Ampguru says +-32V
+-50V to +-55V on 8ohm, +-40V to +-45V on 4ohm
yes, use at least a VA rating >=output power. optimum VA~=1.5*output power. Stronger and more sustained bass if VA>=2*output power.
yes, but Ampguru says otherwise due to the high PSRR.
no.
no, the PCB and topology do not suit separation.
no, if both are designed properly.
I don't know, but I'm inclined to think not.
not yet, but I think RC snubbers on the rectifier are worthwhile. Although of less benefit on this high PSRR than other amps. Cable inductance snubbers may be worthwhile, but how do you calculate suitable values for the R & C?
Excellent response, thanks AndrewT.
A couple of other q's:
1. Any benefit in using more exotic components-black gates etc
2. any particular speaker cable suited for the amp?
3. Anyone mated this beast with an AD815 pre-amp?
Thats about it for now!
A couple of other q's:
1. Any benefit in using more exotic components-black gates etc
2. any particular speaker cable suited for the amp?
3. Anyone mated this beast with an AD815 pre-amp?
Thats about it for now!
AndrewT said:
Good -> Elna audio, Philips, Rubycon, Black Gate, etc...
Big* - > more than 40.000uF per rail
Nice -> at least 300VA per channel
*I prefer small paralleled caps, like 4x 6.800uF + 4x4.700 + 4x2.200uF + 6x1.000uF.
Large capacitance capacitors at high frequencies don't behave as caps, this way you also reduce ESR.
I also bypass all of them with 100nF.
I like to use tons of small capacitors! It's more expensive but I like the result.
PS: In my amp, after the 1.000uF caps I have 10x680nF.
I have deep and fast bass but also a great treable.
I also have low voltage drop.
I just need to be careful with the rectifiers because they "stress" when I turn the amp on....
Hi Xelb,
is that 68mF on each rail?
or
+-34mF on each channel?
or
shared between channels?
What speaker impedance are you driving?
Way back you mentioned 650VA, again is that per channel or for two channels or more?
is that 68mF on each rail?
or
+-34mF on each channel?
or
shared between channels?
What speaker impedance are you driving?
Way back you mentioned 650VA, again is that per channel or for two channels or more?
AndrewT said:
68mF per rail 😉
Now I have 650VA for two channels but I have another trafo of 650VA to make one per channel.
I always bet in large PSU's, better dynamics.
I am driving 6 Ohm speakers but tomorow I will test the amp with a pair of speakers that go down to 2 ohms in the bass.
PS: my amp is runing at +/- 42Vcc
Dr.H said:
Hi Ryan,
1. This amp has a fairly simple layout, so should benefit as much as any. You will see from the schematic a few obvious places for upgrades. We'd all appreciate feedback on any worthwhile changes you find. I'd be very surprised if the standard elcaps couldn't be improved on. I'd also recommend the zener mod (see back a few pages).
2. Good stuff 😉
3. Yup. Two good components makes one good combo.
Trust your common sense with power supplies. Bigger trafos always seem better to me, likewise more bridges. Mono supplies help separation, or do as Rudi and use a trafo for positive rails and one for neg.
That's a great review XELB.
Haven't heard a mermaid sing but I also have a dual mono GB150D and it continues to amaze myself and friends with it's sheer realism - even the piano teacher next door!
Don't know about 2 ohm speakers though, you might hit the current limit.
Haven't heard a mermaid sing but I also have a dual mono GB150D and it continues to amaze myself and friends with it's sheer realism - even the piano teacher next door!
Don't know about 2 ohm speakers though, you might hit the current limit.
Good news!!!
Good news!!!
The kits arrived this morning! No problems with customs, didn't pay any taxes. I was lucky! 🙂
I'm thinking in buying this one: http://pt.farnell.com/jsp/endecaSearch/partDetail.jsp?SKU=9530940
or maybe this more expensive: http://pt.farnell.com/jsp/endecaSearch/partDetail.jsp?SKU=9532013
Should I buy the cheeper one or the encapsulated? I don't want to go with a more powerfull transformer just for now because I'm avoiding using a softstart circuit.
