Step down transformers for Japanese Stereo Equipment

[stereo coffee]

3 minutes ago, sir sanders zingmore said:

 

The linked article might be a bit technical for many people. If it contains important safety info it might be a good idea if you could summarise it so that the less technical amongst us can be safe too

Consumers

Audio equipment is provided meeting standards. Refer any servicing to a technician. Always replace the fuse provided externally with another of the same type and rating. Should the equipment continue to fail having replaced a fuse, refer to a technician or to the equipment manufacturer for service.   Replace frayed or damaged leads with new insulated ones. Never disable the safety earth of equipment or their leads.  

 

Technicians

If you are specifically testing dangerous voltages on the mains side of equipment, then a isolation transformer would be used,, but then in limited circumstances where it is essential. 

 

In all other circumstances precautions apply to using any equipment connected to the mains, where a RCD Residual Current Device, safety switch  should be installed for your safety. 

 

Transformer mounting always be aware of bolts for toroidal types and propensity for creating a shorted turn through the middle where flux is highest, where each side of the case could touch the bolt.

 

Limit current to the expected current when testing. Limit voltage using a Variac to assist  

 

 

 

 

 

 

 

 

 

 

   

 

.

[mbz]

1 hour ago, stereo coffee said:

The reasons for not using the isolated type for general purpose use is explained here :

 https://sound-au.com/articles/iso-xfmr.htm

Think you will find that the article is about 240Vac : 240Vac (ie, 1:1) transformers and does not appear to discuss the merits of isolated v autotransformer. See pix below of image lifted from wiki. Note that the secondary is not isolated from the primary.

 

On the question of 1000W or 600W for a 250W amp, I assumed this was 250W power consumption and not output/channel. 600W will be fine.

[mbz]

Another consideration is, are you likely to purchase other 100Vac items like amps where 600VA might be a little small???

[muon*]

Can we know what the amp is?

[darrelj]

The amp is 250W of power consumption. 

The Amp is  a Sansui 607KX

 

 

 

[darrelj]

i found this brand new for $100. not an isolated though

 

Specifications
Product Code: stxp-j1500
type: autotransformer
Input Voltage: 240v ac
Input Frequency: 50hz
Input Fuse: 8a
Output Voltage: 100v ac
output frequency: 50hz
continuous output: 1000 watts
maximum output over 1 hour period: 1500 watts
dimensions: 21 x 18.5 x 15.5 cms (lxwxh)
weight: 7.8 kgs
input cable length: 59 cms
colour: black

 

any use

[darrelj]

definitely No . this will be the only jap equipment 

Edited May 9, 2024 by darrelj

[muon*]

4 hours ago, mbz said:

It will be fine as long as you don't play at rock concert levels. Most home listening is done at less than 50W assuming you don't have 85dB/1/1 or worse speakers.

 

Isolated transformer is preferred however it's a trade-off. Depends on the mains and wanted voltage, eg 240Vac to 100Vac or 240Vac to 220Vac. Also depends on the value of your amp. An autotransformer is a bit like a volume pot with the wiper fixed in one position. A winding fault(open) may (depending on where open occurs) mean that mains voltage is sent to your amp. A 100Vac amp supplied with 240Vac will cause power supply damage and... Consequences not so severe for a 220Vac amp. Not an issue where a step up transformer is needed.

 

I'd be going isolated if you've snared yourself a nice amp like a sansui alpha, 919, Luxman,,, If it's a nice run of the mill amp (NAD?) then an autotranformer will be fine especially if it's new.

 

https://www.ebay.com.au/itm/194595281395

Tortech have the same item for $190- Prices have crept up, not so long ago they were about $170-

 

 

 

33 minutes ago, darrelj said:

The amp is 250W of power consumption. 

The Amp is  a Sansui 607KX

 

 

 

AS mbz says.

