jacco vermeulen said:
I was thinking a single switch for two 300VA and two GB300S. The switch is rated as "250V 10A inductive Load (15 max resistive Load )"
Is 10A really not enough? Am I setting myself up for misery, grief and a visit from the local fire brigade?
A switch for each side will work, 1 for the whole batch not.
You'll notice yourself whether you will keep the fuse without a softstarter.
Peak inrush current for your dual configuration will easily reach 10 amps and higher.
20 electrolytics in parallel virtually resemble a dead short for a brief moment, same goes for the toroids.
The moment the switch makes contact there will be a nice sparkle.
Pushing the main switch of a washing machine/dryer first, and then switch the program to turn it on makes sense.
You'll notice yourself whether you will keep the fuse without a softstarter.
Peak inrush current for your dual configuration will easily reach 10 amps and higher.
20 electrolytics in parallel virtually resemble a dead short for a brief moment, same goes for the toroids.
The moment the switch makes contact there will be a nice sparkle.
Pushing the main switch of a washing machine/dryer first, and then switch the program to turn it on makes sense.
Hi,
The resistance from distribution board to transformer primary and back determines the peak current at switch on.
If the mains peak voltage coincides with switch on then the peak current could easily exceed 100Apk and possibly 200Apk.
Four amps off a common PSU may not sound as good as separate smaller PSUs dedicated to each amp.
Similarly for the bass amps.
Ampguru's design has inherently good PSSR but why rely on that when you can do better?
much higher.
The resistance from distribution board to transformer primary and back determines the peak current at switch on.
If the mains peak voltage coincides with switch on then the peak current could easily exceed 100Apk and possibly 200Apk.
Four amps off a common PSU may not sound as good as separate smaller PSUs dedicated to each amp.
Similarly for the bass amps.
Ampguru's design has inherently good PSSR but why rely on that when you can do better?
jacco,
The primary side fuse size recommended in the GB300S documentation is 2A for 240V. If I have two GB300S on a single power switch, that adds up to 4A in total.
Am I faulty in my reasoning that the 2A fuses will break way before before the 10A switch gets into trouble?
The building docs for the GB300S does not mention softstart at all, I can't see why having two GB300S on the same switch shoudn't make any difference as far as the fuses are concerned.
Or were you perhaps referring to the fuses in my house?
The primary side fuse size recommended in the GB300S documentation is 2A for 240V. If I have two GB300S on a single power switch, that adds up to 4A in total.
Am I faulty in my reasoning that the 2A fuses will break way before before the 10A switch gets into trouble?
The building docs for the GB300S does not mention softstart at all, I can't see why having two GB300S on the same switch shoudn't make any difference as far as the fuses are concerned.
Or were you perhaps referring to the fuses in my house?
welcome to the ska club
Gert
Your implimentation of the ska looks really professional-nice work!
In my ska gb150 I use a 500va toroid with 27,200uf per side. My amp housing is a B&K st3030 which was 200watts/side. I used the original power switch and fuse which I think was 8 amp. 5-6 amp may be sufficient for me. The ska boards are also fused[2-1.5 a?]. I have little turn on thump [only a nice small one from my phono stage] and no turn off thump at all.
In comparison to gainclone-I have built 4; one outstanding feature is this amp has the most silent background noise of all my amps, and minimal turn on-off thumps.
cheers
Thor
Gert
Your implimentation of the ska looks really professional-nice work!
In my ska gb150 I use a 500va toroid with 27,200uf per side. My amp housing is a B&K st3030 which was 200watts/side. I used the original power switch and fuse which I think was 8 amp. 5-6 amp may be sufficient for me. The ska boards are also fused[2-1.5 a?]. I have little turn on thump [only a nice small one from my phono stage] and no turn off thump at all.
In comparison to gainclone-I have built 4; one outstanding feature is this amp has the most silent background noise of all my amps, and minimal turn on-off thumps.
cheers
Thor
Hi,
if you double the fuse rating then it takes a bigger fault to break the fuse.
It would be better to put T2A fuse on each transformer primary.
and a master fuse at the incomer.
Then if one transformer/PSU/amplifier starts to go wrong that line fuse will blow early, limiting the damage resulting from the lower levels of overheating from the smaller fuse rating.
BTW. I think your 300VA transformer/PSU will not start on a 240Vac supply using T2A fusing
if you double the fuse rating then it takes a bigger fault to break the fuse.
It would be better to put T2A fuse on each transformer primary.
and a master fuse at the incomer.
Then if one transformer/PSU/amplifier starts to go wrong that line fuse will blow early, limiting the damage resulting from the lower levels of overheating from the smaller fuse rating.
BTW. I think your 300VA transformer/PSU will not start on a 240Vac supply using T2A fusing
coolbiz said:
The 2A fuses are slow blow types, on a 300VA i use bigger ones.
We have 240Vac here too.
The main 16A fuses overhere are faster than a T-type fuse.(T stands for slow in the German language here) so the main fuse will trip before the fuses at the amp will.(so it depends on the kind of main fuses you have there)
The combined high inrush currents will not terminate a 10/15Amp switch immediately but it may damage in time.
You do not put a fast fuse(F) before the primary of a toroid.
AndrewT said:
Yes, I'll use one fuse for each transformer.
