Hi And thanks for reading this post.
The ac output on my quad 405-2 amplifier's transformer is 71 volts but keeps going up and down by approximately 0.1- 0.3 volts everytime i measure it. Is this normal and is this the correct voltage. It is quite and old transformer from the 70's and i want to connect some new quad amp boards to it but am not sure if the output voltage is correct, or if anything can be gained by exchanging for a new toroid/audio transformer.
Many thanks in advance. John.
The ac output on my quad 405-2 amplifier's transformer is 71 volts but keeps going up and down by approximately 0.1- 0.3 volts everytime i measure it. Is this normal and is this the correct voltage. It is quite and old transformer from the 70's and i want to connect some new quad amp boards to it but am not sure if the output voltage is correct, or if anything can be gained by exchanging for a new toroid/audio transformer.
Many thanks in advance. John.
Sounds OK to me. The Quad ran on a pseudo -/+50 volt supply. So 100 volts divided by root 2 gives 70.7 volts AC. Spot on.
Hi,
If power supply is not suffient or other problems take a look at
Antek - Your reliable source of transformers, power supplies, and more.
i bought all different types over there: example As4224 (400 watt, 24 volt).
It produces 24 ampere if needed. super silent and purple ground wire really makes it "silent".
It took my L20 amps (350 watt ,4 ohm)to a new level.
also the lead wires and insultation are the best i have seen on many different type of toroidals.
i use them on 230 volt (they are suited for 115 volts and 230 volts).
Also for a DAC i use from them a separate 9 volt (an209)and a 12 volt (an0212)toroidal. great sound.
i used before a combi toroidal 9volt+12 volt.
The sound improvement is dramatic/to a higher next level .
For speaker protect kit : i use in the power amp a AS0512 which is 50 VA.
It sounds high but i works faster and more stable than a 25 VA model.
And this one has a purple ground wire to make pre-amp perfect.
Best regards,
Marco
If power supply is not suffient or other problems take a look at
Antek - Your reliable source of transformers, power supplies, and more.
i bought all different types over there: example As4224 (400 watt, 24 volt).
It produces 24 ampere if needed. super silent and purple ground wire really makes it "silent".
It took my L20 amps (350 watt ,4 ohm)to a new level.
also the lead wires and insultation are the best i have seen on many different type of toroidals.
i use them on 230 volt (they are suited for 115 volts and 230 volts).
Also for a DAC i use from them a separate 9 volt (an209)and a 12 volt (an0212)toroidal. great sound.
i used before a combi toroidal 9volt+12 volt.
The sound improvement is dramatic/to a higher next level .
For speaker protect kit : i use in the power amp a AS0512 which is 50 VA.
It sounds high but i works faster and more stable than a 25 VA model.
And this one has a purple ground wire to make pre-amp perfect.
Best regards,
Marco
Thanks so much for the reply.
For the smoothing capacitors I am thinking of replacing with panasonic fc caps 1000uf x 10. I have tried the panasonic fm's before in a dac and loved the results but unfortunately they are only available up to 50 volts so may give the fc's a try.
Do you think this is a good idea or should i use one large capacitor. I am a little worried about so many soldering joints but it may pay off with lower esr.
Many thanks in advance. John.
For the smoothing capacitors I am thinking of replacing with panasonic fc caps 1000uf x 10. I have tried the panasonic fm's before in a dac and loved the results but unfortunately they are only available up to 50 volts so may give the fc's a try.
Do you think this is a good idea or should i use one large capacitor. I am a little worried about so many soldering joints but it may pay off with lower esr.
Many thanks in advance. John.
Since you posted exactly the same thing on HydrogenAudio, here is the same answer.
Do you think the line Voltage is a constant? It wobbles all over the place. If you try your test with a brand new first time plugged in unit you'll find the same thing. If the line Voltage WAS constant, why would we need regulators? - And nearly every solid state gadget you own has regulators - LOTS of them. Power supply regulators are an art and science of their own.
G²
Hi. Sorry, I didn't know that. I'm not an electrician just a hobbyist.
I have posted the same question elsewhere because sometimes i do not get a reply and also i like to get a few different points of view I hope you do not take it offensively as this is not my intent.
Many thanks for the info.
I have posted the same question elsewhere because sometimes i do not get a reply and also i like to get a few different points of view I hope you do not take it offensively as this is not my intent.
Many thanks for the info.
You'll find both forums to be pretty helpful. Your Voltage shifting is lower than at my house. On hot days with lots of A/C running our line has dropped as low as 99 Volts and as high 125. Some of the old gear gets downright cranky on low Voltage in particular the Technics SH-9010 equalizer. Switching supplies in the PCs and monitors I've seen run as low as 67 when one of the 3 phases failed nearby. BTW it's a good idea to NOT run on the lower Voltages.
I saw the post on Hydrogen and replied and then saw what looked to be an identical post here - it is.
Bottom line - your stuff is fine - at least the transformers.
G²
Hi,
Sorry for my initial answer.
Toroidals FEED the power supply. So i went a step back to get basis right.
2 options: be happy with what you have or change the PSU unit completely.
change........buy DIY complete kit (or have it soldered and tested...few USS extra) or buy BEST components for the price you want to spend. And solder yourself. Test the capacitators before you solder them! So you know what you have bought.....GOOD or BAD components.
Tip: make a drawing and calculate your stuff. And check again. Then your plan will work.
71 Volt on Ac= 100 volt DC after rectification (quite high already).
Or is it 71 volts DC?? ...which is 50 volts AC (before rectification).
Sorry for my initial answer.
