I made a discovery today about how I have wired the output from my DDDAC which I wanted to share.
For a long time now, I have wired direct from NEG to my RCA outer and from POS to the RCA inner. No caps, no transformers. I know a few people are running like this and reporting that it sounds very nice and an improvement over using POS with a cap and COMMON. I found this too.
But someone who was trying this solution (Hi Nige) mentioned that their sound from each channel sounded much nicer when only 1 RCA was plugged into their amp and with both plugged in, it lost some of the detail and sounded flat. I never noticed this because I never had only 1 channel at a time plugged in, always both.
The theory was that with this method, the NEGs will be joined and must share the music signal across the channels, so half of each channel's signal which reaches the speakers is made up of a MONO/mix of both channels.
So I made a test file:
click and tone test file mp3
The left track is a click track, right track is a sine wave tone.
With only 1 RCA plugged in at a time, the left channel just gets the tone, the right channel just gets the click. But with them both plugged in and therefore the neg connections bridged together at the preamp, each channel gets it's own signal, plus a quieter (I guess 1/4 volume?) copy of the other channel as well.
So it seems that unless you have an amp solution with totally separate channels where the signal GND is not joined, this will always be the case and there will always be a Mono/mixed element to each channel when wiring like this.
I have some Cinemags here now. I'll try them later and compare....
Hi dwjames,
That's a very important discovery you made!.
Nice job you did with the test signals.
thanks.
Yes, I'd like to try an R core.
VA Rating is just volts x amps right? So a 300VA 6v supply is the same current as 150VA 12v transformer?
Also, because 2 x 6v in series would only give 1 x 12v output, this means only half wave rectification, right? Not sure if that's a good or a bad thing..
I'm not so sure on the rating though... as I understand, the reason people see benefits from a huge VA transformer is mainly that it uses thicker wire, so is lower impedance. But I was advised that being too large also had it's own problems (although I didn't understand at the time)
Realistically, a 30VA would probably be the technically correct size for me to choose for my 1 deck supply. I'm pulling less than 1A including the bleeder resistor.
Hello James,
According to me if you make 12 volts by putting to six volts in series or use a double 12 volt transformer and put the winndings in parallel If both transformers are 300va you will end up with the same current 300/12= 25A
If i am right you can use 4 diodes with one 12 volts winding ( or 2 12 volts inn parallel or two six volts in series).
Bigger transformer there is less chance for the core to saturate. A big transformer will be harder for the elklectronics but because of the choke input the choke wont let the charging current rise to much. These pulsing current which are kind of equalised by the choke are the ones that make the diodes give a kind of disturbing signals which are hard to tame.
Are you sure 12 volts is enough?
I did go for the 2*15 volts but my first choke will have a higher serie ristance compared to the LL1694 ( 3.4 ohm instead of 1.8 ohm)
Sincere greetings, Edward
According to me if you make 12 volts by putting to six volts in series or use a double 12 volt transformer and put the winndings in parallel If both transformers are 300va you will end up with the same current 300/12= 25A
If i am right you can use 4 diodes with one 12 volts winding ( or 2 12 volts inn parallel or two six volts in series).
Bigger transformer there is less chance for the core to saturate. A big transformer will be harder for the elklectronics but because of the choke input the choke wont let the charging current rise to much. These pulsing current which are kind of equalised by the choke are the ones that make the diodes give a kind of disturbing signals which are hard to tame.
Are you sure 12 volts is enough?
I did go for the 2*15 volts but my first choke will have a higher serie ristance compared to the LL1694 ( 3.4 ohm instead of 1.8 ohm)
Sincere greetings, Edward
Thanks guys,
I've seen a few chinese R Cores with electrostatic shields to wire to mains earth and copper shielding on the outside for not much cash, so I'm going to get one of those. Just trying to find someone who holds stock.
Hello James,
The company in france has lots of models in stock, they are 230 volts and not 220 volts like many Chinese ones on the internet, they all have static screens, they deliver in about a week. They dont have copper shielding but you can put one yourself.
Which voltage you need? I can check which one they have in stock in France so it will be easier for you to order.
Sincere greetings, edward
The company in france has lots of models in stock, they are 230 volts and not 220 volts like many Chinese ones on the internet, they all have static screens, they deliver in about a week. They dont have copper shielding but you can put one yourself.
