Pass B1

[omishra]

Hi Sachin,

What I mean is, we can have a single trafo for both the B1 and the LDR and integrate the power supply circuits in the respective boards. Hope I'm not asking for too much.

Rgds


Rajesh

Yes! we can. Pass B1 works on 18V, you can take that raw 18V and feed to this volume control which itself has on-board 5V regulator.

 

[josephjohnt]

Yes! we can. Pass B1 works on 18V, you can take that raw 18V and feed to this volume control which itself has on-board 5V regulator.

Can I take it a step further? The pdf doc for B1 says the input voltage can be 18-24V. I am building a gainclone from linuxguru which uses 24V. Can I use that same trafo to power the B1 and lightspeed as well. Or is it not advisable to use the same trafo for amp and pre?

 

[omishra]

Can I take it a step further? The pdf doc for B1 says the input voltage can be 18-24V. I am building a gainclone from linuxguru which uses 24V. Can I use that same trafo to power the B1 and lightspeed as well. Or is it not advisable to use the same trafo for amp and pre?

Nothing like that.
You can use same transformer for all of the circuits. Just you need to isolate the power line - putting small value resistors (10 ohm/1 or 2Watts) between PS and these small current circuits, additionally shunting to ground with 10uF/35V or 100uF/35V electrolytic caps and one 0.1uF/50V ceramic cap.

24V -^/\/\/\/\/\^---------|----|------------------output
..................... 10uF/35V == .. == 0.1uF/50V
................................... | .... |
.................................GND GND

 

[captrajesh]

That's great. In that case, do we need multiple taps from the trafo or can the correct voltage be obtained by placing a resistor of appropriate impedance in the current path?

I have a Class D amp which needs DC power of 45 - 60 volts. The ideal voltage at the secondary of the trafo would be 35-0-35. I intend to use the same trafo for all three i.e. the Class D power amp, B1 Buffer pre-amp and the LDR based volume control. Am I correct in assuming that I should get a trafo with multiple trappings of:

1. 35-0-35 - for the power amp
2. 15-0-15 - for the B1 Buffer (or is it 15-0 / 7.5-0.-7.5)
3. 3.5-0-3.5 - for the LDR Volume control (or is it 5-0 / 2.5-0-2.5)

Yes! we can. Pass B1 works on 18V, you can take that raw 18V and feed to this volume control which itself has on-board 5V regulator.

 

[omishra]

That's great. In that case, do we need multiple taps from the trafo or can the correct voltage be obtained by placing a resistor of appropriate impedance in the current path?

I have a Class D amp which needs DC power of 45 - 60 volts. The ideal voltage at the secondary of the trafo would be 35-0-35. I intend to use the same trafo for all three i.e. the Class D power amp, B1 Buffer pre-amp and the LDR based volume control. Am I correct in assuming that I should get a trafo with multiple trappings of:

1. 35-0-35 - for the power amp
2. 15-0-15 - for the B1 Buffer (or is it 15-0 / 7.5-0.-7.5)
3. 3.5-0-3.5 - for the LDR Volume control (or is it 5-0 / 2.5-0-2.5)

This is very high voltage and application is housed with class-D amplifier. So use of resistances in power line is not good idea.

Is PS have a toroidal transformer? If yes then wind some 27 SWG enameled wire over toroid by considering 0.4V per turn. Take doubled wire to wind two coils simultaneously and wind required turns. After that make those two coils in series making center tapped point available. Fix with cello tape and scotch tape.
I have done these thing to EI transformer also. But using needle and enameled Cu wire as thread, doing loop around filled bobbin is tedious and okay for low current like this applications. Otherwise getting extra transformer will be better idea than putting resistances inline. Because class-D has some grounding isolation between analog and switched circuit. This digital noise should not intrude to power line of low level audio signal preamps.

1. 35-0-35 - for the power amp
2. 15-0-15 - for the B1 Buffer (or is it 15-0 / 7.5-0.-7.5)
3. 3.5-0-3.5 - for the LDR Volume control (or is it 5-0 / 2.5-0-2.5)

You will need
1. 35-0-35 - for the power amp
2. 15-0 (or 15-0-15) for the B1 Buffer
3. 5-0 (5-0-5) for the LDR Volume control

 

[captrajesh]

Is PS have a toroidal transformer?

The class D amp is on one board, the power supply along with the capacitor banks (takes 35-0-35 volts of AC current) is on another board. I already have an EI core trafo but I have a feeling that it is not supplying the required amperage of 300va current. I'm planning to buy a Toroid or R core and also, intend to isolate the transformer from all the circuitry.

Because class-D has some grounding isolation between analog and switched circuit. This digital noise should not intrude to power line of low level audio signal preamps.

