stolbovoy said:
Please dont do that.
Before ordering the mains transformer read listed posts carefully:
#1836
#1844
#1845
#1851
#1852
Maybe you will find some beneficial inputs before you finally decide how the mains transformer should look like. Im very concerned about the mains voltage
capability, it should be 110, 115, 120V x 2 for to suit worldwide mains voltage from 110V to 240V (e.g. 110,115, 120, 220, 230 and 240 mains voltage)
Also if implementing the 12v windings there will be an option for soft start and a relay-drive for different protection circuits (not any more expensive than for an extra small transformer including fuses, printed circuit boards etc....
Then............I might be interested in 6-8 transformers depending on price level (also there is some interests in Denmark too I know.)
Regards
The specs from toroid.com has dual 120V primaries, so it should be fine for both Europe and US. If 47V vs 52 on 220 and 110 mains is big concern for someone who is willing to join, I can ask to make a tap for 110V.Flodstroem said:
Please dont do that.
Before ordering the mains transformer read listed posts carefully:
#1836
#1844
#1845
#1851
#1852
Maybe you will find some beneficial inputs before you finally decide how the mains transformer should look like. Im very concerned about the mains voltage
capability, it should be 110, 115, 120V x 2 for to suit worldwide mains voltage from 110V to 240V (e.g. 110,115, 120, 220, 230 and 240 mains voltage)
Also if implementing the 12v windings there will be an option for soft start and a relay-drive for different protection circuits (not any more expensive than for an extra small transformer including fuses, printed circuit boards etc....
Then............I might be interested in 6-8 transformers depending on price level (also there is some interests in Denmark too I know.)
Regards
What's wrong with using separate EI transformer
In Europe the mains voltage are 220, 230 and 240V just for your information
This could change the DC-rails by as much as 4-5 volt up and raise the idle dissipation by 23-24Watts.
A word about an extra EI-transformer: If you would like to put in some noisy magnetic leaking EI transformer in your chassis, go a head, but then I dont get this: you are going to order an electric and magnetic screened totoidal transformer for to receive a silent, noise-free amp and then you are going to put in some of the worse type of.....
Hmmmm I dont understand it.
Dont you think there is a benefit to choose an extra windings on the mains transformer instead of that $ 20 simple transformer and you do forget that it will need the mains fuses too including space to mount it at (far away from the PCB and input circuits for to avoid picking up hum and noice. This isnt cheap I can tell you (you also forgot to add the shipping costs, custom tax etc..) and you have to calculate more bucks for this than those $ 20 you count for, this is my experience.
Better up for to add some more windings on mains transformer dont you think?
Have you checked the price picture for to add windings? The magnetic wire will be thin (0.5Amps? and would be negligible, you mostly pay for work I guess.
Regards
This could change the DC-rails by as much as 4-5 volt up and raise the idle dissipation by 23-24Watts.
A word about an extra EI-transformer: If you would like to put in some noisy magnetic leaking EI transformer in your chassis, go a head, but then I dont get this: you are going to order an electric and magnetic screened totoidal transformer for to receive a silent, noise-free amp and then you are going to put in some of the worse type of.....
Hmmmm I dont understand it.
Dont you think there is a benefit to choose an extra windings on the mains transformer instead of that $ 20 simple transformer and you do forget that it will need the mains fuses too including space to mount it at (far away from the PCB and input circuits for to avoid picking up hum and noice. This isnt cheap I can tell you (you also forgot to add the shipping costs, custom tax etc..) and you have to calculate more bucks for this than those $ 20 you count for, this is my experience.
Better up for to add some more windings on mains transformer dont you think?
Have you checked the price picture for to add windings? The magnetic wire will be thin (0.5Amps? and would be negligible, you mostly pay for work I guess.
Regards
Using 240V primaries for 220V mains will actually lower idle dissipation, but because everything except output stage will be fed from stabilized PS, it should not affect clipping. Anyway we should first figure out is there any people from Europe which are interested in buying the transformer from US (pay extra for shipping, customs, etc) if it will fit their needsFlodstroem said:
Flodstroem, thanks for valuable comments. You are right, I'll quote on Tuesday:A word about an extra EI-transformer: If you would like to put in some noisy magnetic leaking EI transformer in your chassis, go a head, but then I dont get this: you are going to order an electric and magnetic screened totoidal transformer for to receive a silent, noise-free amp and then you are going to put in some of the worse type of.....
