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Step-down Transformer for Marantz 7T


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Hi everyone, 

 

After a number of years of searching, hoping, I have finally hit pay-dirt and scored my unicorn preamp; a Marantz 7T!

 

Coming from the US, it is 110V so I will obviously need a step-down. 

 

Having never had the need for one, I have no idea what I should be looking for in my research:

 

  • Is a standard old step-down sufficient for an audiophile set up?
  • Should I be looking at one specifically made for hifi?
  • pros & cons?
  • brands?

 

Hoping the wise heads of SNA could provide me with some guidance & recommendations.

 

Thanks, 

Ryan.

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The first thing to consider is the operating frequency specified on the back of the 7T and its ability run at 50Hz as well as 60Hz. This will pretty much determine the direction that will need to be taken.

 

If the 60Hz option is only available then resampling and upsampling of the 50Hz AC mains signal available in AU will be required to run the unit at 60Hz.

 

If the dual operating frequency range is available (50-60Hz) then a Tortech 240v to 110v step down transformer is all that is required.

Edited by xlr8or
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Also make sure if the amp draws a max current of xxx Amps/watts that the step down has plenty of head room above that figure.

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26 minutes ago, muon* said:

Also make sure if the amp draws a max current of xxx Amps/watts that the step down has plenty of head room above that figure.

 

Here is the Tortech link that helps explain what @muon* is referring to above:

 

https://www.tortech.com.au/guide-to-selecting-the-right-voltage-converter/

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One thing to remember is if It has too much headroom the step down will be very lightly loaded therefor output levels will likely be a bit above what they should be, as I understand it.

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10 minutes ago, muon* said:

One thing to remember is if It has too much headroom the step down will be very lightly loaded therefor output levels will likely be a bit above what they should be, as I understand it.

Correct, the stepdown specs will show rated voltage is produced at rated VA. So if you get a 2kVA step down and run an amp which consumes 100-150W during quiet passages then the supply voltage will be 4-6% higher than rated voltage. These are generalizations, need to check transformer spec, eg, no load voltage.

 

Need to decide on whether you go for the cheaper auto transformer or the isolated variant. A winding fault on an auto transformer may result in mains 240Vac being presented to your 110Vac amp.

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Thanks everyone! Much appreciated.

 

@muon* @xlr8or I had come across that Tortech website but couldn’t find the amp/watt draw anywhere. 
 

I’ve  located the service manual and it indicates 50-60Hz, so the Tortech is all I need?

 

 

A1799809-FB21-4408-98EE-022335204E6F.jpeg

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It would be fairly low being an SS preamplifier, 100 watts give or take, but others with more experienced like @mbz and @xlr8or would guess better than myself.

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Thanks @muon*.

 

The power requirements in the specs indicate it only draws 9 watts, which is consistent with what I have read on the Internet. Makes sense, it’s a preamp.

 

With all that in mind, it would seem I just require the Tortech, and 100W isolated version would be more that enough? Am I correct here @xlr8or @mbz?

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It appears to be 9 watts in power consumption. The smallest 240v to 110v stepdown that Tortech manufacture is a 50 watt version. As the upper limit is 130v, this unit should be fine. Aim to purchase the isolated stepdown version if possible.

 

Edit: Yeah - the 100 watt version should also be fine.

Edited by xlr8or
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8 minutes ago, xlr8or said:

It appears to be 9 watts in power consumption. The smallest 240v to 110v stepdown that Tortech manufacture is a 50 watt version. As the upper limit is 130v this unit should be fine. Aim to purchase the isolated stepdown version if possible.

 

Edit: Yeah - the 100 watt version should also be fine.


Thanks @xlr8or! I will definitely be getting the isolated version.

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26 minutes ago, Dawso8 said:

Thanks @muon*.

 

The power requirements in the specs indicate it only draws 9 watts, which is consistent with what I have read on the Internet. Makes sense, it’s a preamp.

 

With all that in mind, it would seem I just require the Tortech, and 100W isolated version would be more that enough? Am I correct here @xlr8or @mbz?

Yes, big mistake by me :D

 

How did I miss that :$

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13 minutes ago, muon* said:

Yes, big mistake by me :D

 

How did I miss that :$

Haha all good! Massive help mate, thank you 

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@Dawso8 just something else has caught my eye. The service manual states that the primariers on the power transformer can be split to accommodate 210-270 volts AC mains.

 

You may be able to get a service technician to rewire the 7T for operational use in AU without the use of a stepdown.

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10 minutes ago, xlr8or said:

@Dawso8 just something else has caught my eye. The service manual states that the primariers on the power transformer can be split to accommodate 210-270 volts AC mains.

 

You may be able to get a service technician to rewire the 7T for operational use in AU without the use of a stepdown.


I spotted that also. It will be going to my tech at some point, so I will definitely get it done then. 
 

Thanks mate!

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4 hours ago, foryou said:

7T should be very nice preamp 


It’s been my endgame pre for a number of years. Just couldn’t find the right one at a decent price. The one I found is spectacular. Cannot wait

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On 13/03/2021 at 12:18 PM, GregWormald said:

Having run a transformer on a 120V amp for years, my advice is "get the amp adjusted".:yes:

 

Thanks @GregWormald. I definitely will be eventually. Looks fairly straight forward as well. It will go for a full refurb at some point, so I will get it done then.

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