ALEPH P 1.7 is UP

[Stefanoo]

Hello guys.

I just finished one channel of the P1.7 and it's playing right now in the background.
Unfortunately i don't have enough parts to make the other channel and i have to wait next week to do that.
The voltages are ok and there is no distortion or hum.
I can barely hear a slight 50Hz with my ear by the speaker and volume at max position.

I'm not currently using an heatsink on the MOS but i placed them to share a "double-side" heatsink.
I nevertheless measured the temperature:

On the 610s the temperature is about 35C , instead on the 9110s the temp goes up to 65C (is it too much?)

As test purposes i'm using a 5 steps out volume control and a 5K potentiometer on the control gain.
The volume adjustemnt is not very nce since i don't have eough steps.

Up till now i could start the pre with a variac because if i plug it directly it would blow the power supply (really bad).
Could it be the inrush since i have on the board other 8 X 2200uf capacitor(other than the 15000uf out of board)?
I'm a little confused, since just yesterday i started it up without variac and everything worked out fine....maybe a case?

I dooon't know....any suggestion is welcome!!


i am try to compare the sound with my Electrocompaniet Preamplifier but it is not so easy since the P.7 is running with test tantalium capacitors which are well known for their distortion and a bad quality output switch.

I need to make a definite version first with both channel perfectly working and then start comparing the pre.

Anyways Up till now it seems to me that the pre sounds etter (more dinamic) wiht a 1k output resisor and the volume control on the gain.

Anybody else had experience with this regard wants to share his experience?
Last...i have noticed that the pre when conneced to the input of the amplifier lowers a lot the output voltage (almomust half)!!
Is this normal???
Can i do anything for that?

 

[analog_sa]

Is this normal???
Can i do anything for that?

If i recall correctly you were the one running this circuit in a simulator. Do you really need to ask?

And why call it an Aleph 1.7? With more than 30,000uF, tantalum caps and a "bad quality switch" it should qualify for a 1.9, maybe even 2.0.

Aleph 2.0 Mono

Practically all your questions have been asked and answered multiple times already. Searched?


"Last...i have noticed that the pre when conneced to the input of the amplifier lowers a lot the output voltage (almomust half)!!"


Are you sure this really happens? With a 1k output pot this seems highly unlikely unless your power amp's input impedance is 600ohms.

 

[Stefanoo]

one update....

even if the sound can still be improved the little hum (50HZ) on the output is very low but my EC pre doesn't have that at all.
I have shunted with the +60V that goes to the board right where it wires up with the board a 220nF capactor...but th situation seems to b the same....


any suggestion to improve th situation?

I want to outline that the hum is very low and i don't know if it is because the pre is not inside a case but just to make this clear ...i'm using the power supply of the Electrocompaniet which it runs at 60V and therefore i could use that ..... since the test power supply that i have made didn't work wery well in hums's terms.

The power supply therefore is inside the case of my electrocompaniet (integrated amplifier).
Could it be the layout?
I outline one more time...that the noise is very low...and i don't know if it can be canceled by using a capacitor on the right place or not.

Heeelllppppp

 

[Stefanoo]

Re: Re: ALEPH P 1.7 is UP

If i recall correctly you were the one running this circuit in a simulator. Do you really need to ask?

And why call it an Aleph 1.7? With more than 30,000uF, tantalum caps and a "bad quality switch" it should qualify for a 1.9, maybe even 2.0.

Aleph 2.0 Mono

Practically all your questions have been asked and answered multiple times already. Searched?


"Last...i have noticed that the pre when conneced to the input of the amplifier lowers a lot the output voltage (almomust half)!!"


Are you sure this really happens? With a 1k output pot this seems highly unlikely unless your power amp's input impedance is 600ohms.

You have good memory ubt you don't read as well as your memory goes too.
I didn't say that i have 30000uf tantalium caps.....where did you get that???
I was referring to the 10uf and 30uf caps in serie with the input and output respectivetly.

i don't wanna start an argument so i'll just ignore this rude answer.

