enough and has 2  large 10,000 uF capacitors for each channel.  These were quite expensive in previous years and these days I would expect to see double the amount in such a design.  Then again, if a massive power supply is what you want, there is always the Technics SE-A3 with 22,000uF for each capacitor!  Reading the marketing descriptions you would think that Technics invented the Class AB power amplifier and reinvented negative feedback and called it linear feedback!  Who knows, maybe they did?  The amp does indeed have an offset bias arrangement (class AB) and also a sliding bias that they call Synchro bias.  In fact this is done with a device called a thermistor which is little more than a kind of light bulb that changes it's resistance with temperature The mystical synchro bias circuit!!based in most cases on the current passing through it.  As it takes time to cool, this gives a slow decay to the time taken for it to return to its normal resting resistance value. So this is what is under the mystical Synchro-Bias can on the main amp board.  The actual device used may or may not be solid state, I have never had to check.  It's the same thing that was used in a British GPO 746 telephone to prevent bell tinkle while the rotary dial was pulsing dialed digits when you took your finger out of the whole!  Not exactly high-tech but it does have the effect of lingering the bias at a higher level for a while after it has been set higher for a previous event.  In other words, if something loud HP Digital Spectrum Analyzer Reporthappens, the amp will be progressively more ready if another increase in level occurs soon after.  Regardless of all this, the SE-A5 has specifications for harmonic and intermodulation distortion that make the latest generation of MOS-FET designs struggle to keep up all certified by published measurements recorded on the Hewlett Packard HP3045 digital spectrum analyzer of the day!  They truly do sound great and I have to say that I can't hear the difference when comparing them to my Velleman vacuum tube amplifier.  OneClick to see the Test Sound Report from 1982 thing people often ask about on an SE-A5 is what the "Limited Power" switch is for?  When you press it, the VU meter lights go out and a small red indicator lights up.  What also happens is that the maximum output power is reduced to 30 watts per channel and the power consumption is reduced by half to about 200 watts at the 30 watt level.  Also the idling power usage is reduced to just 33 watts.  With the biasing arrangement the SE-A5 has they appear to run as cold as ice compared with anything other than a plain class B amp, so this feature is of limited use and was not included on any other design as far as I know.  The switch works via a double pole relay that selects different taps on the secondary side of the power transformer and it is easy to change the circuit so that the switch just controls the lights and not the output power.  This makes it useful as a display dimmer if the amp is visible in a home theatre situation, consult this schematic diagram for more information.  Some 120V US market SE-A5's I have found have a different configuration for the tap select relay and actually use two relays, one for each channel that are mounted under the preamp board on the right rather than on the left side of the preamp board itself.  This whole concept of selecting different taps on the transformer is actually derived from the tap selecting in the SE-A3MK2 where the relay is controlled by an impedance detection circuit that allows the SE-A3MK2 to drive the same output power into different load impedances.  Here on the SE-A5 it's almost as if Technics were trying to find some other usage for tap selection by implementing this limited power feature on the SE-A5, but just when you thought it was useless, I did find a real life use case for this switch in 2010 as described in the In-Dash section lower on this page.  Click here to see the SE-A5 user guide and here for the Test Sound Report from 1982.

Linear Feedback - The Making of an Epock!

I just had to add this quote from the SE-A5 Service Manual which I have edited to make it say what I think was intended as something was lost in the translation from Japanese in my English version of the manual:  "This circuit is the essence of multi-feedback technology of an amplifier circuit and is really an epock-making circuit that can theoretically realize zero distortion and output impedance by forming an amplifier having infinite amplification within the Negative Feedback loop.  It is not too much to say that the technical innovation that has been carried out to increase A (bare gain) and to minimize Zo (bare output impedance) and Do (bare distortion) for the improvement of the negative feedback amplifier, sets a new standard in audio power amplifier design.  When bare gain is increased through multi-stage amplification, the phase characteristic of the high frequency range will worsen and it may result in worsening of performance and sound quality because of limitations in negative feedback stability.  Also, if it is intended to reduce the bare distortion, this can be achieved by the circuit configuration of the SLPT (Super Linear Power Transistor) and the synchro bias  circuit, but there exist theoretical limitations because of using active elements.  The linear feedback circuit is the result of further development in realizing infinite bare gain without worsening the phase characteristic of high the frequency range that is recognized as ideal for a negative feedback amplifier."  Hmm, I think that they are just saying "Yeh, this amp rocks baby" and they are very proud of it...

