Leach amp

[jtcc1015]

"Is there anyone out there could advise me on making any modification to the circuit so that I can get more bass output out of the Amps?"

A few questions.

What is the rated impedance of the speakers, and what does the DC resistance measure?

How many dB/2.83V/1M are they?

What is the ±V of your Leach SuperAmp ?

How many VA is the transformer rated?

Size of the main filter caps?

Hi djk,

Thanks for looking into my query. The nominal resistance of my loudspeaker is 8 Ohm. Rated sensitivity is 86dB/W/m. I use 1200VA toroid transformer for each monoblock. Capacitors are 8 x 10000uF, 100V, BHC Aerovox for each monoblock. DC bus voltage is +/-85V.

Hope the above answered your questions. I am thinking of reducing resistance of R19 by 10%. I wonder if that will help.

Regards,
jtcc

 

[rajeev luthra]

reducing R19 will increase the gain , yes it will also change the R/C ratio , but I feel that the bass responce of this amp is pretty good and clean

 

[djk]

I think you may need a tone control, or baffle step correction.

It sounds like the amp is fine.

 

[jtcc1015]

reducing R19 will increase the gain , yes it will also change the R/C ratio , but I feel that the bass responce of this amp is pretty good and clean

I think you may need a tone control, or baffle step correction.

It sounds like the amp is fine.

Hi rajeev & djk,

Thanks for your reply, I am totally agree that the Leach Amp perfrom superbly in any aspect. It can faithfully reproduces and ampilifies the source signal with grace. However, I don't know about yours, my main purpose of spend the money and most importantly my time and effort on DIY project was that I get a freedom of customizing the end product to suit my needs. I know there is no problem with the Leach Amp design, and I may also have compatibility problem between it and my DIY tube pre-amp (Jadis JP200 circuit).
I was simply trying to explore all the aspects of the issue before I start making modification to my system.

Thanks anyway.

Regards,

 

[fab]

...I was simply trying to explore all the aspects of the issue before I start making modification to my system.

Thanks anyway.

Regards,

You can increase the value of feedback DC blocking cap and the value of DC blocking input cap as well. It will preserve more the phase accuracy at 20 Hz if you choose a -3db corner frequency at less than 0.2 Hz for example. Check the 20Hz square wave with an oscilloscope to convince you. This will however not increase dramatically the bass response but only slightly. The problem is maybe your low corner speaker frequency point is a little too high. That is why a "loudness" control designed for low frequency compensation can help. It can also compensate for poor bass response of some recordings. Personnally I use a variable loudness control in my preamp in the feedback path like on this post of this thread:
http://www.diyaudio.com/forums/showthread.php?postid=359125#post359125
see post #7 attachment.

Good luck

Fabien

 

[acenovelty]

The simplest tweek for more bass is to re-examine your bias current setting. Raising it to 125, 150 or 200 etc. will give more bass, but the heatsinks have to take the resultant temperature rise. 'Course, maybe your speakers just ain't puttin out what you expect. I have 2 double barrelled and 4 120W Leach amps driven from a Lexicon CP3 and have nothing but pleasure from them. A pair of subwoofers is driven by one 300 W Leach amp and I seldom increase the volume control beyond 1/4th of the possible gain. And then my speakers have been built to produce what can come out of a Leach amp. But that's a different subject. An amp that seems "weak" can more often be traced back to the power supply and the capacitors that provide the juice for your sound. It would seem from your specs that you have an adequate power supply, but.........
Take a look at this site for a really good power supply design:

http://zero-distortion.com/start.htm

go to the Designing your own power supply section.

After that, maybe you'll want to think about becoming a speaker builder. You can make better speakers than those Mark Levinson boxes.

Prosit

 

[jtcc1015]

Thanks for your advise. I shall give it a try.

 

[rajeev luthra]

acenovelty is very right ,

The following written by him makes lot of sence ;-

1," The simplest tweek for more bass is to re-examine your bias current setting. Raising it to 125, 150 or 200 etc."

2, "An amp that seems "weak" can more often be traced back to thepower supply and the capacitors that provide the juice for your sound. It would seem from your specs that you have an adequate power supply, "