That is the reason why I Intend to isolate the trafo. Going by your post, it appears that I need to isolate the Class D amp as well.

2. 15-0 (or 15-0-15) for the B1 Buffer
3. 5-0 (5-0-5) for the LDR Volume control

Are both same?
By having 15-0-15 trafo we would be seeing 30-0 volts I thought.

 

[omishra]

Are both same?
By having 15-0-15 trafo we would be seeing 30-0 volts I thought.

In case of X-0, you will use bridge rectifier composed of 4 diodes. For X-0-X, you have use full wave rectifier composed of 2 diodes.
X-0 is useful for single ended PS (+V, GND or -V, GND) and X-0-X preferred for dual PS (+, -, GND).

 

[captrajesh]

In case of X-0, you will use bridge rectifier composed of 4 diodes. For X-0-X, you have use full wave rectifier composed of 2 diodes.
X-0 is useful for single ended PS (+V, GND or -V, GND) and X-0-X preferred for dual PS (+, -, GND).

Too complicated for me. I'll do just what you said.

 

[quad]

Capt, it is easy to mod the LDR board to take a 6V AC input as
shown below.

However, since you will probably need a power supply for the B1 buffer,
you can draw the DC from there, as Omishra suggested.
Alternatively, the little diode rectifier shown above
(cost Rs 5/- in local market) can be connected directly on to the
LDR board, or on a small piece of general purpose board.

 

[gopib]

Sachin,

This is now getting interesting. If I am not too late...can I join in for the GB???

TIA

 

[sachu888]

Sachin,

This is now getting interesting. If I am not too late...can I join in for the GB???

TIA

Sure Gopi,you are welcome.Did you complete your CNC phono?

Regards,
Sachin

 

[gopib]

^^ Yes Sachin. Completed in the sense that it is working on a breadboard base. It is being used - two sets of battery done.Lovely soundstage - better than my ancient pre. I have just found an old voltage stabiliser case - the phono will probably go into that...and then I exhibit...

 

[sachu888]

^^ Yes Sachin. Completed in the sense that it is working on a breadboard base. It is being used - two sets of battery done.Lovely soundstage - better than my ancient pre. I have just found an old voltage stabiliser case - the phono will probably go into that...and then I exhibit...

That's good.Please share your experience once you done with the case.

Regards,
Sachin

 

[omishra]

Me and quad able to simplify the layout to make signal path much smaller and thicker. This seems to be latest update unless we get better idea from forum members.

See the tracks upper portion is volume control for audio signal path and lower portion is control part

 

[captrajesh]

@Mishra (omishra), Prasad (Quad) and Sachu888 (Sachin)

You are our leading lights. No one can show light to leading lights.hyeah:

 

[omishra]

@Mishra (omishra), Prasad (Quad) and Sachu888 (Sachin)

You are our leading lights. No one can show light to leading lights.hyeah:

Ohh..I am flattened . Need alkaline battery to increase luminance.

 

[captrajesh]

Ohh..I am flattened .

I intended to flatter you; so sorry to flatten you.:lol:

 

[captrajesh]

Is PS have a toroidal transformer? If yes then wind some 27 SWG enameled wire over toroid by considering 0.4V per turn. Take doubled wire to wind two coils simultaneously and wind required turns. After that make those two coils in series making center tapped point available. Fix with cello tape and scotch tape.
I have done these thing to EI transformer also. But using needle and enameled Cu wire as thread, doing loop around filled bobbin is tedious and okay for low current like this applications. Otherwise getting extra transformer will be better idea than putting resistances inline. Because class-D has some grounding isolation between analog and switched circuit. This digital noise should not intrude to power line of low level audio signal preamps.

You will need
1. 35-0-35 - for the power amp
2. 15-0 (or 15-0-15) for the B1 Buffer
3. 5-0 (5-0-5) for the LDR Volume control

I just found a link to this in another forum: Power amplifier DC supply, BNICS

Would this be sufficient to drive my class D power amp (Operating voltage range is 45 - 60 V) and the LDR (5V) Is there a way to also take out 15 volts for the B1 buffer?

 

[omishra]

I just found a link to this in another forum: Power amplifier DC supply, BNICS

Would this be sufficient to drive my class D power amp (Operating voltage range is 45 - 60 V) and the LDR (5V) Is there a way to also take out 15 volts for the B1 buffer?

Though OT, what are power requirement for your class D amp? is it +39, G and -39?

 

[captrajesh]

Though OT, what are power requirement for your class D amp? is it +39, G and -39?

Sorry for the OT. the operating voltage is 45 to 60 V DC. I'm presently using a 35-0-35 EI core trafo which would give a mean operating voltage of 49.35 (35 volt AC X 1.41)