Those Fantastic VU Power Meters   SE-A5 Power VU Meters!

Power VU Meter.  Photo by Ricardo MondaccaClearly one of the key cosmetic features of the SE-A5 power amplifier design are the pair of beautiful and elegant power meters where the meters for both stereo channels are mounted in the same casing that goes uninterrupted from one side to the other.  This exact same design is shared with the bigger SE-A3 and SE-A3 MK2.  The scales are very large and wide and with the light background and dark scale and pointer needle, they can be seen from a considerable distance which actually makes them quite useful as well as interesting and elegant.  The meters appear to be quite well damped meaning that they have a slightly sluggish movement when they are required to move or change direction quickly.  This is so you get a better opportunity to observe the level at any particular point without the pointer suddenly flicking away in which case it may appear as more of a blur, and it is therefore easier to see the average level.  This damping appears to be of the mechanical verity, a good indication of meter quality, and this can be tested by tipping the amp from side to side (if you are strong enough!).  This also helps stabilize the meters during transport and with normal care, they should never need to be adjusted unless the unit is dropped or other components have been changed.  Quite apart from comments on how fantastic they look, there are a few questions that people often ask about the meters which I'll discus a bit here:

Q: If the scale goes from 0.0001 to 300 watts, how come 1 watt is in the middle and when it says 1 watt, why is it so loud?

First, before we can answer this, we need to understand a bit about sound, decibels (dB's) and power in the context of a power amplifier, so let me state these facts:  The human ear can hear very quite sounds from 0.000000000001 watt/sq. meter up to the threshold of pain at about 1 watt/sq. meter, giving a total dynamic range of 120dB for most people.  Described simply, a decibel or dB is a base 10 logarithmic scale of relative difference between one level and another reference level, sound in this case.  An increase in sound level of 3dB is around the smallest difference that most people can detect.  An increase of 3dB requires double the power to produce!  A sound that sounds twice as loud as a reference sound requires ten times the amount of power to produce!  You can find more explanation about decibels (dB's) here.  So what does all this mean?  I describe it like this:  From the quietest sound you can hear from the amp, and for every doubling in perceived sound, the power meters must read ten times the previous level.  The multiples of ten are marked evenly spaced on the scale, 0.0001, 0.001, 0.01, 0.1, 1 and so on up to 100 and beyond.  So with there being roughly 7 and a bit marks, the value of 1 is roughly in the middle.  In fact even if the amp could manage 1000 or even 10,000 watts, 1Volume control counting counter clockwise in -dB would still be just about in the middle!  So this is why there is little point in making amps of much more than 100 watts per channel, and a 200 watt amp like the Technics SE-A3 could only give you 3dB more which you would only just be able to hear.  So why is 1 watt so much?  It's because it's 10 x 10 x 10 x 10 times more than the quietest amount of power you can hear!  To double the perceived sound again from that point will take 10 watts, and double again a 100!  So when running at 1 watt per channel with average sensitivity speakers, an average of 1 watt is actually quite a bit!  This then answers the question as to how a small amplifier still appears able to make a lot of noise when compared to a much larger one, with the exception of sound quality issues.  When I see the meters floating about the 1 watt mark, I know that the sound is at quite a sufficient average level.  If they are floating too close to the 10 mark, it means I have had too much beer!  Over 10, and the house is rocking baby!!  The dB scale on the meters, actually dBVU (Volume Unit) in this case, being a base 10 logarithmic scale, counts in a more linear manner with respect to the perceived level of sound and is numbered starting at 0 dB at the maximum power level of the amp and counts in + values above that point (called the head room which goes up to 300 watts for the SE-A5 scale), and - values below that point.  You can see a similar counting scheme on the volume control of high-end control amplifiers where the loudest most clockwise setting is marked as 0, and counts down in -dB from that point going counter clockwise.  In theory, if you adjust that volume control by 10 dB, you should see the same 10dB difference on the SE-A5 power meters.  So the reason the scale is like this on the control is that it is easy to see where to set the knob for a doubling in the current level without any guess work.  You can check this out using the 1 kHz tone mentioned below.

