My LM3875 Amplifier

[bill6300gp]

My LM3875 Amplifier for TB4 Speaker.

Inner_1

Inner_2

Speak Protector

LM3875 IC

Outer_1, the main transformer for Amplifier.

Outer_2


Why do I add VR on this amplifier?
Because I don't have any preamplifier, I use them to adjust volume.

The following are wave-test(Square wave) measured by oscilloscope.
I use 8R resistor as load, and output Vp-p is set 20V(+/-10V)
100Hz

1kHz

20kHz

50kHz

100kHz



Thanks for your reading.

[thomgun_lc]

WOW Big Pictures, what about the sound?

[bill6300gp]

Originally posted by thomgun_lc
WOW Big Pictures, what about the sound?

I feel not bad, but I can comfortably listen to music.
(It work about 50hrs)

Compared to LME49810 Amplifier which I made before.
(The article in LME49810 - a new cousin for LM4702 on Post #579 and Post #618)
1. The low frequency in music is not enough low. The speed of them is OK, I mean the sound of low frequency is "Q".
2. The median and high frequency in music has a little sound of tube and a little blur.

[sivan_and]

Which speaker protection circuit is that ?

[bill6300gp]

Originally posted by sivan_and
Which speaker protection circuit is that ?

I use DZ(diyzone) speaker protection, which is given from my friend. And it is already finished.

I can't find its circuit from www.diyzone.net now, so I have no circuit, sorry . I only find the circuit of LM3875 PCB out.

[Luck]

Oh...Two power transformers are on the top of the case?Do you put a preamplifier IC inside?

[bill6300gp]

Originally posted by Luck
Oh...Two power transformers are on the top of the case?Do you put a preamplifier IC inside?

Because the case is too small to put The two transformers , supplying for LM3875 modules, outside.

I let this LM3875 as temporary amplifier for us because I have no preamplifier yet.
I give signal from DAC to the LM3875 amplifier, and only using VR to adjust volume.


The preamplifier and power amplifier is preparing...
The preamplifier: I want to try all transistors' amplifier circuits with remote control module.
The power amplifier: I want to try LME49830 circuits.
But I not sure what time to start.

[s800]

Very nice!

People rave about toroids for gainclones- curious if you have noticed any downsides with the traditional transformers?

Thanks for the pictures, well done.

[pacificblue]

Originally posted by s800
People rave about toroids for gainclones- curious if you have noticed any downsides with the traditional transformers?

Downsides of "traditional transformers" are.

• - They need more height.
  - They need more distance to the audio circuit, due to their wider stray magnetic field.
  - They are slightly less efficient.
  - They are getting ever harder to source, because of the hype around troroids.

But no shadow without light.

• - They need less width and depth.
  - They usually have a higher saturation limit.
  - Their stray magnetic field is wider dispersed, thus weaker.

[bill6300gp]

If we only consider feel of hearing without other factors, EI- transformers(traditional transformers) and wreath-transformers(toroids) having some different feel.
Due to this, some of people still like to use EI-transformer.

But...
If I make power amplifier for us, LME49810 upto 300W for example, I will want to use wreath-transformers.
(The LME49810 amplifier,I made before, is for friends.)
When I make amplifier by tubes, I will only use EI-transformer because of feel of hearing.

Thanks for your suggestion.