Dear Friends,
I am selecting a new 200VA - 24V-0-24V mains transformer for an upgrade of a small integrated (NVA AP10).
I am undecided between a good quality toroidal (i.e. Nuvotem) and a Walsall model of the EI type.
The regulation is better for the EI type (4%).
Some time ago I read an article stating the superiority of EI transfomers for audio purpose (better isolation from the electrical grid).
Nevertheless toroids are smaller and more handy.
I would like to get some kind advice about the best possible choice.
I thank you all very much indeed.
Kind regards,
beppe
I am selecting a new 200VA - 24V-0-24V mains transformer for an upgrade of a small integrated (NVA AP10).
I am undecided between a good quality toroidal (i.e. Nuvotem) and a Walsall model of the EI type.
The regulation is better for the EI type (4%).
Some time ago I read an article stating the superiority of EI transfomers for audio purpose (better isolation from the electrical grid).
Nevertheless toroids are smaller and more handy.
I would like to get some kind advice about the best possible choice.
I thank you all very much indeed.
Kind regards,
beppe
Toroids have less magnetic emissions and are smaller and better regulated for the same VA, if designed properly.
EI have lower bandwidth so mains noise might not pass through them so readily. They don't have such big inrush current and are less susceptible to mechanical hum due to DC on the mains.
Take your pick!
EI have lower bandwidth so mains noise might not pass through them so readily. They don't have such big inrush current and are less susceptible to mechanical hum due to DC on the mains.
Take your pick!
Originally posted by richie00boy
Toroids have less magnetic emissions and are smaller and better regulated for the same VA, if designed properly.
EI have lower bandwidth so mains noise might not pass through them so readily.
They don't have such big inrush current and are less susceptible to mechanical hum due to DC on the mains.
Take your pick!
Thank you very much for your kind and helpful advice.
As I feel that mains noise is really an issue at my house I have just ordered one of this:
http://www.rs-components.it/cgi-bin...djggcefeceeldgkidhgf.0&cacheID=itie&Nr=avl:it
The original one was already a Walsall 20VA EI type.
Thanks again and kindest regards,
beppe
Toroids have less magnetic emissions and are smaller and better regulated for the same VA, if designed properly.
EI have lower bandwidth so mains noise might not pass through them so readily.
They don't have such big inrush current and are less susceptible to mechanical hum due to DC on the mains.
Take your pick!
Thank you very much for your kind and helpful advice.
As I feel that mains noise is really an issue at my house I have just ordered one of this:
http://www.rs-components.it/cgi-bin...djggcefeceeldgkidhgf.0&cacheID=itie&Nr=avl:it
The original one was already a Walsall 20VA EI type.
Thanks again and kindest regards,
beppe
Originally posted by richie00boy
Toroids have less magnetic emissions and are smaller and better regulated for the same VA, if designed properly.
EI have lower bandwidth so mains noise might not pass through them so readily.
They don't have such big inrush current and are less susceptible to mechanical hum due to DC on the mains.
Take your pick!
Thank you very much for your kind and helpful advice.
As I feel that mains noise is really an issue at my house I have just ordered one of this:
http://www.rs-components.it/cgi-bin...djggcefeceeldgkidhgf.0&cacheID=itie&Nr=avl:it
The original one was already a Walsall 20VA EI type.
Thanks again and kindest regards,
beppe [/B][/QUOTE]
Toroids have less magnetic emissions and are smaller and better regulated for the same VA, if designed properly.
EI have lower bandwidth so mains noise might not pass through them so readily.
They don't have such big inrush current and are less susceptible to mechanical hum due to DC on the mains.
Take your pick!
Thank you very much for your kind and helpful advice.
As I feel that mains noise is really an issue at my house I have just ordered one of this:
http://www.rs-components.it/cgi-bin...djggcefeceeldgkidhgf.0&cacheID=itie&Nr=avl:it
The original one was already a Walsall 20VA EI type.
Thanks again and kindest regards,
beppe [/B][/QUOTE]
Originally posted by AndrewT
Hi Beppe, that's a nice transformer you have chosen.
I would never have looked at 400Vac control panel transformers, just goes to show what can be sourced when you search
Dear Mr Andrew,
I have a great opinion of Walsall products.
The original one in the NVA unit is from this same brand as well.
They look very well built and with very good regulation figures.
A big jump from 20VA to 200VA.
Are you planning to house it in a separate box?
It's a great jump indeed but I hope to gain some power in the bass.