I think I'll be ordering it from Farnell (first time costumer) because I can't find a toroidal at Dimofel or Leiritronica. Dont' know where else to find one.
And what about the case? XELB, where did you buy your box (chassi) for the amp?
Cheers,
Paulo.
Good news!!!
The kits arrived this morning! No problems with customs, didn't pay any taxes. I was lucky! 🙂
I don't know that store. What's it's name?
I'll be using the GB300S from Greg to power both channels with one toroidal transformer.
I'm thinking in buying this one: http://pt.farnell.com/jsp/endecaSearch/partDetail.jsp?SKU=9530940
or maybe this more expensive: http://pt.farnell.com/jsp/endecaSearch/partDetail.jsp?SKU=9532013
Should I buy the cheeper one or the encapsulated? I don't want to go with a more powerfull transformer just for now because I'm avoiding using a softstart circuit.
I think I'll be ordering it from Farnell (first time costumer) because I can't find a toroidal at Dimofel or Leiritronica. Dont' know where else to find one.
And what about the case? XELB, where did you buy your box (chassi) for the amp?
Cheers,
Paulo.
Hi,
quality wise there is no difference between encapsulated and exposed.
300VA 3*35Vac is just perfect for a single GB150 driving 6ohm speakers (or 6 to 8ohm, or 8ohm). Do not use 4ohm speakers.
Use separate rectifier and smoothing caps for each channel.
You can run two sets of rectifier/smoothing off a 500VA to supply two channels. Slightly reduced performance off 400VA, and a big reduction off 300VA. Any gains above 500VA will be small if not undetectable.
Twin transformers to power the positive and negative rails separately result in a poorer regulation for each smaller transformer. You sometimes find twin transformers in very high power PSUs, but this is more to do with obtaining good power/price when above 1kVA. Two standard 750VA are probably cheaper than one special 1.5kVA
quality wise there is no difference between encapsulated and exposed.
300VA 3*35Vac is just perfect for a single GB150 driving 6ohm speakers (or 6 to 8ohm, or 8ohm). Do not use 4ohm speakers.
Use separate rectifier and smoothing caps for each channel.
You can run two sets of rectifier/smoothing off a 500VA to supply two channels. Slightly reduced performance off 400VA, and a big reduction off 300VA. Any gains above 500VA will be small if not undetectable.
Twin transformers to power the positive and negative rails separately result in a poorer regulation for each smaller transformer. You sometimes find twin transformers in very high power PSUs, but this is more to do with obtaining good power/price when above 1kVA. Two standard 750VA are probably cheaper than one special 1.5kVA
Re: Good news!!!
I am using the chassis of an old Pioneer 😉
The shop is called "Total Electronica" and they have toroidal transformers, 350VA 35V and 650VA 30V for the same price that the ones you posted.
( think the 350VA is arround 35 Euros )
I didn't add any problems without softstart!
I just made solenoid bobbin with the 230V cable that feeds the transformer. 😉
Total Electronica:
From rotunda do Areeiro to Alameda, by Av. Almirante Reis 😉
paufon said:
I am using the chassis of an old Pioneer 😉
The shop is called "Total Electronica" and they have toroidal transformers, 350VA 35V and 650VA 30V for the same price that the ones you posted.
( think the 350VA is arround 35 Euros )
I didn't add any problems without softstart!
I just made solenoid bobbin with the 230V cable that feeds the transformer. 😉
Total Electronica:
From rotunda do Areeiro to Alameda, by Av. Almirante Reis 😉
An externally hosted image should be here but it was not working when we last tested it.
Hi,
the shadows from the cars? look like headstones in a graveyard.
Is this a roundabout way of telling us you have spent all your money on your DIY hobby and can only afford to doss (sleep) in a graveyard?
the shadows from the cars? look like headstones in a graveyard.
Is this a roundabout way of telling us you have spent all your money on your DIY hobby and can only afford to doss (sleep) in a graveyard?
Thank you for your answer, AndrewT. I have yet a lot to learn so any help is precious! 🙂
I want to avoid a softstar circuit because I don't know how to disign one. I want so start simple and make improvements from there. Probably I'd go for two 300VA transformers, one for each channel. Filtering should be 40000mF and up, right?