Q: Can the meters be adjusted to make sure the reading is correct?SE-A5 MkII meter calibrated to 100 Watts

The SE-A5 service manual describes the meter adjustment sequence as follows:

    1. Connect an oscillator to the input (normal) and apply a 1 kHz signal.
    2. Connect a 100W load resistance and AC volt meter to the speaker terminal.
    3. Set the input level adjusting VR to the maximum point.
    4. Adjust the output level of the oscillator so that the output from the speaker
        terminal is 28.3V. The formula is U2 / R = P gives 28.3*28.3 / 8 = 100.
    5. Adjust VR201 (left channel) and VR202 (right channel) so that the meter indicates 100W.

There are a couple of things about this.  First, you need an oscillator to generate the 1 kHz tone.  That's easy, just download the 1 kHz -10dB sine wave from here (right click, Save Target As...).  You can either plug your computer sound card into your preamp AUX input, or download the .wav file and burn it onto a CD and play it in your stereo.  Next they say you need a 100W 8 ohm resistor.  Believe me, that would be the mother of all resistors and very hard to find and you could easily set yourself on fire if you messed it up!  Since the meters are in fact just AC volt meters and assume a linear resistance across the power bandwidth (never so with any real speaker), there is no need for that and the voltage can be measured just as easily with no load resistance.  Look at the level displayed when the tone is playing, and note that the meter position is the same regardless of whether the speakers are on or not.  Remember to make sure that the speakers are NOT connected during the procedure when the level needs to be turned up to 100 watts!  When adjusting, make sure you you look at each meter individually with one eye directly in front of the mark.  The only thing missing from the SE-A5 meters are mirror scales like you see on high quality test equipment or even the Onkyo M-504 power amp that enable an exact reading to be taken.  Having said that I don't think a classic curved mirror would suit the SE-A5, as the meters look great as they are!  One further point to note is that you can also use the input level controls on the rear of the SE-A5 to calibrate your entire system from CD player to control amp volume setting to meter reading.  As the test tone is recorded at exactly -10dB, if you play it with your control amp control set to 0dB, you can adjust the SE-A5 input levels so the meters then read  -10dB.  A better way to do this is to set the volume control to -10dB so this should then read as a total of -20dB on the meters (about 1 watt) which is the most accurate part of the scale because it is in the centre.

Q: If this is a 120 watt per channel amplifier, why is the 0dBVU reference point set at the 100 watt mark on the scale?

I don't know the answer to this question and it remains a mystery as to why this is so?  If you know anything about this, please let me know!  Maybe some guy at Technics made a mistake that could not be reversed by the time it was noticed, but then again even the 150 watt per channel SE-A5 MK2 has the same scale layout even though the meter and scale design were completely revamped!  Clearly the 0dBVU reference point should be at the maximum power output level of 120 watts and not 100 assuming it is an 8ohm RMS scale, although it says watts (8ohms).  Then again, 120 is only a very small amount beyond 100 and another and maybe more convenient way of looking at it, is now the readings can be taken to mean power levels in %.  So 0dBVU is 100% like the scale says and 1 would be 1% and so on, and so the reading is always a percentage of the maximum no matter what the load impedance of the speakers.  This in fact makes this scale very convenient, so maybe the real question is why doesn't it just say Power % rather than watts (8 ohms)?  Either way, keeping an eye on the area between 1 and 10 can tell you a lot about yourself as well as the sensitivity of your speakers!

