Younger brother of the LM3886 - LM2876 in parallel

[pbilous]

Hi all,

Because LM3886 is nowhere to find I got two LM2876s and paralleled them. These are the same Overture series as LM3886 and sound equally good, except not as powerful.

I was able to get 40W into 8ohm and 60W into 4ohm loads.

30V power supply 22V transformer

1khz
8ohm at 40W out - 0.0011% THD, 0.0022% THD+N
8ohm at 5W out - 0.00065% THD, 0.0045% THD+N

4ohm at 60W out - 0.0028% THD, 0.0037% THD+N
4ohm at 5W out - 0.00083% THD, 0.0064% THD+N

Given situation with LM3886 out of stock everywhere, would one go for something like this?

 

[aditya]

Given situation with LM3886 out of stock everywhere, would one go for something like this?

Yes - I would also be wondering if we could use LM2xxx on My Ref circuits without much change

 

[HAYK]

I tried out a Chinese version of TDA7294V from Sanxin, a serious chip maker for medical domain.
It costs $1.5 only and has much better sound than LM3886.
I used it for bellow circuit, with LM3886 is stupid sounding.
The LM2876, although TI selling for $2.5k/1k units, I couldn't find better than $19 a pair.

 

[pbilous]

Lm2876 and

Yes - I would also be wondering if we could use LM2xxx on My Ref circuits without much change

same pinout

 

[HAYK]

Oops sorry.

https://www.aliexpress.com/item/1005003386510801.html?spm=a2g0o.productlist.main.65.4f2c63cc7CNYtb&algo_pvid=c10691f9-2795-457b-97f5-af300e6ecf83&algo_exp_id=c10691f9-2795-457b-97f5-af300e6ecf83-32&pdp_npi=3@dis!USD!2.29!2.29!!!!!@212279a216845714215352361d07dc!12000027678827307!sea!TH!4284450371&curPageLogUid=0NMHxyCUf0Jd
https://www.aliexpress.com/item/100...order_list.order_list_main.263.21ef1802DN4wBd

 

[pbilous]

I tried out a Chinese version of TDA7294V from Sanxin, a serious chip maker for medical domain.

It would be interesting to compare (and measure) sanxin and original versions. Is it possible that both original so to say and those are coming from the same place of manufacture?
Btw, I really like simple idea of the inverter 2N7000 with CCS - only three transistors. How does it sound and measure?

 

[HAYK]

The purpose of the circuit is to simulate open loop SE triode sound of my 2A3C by low cost chip amp. The problem with chip amps and many bad designed amps, is the low NFB measured @20khz. The feedback with low NFB, generates a distortion that occurs when multiple voices of same note sing simultaneously. It can be large vocale, as the requiems of Verdi or Mozart for the worst case, or large Jazz orchestras. Instead of hearing a pleasant beat, you hear distorted sound. To avoid such distortion, either the open loop should be higher than 20khz to avoid phase shift or the NFB must exceed 60db@20khz. To have the requiem of Mozart inspiring spiritual emotion, the amp must have celestial voice and it gets with 70db. The purpose of the MOSFET is to generate second order harmonics as SET and pull the NFB from 24db to 70db @20khz. The MOSFET and the I/V chip now is corrected 200 times more @20khz than before. The distortion of LM3886 is not modeled, but the noise is and it is reduced by 170 fold. In other words the circuit cleans the nonlinearities of the chip and replaces by that of the MOSFET.
The sound of the Sanxin TDA has a very beautiful texture at midrange that reminds me the 45 rpm records.
Never buy original TDA from Ali because they are originals but defective.

 

[pbilous]

Got new device in the mail and now I am able to measure distortion with greater precision.

Output power graph is for 4 ohm load.

At 5W into 4ohm load THD+N is 0.00144% or -96.8dB

 

[pbilous]

I had a chance to swap transformer for 24V-0V-24V AC secondary - gives 33.6V DC.

Output power increased to 80W into 4ohm at THD+N <0.1%
and 50W into 8ohm at THD+N <0.1%