Hi doggy,
In standard Class AB form, I expect the GB150D to be run from +/- 45V to +/-55V supplies, the lower for 4 ohm and higher for 8 ohm. The VA rating of the transformer can be 300VA min for stereo or 160VA (I use) for monoblocks. Larger VA is fine but ensure supplies are in range.
So, yes 400 VA at 36V-0-36V AC would be perfect. This would bridge rectify plus regulation up to +/- 53V. Output stage losses are lower than other (SF) amps so makes better use of the VA.
If you have a very low efficiency speaker and high levels, it's best to go for lower supplies.
Cheers,
greg
In standard Class AB form, I expect the GB150D to be run from +/- 45V to +/-55V supplies, the lower for 4 ohm and higher for 8 ohm. The VA rating of the transformer can be 300VA min for stereo or 160VA (I use) for monoblocks. Larger VA is fine but ensure supplies are in range.
So, yes 400 VA at 36V-0-36V AC would be perfect. This would bridge rectify plus regulation up to +/- 53V. Output stage losses are lower than other (SF) amps so makes better use of the VA.
If you have a very low efficiency speaker and high levels, it's best to go for lower supplies.
Cheers,
greg
Hi Greg,
just out of interest🙄 would this work on 35volt DC rails?
Without compromising sound quality of course- I'd accept the reduction in power to 50 watts or so?
Cheers
just out of interest🙄 would this work on 35volt DC rails?
Without compromising sound quality of course- I'd accept the reduction in power to 50 watts or so?
Cheers
Hi Float,
Yes of course, +/- 35V is fine and would not degrade sound quality at all.
There are 4 resistors that would need to be changed to re-establish optimum biassing and adjustment range. I can supply or advise on these.
Cheers,
Greg
Yes of course, +/- 35V is fine and would not degrade sound quality at all.
There are 4 resistors that would need to be changed to re-establish optimum biassing and adjustment range. I can supply or advise on these.
Cheers,
Greg
Cheers Greg, that means at least I wouldn't need to buy more transformers(yet).
You clearly have some pedigree; this amp is quite hard to resist..
TBH I'm just waiting for more subjective impressions. Us diyers are getting spoiled for choice here, with the symasym, my-ref, the (pricier) UcDs and your SKA.
Do you consider this one real high-end, or was that your eidetic amp?
Thanks again
You clearly have some pedigree; this amp is quite hard to resist..
TBH I'm just waiting for more subjective impressions. Us diyers are getting spoiled for choice here, with the symasym, my-ref, the (pricier) UcDs and your SKA.
Do you consider this one real high-end, or was that your eidetic amp?
Thanks again
Hi Float,
I'm in Australia - east coast.
The early 1990's Eidetic was a nested feedback chip driven conventional fully symmetric complementary amplifier of 150W.
I do not have one left to do a direct comparison, though, as soon as I sort the metalwork for a case for the SKA I will visit a friend who has 3 (triamp).
Cheers,
greg
I'm in Australia - east coast.
The early 1990's Eidetic was a nested feedback chip driven conventional fully symmetric complementary amplifier of 150W.
I do not have one left to do a direct comparison, though, as soon as I sort the metalwork for a case for the SKA I will visit a friend who has 3 (triamp).
Cheers,
greg
power supply
just some questions please; is it 4700mfd. x6 per side? about 30,000mfd total? I confess I am not the most experienced at this; the 6amp discrete bridge, is it ok with a 330-possible 500va torroid?Avel lindberg have these at parts express. for not much price difference.
cheers
doggy
🙂
just some questions please; is it 4700mfd. x6 per side? about 30,000mfd total? I confess I am not the most experienced at this; the 6amp discrete bridge, is it ok with a 330-possible 500va torroid?Avel lindberg have these at parts express. for not much price difference.
cheers
doggy
🙂
Hi doggy,
Yes the inrush currents from a 500VA are likely a bit high for 4 x 3A diodes driving 14,100uF/14,100uF without some limiting R in series. I use the power supplies with 160VA (monoblock) and 300VA (stereo)
Cheers,
Greg
Yes the inrush currents from a 500VA are likely a bit high for 4 x 3A diodes driving 14,100uF/14,100uF without some limiting R in series. I use the power supplies with 160VA (monoblock) and 300VA (stereo)
Cheers,
Greg
amplifierguru said:
Hi Greg,
So then would a 25-0-25 400vA transformer be sufficient for a stereo version and would it run at 4ohm comfortably?
Also, I'm sure it has been said somewhere but is the SKA and the GB150D the same amp?