Toroidals FEED the power supply. So i went a step back to get basis right.
2 options: be happy with what you have or change the PSU unit completely.
change........buy DIY complete kit (or have it soldered and tested...few USS extra) or buy BEST components for the price you want to spend. And solder yourself. Test the capacitators before you solder them! So you know what you have bought.....GOOD or BAD components.
Tip: make a drawing and calculate your stuff. And check again. Then your plan will work.
71 Volt on Ac= 100 volt DC after rectification (quite high already).
Or is it 71 volts DC?? ...which is 50 volts AC (before rectification).
Hi. Thanks for the replies,.
I am measuring 72.5 volts across the transformer with my Mills multimeter set on ac, 49 volts dc across the smoothing capacitors, then 96 volts dc across the two wires which go to the positive and negative terminals of the amp boards. The amp boards are disconnected for protection just in case the power supply may have been faulty. Does this appear to be okay.
I am going to follow up on your suggestion and replace the power supply, new transformer, bridge rectifier and smoothing capacitors, put the old parts on ebay as there are quite a few Quad groupies on there.
I didn't get a reply to the idea of using several small capacitors in parallel rather than one large one. Is this a stupid question?
For the transformer should i get a toroidal 35-0-35, and what should the current capacity be, There is a 2.5 amp mains fuse before the Quad transformer.
Many thanks. John.
I am measuring 72.5 volts across the transformer with my Mills multimeter set on ac, 49 volts dc across the smoothing capacitors, then 96 volts dc across the two wires which go to the positive and negative terminals of the amp boards. The amp boards are disconnected for protection just in case the power supply may have been faulty. Does this appear to be okay.
I am going to follow up on your suggestion and replace the power supply, new transformer, bridge rectifier and smoothing capacitors, put the old parts on ebay as there are quite a few Quad groupies on there.
I didn't get a reply to the idea of using several small capacitors in parallel rather than one large one. Is this a stupid question?
For the transformer should i get a toroidal 35-0-35, and what should the current capacity be, There is a 2.5 amp mains fuse before the Quad transformer.
Many thanks. John.
There's nothing wrong with the Quad transformer.
A 35 volt toroid might give over the voltage you want simply because it will be specified as 35 volts at max current draw. You'll have to multiply the 35 volts by the "regulation figure" of the transformer which should be quoted and will be in the 5 or 6% region for a 250va transformer.
Lots of small caps. Some prefer that approach. A practical problem is that the wiring adds fractions of an ohm here and there and could mean that the caps nearest the bridge wiring wise do more of the work. The ripple current won't be spread equally.
Toroidal transformers draw huge switch on surges and for ratings above 300va a soft start circuit is recommended to prevent random fuse blowing. A 250 va transformer would probably get away with a T3.15A fuse (time lag delay).
A 35 volt toroid might give over the voltage you want simply because it will be specified as 35 volts at max current draw. You'll have to multiply the 35 volts by the "regulation figure" of the transformer which should be quoted and will be in the 5 or 6% region for a 250va transformer.
Lots of small caps. Some prefer that approach. A practical problem is that the wiring adds fractions of an ohm here and there and could mean that the caps nearest the bridge wiring wise do more of the work. The ripple current won't be spread equally.
Toroidal transformers draw huge switch on surges and for ratings above 300va a soft start circuit is recommended to prevent random fuse blowing. A 250 va transformer would probably get away with a T3.15A fuse (time lag delay).
if you measure your transformer; it gives you 1 result=corrrect AC voltage.
THis is really important. Is this one 2 pieces transformator combined together to feed 2 PSU and than 2 power amp boards. Otherwise you don get this high output on AC.
rule 1 = 100 watt RMS per amp board= 200 watt toroidal , my advice; take 2x 300 watts toroidal or 1 x 500 watt.
to get 49 volts DC= ac voltage x 2square root (ac voltage x 1,4142) with 35 volts it will give 49,49 volt DC. take 34 volt or 32 volts AC (antekinc.com) example: type AS-3434 AS versions have purple ground wire. sound better.
Try to find lowest and highest working DC voltage for Quad power amps. if it is 40-49 volts DC...try to get 44 to 45 volts DC. Then you are SAFE. And it will work.
If DC = below 50 volts ....so max 35 volts AC you can use 2x of this kit
POWER SUPPLY BOARD FOR AUDIO POWER AMPLIFIER AMP DIY KIT | eBay
i use them als to feed my L20 power amps (350 watt RMS 4 ohm)
Good luck.
First you measure and calculate.....and again.
THis is really important. Is this one 2 pieces transformator combined together to feed 2 PSU and than 2 power amp boards. Otherwise you don get this high output on AC.
rule 1 = 100 watt RMS per amp board= 200 watt toroidal , my advice; take 2x 300 watts toroidal or 1 x 500 watt.
to get 49 volts DC= ac voltage x 2square root (ac voltage x 1,4142) with 35 volts it will give 49,49 volt DC. take 34 volt or 32 volts AC (antekinc.com) example: type AS-3434 AS versions have purple ground wire. sound better.
Try to find lowest and highest working DC voltage for Quad power amps. if it is 40-49 volts DC...try to get 44 to 45 volts DC. Then you are SAFE. And it will work.
If DC = below 50 volts ....so max 35 volts AC you can use 2x of this kit
POWER SUPPLY BOARD FOR AUDIO POWER AMPLIFIER AMP DIY KIT | eBay
i use them als to feed my L20 power amps (350 watt RMS 4 ohm)
Good luck.
First you measure and calculate.....and again.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.