And what about a stabilizer IC after the filter capacitors? Would it improve regulation?
Can anyone comment about this toroid? http://pt.farnell.com/jsp/endecaSearch/partDetail.jsp?SKU=9530940
It doesn't say "Extremely low radiated magnetic field, suitable for sensitive electronics" like some say so I'm thinking it might be bad for audio, I don´t know.
Still the problem with the case/chassi. Don't know were to find one in my country. Any ideias to build/buy a box?
Thanks!
Regards,
Paulo.
Are you using a softstart circuit?
I want to avoid a softstar circuit because I don't know how to disign one. I want so start simple and make improvements from there. Probably I'd go for two 300VA transformers, one for each channel. Filtering should be 40000mF and up, right?
And what about a stabilizer IC after the filter capacitors? Would it improve regulation?
Can anyone comment about this toroid? http://pt.farnell.com/jsp/endecaSearch/partDetail.jsp?SKU=9530940
It doesn't say "Extremely low radiated magnetic field, suitable for sensitive electronics" like some say so I'm thinking it might be bad for audio, I don´t know.
Still the problem with the case/chassi. Don't know were to find one in my country. Any ideias to build/buy a box?
Thanks!
Regards,
Paulo.
AndrewT said:
Do you want to know how much money I have ? 🙄
Don't worry, I will not ask you money
Hi,
I am aware of two techniques to reduce interference emanating from toroids.
Gauss band wound around the outside of the toroid and usually made from magnetic material.
Electrostatic screen wound between the primary and secondary windings (but not forming a shorted turn) and connected to ground (which? audio ground or safety earth).
Both these add cost and are non standard in ordinary toroids.
Some manufacturers claim these additions make their product more suitable for High-End audio (audiophile) duty.
I have not used either technique YET. But I have acquired one transformer that has an electrostatic screen, but would not know how to measure it's effectiveness. I suspect it might have neglible effect on the audio quality (see where my bias lies with regard to expensive audio grade components).
Go ahead with your cheap purchase. Personally I would choose the 650VA (with twin rectifier/smoothing) and save money.
Soft start increases complexity, agreed. Develop more DIY skills and then add soft start later (designs abound on this Forum and ESP details all you need). But without soft start you MUST fit larger mains (primary) fusing. This has a marginal effect on overall safety.
There is a very simple soft start that you can incorporate at this early stage of your learning. A Thermistor in the primary to the transformer achieves much of the current surge control and due to it's relatively low warm resistance has little effect on running voltage. It does not need a relay/delay circuit to cut it out. BUT wired this way it does little to protect the fuse on a short term mains interuption.
I am aware of two techniques to reduce interference emanating from toroids.
Gauss band wound around the outside of the toroid and usually made from magnetic material.
Electrostatic screen wound between the primary and secondary windings (but not forming a shorted turn) and connected to ground (which? audio ground or safety earth).
Both these add cost and are non standard in ordinary toroids.
Some manufacturers claim these additions make their product more suitable for High-End audio (audiophile) duty.
I have not used either technique YET. But I have acquired one transformer that has an electrostatic screen, but would not know how to measure it's effectiveness. I suspect it might have neglible effect on the audio quality (see where my bias lies with regard to expensive audio grade components).
Go ahead with your cheap purchase. Personally I would choose the 650VA (with twin rectifier/smoothing) and save money.
Soft start increases complexity, agreed. Develop more DIY skills and then add soft start later (designs abound on this Forum and ESP details all you need). But without soft start you MUST fit larger mains (primary) fusing. This has a marginal effect on overall safety.
There is a very simple soft start that you can incorporate at this early stage of your learning. A Thermistor in the primary to the transformer achieves much of the current surge control and due to it's relatively low warm resistance has little effect on running voltage. It does not need a relay/delay circuit to cut it out. BUT wired this way it does little to protect the fuse on a short term mains interuption.
Hi,
the safety earth is mandatory.
Make sure you understand what it does and why it is needed BEFORE you start building.
