According to Quad "Current dumping technology" Current Dumping Technology | QUAD | the closest approach to the original sound
Attachments
LM1876+ClassB booster ( not Current Dumping )
Vin=1vpp 20khz, 22x out=22vpp, THD=0.57
LM1876+ClassB-Current-Dumping booster (use QUAD 405 network)
Vin=1vpp 1khz, 20x out=20vpp, THD=0.018
Vin=1vpp 20khz, 20x out=20vpp, THD=0.22
QUAD 405 network Z1/Z2/Z3/Z4 is 500R/ 120pf/ 50R/ 3uh
The LM1876 can delevery 3.5A output to load , so I change netwaork , get more low THD:
Z1 /Z2/ Z3/ Z4/ R2 vulue
500R/ 120pf/ 50R/ 3uh/ 250R Vout=20vpp/2R, THD=0.22
2.5kR/ 120pf/ 10R/ 3uh/ 125R Vout=20vpp/2R THD=0.19
5kR/ 120pf/ 5R/ 3uh/ 2.5kR Vout=20vpp/2R THD=0.17
12.5k/ 120pf/ 2R/ 3uh/ 625 Vout=18.5vpp/2R THD=0.10
25k/ 120pf/ 1R/ 3uh/ 1.2k Vout=18.5vpp/2R THD=0.067 ( almost 80w/2R load )
Vin=1vpp 20khz, 22x out=22vpp, THD=0.57
LM1876+ClassB-Current-Dumping booster (use QUAD 405 network)
Vin=1vpp 1khz, 20x out=20vpp, THD=0.018
Vin=1vpp 20khz, 20x out=20vpp, THD=0.22
QUAD 405 network Z1/Z2/Z3/Z4 is 500R/ 120pf/ 50R/ 3uh
The LM1876 can delevery 3.5A output to load , so I change netwaork , get more low THD:
Z1 /Z2/ Z3/ Z4/ R2 vulue
500R/ 120pf/ 50R/ 3uh/ 250R Vout=20vpp/2R, THD=0.22
2.5kR/ 120pf/ 10R/ 3uh/ 125R Vout=20vpp/2R THD=0.19
5kR/ 120pf/ 5R/ 3uh/ 2.5kR Vout=20vpp/2R THD=0.17
12.5k/ 120pf/ 2R/ 3uh/ 625 Vout=18.5vpp/2R THD=0.10
25k/ 120pf/ 1R/ 3uh/ 1.2k Vout=18.5vpp/2R THD=0.067 ( almost 80w/2R load )
Many thanks. Absolutely respectable values in 2R. You may bring the THD further down by using R22-R33 emitter resistors on the two push-pull power transistors.
I may try the concept one day, with LM1875 in particular. Had spurious oscillation at the output when the output current approached the limit. No problem with 16 Ohm load. With this idea, the LM1875 will not be loaded so much.
Thanks for the disclosure.
I had simulation use LM1875/LM1876/LM3886 they all worked.
But failed use OPA445/OPA547 high voltage OP-amp , may be current or some thing wrong.
But failed use OPA445/OPA547 high voltage OP-amp , may be current or some thing wrong.
With a Z3 of 1R, the push-pull transistors start conducting at an output current near 600-700mA. OPA445 can absolutely not deliver such current and not even OPA547 (0.5A typ.). You need a real power amplifier chip like one of the three you suggest. LM1875 is my favorite for the simplicity in use and the sound, LM1876 I only know for good sound and LM3886 I have not tested yet. LM3886 is said to have superior sound but also a powerful output stage such that the external push-pull stage is hardly needed.
Yeah the numbers into 2 Ohm are quite interesting.
How about a frugal version with something like a TDA2030A and TIP35/36? Running at something like +/-20V? That would be an interesting alternative to many TDA+booster pair circuits here..
How about a frugal version with something like a TDA2030A and TIP35/36? Running at something like +/-20V? That would be an interesting alternative to many TDA+booster pair circuits here..
I guess the TDA2030 will be fine in technical , I do not found TDA2030 spice model so can not simulate it.