Thanks, Terry
Hi 4given, you is a hard worker
I am not sure I am competent, but when you lower power to half of its original you should be quite safe with low impedanse, 4ohm is not so hard with proper supply
I am not sure I am competent, but when you lower power to half of its original you should be quite safe with low impedanse, 4ohm is not so hard with proper supply
To still4given
As far as I know you will "do your own" - wouldnt you
Seeking support on such simple matters as you do I adwise you to buy Gregs full kit.
And even bare boards would not give any support - if normal and understandable procedure - I dont know this with Greg though
As far as I know you will "do your own" - wouldnt you
Seeking support on such simple matters as you do I adwise you to buy Gregs full kit.
And even bare boards would not give any support - if normal and understandable procedure - I dont know this with Greg though
tinitus said:
tinitus said:
Hi Tinitus,
I am a bit confused about which amp is which. I guess I should just try to find time to read through all of the posts. Everyone is calling this the SKA, but when I go to Greg's website I don't find any mention of it. The more I read about it the greater my interest in building it. I have just finished building the boards for a Symasym and have only to mount it into a chassis. I am using one of my 25-0-25 400va transformers for it but I still have 3 left. I am getting about +/- 38VDC on the rails with this transformer. If they will work for this amp I would like to use one for it or two if that would be better.
I had planned on buying the full kit but I want to be sure of what I am buying. I like the idea that Greg is matching the parts. the matters I seek support in may seem simple to you, but it is where I am at in my path of learning.
Blessings, Terry
Still4given - believe me I understand, I am no better myself
SKA is as you have guessed right, Gregs amp as offered by him
I dont know, but it seems like you have a little high voltage in your house, or you trafos have been made fore a little lower voltage, and it will probably drop when loaded - but no worry, I still think you will get about 80watt - should be good for sonics too.
But I am not sure about Gregs supply, if it is sufficient in 4ohm load - but I would definately build monoamps with one bridge in each rail
I think when you order and inform Greg about your supply voltage
measured dc +/-, he will deliver parts needed and I am sure it will work right on., you worry too much - must be from all the trouble you have had.
http://members.dodo.com.au/~gregball/guru_001.htm
SKA is as you have guessed right, Gregs amp as offered by him
I dont know, but it seems like you have a little high voltage in your house, or you trafos have been made fore a little lower voltage, and it will probably drop when loaded - but no worry, I still think you will get about 80watt - should be good for sonics too.
But I am not sure about Gregs supply, if it is sufficient in 4ohm load - but I would definately build monoamps with one bridge in each rail
I think when you order and inform Greg about your supply voltage
measured dc +/-, he will deliver parts needed and I am sure it will work right on., you worry too much - must be from all the trouble you have had.
http://members.dodo.com.au/~gregball/guru_001.htm
tinitus said:
I measured last night on my Symasym while it was playing at a fairly good level. AC at primary side of the Transformer was between 121V and 122V. The rails measured between 38,5VDC and 39,3VDC
John Ngo, who make these transformers told me that his tranformers measure higher than their rating. I guess he's right. If I cranked the Symasym up to uncomfortible levels, it never dropped below 38VDC.
I may wait a week or so to order. I would like to hear a few more reviews. I am very interested though.
Blessings, Terry
Terry,
the secondary voltage specified is usually at full load, so you will usually get a higher value, depending on the load and depending on the transformer. For large transformers the difference between full load and no load is usually not more than some 10 %, while it can be much more for small transformers. This has to be taken into account, since one can be in for quite a surprise otherwise.
the secondary voltage specified is usually at full load, so you will usually get a higher value, depending on the load and depending on the transformer. For large transformers the difference between full load and no load is usually not more than some 10 %, while it can be much more for small transformers. This has to be taken into account, since one can be in for quite a surprise otherwise.
patent
Hi Guru,
Where can I find your patent writing? I've searched through uspto.gov but found none under your name. I am interested to know how you achieve the Killer sound.
Thanks. 😉
Hi Guru,
Where can I find your patent writing? I've searched through uspto.gov but found none under your name. I am interested to know how you achieve the Killer sound.
Thanks. 😉
I don't know if anyone else has completed the amp.
I should have some details to post within a day or so!
macka
I should have some details to post within a day or so!
macka
This was posted by admin at 10th of january.
Was one week ago today.
His profile says 'sinbin'.
I wonder if amplifierguru is soon back?
I am sure there are a few more than me, that miss him.
He was last around yesterday. Reading.
🙂
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