You must connect all exposed conductive parts to a permanent safety earth which must connect via the earth pin into the house protective system.
Is that gobbledegook? If so then research starts here.
the safety earth is mandatory.
Make sure you understand what it does and why it is needed BEFORE you start building.
You must connect all exposed conductive parts to a permanent safety earth which must connect via the earth pin into the house protective system.
Is that gobbledegook? If so then research starts here.
I've seen an idea I intend to use: that of using the voltage on the filter caps to control inrush current.
You can use an in-line resistor in the transformer primary and short it out when the voltage on the caps reaches a certain value of charge. There are plenty of adjustable solid state relays on the surplus market that you can trigger from the voltage on the filter caps, and adjust the trigger voltage of the relay used to bypass the in-line resistor. Therefore, the resistor bypassing is not directly triggered by time, per se, but on the charge voltage of the caps.
If the relay is not robust enough to conduct the line current, it could be used to trigger another relay or contactor to bypass the resistor and supply full load current.
You can use an in-line resistor in the transformer primary and short it out when the voltage on the caps reaches a certain value of charge. There are plenty of adjustable solid state relays on the surplus market that you can trigger from the voltage on the filter caps, and adjust the trigger voltage of the relay used to bypass the in-line resistor. Therefore, the resistor bypassing is not directly triggered by time, per se, but on the charge voltage of the caps.
If the relay is not robust enough to conduct the line current, it could be used to trigger another relay or contactor to bypass the resistor and supply full load current.
Hi Pooge,
I did that about twenty years ago when I was young and stupid. I'll not repeat the joke that follows (that was yesterday).
It will fall down on three counts.
As the voltage continues to rise above the trigger level dissipation in the resistors and relay coil increases disproportionately. Result: blown relay or blown relay feed resistors.
If the mains voltage is low then the circuit may delay triggering or even fail to trigger and both senarios could/will overheat the resistor. Result: blown in-line resistor.
A short period mains drop out will leave the voltage on tha smoothing caps hogh to keep the relay pulled in. But the magnetic flux in the toroid will have stuck at it's power off level.The current surge will now recurr without the benefit of the in-line resistor. Result: blown fuse.
Not too clever without a lot of further thought/complexity to avoid these and maybe other pitfalls.
I did that about twenty years ago when I was young and stupid. I'll not repeat the joke that follows (that was yesterday).
It will fall down on three counts.
As the voltage continues to rise above the trigger level dissipation in the resistors and relay coil increases disproportionately. Result: blown relay or blown relay feed resistors.
If the mains voltage is low then the circuit may delay triggering or even fail to trigger and both senarios could/will overheat the resistor. Result: blown in-line resistor.
A short period mains drop out will leave the voltage on tha smoothing caps hogh to keep the relay pulled in. But the magnetic flux in the toroid will have stuck at it's power off level.The current surge will now recurr without the benefit of the in-line resistor. Result: blown fuse.
Not too clever without a lot of further thought/complexity to avoid these and maybe other pitfalls.
AndrewT said:
As I am talking about a solid state relay that gates a triac/scr, the current into it would be very low. It is voltage controlled, and has a very wide input voltage range.
AndrewT said:
I get your point, but once the caps have a certain amount of charge, the current through the resistor should reduce. It would also be advantageous to use a heat sink type resistor for reliablity with any type of soft start. A resistor adequate enough to supply continuous transformer magnetizing current, at a minimum, should be specified. Heat-sinked resistors are very available on surplus market.
AndrewT said:
Are you lowering the fuse too much? A fuse lower than that needed to supply the flux current in the transformer with charged capacitors doesn't seem sufficient.
Re: GB150
There may well be a benefit. The PSRR of the GB150 is high, but it's not clear exactly how high it needs to be to be inaudible. Certainly Greg hasn't dismissed it. It's one of those "suck it and see" situations.
Dr.H said:
There may well be a benefit. The PSRR of the GB150 is high, but it's not clear exactly how high it needs to be to be inaudible. Certainly Greg hasn't dismissed it. It's one of those "suck it and see" situations.
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