Amplifier used at 6 volts and not the correct 9 volts.

[john curzon]

Have an external Sony Speaker Amplifier SRS T1 that can plug into a Radio. It runs of four AA batteries. It could also run off a 9 volt power supply mains transformer, but i don't have one. I do have a Sony one but it is only 6 Volts. Would it damage this type of amplifier if I use it at six volts rather than the correct 9 volts ? The Polarity is OK.

[Theo]

It is doubtful it would - if it's designed to run off 4 batteries it will likely work down to about 4.5V, so it must be tolerant of a large voltage range. It is possible there's a different pathway from the batteries and the external input, but even if there was I wouldn't expect damage to occur from undervoltage.

Try it and see?

Theo

[Brian Gaff]

I suspect there is an internal regulator for 6v as that is what the batteries will be. I don't think it will damage it, but it might now work very well as the regulator could just refuse to pass current if you gave it less voltage. More to the point, what is the current drain and does it need a psu with very good smoothing before its connected, since the hum may well be annoying otherwise. Many linear psus have no regulation. However 5v plug in ones do and often do not operate equipment very well,I find. Most are chargers so have special circuits in them to pulse the voltage if it sees that the voltage is high. Online there are many cheap psus, and as long as the polarity is right, the plug correct and the device can take the current its going to work. I have a Truecall answering device where the switch mode original started to behave like a radio jammer, and I found an old analogue one from an old modem that fit the bill and it ran it fine. Brian

[Cursitor Doom]

Short answer: no. The designer would need to factor into account the fact that batteries go flat and any design that failed to account for that wouldn't get as far as a production line. Low supply voltage just normally shows up as distortion, which is annoying but harmless.

[Paul]

Uses three amplifier chips, likely all running in bridged mode (to avoid a coupling cap). The tweeter amps are elegant. The sub amp chip is a bit more of a knuckle-dragger (in that, the datasheet is worse than useless, no good theory of operation).

Downloader sites, never give direct links. You must follow the ceremony (the minefield) to get your sheet.

Name: sony_srs-t1_t1pc_sm.pdf Size: 1231807 bytes (1202 KiB) SHA256: 0475675BDCE71784D5006463028BEAF13D40A88FF6F7C526DC3252EF2BD3DC50

New Japan Radio amplifier chip NJM2073 - wide range supply.

STmicro TEA2025 B/D amplifier chip (letter affects IC packaging details) Relatively wide range supply, with some sort of boost for battery op. Quiescent current draw is a bit high.

The barrel input, is the usual two current carrying contacts, plus it has a "side-contact" that pushes out of the way, and disconnects the internal battery.

Since there are no regulators inside the device, YES, you can run it off your 6V 1 ampere regulated DC adapter.

One other disturbing artifact, is there seems to be no low-batt cutoff. If you were using rechargeables, I would guess as the user, as soon as you see the power LED go off, immediately turn off the device to avoid rechargeable battery damage. I was hoping to see cutoff pins on the amp chips, driven by a low batt, but there appears to be no such feature. Thus, it really is intended to ruin one set of alkaline after another. Like a giant battery gobbler. The adapter input is pretty well mandatory, to keep your sanity.

[Picture] Essential bits of Electrotanya doc ("Download Original")

The voltages marked on the schematic, are for when the circuit is supplied with 9V input. This means the design is "centered" on 9V and gives more power output (to sub) on 9V. Using 6V battery is a slightly inferior experience. But, as near as I can tell, it should work. The power LED may disappear when the zener detects the voltage is too low (a little less than 4V). But there are no MOSFETs in there to cut off the batteries completely (if on battery). This could damage things like NiMH if you used them and fell asleep listening to the device (the NiMH would get reverse biased).

Paul

[alan_m]

The circuit diagram can be found at

If the external source is 6V DC, has the necessary smoothing components and the polarity is correct it should be OK. There is a internal 100uF

16V capacitor across the supply.

The jack socket which accepts the incoming power supply just disconnects the battery (4x AA batteries) and routes in the external supply.

[Fredxx]

If the circuit runs down to 4V then the alkalines will be toast anyway.

I was drawn to the fact that the battery -Ve terminal seems to be floating, there being no connection between TP13 and TP14

Agreed about using rechargeables.

[Harry Bloomfield Esq]

It will be fine, providing it can provide the current and has adequate smoothing. Worst that can happen, is some buzz from poor smoothing, and,or distortion. No damage.

[Fredxx]

Did you notice that D103 is a nominal 3.7-3.97V zener that will drain the battery for no good reason? At 6V it will be taking 20mA through R51. Talk about a cheapskate way of making the LED a constant brightness!

[Fredxx]

There's no regulator. Battery volts or PSU volts are applied directly to the amps.

[Brian Gaff]

Be interesting to see what happens. I remember myself once when I could see making a dummy battery for an amp with no power plug, Basically a bit of wood long enough to touch the battery connections, two bits of double sided pcb, though single sided would do, and a small rubber washer under one end. Then file a tiny slot each end of the battery cover for the wires to come out. Bodgers R Us.