[mbz]

8 hours ago, darrelj said:

Product Code: stxp-j1500

Fairly sure this is a chinese "product". On paper it looks fine (240/100Vac, 1000VA...) but it will be 230Vac/100Vac like most/all the others. Difficult to assess the quality. You've got a nice amp, need to feed it clean power. Will search for a pix of the stxp internals to see components used and how well put together it is.

[pete_mac]

8 hours ago, darrelj said:

i found this brand new for $100. not an isolated though

 

Specifications
Product Code: stxp-j1500
type: autotransformer
Input Voltage: 240v ac
Input Frequency: 50hz
Input Fuse: 8a
Output Voltage: 100v ac
output frequency: 50hz
continuous output: 1000 watts
maximum output over 1 hour period: 1500 watts
dimensions: 21 x 18.5 x 15.5 cms (lxwxh)
weight: 7.8 kgs
input cable length: 59 cms
colour: black

 

any use

 

That sounds like the Wallcann 8ZED model unless I am mistaken. I have that exact model for a long time now with my big Sansui AU-alphas. Performs flawlessly. I've referred quite a few JDM 100V amp users to that model.

 

I've read about the theoretical worst-case-scenario risk factor with an autoformer-based stepdown but I'm yet to hear of anyone actually having a first-hand issue with them. 

[xlr8or]

12 hours ago, darrelj said:

both you and Kirk have directed to the same transformer on eBay , nice. They are 1000VA. How about this https://www.ebay.com.au/itm/355154957732?

 

 

Stick with the Tortech ones. If anything go with your initial recommendation of using the 600w isolated one. It should be fine for 250w with plenty of headroom left in reserve. Just don't plug a second unit into it.

[darrelj]

1 hour ago, mbz said:

Will search for a pix of the stxp internals to see components used and how well put together it is

Thanks and much appreciated.

[darrelj]

1 hour ago, pete_mac said:

I have that exact model for a long time now with my big Sansui AU-alphas. Performs flawlessly.

 

Nothing like getting first hand info from the user itself. I was waiting to hear from someone who actually uses a transformer and whether it was a auto step-down or an isloated one. 

Gives me more confidence.

[mbz]

9 hours ago, darrelj said:

I was waiting to hear from someone who actually uses a transformer and whether it was a auto step-down or an isloated one. 

I run a 1kVA isolated for my Japanese items. It's a DIY job, so I could spec my own components, housed in a jcar "box". Would have been cheaper to buy off the shelf but todays prices are a concern.

[xlr8or]

@darrelj I have 10 Japanese tube amps, with 3 in current circulation, all running at 100v AC mains. I have a combo of 4 isolated and non-isolated stepdowns. I use Tortech and non-Tortech units, including 300, 1010, 2000 and 2400w ones. They all work fine.

 

The one you shared in your last link unfortunately at a friend's house measured 112v as it was a 220-230v model. He got rid of it straight away and replaced it with a 1010w isolated one from Tortech, which measured at 100v.

[darrelj]

39 minutes ago, xlr8or said:

measured 112v

Oh that’s not good. in that case, the one I sent will have to be out of the equation. Thanks for the info

[muon*]

Even though our official voltage is 230v most residential homes experience 240v or higher.

 

So it helps to get a step down that is 240v like what Tortech provide.

[darrelj]

A friend told me 230v + 10 or - 10 is not a big deal. How correct is this.

Edited May 12, 2024 by darrelj

[muon*]

3 hours ago, darrelj said:

A friend told me 230v + 10 or - 10 is not a big deal. How correct is this.

Any difference will be reflected in the output of the step down.

 

Why entertain anything other than 240vac model when they are available from a good manufacturer.

 

Edit: solid state gear is a bit more tolerant than tube gear as the secondaries are regulated, but even then you do not want too large a disparity.

We had a solid 250vac at the wall here for years.

Edited May 12, 2024 by muon*

[mbz]

25 minutes ago, darrelj said:

A friend told me 230v + 10 or - 10 is not a big deal. How correct is this.