Q: Where can I get replacement bulbs for the meter lights?

The correct original part for the meter light pilot lamps is Technics part number XAMR74S17 and you may be able to order them here although even if they are available they are $2.33 each!  You can also getRS 655-9693 axial lamps something similar from Radio Spares in the UK which are R.S. Part number 655-9693 which can be ordered here if you are in the UK.  The spec is T3.8, axial lamp 10/15V, 55ma, 3/4 inch in length.  Click here to see the spec for the RS version.  There are sixteen lamps used in total.  Another idea for replacing just one or two is to use a 100mA lamp like this and put two 1 watt 39 ohm resistors in parallel with each other then in series with the lamp.  Don't do more than three like this though as it will be too much load for the power supply.  I have seen some lamps replaced with 8 100mA lamps rather than the 16 55mA versions.  This looks OK for a few months until you find that one of the lamps has made an orange/brown burn in the top of the meter casing.  Don't do that!  Unfortunately R.S. in the UK won't 12V 35mA lead lamp from Parts Expressship to the USA and their American agent Allied Electronics will not ship R.S. lamps from the UK because of the breakage problems they have had in the past.  Another alternative is to order some 12V 55mA DA613 lamps from JKL here where they are just $1 each at the time of writing, so currently that is the best choice and they sell them in packs of 20.  Some people have also asked me about the four signal lamps on the front.  These are 12V 45mA and can be found most any place, even at Radio Shack.  Parts Express do a 12V 35mA lamp which works OK and can be ordered here.  Replace all four if you're doing that so they all look the same.

Normal / DC inputs

Normal & DC line inputs

The Technics SE-A5 is equipped with two sets of line level inputs marked "DC" and "Normal".  The "Normal" inputs are coupled by a capacitor like with an ordinary amplifier.  In this case, the amplifier operates as a normal AC amplifier with a low end cutoff frequency of about 2Hz.  As a capacitor is a reactive device that can introduce phase changes, this is considered to be undesirable, so the SE-A5 has been designed as a DC amplifier where there are no capacitors in the signal path at all!  So using the "DC" input gives a completely flat frequency response right down to 0 Hz with no reactive phase effects of any capacitors!  One possible issue with doing this is in case of a fault in the device connected to the input.  If for some reason there is a DC component in the input signal, this will result in the speaker cones being pushed and held there which will cause the voice coils to burn because of the very low DC resistance compared to about 8 ohms of AC resistance (or inductive reactance), although the internal output protection circuit will operate to save the speakers from this.  So if it is desired to operate with such an input, the "Normal" inputs are provided to ensure compatibility and are simply coupled to the "DC" inputs via a capacitor which eliminates the DC component of the signal.  When ever possible, the amp should be operated using the "DC" input and only one set of the inputs should be connected at one time.  Some other Technics power amp designs have just one set of inputs with a switch that has the "Normal" and "DC" settings.

My SE-A5's

My original SE-A5 on topThe first SE-A5 I had was in October 1983 and was bought new from Jack White in Cambridge England at a cost of 400 GBP to go with my very first CD player, the Sony CDP-101.  At the time I was 21 and still just about living with my parents, so this was part of my last "bedroom system" and is still working in my latest 5.1 system today.  If you buy high quality high end equipment, it really will last a lifetime!  I have all the original manuals and you can download a copy of the SE-A5 schematic circuit diagram here.

SE-A5 as seen on eBayThe second SE-A5 I acquired from eBay in 2003.  I bid $550 for it and at the end of the auction it sold for $380 plus shipping.  When it arrived a couple of weeks later I was amazed to find that it was in perfect condition just like my original unit, however it appeared to be covered in a thin but tough film of nicotine!  I presume therefore that it came from the estate sale of the previous now deceased owner!  It was also very clean inside.  I dismantled the case to expose the meters and cleaned everything.  When it was reassembled it really did look like new and is working perfectly!  These days such units go for nearer $800 on eBay, so not a bad investment!