I did only want to share this project with the DIYs....is' this the purpose of this forum...is it?

By the way the input impedence of the amp is about 330kohm soooo....there must be a reason of why the output goes down.


I would like to understand why the pre blows the power supply when connected directly to the 220V and how and if it is possible to eliminate the small hum.

 

[Babowana]

Heeelllppppp

I think you need to help me first with your question

 

[analog_sa]

Re: Re: Re: ALEPH P 1.7 is UP

You have good memory ubt you don't read as well as your memory goes too.
I didn't say that i have 30000uf tantalium caps.....where did you get that???

Yes, i can read and also write. You may have noticed the comma sign between 30,000 and tantalum. Neither is specified for an Aleph 1.7. Not that this will fix your problems. It's just wrong to call it Aleph 1.7.

 

[Stefanoo]

Sorry i miss-interpretated you then.
Yes, i know that the tantalium caps are bad sounding....i just put them on to test if the layout and everything else was allright.
Of cours that i'm going to get good caps.
I don't think that this fact could affect the hum...does it?

I'm trying to figure this little hum out.
I don't know if there is a good rule of thumb for this slight hum.
Even thought by reaserching on the forum i have noticed that hum is generally correlated to a wrong wiring on the power supply.
As i said efore, i'm using the internal power supply of my electrocompaniet, which is deadly silent with it and therefore i can think that the little hum is caused from something else on my board.

 

[Stefanoo]

I think you need to help me first with your question

Maybe i wasn't able to express my self.
My questions are:

- I have a little hum...which is very low but still it's there: is there any good rule of thum to figure this issue out? maye i need a thermistor? i don't even know what this component does

- When i hook the board the power supply blows...is it normal? if so, what can i do to solve this prolem? do i have to start the board with a variac everytime

- About the volume control...i have noticed that the pre seems to soud better if there is a resistor on the output and i control the volume through the gain control (but that could be caused from a bad quality switch i don't know)

-Looking at the signal at the output with my scope i could see that when the pre is connected to the input of the amp the voltage at the output of the pre lowers a lot (maybe i'll check this thing one more time...ut i'm preatty sure)

That's all...if there is anything that is not clead, please ask me and i'll try to explain it better.


In the meantim thanks for the attention.

 

[Babowana]

- I have a little hum...which is very low but still it's there: is there any good rule of thum to figure this issue out? maye i need a thermistor? i don't even know what this component does

- When i hook the board the power supply blows...is it normal? if so, what can i do to solve this prolem? do i have to start the board with a variac everytime

- About the volume control...i have noticed that the pre seems to soud better if there is a resistor on the output and i control the volume through the gain control (but that could be caused from a bad quality switch i don't know)

-Looking at the signal at the output with my scope i could see that when the pre is connected to the input of the amp the voltage at the output of the pre lowers a lot (maybe i'll check this thing one more time...ut i'm preatty sure)

- The hum is a terrible thing. In my case I had such hum mostly due to poor ground loop arrangement. I hope you will re-check the grounding. And, I recommend to keep certain distance between the transformer and the wires carrying the input signal. I always count the amount of current in the grounding path of the left channel and the right channel, and compare whether the numbers are symmetrically the same before they are connected to the common ground path. Of course, all the ground path should avoid the dirty roads where the polluted current are also using as their path.

- It is unusual when the finish is built according to the proven circuit drawing.

- Thanks for the info.

- The pre amp is a Thevenin equivalent circuit while the power amp is an equivalent load resistor. So, you know . . . I think.

 

[Stefanoo]

i missed th final part......but ohh welll

I will check the current on the ground path on the left and right channel.
Just so you know this time i only had one channel connected...so....i don't know if the hum could have been reconducted to that case there.
Anyways.....i arranged the board a little different, by keeping it far away from the transformer and signal cable away from the power chird and the hum disappeared...so i bet that once the pre wil be cased and isolated the hum won't be there...those are my to cents....i'll keep you guys posted.