Hmmmm I dont understand it.
Dont you think there is a benefit to choose an extra windings on the mains transformer instead of that $ 20 simple transformer and you do forget that it will need the mains fuses too including space to mount it at (far away from the PCB and input circuits for to avoid picking up hum and noice. This isnt cheap I can tell you (you also forgot to add the shipping costs, custom tax etc..) and you have to calculate more bucks for this than those $ 20 you count for, this is my experience.
Better up for to add some more windings on mains transformer dont you think?
Have you checked the price picture for to add windings? The magnetic wire will be thin (0.5Amps? and would be negligible, you mostly pay for work I guess.
Option A: additional 2*65V*1A and 2*12V*0.5A (for protection and soft start)windings
Option B: additional 2*27V*1A (to add "on top" of 2x38V*12A) and 2*15V*0.5A (for protection and soft start) windings
I'm not sure that we need option A, because 38V*12A windings will be coupled pretty well with 2*60V*0.7A anyway
Is 65Vac enough to build decent stabilized PSU with 55-56V output and use RC filtering, or should be go for something higher?
I think option "A" sound most interesting and I cant see any reason for it to be more expensive than option "B".
Both models from KRELL, the KSA-80 and KMA-160 had ±39V and ±75V DC regulated power supplies for the LTP and driver stage and if using this as a starting point we could think of a DC drive between 39V + 65-75V depending on application or personal solution in the KSA-100 mkII project.
Regarding the 2 x 65V winding Im wandering if this is to high voltage, 65 x √2=92V-2volt=90V DC over filter caps and if regulated to 65-75V DC there will be plenty of Voltage for the purpose, but heat dissipation could be a problem due to high voltage and perhaps 0,3 to 0,4A idle currents thru drivers. 90-65=25V and heat dissipation would be approx. 25V x 0,4A = 10W and a totals of 20W worse case, both rails.
For to get 75V regulated voltage at 50 Hz mains freq. the DC voltage over filter caps should be at least 10% more than output = 82,5 volt after rectifier, add 2 volt for that rectifier and you will end up with 84.5/√2=approx. 60V AC, exactly the same AC as in the KSA-80 and KMA-160.
Regarding primaries it could be: 0V-110V-120V x 2 then we should have an option for the must common mains voltage (110, 120, 220, 230 and 240V) but for those in the US that have the 115 V could choose to wire the transformer for either 110 V (higher power outputs (approx. 4.5%) or wire it for 120V and get less heat dissipation and less power output (approx. 4%).
So If you agree to it:
option "A" I would like to suggest to be 2 x 60 V AC @ 0,7-0,8A and 2 x 15V AC for protection circuits etc.
You should also rise the 38 V windings to be 39V to be more equal to Krell original transformer (at no extra costs)
If keeping those 10V, 12A windings this could be useful to those who wants to build a 200+ watts version of the KSA-100 (KMA-160 or similar, 39+10V=49V AC), or to those that is in the need of a power transformer for the KSA-50 project (39-10V= 29V AC)
Mains voltage: (0V-110V-120V) x 2
This solution must be considered due to interests of the members of this tread (and the KSA-50 tread) and if a low interest this transformer will be expensive I think but you should do a search for interested builders.
Or consider a GB.
Regards
Both models from KRELL, the KSA-80 and KMA-160 had ±39V and ±75V DC regulated power supplies for the LTP and driver stage and if using this as a starting point we could think of a DC drive between 39V + 65-75V depending on application or personal solution in the KSA-100 mkII project.
Regarding the 2 x 65V winding Im wandering if this is to high voltage, 65 x √2=92V-2volt=90V DC over filter caps and if regulated to 65-75V DC there will be plenty of Voltage for the purpose, but heat dissipation could be a problem due to high voltage and perhaps 0,3 to 0,4A idle currents thru drivers. 90-65=25V and heat dissipation would be approx. 25V x 0,4A = 10W and a totals of 20W worse case, both rails.
