Step down transformers for Japanese Stereo Equipment

[darrelj]

8 hours ago, Peterbean said:

1000 or 2000 watt models.  

 

Quite expensive when compared to the price of the amp. I purchased my sansui for just over A$ 400 and if I got to pay a similar amount for the transformer it is expensive for me. If at all i will decide on a 500 or 600 w Tortech Isolated which is affordable and enough capacity for the amp which is rated 250W power consumption

[darrelj]

How about this one- not an isolated one- but I can get this for under A$100 

https://www.ebay.com.au/itm/125622902414?

 

Edited May 13, 2024 by darrelj

[muon*]

1 hour ago, darrelj said:

 

Quite expensive when compared to the price of the amp. I purchased my sansui for just over A$ 400 and if I got to pay a similar amount for the transformer it is expensive for me. If at all i will decide on a 500 or 600 w Tortech Isolated which is affordable and enough capacity for the amp which is rated 250W power consumption

Buy from Tortech and ask them what you need, they are very good and know their stuff (It's their business)and are big enough to not have any interest in up selling you.

 

Edit: and will be more suitable being for 240Vac mains.

Edited May 13, 2024 by muon*

[muon*]

43 minutes ago, darrelj said:

How about this one- not an isolated one- but I can get this for under A$100 

https://www.ebay.com.au/itm/125622902414?

 

That's for 230v mains.

 

It also has a Type A mains plug

Australia mains accept Type l

 

This mean you will have to get the mains side plug changed or use a crappy adapter.

 

Sockets for output are Type A and Type C

In Japan, power plugs and sockets (outlets) of type A and type B are used.

Edited May 13, 2024 by muon*

[metal beat]

9 hours ago, Peterbean said:

What specs for transformers that you use on your turntable?

 

I use the Japanese isolated transformers. 

 I use the SD100-500, 500 watt model which has two sockets so ran two tables.

 

I moved one turntable, so bought the SD100-100, 100 Watt model for that.

 

Cheers

[darrelj]

I have been gifted a step-down transformer 500VA . I checked the output voltage  and it shows 107 on my multimeter. Is this too high and unsafe for my Japanese 100v amp

Edited May 27, 2024 by darrelj

[andyr]

3 hours ago, darrelj said:

I have been given a step-down transformer 500VA . I checked the output voltage and it shows 107v on my multimeter. Is this too high and unsafe for my Japanese 100v amp

 

NO!

 

You are reading 107v, I suspect, bcoz you haven't yet plugged your Japanese 100v amp into the step-down transformer.  IOW ... the step-down is not 'loaded'; once it is ... the output voltage of the step-down ... will reduce.

 

You may have a problem, I suggest, with the transformer's 500VA (ie. 500 watt) rating.  What power is your Japanese 100v amp rated at?

 

[darrelj]

11 minutes ago, andyr said:

I suspect, bcoz you haven't yet plugged your Japanese 100v amp into the step-down transformer

 

You are right. It has not been plugged in yet. The amp is rated as 250W

[andyr]

15 minutes ago, darrelj said:

You are right. It has not been plugged in yet. The amp is rated as 250W

 

OK ... is that 250w per channel output - which means 500w output in total - or 125w per channel so 250w overall?

 

Or is the 250w the total sucked from the power point?

 

[muon*]

Probably 250w the total sucked from the power point.

Rated power consumption250W

https://audio-database.com/SANSUI/amp/au-alpha607kx-e.html

[darrelj]

5 hours ago, muon* said:

Probably 250w the total sucked from the power point.

Rated power consumption250W

https://audio-database.com/SANSUI/amp/au-alpha607kx-e.html

 

Exactly. This is the model too.

[mbz]

12 hours ago, darrelj said:

I checked the output voltage  and it shows 107 on my multimeter. Is this too high and unsafe for my Japanese 100v amp

This is the "no load voltage" as pointed out above. Once loaded it will drop to 103-104Vac. This voltage will further decrease (to 100Vac) as you increase the load (turn up the volume) to 500VA.

 

103-104Vac "mains" is fine for the amp, if you have OCD and are diy capable you could check the bias at these slightly higher voltages, better to button it up and enjoy the music.

[pete_mac]

1 hour ago, darrelj said:

 

Exactly. This is the model too.

 

Interestingly, Sansui measures the rated consumption of their amps differently than you'd expect - it does not appear to be a maximum consumption figure.

 

An amp such as yours which is rated at 90WRMS/ch, 2 channels driven at 8 ohms (180W total output at full noise) at, say 50% efficiency for a Class AB amp, means it will draw at least 360W at full noise, plus a handful of extra watts for the rest of the amp circuitry.  250W is too low.