Which voltage you need? I can check which one they have in stock in France so it will be easier for you to order.
Sincere greetings, edward
Hi James,
That's a nice discovery! I do not have this mono problem because I use input transformers with floating input wires, I made them floating when I started using direct pos/neg out. Otherwise you would tie the neg side to ground and that will stop it functioning as a balanced amplifier. However there is still another advantage using pos/neg direct out even when you use mono single ended amps and tie the neg to ground: you balance out the bias voltage this way so you can lose the output capacitor.
Regards,
That's a nice discovery! I do not have this mono problem because I use input transformers with floating input wires, I made them floating when I started using direct pos/neg out. Otherwise you would tie the neg side to ground and that will stop it functioning as a balanced amplifier. However there is still another advantage using pos/neg direct out even when you use mono single ended amps and tie the neg to ground: you balance out the bias voltage this way so you can lose the output capacitor.
Regards,
VAT charge to USA
Buyers in the USA beware! The first order I made directly from Doede did not include a VAT charge. My second order from Audio-Creative did have a VAT charge.
Contact with Audio-Creative reaffirmed the need for them to charge a VAT/BTW for exports to the USA. This doesn't sound right to me. Can anyone clarify?
Buyers in the USA beware! The first order I made directly from Doede did not include a VAT charge. My second order from Audio-Creative did have a VAT charge.
Contact with Audio-Creative reaffirmed the need for them to charge a VAT/BTW for exports to the USA. This doesn't sound right to me. Can anyone clarify?
That's not correct. They should only charge vat for orders being shipped within the EU. Anything being sent outside of the EU should not carry a VAT charge. You get your tax applied at the point when it enters your tax zone instead.
If they will not credit this make a claim to your credit card issuer or to PAYPAL.
That is not good news.
Please let us know if this is not resolved.
I think there is no need to start claiming credits throug PayPal etc. just take this on with audio creative. the tax rules are complicated but very clear. so this need to cleared administratively. I will check this as well.
please do not forget I always send my kits as private person, so there was never vat on it, it is not to compare with the official way of doing business.
please do not forget I always send my kits as private person, so there was never vat on it, it is not to compare with the official way of doing business.
Hello ,
Just use google.
Also depends if you want choke input or not. If you use choke input it is better to have a bleeder so there will always be a current. If there is no current with choke input the voltage will go up high and maybe destroy your caps.
With choke input. The higher the induction the lower the current has to be to make it work as a choke input.
Which chokes do you have?
With choke input you will also need a transformer which has higher output voltage.
Sincere greetings, Edward
Just use google.
Also depends if you want choke input or not. If you use choke input it is better to have a bleeder so there will always be a current. If there is no current with choke input the voltage will go up high and maybe destroy your caps.
With choke input. The higher the induction the lower the current has to be to make it work as a choke input.
Which chokes do you have?
With choke input you will also need a transformer which has higher output voltage.
Sincere greetings, Edward
Hello,
Yes the bleeder is connected across the cap. Maybe you can use choke input with the 9 volts transformer. Use the choke as common mode choke ( see data sheet LL1694), then cap then the choke from France and then thje last cap with the bleeder.
Sincere greetings, Edward
The choke from France has very low serie resistance so very low voltage drop.
The bleeder must be big because it will get hot!!!
Yes the bleeder is connected across the cap. Maybe you can use choke input with the 9 volts transformer. Use the choke as common mode choke ( see data sheet LL1694), then cap then the choke from France and then thje last cap with the bleeder.
Sincere greetings, Edward
The choke from France has very low serie resistance so very low voltage drop.
The bleeder must be big because it will get hot!!!
No VAT to the USA
Audio-Creative researched this issue further and concluded that there should be no VAT/BTW charge to countries outside the EU like the USA.
They refunded the VAT charge to me. No reason not to buy items from Audio-Creative. The board I bought from them was well packaged and shipped fast.
Audio-Creative researched this issue further and concluded that there should be no VAT/BTW charge to countries outside the EU like the USA.
They refunded the VAT charge to me. No reason not to buy items from Audio-Creative. The board I bought from them was well packaged and shipped fast.