My SE-A5 MK2

Technics SE-A5MK2 Stereo DC Power Amplifier

SE-A5 MKIIThe SE-A5 MK2 that I have also came to me via eBay for about $380 and I have recently seen them sell for over $700 so I guess I should buy more!  Inside it looks very similar to its SE-A5 predecessor.  From what I can make out, the Synchro-Bias system employed in the original SE-A5 has been augmented and enhanced with a system called "Computer Drive" described further below.  It has a nice illuminated logo on the front but is lacking the detail of the original Computer Drive display on the SE-A3 MK2.  The front of the casing on the SE-A5 MK2 is also changed with the power meters being tilted back at the top and the meter scales are black & red and in two different layers.  The sides of the meter window are also changed to a lighter color that matches the rest of the surround.  In the Japanese market version seen here, the meter surrounds are dark which looks much better.  All in all, in my opinion, the original version looks best and tilting the meters back does no good if you are too much higher than the unit itself because the top of the meter is further back in the case.  Being slightly more powerful at 150 watts RMS per channel into either 4 or 8 ohms with its output impedance detection, the SE-A5 MK2 sure packs a good punch and runs slightly hotter than the original SE-A5 but still cool compared to it's big Computer Drive brother, the SE-A3 MK2.  One thing that you won't notice about the SE-A5 MK2 unless you have a regular SE-A5 or SE-A3 right there is that the meter movement is very sluggish (over damped) and is almost boring to look at by comparison.  The very best Technics fast attack meters are only to be found on the SE-A3 MK2.

SE-A5 MK2 Computer Drive

Computer Drive PCB layoutThe Computer Drive used in the SE-A5MK2 is a customComputer Drive New Class A Technics MN1404STE chip, based on the larger and more complicated MN1421STE employed in the first Computer Drive amp, the SE-A3 MK2.  The MN1404 is simpler in that it only has one 60oC temperature sensor input and a common 2V signal input for both the left and right channels and then two separate 5V signal inputs for each channel.  The purpose of this is to be able to adjust the biasing of the output stage (the ICQ) with some intelligence MN1404STE Pin Descriptionsbased on the temperature and the level of the signal passing through the output stage and also to provide startup protection and a quick warm up.  This should also give the amp longevity because under low signal conditions (the most usual case) the bias need not be set too high resulting in lower output transistor temperatures.  The MN1404STE does a better job in this respect than the MN1421STE in the SE-A3 MK2 which runs too hot to touch all the time resulting in fatigue and ultimate output stage failure.  The table to the left shows the pin assignments of the MN1404STE.  Like the MN1421STE it runs at a modest rate,  in this case 415kHz.


The next chart to the left shows the conditions on the input port A and the corresponding conditions on the output port C of the MN1404STE over time.  The Power "on" mode section shows how the safety indicator is blinked and then remains in the on condition as it's normal state.  This is unusual and in fact opposite to the normal state on the SE-A5 where an illuminated indicator indicates a fault.  After this the preheat continues for another 14 seconds and once that is complete the green "auto on" lamp lights.  In the DC Detection section, the chart shows how the safety lamp and the output relay act in case of DC detection or output short circuit condition. The ICQ control section shows how port C acts with varying voltage and temperature conditions on port A. As you can see, there is a direct relationship between A12 and CO0, A11 and CO1, A10 and CO2 and all CO outputs go high when there is a temperature detection.  SoComputer Drive New Class A all in all, this is a pretty simplistic system with only 2 ICQ settings per channel but it does have a great illuminated logo!  For more info, click here to see the SE-A5 MK2 service Manual.