Comes back to design... You would be unlucky if it caused a serious failure, more likely to shorten the working life, eg, Vintage Yamaha CA-800 has 50V caps on unregulated nominal 50V rails. If there is a bounce in mains then the unregulated 50V will also bounce, no big deal as caps can handle some degree of surge. AU is still mostly 240Vac +/-6% (or is it seven??). Things get interesting if we have an allowable bounce to say 255Vac into your 230Vac/100Vac stepdown, so you would expect about 106Vac on the secondary???

 

Not quite. Step down transformers are designed to output designated (eg) 100Vac at rated power, ie, when you are drawing 1kVA. Stepdowns also have a parameter "No load Voltage", this is the secondary voltage when no load (=amp) connected, typically 4% higher, eg, 104Vac. During operation the amp will be drawing 50-100W(??) so the 1kVA stepdown is "mostly" unloaded so expect 103Vac(?) add the 255Vac surge and you could see 108-109Vac.

Still not fatal however the 255Vac surge may last for several minutes depending on industry in your suburb...

 

Very few people make true 240Vac transformers, possibly UK maybe someone in AU??? Items sourced from China will be 230Vac for the world market.

 

I've had cause to work on 3 x Yamaha CA-800's. Only 1 had badly deformed main filter caps possibly caused by mains voltage drift or class A usage or...

[muon*]

Tortech do 240v.

 

Some Chinese ones may be 220Vac, even if they say otherwise.

Edited May 12, 2024 by muon*

[Addicted to music]

On 09/05/2024 at 8:32 AM, sir sanders zingmore said:

 

The linked article might be a bit technical for many people. If it contains important safety info it might be a good idea if you could summarise it so that the less technical amongst us can be safe too

 

 

Quote direct from the article:

 

This article is based on the use of a 1:1 mains transformer (120V or 230V), used to isolate the mains input so there is no neutral (earthed) conductor on the secondary side.  These are commonly used as a 'safety' measure, but as described here, this is often inappropriate and can be dangerous.  It has long been believed by many people that using an isolating transformer on the test bench is a good safety measure, and will somehow protect the service tech from harm.  In reality, for most products, this is false.  If you always use an isolation transformer, it can let dangerously faulty equipment pass undetected.

 

Please observe that's all in bold....   its a false reality that because its isolated, in other words the primary is totally isolated from the secondary is assumed "safe". it isn't.   

Most audio gear will use isolation transformers,  the primary winding is isolated from the secondary.   There are also equipment that uses auto transformer that physically taps the primary as a secondary.   

If you dont know what you're doing, physically remove from the mains if you wanna play with you fingers so you don't electrocute yourself!  period!    and even if you do you need to wait till all the caps are discharged otherwise you will still get an electric shock!  just be aware that the secondary voltage can be as hugh as 100VDC!  

 

For the OP considering a step down, trannie,  you need to advised the supplier what the total wattage of the load (product) in watts that the step down treannie is required drive.

Edited May 12, 2024 by Addicted to music

[bob_m_54]

37 minutes ago, Addicted to music said:

Most audio gear will use isolation transformers,  the primary winding is isolated from the secondary. 

The difference is that an "Isolation Transformer" won't have a common ground with the secondary, like it will in "most audio gear"

[Addicted to music]

9 hours ago, bob_m_54 said:

The difference is that an "Isolation Transformer" won't have a common ground with the secondary, like it will in "most audio gear"

some times a used term for this is “floating source” 

[Peterbean]

On 23/1/2024 at 8:02 PM, metal beat said:

I use the Tortech step downs for my Japanese turntables and phono.

  Highly recommended. 

 

Personally for power amps, I would go with the 1000 or 2000 watt models.  

 

https://www.tortech.com.au/product/voltage-converters/step-down/isolated/isolated-japanese-step-down-transformer/

 

 

What specs for transformers that you use on your turntable?