As the original case is little the separate box solution is mandatory.
Next step two better power supply caps.
A powerful power supply is a good starting basis for a nice sound, I hope.
Thank you very much.
Kind regards,
beppe
Hi Beppe, that's a nice transformer you have chosen.
I would never have looked at 400Vac control panel transformers, just goes to show what can be sourced when you search
Dear Mr Andrew,
I have a great opinion of Walsall products.
The original one in the NVA unit is from this same brand as well.
They look very well built and with very good regulation figures.
A big jump from 20VA to 200VA.
Are you planning to house it in a separate box?
It's a great jump indeed but I hope to gain some power in the bass.
As the original case is little the separate box solution is mandatory.
Next step two better power supply caps.
A powerful power supply is a good starting basis for a nice sound, I hope.
Thank you very much.
Kind regards,
beppe
Originally posted by richie00boy
20VA... so it was for a pre-amp?
Good afternoon !
This has been my same reaction.
Actually a 20VA transfo is more usually seen in a preamp than in an integrated, even if a low power one (15W/channel on 8 ohm load).
I would not have ordered 10x more VA in that case, any mains noise transfer would be worse than the lower rated VA unit, along with more inrush current.
At first I looked at the power supply caps, a pair of 4700uF of decent quality.
They are also directly soldered to the pcb and not easy to replace.
So I decided to go first with a new and beefier transformer.
My intention would be to gain some more drive in the bass leaving any other things the same.
Thank you and kind regards,
beppe
20VA... so it was for a pre-amp?
Good afternoon !
This has been my same reaction.
Actually a 20VA transfo is more usually seen in a preamp than in an integrated, even if a low power one (15W/channel on 8 ohm load).
I would not have ordered 10x more VA in that case, any mains noise transfer would be worse than the lower rated VA unit, along with more inrush current.
At first I looked at the power supply caps, a pair of 4700uF of decent quality.
They are also directly soldered to the pcb and not easy to replace.
So I decided to go first with a new and beefier transformer.
My intention would be to gain some more drive in the bass leaving any other things the same.
Thank you and kind regards,
beppe
Originally posted by richie00boy
If it is a power amp then it's not so bad
Yes. It is a small but fine sounding to me little integrated.
Maybe the increase in VA can be excessive.
I thought " better a little more than a little less", maybe wrongly.
I have it know at hand.
What impresses me is the diameter of the wires on the secondaries, very very thick. I think this is very good for current.
It looks like 1,5 sqmm section !
I strongly feel this transformer will not be a bottleneck for current.
As soon as I will try it I will report my impressions.
Thank you very much indeed.
Kind regards,
beppe
If it is a power amp then it's not so bad
Yes. It is a small but fine sounding to me little integrated.
Maybe the increase in VA can be excessive.
I thought " better a little more than a little less", maybe wrongly.
I have it know at hand.
What impresses me is the diameter of the wires on the secondaries, very very thick. I think this is very good for current.
It looks like 1,5 sqmm section !
I strongly feel this transformer will not be a bottleneck for current.
As soon as I will try it I will report my impressions.
Thank you very much indeed.
Kind regards,
beppe
bass preamp and power amp transformers
Hi all,
I am going to be building a bass guitar preamp and power amp here soon and I am collecting as much information as possible. I know a little bit about transformers, what they do and how they do it but I don't recall the xx-yy-zz specification of transformers i.e. 24-0-24. Is this the voltage at each winding? then what is the 0 for? center tap transformer? sorry about the newbishness. if i am using a transformer to convert main power(house outlet) to power for my preamp i would need to step it down. 110v ac to say 24v ac this thread has somewhat confused me about transformers. HELP!
Hi all,
I am going to be building a bass guitar preamp and power amp here soon and I am collecting as much information as possible. I know a little bit about transformers, what they do and how they do it but I don't recall the xx-yy-zz specification of transformers i.e. 24-0-24. Is this the voltage at each winding? then what is the 0 for? center tap transformer? sorry about the newbishness. if i am using a transformer to convert main power(house outlet) to power for my preamp i would need to step it down. 110v ac to say 24v ac this thread has somewhat confused me about transformers. HELP!
Re: bass preamp and power amp transformers
Note that the voltage quoted by the manufacturer is usually the full power voltage when all the windings are carrying their rated current into resistive loads. If you measure the secondary voltage when the mains is at the correct rated input voltage the measurement will be the open circuit voltage and this will be much higher than the rated voltage. Don't be alarmed, this is quite normal. But this must also be taken into accounrt when selecting rectifier and smoothing capacitor voltage ratings so that all downstream components are kept within their rated working voltages.