For to get 75V regulated voltage at 50 Hz mains freq. the DC voltage over filter caps should be at least 10% more than output = 82,5 volt after rectifier, add 2 volt for that rectifier and you will end up with 84.5/√2=approx. 60V AC, exactly the same AC as in the KSA-80 and KMA-160.
Regarding primaries it could be: 0V-110V-120V x 2 then we should have an option for the must common mains voltage (110, 120, 220, 230 and 240V) but for those in the US that have the 115 V could choose to wire the transformer for either 110 V (higher power outputs (approx. 4.5%) or wire it for 120V and get less heat dissipation and less power output (approx. 4%).
So If you agree to it:
option "A" I would like to suggest to be 2 x 60 V AC @ 0,7-0,8A and 2 x 15V AC for protection circuits etc.
You should also rise the 38 V windings to be 39V to be more equal to Krell original transformer (at no extra costs)
If keeping those 10V, 12A windings this could be useful to those who wants to build a 200+ watts version of the KSA-100 (KMA-160 or similar, 39+10V=49V AC), or to those that is in the need of a power transformer for the KSA-50 project (39-10V= 29V AC)
Mains voltage: (0V-110V-120V) x 2
This solution must be considered due to interests of the members of this tread (and the KSA-50 tread) and if a low interest this transformer will be expensive I think but you should do a search for interested builders.
Or consider a GB.
Regards
I decided to go little bit higher to be able to use RC[RC] filtering, which should be better(cleaner) for low power regulated supply. In this case it will be lower then 90 volts ant heat dissipation will be not that bad. Considering the case of R =0, amp (each channel) dissipates 250-350W on idle - will extra 20W be a problem?
I'll include 110V primaries in the final specs.
Who's in?
It would be nice to have 4 more people to get price per transformer without shipping in $210 range.
When we'll agree on specs, I'll start GB thread
It should give 38V under 12A load. With no load it is 39.5V. So it would be close to 39V on idle. In the original it needs extra headroom to feed the rest of the circuit, here it is only for output stage. These unnecessary extra volts will create much more excess heat then 5 extra V on 0.7A windings.Flodstroem said:
stolbovoy said:
If considering the total dissipation of 270W heat, adding another 20W does not matter, BUT to ad 20W heat to a small power supply PCB well, then you need a BIG heat sink for that matter make this board large (e.g a couple of, 10 W each).
You will need two heat sinks large enough to handle this power dissipation with a K-value of 2-3°C/watts if thinking of ambient of approx. 40-50°C (inside the main chassis). This will make the power supply PCB large but maybe this isnt a problem.
Maybe a power supply board should have the same dimensions as the main amp. board? Then, both boards could be stacked to each other including an aluminum plate in between for to mount both boards to the chassis ?
A suitable power supply board could be design for this purpose and this would make the building much easier I think.
Im in the position to be able to design PCB myself (only for my own needs) but less people are in that position so a GB for a power supply board would be beneficially I think, (PWatts is our chef-designer, hehehe) but I dont know if he has the time for this "small" project? The schematics could be the Krell original KSA/KMA to make things easier. Otherwise I could also suggest that PWatts could design a new power supply board including some modern IC´s for to get a better/silent regulation (thought he is a power supply designer if my memory dont fool me).
This power supply board could also be useful if someone wants to build an even bigger KRELL clone (Mark perhaps?) so I can see a lot of benefits for to design and make a board.
Another possibility (maybe) would be to copy the KSA/KMA power supply board, but I have no idea of what are those boards physical formats.
Anyone els who wants to step in her with comments/ideas?
Regards
AVWERK said:
Note : Real Full Class A, not sustained bias plateau.
An entire deck of these amps went on a publicity world tour with ML's gigantic Statement 1st edition in 1988/89.
Likely the most expensive LS system ever made, making the Statement Evo-2 a bargain at $70k, the Krell amp bank that accompanied the ML's carried a similar price tag.
If you care to see what the 1st ed. looks like: Martin Logan still has a brochure of the Statement in the historic download section.