C1L with pre-out

[digi01 0]

pic only

 

 

 

Edited September 17, 2004 by digi01

[digi01 0]

Goondu,

YGPM

 

 

[Mackie 0]

I believe Goondu intends to use this amp for his HD650. digi01, any comments on this partnership?

Edited September 17, 2004 by Mackie

[digi01 0]

This amp is again an opamp + discrete design. However, the design is slightly different from afterburner’s amp. The idea of the discrete output is from EATON amp.

you can find some detail here:

http://headwize.com/projects/showfile.php?file=eaton_prj.htm

this is a europe diyer work:

http://www.justchords.com/docs/eaton.html

With slight modification, the amp uses AD823 opamp to drive a pair of matched B647/D667 audio grade transistors, running in AB mode. Input stage using ERO caps and dale resistors; Elna 220uF BP non-polar caps are used as output; PSU with Telecom. Grade Siemens Caps and FC; Alps potentiometer; Gold plated RCA jack, and pre-out ( can serve as dedicated preamp.the amp voltage gain setting in 11) as requested.

in fact,the amp style can drive a wide range of headphones with different impedance.it certainly can drive HD650, it can even drive AKG K1000 with PSU upgrade.

Edited September 17, 2004 by digi01

[digi01 0]

sorry,have to write in simplicity chinese again

 

我用来调整放大器的耳机有三个.包括低阻抗的HD495,CD3000和高阻抗的K141M.这些耳机都是非常有个性而且很难伺候的.这个机器虽然很小,但输出的电流很实在.我用DISCO里面经常放的舞曲做测试,低音的控制力很好.高阻抗的k141m,在音量电位器开到11点钟的位置就进入满功率状态了.

eaton buffer 的缺点是声音比较干，没有一点优雅的味道,基本是不作修饰的把信号放大.后来我在推动级的op上作了一些补偿,芯片也换成口碑不错的ad823.原来使用过ne5532,发现声音有点浑浊.

输出晶体管也用了比较好的B647/D667(120V1A0.9W),声音比较人性化一点.

 

 

 

[Mackie 0]

Let me translate your comments:

 

"I use three different pairs of headphones to tune this amp; HD495 and CD3000 of lower impedance and K141M of higher impedance. These cans, in my opinion, exhibit certain sonic signatures and are difficult to handle. Although the amp is small in stature, its current output is by no means meagre. Using disco/trance music tracks, the amp exudes good control of bass while adjustment of volume knob to 11 o'clock position is sufficient to drive the high loading K141M to full efficiency. A quipple concerns eaton buffer which tends to sound dry, a lack of elegance but truthfully amplifies the signal without colourations. Subsequently, I made some tweakings in the op amp section and also employed ad823 FET input amplifier. I also tried ne5532 but sound was less coherent. Finally, I chose B647/D667(120V1A0.9W) transistors to inject some life to the resultant sound."

 

Please pardon me if I've erred in parts of the above translation. Chinese terms of electronic components certainly baffles me.

Edited September 20, 2004 by Mackie

[huangyong 0]

晶体管 refers to transistors in this case.

 

Good Translation. Mackie.

[digi01 0]

wow,good translation.

thank you mackie,you are so conscientious and friendly

 

 

[bpribadi 0]

Another great amp from Digi, the Amp Expert !!!

 

Elna 220uF BP non-polar caps are used as output

With precise biasing on the transistor side, with carefully match resistors, and precise regulated supply voltage, would it be possible not to use the output cap?

 

Probably need to modified the Eaton circuit a bit, instead of one LED to bias the transistor into class AB, use 2 LEDs, and the op-amp output connected to the junction between the two LED (must be handmatch for equal voltage drop).

 

Do you use voltage regulator? I can't see them

 

Well done Digi!

Edited September 17, 2004 by bpribadi

[digi01 0]

thank you bram,and sorry for slow response.

I am very busy during weekend,attend my cousin's wedding

yes,you can remove the output caps under kind of risk.solid state buffer does not have output limit and protection.

 

for led problems,you can use a couple of 1n4148 setting the solid stage bias.just like the C1 amp that i diy for afterbruner is in this way.

 

yes,the psu is unregulated.