You could equally well use a twin secondary transformer 24-0 & 24-0Vac.superseadragon said:
Note that the voltage quoted by the manufacturer is usually the full power voltage when all the windings are carrying their rated current into resistive loads. If you measure the secondary voltage when the mains is at the correct rated input voltage the measurement will be the open circuit voltage and this will be much higher than the rated voltage. Don't be alarmed, this is quite normal. But this must also be taken into accounrt when selecting rectifier and smoothing capacitor voltage ratings so that all downstream components are kept within their rated working voltages.
In the end I tried it, an external 200VA EI type transformer (ten times the original 20VA !) connected with an umbilical cable to the original diodes bridge.
I have found the sound better, cleaner, more precise and stronger. Noise is very low even with the volume at max.
Overall I am quite pleased.
I am sure that also a filter caps upgrade would be extremely beneficial.
But a friend made me notice that the famous Gaincard comes with just 1000uFx2 of filter capacitance (and a 170 VA transformer).
Nevertheless I still think that 10.000uFx2 of good quality would be better (two nice Siemens are waiting in the drawer).
My last question is: are there any limitations for the length of an umbilical power cord ?
As I said the new transformer is so big that must be placed outside the amp.
Is the umbilical cable length a critical parameter ?
Thank you very much indeed to everyone.
Kind regards,
beppe
I have found the sound better, cleaner, more precise and stronger. Noise is very low even with the volume at max.
Overall I am quite pleased.
I am sure that also a filter caps upgrade would be extremely beneficial.
But a friend made me notice that the famous Gaincard comes with just 1000uFx2 of filter capacitance (and a 170 VA transformer).
Nevertheless I still think that 10.000uFx2 of good quality would be better (two nice Siemens are waiting in the drawer).
My last question is: are there any limitations for the length of an umbilical power cord ?
As I said the new transformer is so big that must be placed outside the amp.
Is the umbilical cable length a critical parameter ?
Thank you very much indeed to everyone.
Kind regards,
beppe
Originally posted by richie00boy
There is no magic/critical length, just the shorter the better
Thank you very much. I will keep it as short as possible then.
It is a very convenient and flexible 3x1,5 sqmm cable.
If the cable is too long (can't say how long that will be, it will depend on the amp) then it will make the amp unstable if there is no big rail caps inside the amp case
Very useful advice.
I will try to place bigger caps inside the case.
I see this solution (with a separated transformer) in some preamps, power amps and integrated.
Usually the diodes bridge and the filter caps are placed very close to the amplification circuits.
Thank you very much again.
Kind regards,
beppe
There is no magic/critical length, just the shorter the better
Thank you very much. I will keep it as short as possible then.
It is a very convenient and flexible 3x1,5 sqmm cable.
If the cable is too long (can't say how long that will be, it will depend on the amp) then it will make the amp unstable if there is no big rail caps inside the amp case
Very useful advice.
I will try to place bigger caps inside the case.
I see this solution (with a separated transformer) in some preamps, power amps and integrated.
Usually the diodes bridge and the filter caps are placed very close to the amplification circuits.
Thank you very much again.
Kind regards,
beppe
Hi Beppe,
Overall do you think it is a worthwhile effort in terms of cost+time over improvement?
How did you solve the problem of the acrylic case? Do you use a new case all together or cut open the acrylic case which are glued together?
By the way, what speakers are you using with teh NVA?
I own a AP10P and very happy with it.
Like you I once thought of increasing the transformer capacity but was put on hold due to the case. Also I am thinking of trying their A40 mono block as NVA allow trade-in.
Are you thinking of upgrading the smooting caps? If yes look at the BC Component 114 series. I had great suceess with these in my previous Naim upgrade.
Overall do you think it is a worthwhile effort in terms of cost+time over improvement?
How did you solve the problem of the acrylic case? Do you use a new case all together or cut open the acrylic case which are glued together?
By the way, what speakers are you using with teh NVA?
I own a AP10P and very happy with it.
Like you I once thought of increasing the transformer capacity but was put on hold due to the case. Also I am thinking of trying their A40 mono block as NVA allow trade-in.
Are you thinking of upgrading the smooting caps? If yes look at the BC Component 114 series. I had great suceess with these in my previous Naim upgrade.
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