SE-A5 Problems

Q311 & Q315 replaced with new heat sinks

I did have one failure on my original SE-A5 in 1997.  At that time we were living in Sterling VA and I didn't have all my electronics stuff there so I ended up packing it away for a while.  Eventually in 2003 six years after it broke and some twenty years since first buying it, I finally got around to getting it working again.  The problem manifested itself as a failure of the protection circuit to switch off after power up.  Upon2SA1124 Transistor further investigation I found this to be a blown transistor in the left channel, Q311, a 2SA1124 available from DigiKey for the princely sum of 74 cents.  This is used as a class A amplifier in the preamp section in front of the class A pre-drive (Q613).  The whole thing appeared to be fused with all legs being short circuit, so most all of the positive voltage line was connected into the signal path, so the protection circuit activated as there was now a DC potential always at the speaker output.  To keep things in balance I also changed out Q312 in the other channel and their complementary NPN counterparts Q315 & Q316 (used as current regulators), 2SC2632 devices at just 66 cents each.  It appeared that all four of these transistors run on the hot side for TO-92 style cases, so I also fitted a small heat sink to each of them to make sure there were no further problems.  At the time as I didn't have a service manual, I just used a systematic approach of removing each transistor one at a time working from the output transistors back into the amp and testing each one for short circuits between the legs.  TO-92 heatsink HS251-ND from DigiKey.comYears later in 2017, I had a problem with my other SE-A5.  This time the protection started to come on after100 ohm for R347 & R348 the amp heated up for a short while, so an intermittent protection fault.  As this SE-A5 still had the old original transistors for Q311, Q312 and Q315, Q316, I decided to just change those out for new ones and sure enough, that fixed the problem!  Then, as I now finally have a service manual for the SE-A5, I finally decided to read it, and guess what? There is an addendum at the end from 1985 that describes problems with these very transistors and recommends replacing R347 & R348 with 100 ohm resistors rather than the original 68 ohm ones to reduce current flow.  So now finally, 32 years after Technics first identified this problem, I have finally implemented this change!  Having said that, my original SE-A5 that just had the new transistors with added heat sinks worked like that for 14 years and probably would have gone on for much longer, so I think that the heat sinks are still a good idea to make sure the SE-A5 keeps on running.  You can use heat sink HS251-ND from DigiKey.  You may have to open the jaws a little but they will fit.  Thanks to Ricardo Mondaca from Chili for sending me that version of the service manual in 2010 and next time I'll make sure to pay more attention to his emails!

2SC2291-GAnother small issue I have noted since using my U.K. market unit in the U.S.A. is that there is sometimes a small irregular whizing sound from both channels.  Just as a guess, I decided to disconnect the ground connection from the three core mains cable and the problem went away, so it appeared to be some kind of ground (earth for the English) loop problem.  As the transformer is fully double insulated and the only places in the case that mains is exposed is at the voltage selector, I decided to just leave it like that.  The American market version is like that anyhow with the input fuses exposed in the same way and only connected with a two core mains cable. If you need it I have a copy of the schematic circuit diagram here.  Another thing I noticed while dismantling the amp to find the Q311 problem, was that the silicone heat sink compound on the back of the power transistors was showing signs of drying up.  So to rectify that, I removed them all, cleaned them and replaced them again with new compound to prevent any trouble in the future.  The best place to search for original Technics/Matsushita replacement parts is  Another component I have had trouble with in other Technics Amps is the 2SC2291-G, a funky device with 5 legs containing two matched back to back NPN/PNP transistors with a common base terminal, and this is also used in the SE-A5.  Luckily UED has a page for the device if you need one.  When it starts to fail it produces a crackling sound on the effected channel.  Finally the last modification to my SE-A5's has been to replace the old twisting speakers terminals for some new binding posts that can actually accept a modern sized speaker wire as shown above to the right.

Protection Circuit Diagnostics

The following diagram can be useful in some cases (although not in my case described above) to isolate the location of a failed transistor when the protection circuit is stuck on all the time.  In cases where the protection indicator blinks (and the speaker relays click on and off) it indicates that there is a short in the speaker wires, so try to turn off the speaker switch and see it it settles down.  If so, you just have to find the short in the speaker wires.  If you think that your unit just needs adjusting, you can follow the procedure in the next section.

