100W Ultimate Fidelity Amplifier

[rsavas]

First, Is there a layout for the MM28?

Do not know

Second, isn't P30 CFA?

yes mm28 is same/similar topology, I am looking at the differences.
I am assuming MM28 is for MM phono cart.

 

[still4given]

I have a nice phono. Haven't used it in years. I'm too lazy to get up every 30 minutes to flip the record over. Unless MM28 has something to offer that the P30 doesn't I don't see the point.

 

[apexaudio]

That is so cool Mile, now for the complete set MC28 🙂

You can add MC4 on MM28 input and get MC preamp, P30 is line level CFA preamp, MM28 is CFA phono MM RIAA preamp.

 

[apexaudio]

You can find SR PP8 and SR PP12 folded cascode VFA preamp or headphone amp in thread: http://www.diyaudio.com/forums/solid-state/173462-studio-reference-amplifier-180.html

 

[rsavas]

I'm too lazy to get up every 30 minutes to flip the record over.

Isn't that about the same time it takes to etch a board 🙂

You can find SR PP8 and SR PP12 folded cascode VFA preamp or headphone amp in thread:

thx, for all your designs.

On MC4, is it possible to parallel the inputs to reduce noise further?

 

[still4given]

Isn't that about the same time it takes to etch a board 🙂

Yes, but then I get to spend the rest of the day populating and testing. 😀

Hi Mile,

Is the reason you suggested MM28 when I showed P30 is just another choice or do you think the MM28 is superior?

 

[apexaudio]

Isn't that about the same time it takes to etch a board 🙂

Yes, but then I get to spend the rest of the day populating and testing. 😀

Hi Mile,

Is the reason you suggested MM28 when I showed P30 is just another choice or do you think the MM28 is superior?

MM28 is only phono preamp and must be connect to P30 input.
Regards

 

[still4given]

Hi Mile,

OK, I see now. 28 device mono phono stage? So 56 devices for just the phono alone? Wow! 😱

 

[still4given]

Just finished ...after few my mistakes is running.... Offset is OK, but bias still no OK. When I set bias 50mA, after On/Off procedure is 100 mA and slowly decreasing back to 50mA...maybe some temperature compensation, or something totally different 🙂 I have to check it tomorrow..

My A40 does this. It scared me at first and I dialed down the bias but then I noticed that after a few minutes the bias would be too low. So I just waited for the amp to settle and set the bias back up. It now starts up at over 100mA at start up but drops down to around 50mA. I just assumed it is in front end or VAS. I have felt all the devices and none of the run hot and 100mA won't hurt anything. Maybe others will comment on this.

Blessings, Terry

 

[rsavas]

OK, I see now. 28 device mono phono stage?

Just like a monolythic opamp, this is why I think smt is the best to use for such a design.
I would have to say it is the most elaborate MM phono yet for me to lay my eyes on!! and I do not know of any other CFA type phono pre-amp either.

 

[smartx21]

MM28 is only phono preamp and must be connect to P30 input.
Regards

Now, there's only one missing stage: TONE CONTROL (for those who appreciate).

 

[apexaudio]

Now, there's only one missing stage: TONE CONTROL (for those who appreciate).

MM28 can be TONE CONTROL instead RIAA if you want.

 

[apexaudio]

My A40 does this. It scared me at first and I dialed down the bias but then I noticed that after a few minutes the bias would be too low. So I just waited for the amp to settle and set the bias back up. It now starts up at over 100mA at start up but drops down to around 50mA. I just assumed it is in front end or VAS. I have felt all the devices and none of the run hot and 100mA won't hurt anything. Maybe others will comment on this.

Blessings, Terry

It is OK for bias servo in A14 and A40 with diamod OS.
Regards

 

[maxwell007]

uff..I thought, that I make some another mistake, good news mr. Mile...😀😀😀 so, It's very good playing amp, very clear highs, good bass... little bit better, than AX14..

short movie
https://youtu.be/1Kja7r3V3_k

 

[maxwell007]

I started work on P30...PCB is ready....then I decided to make A40 😀

 

[apexaudio]

uff..I thought, that I make some another mistake, good news mr. Mile...😀😀😀 so, It's very good playing amp, very clear highs, good bass... little bit better, than AX14..

short movie
https://youtu.be/1Kja7r3V3_k

Nice work,
Regards

 

[olafk]

If anybody needs a suitable VU meter...
http://www.diyaudio.com/forums/analog-line-level/273614-vu-meter-xxl-led-stripe.html

regards Olaf

 

[apexaudio]

If anybody needs a suitable VU meter...
http://www.diyaudio.com/forums/analog-line-level/273614-vu-meter-xxl-led-stripe.html

regards Olaf

Nice light show 🙂
Regards

 

[rakesh_sharma23]

Testing with +-30Volts with 4.5ohm 10W resistance instead of fuse.

Getting +30v from speaker out , BD139 getting hot, if 1K pot is turned to reduce resistance both Power transistors started to heat, Please have a look and some solution

 

[thimios]

Testing with +-30Volts with 4.5ohm 10W resistance instead of fuse.

Getting +30v from speaker out , BD139 getting hot, if 1K pot is turned to reduce resistance both Power transistors started to heat, Please have a look and some solution

Is input GND connected to star GND?