100W Ultimate Fidelity Amplifier

[bimo]

I swapped out the 47R for 100R and the Q5 and Q6 are smoking hot - they would burn your finger if touch more than 1 second. It plays music and sounds nice but don't know how long that will last. I have it set for 100mA bias current at present. Based on how hot those two VAS transistors are, I would imagine 680R is what is needed to get temps down to reasonable level.

Or go with TO126 like MJE340/350

There is an occasional crackling or popping sound right now - perhaps imminent failure of the 2N5401/2N5551?

With 68R VAS degen., VAS current is about 4,7mA and dissipation is 150mW. May be you have bad transistors.

 

[bimo]

For debugging. To calculate voltage, use ohm law.

 

[apexaudio]

For debugging. To calculate voltage, use ohm law.

Thre is over 9V on Vbe multiplayer in your schematic !?

 

[bimo]

Thre is over 9V on Vbe multiplayer in your schematic !?

No, There are collectors current, not voltage.

 

[apexaudio]

No, There are collectors current, not voltage.

I see schematic in low resolution and MPSA13 instead MPSA18. Current is ok and VAS transistor can not be too hot with this disipation.

 

[apexaudio]

I swapped out the 47R for 100R and the Q5 and Q6 are smoking hot - they would burn your finger if touch more than 1 second. It plays music and sounds nice but don't know how long that will last. I have it set for 100mA bias current at present. Based on how hot those two VAS transistors are, I would imagine 680R is what is needed to get temps down to reasonable level.

Or go with TO126 like MJE340/350

There is an occasional crackling or popping sound right now - perhaps imminent failure of the 2N5401/2N5551?

What is R6 resistor value and voltage on it? What is voltage (current calculation) on 47R resistors?

 

[xrk971]

With 68R VAS degen., VAS current is about 4,7mA and dissipation is 150mW. May be you have bad transistors.

You might be right. Let me pull out those VAS and out in fresh pair - that's just way too hot. These were not replaced yet along with the BD's which got fresh units after my silicone insulator pad leak through which conducted full rail to rail voltage between the collectors of both BD drivers.

 

[xrk971]

What is R6 resistor value and voltage on it? What is voltage (current calculation) on 47R resistors?

I will check later tonight when back in the lab.

 

[apexaudio]

F8

 

[thiagomogi]

awesome ... could draw with HEXFET and VBE ?

Regards

Thiago

 

[ivanlukic]

I will check later tonight when back in the lab.

May be that you used 10R resistor instead of 100R?

 

[Bangla H]

Same thought like thiag- awesome Mile.
Is the fixed bias done by 4007?- my thought to pecebe- you know, my basic knowledge.

Cheers Bangla.

 

[xrk971]

awesome ... could draw with HEXFET and VBE ?

Regards

Thiago

Then it might resemble the CFH7 +2 with another driver stage.

 

[apexaudio]

A5 Pcb

 

[apexaudio]

awesome ... could draw with HEXFET and VBE ?

Regards

Thiago

Or with BJT and bias fixed by LED

 

[xrk971]

Hi Apex,
CA10 looks really cool. I like it a lot. Is this something from past post or brand new?

 

[apexaudio]

Hi Apex,
CA10 looks really cool. I like it a lot. Is this something from past post or brand new?

It is new and not tested.

 

[ammel68]

With a trimmer pot for DC offset in the CA10, does this mean the BC546/556 don't have to be matched?

 

[xrk971]

Scratchy clipping like sound on AX11

May be that you used 10R resistor instead of 100R?

Good call.

Replaced the 10R with 100R, and got new 2N5551 and 2N5401 for Q5 and Q6. Temperatures are down now - can touch the units but still quite warm, but not burning.

However, bias could not go higher than 20mA. So I changed R14 from 1.3k to 820R and am able to adjust bias to whatever I want. Tried it at 100mA and 30mA. Sounded ok at first but then when music seems to have peaks, a terrible scratchy popping sound occurs. With DMM connected to speaker output, regular levels were 2-4v AC and when scratchy noise occurs, it hits 11v or 12v.

My amp is using suggested resistors for the LED and 1N4148 option as recommended by Apex Audio: R4=10k, R6=470R.

Here is a recording of the clicking popping noise - change extension from .asc to .mp3 to listen.

So much trouble with getting this amp to work.

 

[ivanlukic]

I would say that some of the components used is not OK.