SE-A5 Measurement and Adjustment

New pin in TP3If you have reason to to change out any major components in the circuit at any time or if the protectionVolt meter circuit is unstable, you will need to adjust a few items to make sure the amp is running correctly and these are the procedures that need to be followed.  All you will need is a DC voltmeter that can measure down to 0.1mV DC.  After these adjustments, you should adjust the meters as described above.  This is a good time to mention the fact that no SE-A5 I have ever seen actually has the pins inserted in TP1 to TP4 on the main board where you will need to be to measure the clamp voltage and ICQ.  Now while you could probably find some places in the circuit to clip onto, I recommend fitting proper pins into the test point locations.  You can see a new pin fitted in TP3 in the picture above.

Startup precautions
Set VR601, VR602, VR603 & VR604 fully coulter clockwise before turning on.
Set the limited power switch to "Full" and the "Main" speaker switch on but with no speakers connected.
Let the amp run for at least 15 minutes or more if you have time.

Constant voltage check
(Left) Check that TP401 measures +23V to +25V with respect to ground.
(Right) Check that TP402 measures -23V to -25V with respect to ground.

Adjustment of DC balance
(Left) Connect the voltmeter (30mV range) to the left speaker outputs and adjust VR301 so that the reading is 0.
(Right) Connect the voltmeter (30mV range) to the right speaker outputs and adjust VR302 so that the reading is 0.
If it is not possible to get the reading to 0, try cutting the jumper wire J301 (Left) and J302 (Right).

Adjustment of clamp voltage
(Left) Connect the voltmeter between TP1 and TP3 and adjust VR603 to 0.1mV.
(Right) Connect the voltmeter between TP2 and TP4 and adjust VR604 to 0.1mV.

Adjustment of ICQ
(Left) Connect the voltmeter between TP1 and TP3 and adjust VR601 to 15mV.
(Right) Connect the voltmeter between TP2 and TP4 and adjust VR602 to 15mV.

Recheck of ICQ
ICQ is unstable for about 15 minutes after turning on so at this point you should leave the amp to sit and age for at least another 15 minutes, then go back and recheck the voltage between TP1 & TP3 (Left) and TP2 & TP4 (Right) and make sure the voltage is in the range of 1mV ~ 20mV.

The Mother of All In-Dash Stereos Technics SE-A5

So you like to listen to some music while you drive?  How about 120 Watts per channel of Technics SE-A5 with KEF Cadenza speakers along with a soundfield processor, 600 disc DVD changer, HDTV tuner and a ROKU streaming box all connected to a 5 foot wide DLP projector screen!  This is the setup in my American Tradition touring coach!  The whole stereo is in a lift that rises up out of the dash when the vehicle is parked!

So here we have the most unlikely case conceivable by the Technics engineers that designed the SE-A5, however it is indeed a real use case for the infamous Technics SE-A5 Limited Power switch!  Large modern rear engined diesel coaches like my Fleetwood American Tradition have three sources for 120V AC power.  The first is of course shore power, a term that comes from hooking up boats that are moored at a marina to power on the shore, in other words you just plug the whole thing into a fixed land power receptacle typically at a camp site, 120V 50A in the case of this coach.  The second source of power is a 7500 watt diesel generator which can run for weeks on the 150 gallon diesel tank and as well as powering the stereo is most usually used for running the two large air conditioners on the coach.  The third and most interesting source of power on the American Tradition is a 2000 watt inverter.  This device draws power from 4 very large 6 volt deep cycle batteries.  These batteries are intended to run the 12V lights, control box for the gas fridge, and via the inverter that converts the 12V DC into 120V AC, the microwave, TV, washing machine or sometimes even the water heater if your out of propane gas and of course, the big stereo.  The catch is, what comes out, must have gone in before!  In other words, there are limits on how long even those monster size batteries will last on any given day depending on how much charge they have had.  So if your parked for the night someplace and you don't want to waste diesel by running the generator for just powering the stereo and projector, you can extend battery life by running the Technics SE-A5 in Limited Power mode and it makes a real difference!  With running a big DLP projector like the Sharp XV-Z9000U already putting quite a strain on the batteries (even with it also running in ECO mode), being able to save some power on the power amp can extend battery life enough to watch another entire feature film in the same evening on the same charge of the batteries.  Who would have ever thought that there would be such a useful case for Limited Power!  Don't try this with a Technics SE-A3MK2! No more movies for you today!