 

Similarly,  my AU-alpha 907MR has 400W on the rear panel, whilst it will draw far more at full noise (160WRMS/ch = 320W total, and at 50% efficiency that's at least 640W).

 

 

 

 

 

 

[andyr]

In light of this, Darryl:

 

11 minutes ago, pete_mac said:

Interestingly, Sansui measures the rated consumption of their amps differently than you'd expect - it does not appear to be a maximum consumption figure.

 

An amp such as yours which is rated at 90WRMS/ch, 2 channels driven at 8 ohms (180W total output at full noise) at, say 50% efficiency for a Class AB amp, means it will draw at least 360W at full noise, plus a handful of extra watts for the rest of the amp circuitry.  250W is too low.

 

... given this comment of yours:

 

1 hour ago, darrelj said:

Exactly. This is the model too.

 

... I would suggest the 500VA step-down transformer you bought ... may be 'throttling' the performance of your amp - unless you play it at a low level.

 

[mbz]

For a Class AB amp I would expect better than 50% efficiency, closer to 70%???

 

What is the value of the main fuse? 5A??? That would give an input VA of 500, with 250W output that would ballpark to 50%. Yes this is a very crude estimation.

 

Value of main fuse??? Hopefully I will learn something...

[darrelj]

1 hour ago, mbz said:

What is the value of the main fuse? 5A???

Where do you find this information? 

[andyr]

15 minutes ago, darrelj said:

Where do you find this information? 

 

Should be on one of the fuse end plates.

 

[mbz]

Well I learned I'm still lousey at math (struggled with complex hyperbolic functions).

The power in can be roughly ballparked by fuse x 100. The power out will be the rated power output, ie, 2x90W.

 

I checked some online pix, did not show any rear panel mounted fuses, so it's internal, not worth lifting the lid, will try and find a schematic/service manual.

[darrelj]

12 minutes ago, andyr said:

Should be on one of the fuse end plates

Excuse my ignorance here. I guess you are referring to the transformer? I can see a fuse on the back of the transformer alongwith  the 240v input socket .  The electrician inserted a 3 amp slowblow fuse here and said let's see how it goes. If it fuses - he said we wil increase to 3.5. But reading Tortech step-down transformer specs for a Japanese Isoltated model of 500W- it said that the replacment fuse is 5 amp. 

[andyr]

53 minutes ago, darrelj said:

Excuse my ignorance here. I guess you are referring to the transformer?

 

No - I thought you were looking for the fuse on/in your amp (in answer to a Qu which 'mbz' asked you).

 

53 minutes ago, darrelj said:

I can see a fuse on the back of the transformer along with  the 240v input socket .  The electrician inserted a 3 amp slowblow fuse here and said let's see how it goes. If it fuses - he said we will increase to 3.5. But reading Tortech step-down transformer specs for a Japanese Isolated model of 500W- it said that the replacement fuse is 5 amp. 

 

The fuse on the step-down traffo is not the important one; I would agree with your sparkie - try a 3a ... and then go up a bit, if it blows.

 

If Tortech's documentation says '5a' ... maybe they're referring to a "quick-blow" fuse, rather than a "slo-blo"?

 

[pete_mac]

3 hours ago, mbz said:

For a Class AB amp I would expect better than 50% efficiency, closer to 70%???

 

 

Perhaps so... I've seen 60% bandied about as being a more realistic figure, although it depends upon the design and biasing approach taken with the amp. 50% was used for ease of calculation whilst posting on the phone

[mbz]

Think we've drifted off topic, apologies.

 

There was some question whether a 500VA stepdown would be suitable for the 607KX. There is also some question as to how the 250W consumption for the Sansui is derived.

 

I would lean towards trusting the 250W consumption as it's a published figure that can be easily verified so 500VA stepdown will be ok.

[andyr]

2 minutes ago, mbz said:

I would lean towards trusting the 250W consumption as it's a published figure that can be easily verified so 500VA stepdown will be ok.

 

I think that's rather a bold statement!

 

The only way it can actually be proven ... is by buying a 1KVA step down, and then listening to the amp when it is plugged into one ... and then the other.

 

[darrelj]

35 minutes ago, andyr said:

and then listening to the amp when it is plugged into one ... and then the other.

what difference would one notice?

[andyr]

26 minutes ago, darrelj said:

what difference would one notice?

 

Yeah, good question; my answer is ... the difference between an amp which sounds 10 out of 10 - vs. 6 out of 10.