My Leach Amp Clone (LEACH 150)

[panson_hk]

I am finishing my LEACH 150 amp. It is a kit available from DIYZONE in Taiwan. The schematic in pdf can be download from http://www.diyzone.net/images2/LEACH1006SCH-1.pdf. The amp is constructured in mono-block fashion. Each channel has a big toroidal transformer capable of delivering 150 WRMS output.

The figure shows you the assembled PCB and transformers. I will measure the amp using AP System One. I will follow the measurement procedures used in Stereophile equipment review.

Will this clone perform as good as the original LEACH. Some measured data are available from Prof. Leach web site.

 

[panson_hk]

After 30 min 1/3 output power (50 W, 8 Ohm) warm up, THD vs output power is measured. The result is shown in the attached figure. At the moment, the heat sink temp is about 62 C. The amp meets the designed output power level, 150 W, before clip.

 

[panson_hk]

Here you can see the FFT of 50 W, 8 Ohm load. There are so many harmonics and the level is rather high!

Something wrong!? Circuit or assembly? Need to investigate ....

 

[taj]

If you normalize the graph it wouldn't look so bad. Approx. -80dB 2nd and 3rd harmonic. I have no idea what is normal or typical for any amp.

..Todd

 

[taj]

The schematic link you posted doesn't seem to work. Does it differ from the *real* Leach schematic?

..Todd

 

[timbarnes]

There's an extra dot at the end of the schematic URL

I found it works if I try to load it, then delete the last character so the URL ends in [.pdf] rather than [.pdf.]

 

[taj]

Correct you are. Good eye, Tim!

The schematic is 90% Leach, but its Q7/Q8 are configured much differently than the corresponding transistors in Leach's circuit. I don't think it's just because it's drawn differently. And the servo points are not Leach.

..Todd

 

[panson_hk]

In this clone, active current source is used in the differential stage. Its VAS is not cascode where Leach v4.5 does. No output stage protection is employed.

 

[panson_hk]

Hi Todd,

I want to see whether it can reach something like NAD M3. Sterephile reviewed it earlier. The results can be found at http://www.stereophile.com/integratedamps/107nad/index4.html
, in particular THD performance.

I don't like those higher harmonics, > 3 rd.

THD residual at 50 W, 8 ohm is shown here.

 

[jaycee]

The VAS is not cascoded in the original Leach. The extra transistor is configured as a protection device to avoid VAS saturation when the output protection activates.

 

[panson_hk]

jaycee, thanks for your correction.

 

[Bonsai]

what are you using to do your measuements panson? Are you using a sound card?

 

[destroyer X]

Panson...can you provide me, please, the schematic values?

I want to keep this one in my computer...i have some ideas related modified Leach units.

Send me directly if you cannot post here:

panzertoo@yahoo.com

Thanks in advance.

regards,

Carlos

 

[panson_hk]

Hi Bonsai,

I use Audio Precision System One. It is a PC controlled audio analyzer. You can find its info from www.ap.com

Hi Carlos,

The schematic and BOM are available from

http://www.diyzone.net/images2/LEACH1006SCH-1.pdf
http://www.diyzone.net/images2/LEACH1006BOM.XLS

Let us know your idea.

 

[destroyer X]

Already downloaded..thank you Panson

Good luck with your leach!

regards,

Carlos

 

[zerohead_ak47]

I am finishing my LEACH 150 amp. It is a kit available from DIYZONE in Taiwan. The schematic in pdf can be download from http://www.diyzone.net/images2/LEACH1006SCH-1.pdf. The amp is constructured in mono-block fashion. Each channel has a big toroidal transformer capable of delivering 150 WRMS output.

The figure shows you the assembled PCB and transformers. I will measure the amp using AP System One. I will follow the measurement procedures used in Stereophile equipment review.

Will this clone perform as good as the original LEACH. Some measured data are available from Prof. Leach web site.

The page cannot be found

 

[Bonsai]

Panson, can you do a distortion vs frequency analysis with your ap system - typically at 1W or 10W out?

 

[cyril_hk]

those transformers looking good with your great amp...

Hi Panson where do you get your transformers, seem likes some kind of low profile version. Looks really great!
Anyway, I just finished mine right early of May, no current limiter too, with all home made PCBs.
http://hk.geocities.com/cyrilwoo/

Cheers

 

[AndrewT]

Hi Zero & Panson,
the link does not work because this site adds a "." to the address.
The poster did not bother to check that his link worked (bad boy).
See post6.

Due to his laziness/oversight your work around is to right click, copy, paste, delete the extra "." at the end of PDF and go.

 

[panson_hk]

Panson, can you do a distortion vs frequency analysis with your ap system - typically at 1W or 10W out?

Hi, I can do later. Here is 50 W, 8 Ohm THD vs freq with different bandwidths.