PSU1 is 13 amp fuse ok?
Printed From: Graham Slee Hifi System Components
Category: Headphone Audio
Forum Name: Graham Slee Headphone Amps
Forum Description: Questions, answers and product information zone for Graham Slee Headphone Amplifiers
URL: https://www.hifisystemcomponents.com/forum/forum_posts.asp?TID=4848
Printed Date: 27 Mar 2026 at 2:14am
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Topic: PSU1 is 13 amp fuse ok?
Posted By: Nunnother
Subject: PSU1 is 13 amp fuse ok?
Date Posted: 07 Jan 2020 at 7:27am
| I have recently purchased a GS Solo Ultra Linear DE with PSU1 power supply. The supplied power lead appears to have a 3 amp fuse. Looking at new audiophile power leads most of them contain 13 amp fuses. This is probably a daft question but is it ok to use a power lead that contains a 13 amp fuse with the PSU1 and GS Solo Ultra Linear DE? |
Replies:
Posted By: sheepskinstu
Date Posted: 07 Jan 2020 at 9:40am
I thought 13amp fuses were used in washing machines and kettles! 
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Posted By: BackinBlack
Date Posted: 07 Jan 2020 at 11:05am
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I'd be inclined to stick with the recommended fuse rating, it's there to protect the cable, equipment and you. Many devices have their own internal fuses designed more specifically for the circuits they protect. Only monstrous power amplifiers might justify 13A fuses, which at 240V are appropriate for power ratings of up to 3kW!, ie kettles and the like. ------------- Just listen, if it sounds good to you, enjoy it. |
Posted By: Ash
Date Posted: 08 Jan 2020 at 7:52am
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You can use the 13A fuse but it won't offer the PSU1 any protection against excessive current draw. Isn't the max or standard draw current in the range of 200mA? Component damage would occur long before the fuse filament melts to break the circuit. I think the PSU1 has internal protection as well though. Thermal cutoff?
Can the fuses be swapped?
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Posted By: Nunnother
Date Posted: 09 Jan 2020 at 6:32pm
| Thanks for the replies. I've decided to buy some AMR 3 amp fuses which I will use with the lead to my PSU1. |
Posted By: Graham Slee
Date Posted: 09 Jan 2020 at 8:05pm
"Lead us not into temptation..." ------------- That none should be able to park up and enjoy the view without a smartphone and the knowledge in how to use apps |
Posted By: John C
Date Posted: 10 Jan 2020 at 10:13am
Is this an ROHS related joke?   ------------- http://www.gspaudio.co.uk - Turntable and Headphone Audio |
Graham Slee wrote:Posted By: John C
Date Posted: 10 Jan 2020 at 10:20am
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UK plug fuses are only there to protect the cable, not the equipment. Most appliances will have some form of protection internally. I worked in electrical inspection and test for 7 years so this was often a question that came up. The PSU1 has either thermal protection in the current (sorry) model and fuse in the older models. This is made clear on the rating plate. ------------- http://www.gspaudio.co.uk - Turntable and Headphone Audio |
Posted By: Aussie Mick
Date Posted: 10 Jan 2020 at 2:08pm
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Don’t be sorry, John. Excellent work with far more subtlety than the current (sorry) spate of 20/20 vision puns. Mick. ------------- Rega RP8 - Apheta 2 - Accession MC Enigma PS -Solo ULDE (Focal Utopia) - PS Audio M700 - Fical Kanta No2 |
Posted By: BackinBlack
Date Posted: 10 Jan 2020 at 2:35pm
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£15 for a fuse?? I'd rather add another piece of vinyl to my collection. Not that I'm sceptical. ------------- Just listen, if it sounds good to you, enjoy it. |
Posted By: CageyH
Date Posted: 10 Jan 2020 at 5:07pm
Are those alternate (sorry) methods of protection? ------------- Kevin European loan coordinator, based near Toulouse, France. Funkified SL1200 Mk.II, BB3, Firebottle Kin , ADI-2 DAC FS, Modulus 686, PD-S703, Solo UL, Triangle Antal EZ |
Posted By: Graham Slee
Date Posted: 11 Jan 2020 at 4:18pm
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The mains fuse protects the cable, not the product being powered, and a fuse can only be fitted to a British appliance plug. To meet IEC/CSA/ISO/BS 60950 - the standard in force when the PSU1 was tested - requires the product to fail safe, and the smallest mains fuse (3 amps) will not do that. The 230V version used a 63mA internal fuse; the 115V version had a 125mA fuse. Later models have a winding fuse built-into the transformer. It is not a "one shot" and will reset after disconnection from the mains, after it cools. If not for such protection the power supply used in a fault condition could cause fire or electric shock, and to receive its KEMA Quality certification (CB certificate) had to undergo considerable testing, as well as on-test development. The required development was done by me on the advice of KEMA labs in Holland, following the requirements of the standard at all times. It was identified that during short circuited operation that although the output shutdown prevented damage to the power supply, the heat generated by the transformer was in excess of the case plastic rating. As such, the PSU1 had to be de-rated such that a fuse value (as stated above) would open before the transformer reached that temperature. On-load temperatures had to be measured by the "resistance method" which was compared with thermocouple measured results to substantiate the "resistance method". Each test lasted 72 hours at an ambient temperature of 25c (required by the standard), which took some doing as it was during the winter months in a draughty workshop. The case plastic material (ABS) proved to be a major problem, and the transformer had to be isolated from the base with an FR4 glass-fibre panel. Internal wiring also had to be temperature rated using wire with approved insulation, and carrying the required markings, and from an approved manufacturer. It also had to be proved that output wiring could never come into contact with mains-side wiring. All this and a lot more went into the design of the PSU1 to ensure it met with every application of the standards. ------------- That none should be able to park up and enjoy the view without a smartphone and the knowledge in how to use apps |
Posted By: Graham Slee
Date Posted: 11 Jan 2020 at 4:40pm
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Now, in addition to the above 1. The standard dictates an instant method of disconnection from the mains must be used. This must be on the product itself. Therefore a plug and socket arrangement had to be used. Captive wiring is not allowed. Consider that mains power therefore passes two contacts, the live and the neutral of the plug-socket. The plug-socket arrangement must also comply with the standard. These are nickel plated and conduct quite nicely and any corrosion is flashed away by disconnecting and reconnecting the live power cable. So much then for gold plated mains fuses! They simply reduce the chance of corrosion between the fuse clips of the plug, and the fuse caps; but what about where the pins make contact in the mains socket? The fuses themselves are ceramic bodied bought-in fuses which are "boob printed" with a logo, and are then immersion or brush gold plated in electro less jewellery plating solution. There is no way this can be electro-plated unless done one end at a time. The gold plating is jewellery flash plated which is for decorative purposes and is soft high carat gold and a very thin deposit. It will soon wear off if changed over a few times. 2. Audiophile aftermarket cables will not meet the standard unless they are CB certificated and display the required standard markings (CE is insufficient). If used and they result in danger, the manufacturer of the power supply could be unfairly blamed through no fault of his own! These are two reasons why I don’t join in enthusiastically with these conversations. ------------- That none should be able to park up and enjoy the view without a smartphone and the knowledge in how to use apps |
Posted By: Aussie Mick
Date Posted: 13 Jan 2020 at 12:11pm
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Thanks for the explanation, Graham. I’m glad you think about that stuff, and just plug things into the wall and listen. Mick. ------------- Rega RP8 - Apheta 2 - Accession MC Enigma PS -Solo ULDE (Focal Utopia) - PS Audio M700 - Fical Kanta No2 |