AndrewT said:
I'm not sure what you mean by that, but if T2A keeps breaking, I'll just use T3A or maybe even T5A instead.
jacco vermeulen said:
Thanks for pointing that out, jacco. I think I'll simply start off with a single 10A switch for two 2 x 300VA and see what happens. Should the switch wear out prematurely, I'll either replace it with something beefier or use a seperate switch for each transformer or reconsider the use of a softstart module.
Switches are not only rated for resistive and inductive loading.
Also for contact and isolation resistance, maximum voltage level it can withstand, allowable peak current levels, mechanical/electrical operations longevity and temperature range. Just like relays.
e.g. :
the life expectancy in number of switch operations between gold or silverplated switches often is in the order of 5 to 2.
That kind of information can be hard to come by, so its trial and error or just use the safety factor rule.
I'm not even a professional electronics person, yet i've replaced so many underrated switches. Some audio designers chose heavy industrial switches for their products.
Also for contact and isolation resistance, maximum voltage level it can withstand, allowable peak current levels, mechanical/electrical operations longevity and temperature range. Just like relays.
e.g. :
the life expectancy in number of switch operations between gold or silverplated switches often is in the order of 5 to 2.
That kind of information can be hard to come by, so its trial and error or just use the safety factor rule.
I'm not even a professional electronics person, yet i've replaced so many underrated switches. Some audio designers chose heavy industrial switches for their products.
Hi,
20mm fuses come in T, standard (no prefix) and F a few manufacturers also list ultrafast.
We are dealing with T (time delay or anti surge) here and they are available in 2, 2.5, 3.1, 4 and 5A.
I hope you can manage with 3A or less.
If you have to go to 4 or 5A on each transformer, then seriously consider soft start.
With soft start you may find you can run each transformer off T1.6A giving the advantage of close protection.
20mm fuses come in T, standard (no prefix) and F a few manufacturers also list ultrafast.
We are dealing with T (time delay or anti surge) here and they are available in 2, 2.5, 3.1, 4 and 5A.
I hope you can manage with 3A or less.
If you have to go to 4 or 5A on each transformer, then seriously consider soft start.
With soft start you may find you can run each transformer off T1.6A giving the advantage of close protection.
gbyleveldt: nice looking amp.
I'm just playing with case designs for my GB150, this got me thinking My heatsinks are very long (8-12") and will be running down either side of the chassis, I have two basic layouts both have a common back pannel with the power socket in the middle and the audio ins and outs at the edges of the back pannel next to the heatsinks, is one any better than the other?
A) Would have the amp boards at the back of the ampso the audio inputs and outputs cable runs onto the boards are VERY short, the torroids would then be at the front of the amp next to each other near the centreline of the amp, this would leave me with mains power running the full length of the chassis down the middle.
B) would have the torroids at the back in the midlle of the chassis so the mains power cable is VERY short from the input socket. the Amp boards would then be at the front of the amp on the heatsinks and the audio in and outs would be on much longer cables running down the edge of the amp along the heatsinks.
Is one layout preferable to the other? I'm considering transformer coupling the inputs to give me balanced inputs does this change anything.
thanks
I'm just playing with case designs for my GB150, this got me thinking My heatsinks are very long (8-12") and will be running down either side of the chassis, I have two basic layouts both have a common back pannel with the power socket in the middle and the audio ins and outs at the edges of the back pannel next to the heatsinks, is one any better than the other?
A) Would have the amp boards at the back of the ampso the audio inputs and outputs cable runs onto the boards are VERY short, the torroids would then be at the front of the amp next to each other near the centreline of the amp, this would leave me with mains power running the full length of the chassis down the middle.
B) would have the torroids at the back in the midlle of the chassis so the mains power cable is VERY short from the input socket. the Amp boards would then be at the front of the amp on the heatsinks and the audio in and outs would be on much longer cables running down the edge of the amp along the heatsinks.
Is one layout preferable to the other? I'm considering transformer coupling the inputs to give me balanced inputs does this change anything.
thanks
Thanx Puggie!
I would imagine that option A would be better than B. I also used 12" heatsinks, got them from Fisher.
I spoke to Greg last night about balancing the input stage on the SKA. Pop him a mail, he has some details about doing that. It is similar to what the guys are doing with the Aleph X amps. My initial idea was to use an opamp as a balanced RX, but decided against it.
I would imagine that option A would be better than B. I also used 12" heatsinks, got them from Fisher.
I spoke to Greg last night about balancing the input stage on the SKA. Pop him a mail, he has some details about doing that. It is similar to what the guys are doing with the Aleph X amps. My initial idea was to use an opamp as a balanced RX, but decided against it.
jacco and AndrewT,
Thanks for sharing your considerable knowledge. I'll set off with a 10A switch, no softstart, and T3A fuses. I'll let you know if I find something interesting.
I still havent taken delivery of cabinets and switches.
Thanks for sharing your considerable knowledge. I'll set off with a 10A switch, no softstart, and T3A fuses. I'll let you know if I find something interesting.
I still havent taken delivery of cabinets and switches.
yggdrasil said:
Dra på Lopphavet!
I was hoping you might live somewhere in the south and that I might have a chance to listen to your SKAs, but 1400km is a long way to go for a listening session.
Feel free to drop me a line I you are ever in the Stavanger area.
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