Compact Sized LME49810/11 +ThermalTrak Amp

[panson_hk]

Ah ok... I thought maybe there was some rule of thumb could use to choose right ballpark of current, guess experiment away. Need to get scope.

May be there are guidelines. Let see other replies.

 

[panson_hk]

Hello Panson,

about possible compensation optimization. Have you tried it?

Please take a look this http://www.diyaudio.com/forums/chip-amps/143163-comparing-lme49810-49830-49811-a-35.html#post2077487

 

[blueskynis]

Will do. Thanks.

 

[Radioman62]

Output inductor & Zobel network

Hi panson
A question about using your compact amplifiers inside active speakers. One amp to each element.

Is it really necessary to use those inductors and Zobel network when the connections between amplifier and speaker is only about 10 inch?
The answer is maybe the same for any other typical audio endstage?

 

[AndrewT]

at very high frequencies the inductance of the Voice coil and the capacitance of the cable may not provide a nice benign load for the amplifier.
The Zobel guarantees an R+C load at VHF and this helps stabilise the amp.

 

[panson_hk]

Hi panson
A question about using your compact amplifiers inside active speakers. One amp to each element.

Is it really necessary to use those inductors and Zobel network when the connections between amplifier and speaker is only about 10 inch?
The answer is maybe the same for any other typical audio endstage?

Hi Radioman,

As AndrewT you need to take care of voice-coil inductance. However, cable effect is negligible for direct connection. I would recommend to have those parts to avoid problem in this part.

 

[Sebastiaan]

Dear,

Always use the zobel and the output inductor/resistor.

I was stubborn and did it without (also active speaker project) but on some occasions I got oscillations in the far MHz. The Zobel solved this problem.

With kind regards,
Bas

 

[panson_hk]

New Compact 4981x ThermalTrak board being made

I revised the schematic to include Vbe multiplier, two-pole compensation and ThermalTrak diode current by-pass. We now have many things to try!!!

The new board is being made. Here is the new schematic.

 

[Sebastiaan]

I revised the schematic to include Vbe multiplier, two-pole compensation and ThermalTrak diode current by-pass. We now have many things to try!!!

The new board is being made. Here is the new schematic.

Dear Panson.

What is your reason to add the VBE transistor? My understanding was that the benefit of the Thermaltraks was that you don't need a VBE transistor anymore.

With kind regards,
Bas

 

[panson_hk]

Dear Panson.

What is your reason to add the VBE transistor? My understanding was that the benefit of the Thermaltraks was that you don't need a VBE transistor anymore.

With kind regards,
Bas

Hi Bas,

Good question! This is added for user to compare different bias schemes. I want users to have more fun with the new board. We can do simple bias with solely TT diodes, conventional Vbe without using TT diodes, Leach like Vbe with TT diodes, etc.

Cheers,
Panson

 

[Sebastiaan]

Hi Bas,

Good question! This is added for user to compare different bias schemes. I want users to have more fun with the new board. We can do simple bias with solely TT diodes, conventional Vbe without using TT diodes, Leach like Vbe with TT diodes, etc.

Cheers,
Panson

Thank you Panson. Ever have plans to develop a huge class A variant?

With kind regards,
Bas

 

[panson_hk]

Thank you Panson. Ever have plans to develop a huge class A variant?

With kind regards,
Bas

Yes, I will but no more than 50W/8Ohm. It is too expensive for higher power!!!

 

[Shaun]

I would personally like to see class B versions in 50W/8R, 100W/8R and 300W/8R.

 

[panson_hk]

I would personally like to see class B versions in 50W/8R, 100W/8R and 300W/8R.

The boards currently available do these already.

 

[Radioman62]

balanced input?

Hi has anyone tried balanced input?

Even if it's a driver IC with two inputs I want some hints how to best connect it as a balanced input amplifier. Mostly to take advantage of my Behringer three way active filter, arriving this week.
The ground connection isn't important in my active speaker project so I may have no worries?

 

[panson_hk]

Hi has anyone tried balanced input?

Even if it's a driver IC with two inputs I want some hints how to best connect it as a balanced input amplifier. Mostly to take advantage of my Behringer three way active filter, arriving this week.
The ground connection isn't important in my active speaker project so I may have no worries?

You can get some info from this thread http://www.diyaudio.com/forums/chip-amps/131099-lme49810-fully-balanced.html#post1628650

 

[panson_hk]

New boads back and tested. Super performance!!!

The new boards are back from the PCB house today. I just assembled one for LME49811 with single-pole cap = 22 pF. The performance is super!!! The THD+N for 1 kHz 50 W into 8 Ohm is 0.00053 %.

 

[Shaun]

Excellent!

 

[Radioman62]

Bias curent trough the TT diodes

Hi panson
Great work and in progress of more goodies? Easy balanced unbalanced approach?

I have a question regarding adjustment of the bias current trough the Thermal Trak diodes. How much is the best for using the LME49811?

 

[klewis]

Hi Panson,

Very nice! Are you using pre-drivers? And what drivers are you using?

Ken