I'm still trying to figure out if it is normal that the power supply lows if i connct directlly the prfe to the network or not?
Can i do anything for that?

Cna anybody kindly explain me what rules the thermistor plays on the circuit?
What does it exactly do?
Does it act as a soft start (but does a preamplifier need a soft start circuit?) ?
Or does the theristor lower the hum noise on the output?
Sorry for my ignorance guys

Hope to receive good advice.

 

[Babowana]

Cna anybody kindly explain me what rules the thermistor plays on the circuit?

NTC (Negative Temperature Coefficient) thermistor is a resistor.
But, it changes its resistance with changing temperature.
When it has room temperature, the resistance is e.g. 10 Ohms
(or other values according to maker's types), and when its
temperature goes up due to P=I x I x R, the resistance drops
until it reaches the steady-state condition among the current
flowing thru, room-thermistor temperatures and the final resistance.

NTC thermistor itself is not a hum killer at all.

This is all I know . . .

 

[Stefanoo]

non interest on this subject?

 

[Bill Fuss]

Hi Stefano,
Your PS is probably blowing fuses because of the amt of capacitance you are using. Try a slow blow fuse of the same rating.
The thermistor is only for protection in case of failure.
A 1k load on the output decreases your gain considerably, try 2.7k or more.
A shunt OP circuit will work fine, dont worry about the changing impedence, the Aleph P doesn't care. Just stay 1/10th or lower than the input on your amp.
I'm using a 5k ladder relay circuit into a 47k amp input and its just fine.
Best, Bill

 

[Stefanoo]

thanks for your post.
The circuit , when plugged in directly, blows the transistor of the power supply and LEAVES the fuse untouched.
That could be caused by the fact that i have 8X2200uf capacitors on board as extra filter capacitance.
But when i plugged the circuit in the first times i didn't have any problem.
I'll try to lower the capcitance maybe that will help.

I have ...indeed....still.....an issue with the hum (i think it is hum....it is a little noise JUST on the woofer of the loudspeaker...dont' really know difference with buzz).

I am currently using the power supply of a commercial amplifier to ensure that not hum is injected on the board.
Even with that thought, i have a little, but audible, noise that i would like to get rid of.

I have tried to shunt a 47nF capacitor right on the 60V power supply inlet ....but nothing.....

i have tried to brake eventual ground loops by installing a 10ohm resistor in serie with the ground of the power supply and then with the ground input signal....respectivetly ..... but without any result.

I took the capacitors that i had on board off of the pcb to try to evaluate if those capacitors were source of that noise....but nothing.....still the same.

I don't know what else to do....

The only thing i can try to think more of.... is.... if i twist the output wires assuming that short unshielded untwisted wires could pick up noise.

Please any advice is welcome....

one more detail .... if it helps...

I have the power and signal ground in common...since i have a ground plane with a mask that covers the two layers and goes through every single track on the board....i don't know if this is something that has to be avoided.
I thought that could have been something positive since i have a ground shield passing by each net.

 

[Bill Fuss]

Hi Stefano,
Too much capacitance can blow a diode so I'm sure it can also blow a transistor. You really need to build your supply. 4000uf would be plenty with a 1 ohm series resistor and another 1000 on the board.
I think you definately have a ground loop problem. Your supply should run to the board at one point and nowhere else. Your input and output jack grounds should be tied together, then run to the board and nowhere else, and definately not connected directly to the case.
If this is the setup you now have then try a .22uf film cap from signal ground to the case, sometimes its all you need. I am assuming the case is earth grounded as it should be.
Thats it for now, good luck, Bill

 

[Stefanoo]

ok...i understand the capacitance's issue.

I want to highlight that i DON'T have any casing right now for the preamplifier...and therefore i can't run any earth or ground to chassies ...since i don't have it

ONLY the power supply...since i'm using a power supply of a commercial amplifier to insure that the PSU wouldn't contribuite to the hum at the output....is inside its own chassies with the integrated amplifier.