Other Technics SE-A Power Amp designs








Over the years Technics have made some beautiful high quality power amplifiers but not much of it is or ever was available in the U.S.A.  Europe and Japan is the biggest market for this stuff and it's not unusual to see SE-A5's and SE-A3's come up for auction on eBay in those markets.  I have an SE-A3 which you can see here and an SE-A3 MK2 here.  If I can ever find out how to get a 50lb SE-A3000 or SE-A7000 into the U.S.A. for less than the cost of going to Germany and getting it myself, I'd do that too!  Below is the Technics SE-A3000.  At 120 watts per channel it is the most present day MOS-FET equivalent at the time of writing of the now 20+ year old SE-A5.  Hmm, it would be good to set them up head to head to see what 30 years of electronics evolution has done for the high-end power amplifier.  Until I know otherwise for sure, my money is on the bi-polar SLPT transistors of the good old SE-A5!  There is more information on Technic's amps from other guys like me at Axel Dahl's website,  Thanks to the many to many people to mention from around the globe that have commented on and added value to this page!

Technics SE-A3000, but not in the USA!

Current usage

Today the two SE-A5's are used in my home theatre system to drive a single JBL SVA-2100 each.  The left channel of each SE-A5 is used to drive the woofers and the right channel drives the tweeter of each speaker.  So the single center channel of the 5.1 surround sound system has 4 X 120 watts of bi-wired & bi-amped SE-A5 power driving a pair of massive JBL SVA-2100's amounting to almost half a kilowatt of center channel power! Cool!  The Speakers lie on their sides with the subwoofer in between them and each SE-A5 sits on top of its own speaker and apart from the other speakers are the only equipment in the room.  The power to switch them on is remotely controlled via X10 and I have also setup the meter lights on a separate X10 circuit so that they can be smoothly dimmed up and down when it's time to switch from music to projection!

I use the SE-A5 MKII as the power amp for the system in my office.  There it is paired up with a Technics SU-A60 that I purchased new in 1989 to use with my original SE-A5 and a Technics SL-P1000 CD player from 1987.  Here is a picture of them all together!

Pictures & Reference

All three of my SE-A5 amps Pair of SE-A5 amps All three SE-A5's in natural light Pair of SE-A5 amps in natural light
eBay image of my second SE-A5 eBay image of the inside of my second SE-A5 eBay image of my SE-A5 MKII eBay image of the inside of my SE-A5 MKII

Complete center system

Matching SU-A60 pre amp and SL-P1000 CD player

Brochure page 1 Brochure page 2 Brochure page 3 Brochure page 4

Here are some extra pictures sent to me by Ricardo Mondaca from Chile of his SE-A5's and other Technics equipment including SU-A4.

In some markets the SE-A5 was just badged as simply A5.  Here is a picture of a 100V AC A5 sent to me by Nguyen Quang from Vietnam where he found it in a street market!




Technics SU-A6 preamp

The Technics SE-A5 is of course just a power amp and Technics produced the SU-A6 preamp to go with it to form a complete amplifier system.  I never owned one of these myself but I do have an SU-A60 (click here for user guide) from 1988 that I have owned form new that you can see here with my Technics SL-P1000 CD player.  While any number of big power amps like the SE-A5 can be used in modern 5/7.1 systems, the preamps that were intended to go with them are of somewhat limited use unless you are setting up an entirely vintage system, and even then you only need one.  At lease my SU-A60 has some digital inputs and switching capacity although the older SU-A6 does look cool!  Here are some pictures sent to me by Daniel Zumsteg from Switzerland of his SU-A6 and of course SE-A5.

SE-A5Mk2 Pictures