I have build leach 4.5 amplifier with standard components
I like the sound but feel that It can be better
Would some of you which have done upgrade of components to the amplifier tell me what components need to be changed (for better sounding) compared to http://users.ece.gatech.edu/~mleach/lowtim/part3.html
Your choise of transistors, condensators and etc
I like the sound but feel that It can be better
Would some of you which have done upgrade of components to the amplifier tell me what components need to be changed (for better sounding) compared to http://users.ece.gatech.edu/~mleach/lowtim/part3.html
Your choise of transistors, condensators and etc
Samoloko,
the trick of the low-tim amplifier is to have a very linear amp, aka large bandwidth amp, with the lowest number of stages.
Which is achieved by employing a triple darlington output stage, the combined high current gain enables the relatively low fT output devices to perform at audio frequencies.
Secondly, by linearising the Vas stage with the aid of a fast small helper, Q8/Q9 in the Leach schematic.
Making it sound better means making the amp even faster or reduce the number of stages, while keeping it unconditionally stable.
Download a schematic of an early ElectroCompaniet if you like to know more.
What you can do is discussed a zillion times at the large Leach thread.
Just tossing in some fancypants parts will not make it sound any different.
C6 should be non-polar, as advised by Prof Leach, or leave it out and use a quality DC-servo.
A stereo blue velvet Alps RK27 still is best value for money, anything better costs much more, you are the only one who can look inside your wallet.
the trick of the low-tim amplifier is to have a very linear amp, aka large bandwidth amp, with the lowest number of stages.
Which is achieved by employing a triple darlington output stage, the combined high current gain enables the relatively low fT output devices to perform at audio frequencies.
Secondly, by linearising the Vas stage with the aid of a fast small helper, Q8/Q9 in the Leach schematic.
Making it sound better means making the amp even faster or reduce the number of stages, while keeping it unconditionally stable.
Download a schematic of an early ElectroCompaniet if you like to know more.
What you can do is discussed a zillion times at the large Leach thread.
Just tossing in some fancypants parts will not make it sound any different.
C6 should be non-polar, as advised by Prof Leach, or leave it out and use a quality DC-servo.
A stereo blue velvet Alps RK27 still is best value for money, anything better costs much more, you are the only one who can look inside your wallet.
Hi, After assembling my Leach amp I found that increasing the bias made a major improvement in the sound quality. Dr. Leach has some comments on the Leach website about this. Watch out for the heat and give everything time to settle in on each attempt at adjusting the bias. It can take awhile for the outputs to stabilize. Also, allow good air circulation inside the enclosure not just around the heatsinks fins. Tad
Hello again;
As per the original thread, I have a commercial Leach amp: The Leach Amp manufactured by LSR&D back in the 80's. In the course of having the amp re-capped, it became evident that the power supply electrolytics are no longer available in the same size as originally supplied in the amp. The problem is that the space available in the case only allows for the same diameter and length as the original (it is a very tight fit). Any suggestions on where to look for caps in the original size? I would like to replace them, as I am sure they are getting tired.
thanks,
Paul
As per the original thread, I have a commercial Leach amp: The Leach Amp manufactured by LSR&D back in the 80's. In the course of having the amp re-capped, it became evident that the power supply electrolytics are no longer available in the same size as originally supplied in the amp. The problem is that the space available in the case only allows for the same diameter and length as the original (it is a very tight fit). Any suggestions on where to look for caps in the original size? I would like to replace them, as I am sure they are getting tired.
thanks,
Paul
The drivers are fine. Flat pack devices are not recommended with this PCB, but there is a redesign by Jens Rasmussen that allows this: http://www.delta-audio.com/Leach-Clone.htm
MPS8099/8599 are available from On Semiconductor. If you are having trouble getting them then you can use MPSA06/56, they are not as good, but they will work.
I suspect the devices you are having trouble with are the 2N3439 and 2N5416. For these, MJE340/350 is often substituted but they are a different package and not easy to use with Leach's PCB.
MPS8099/8599 are available from On Semiconductor. If you are having trouble getting them then you can use MPSA06/56, they are not as good, but they will work.
I suspect the devices you are having trouble with are the 2N3439 and 2N5416. For these, MJE340/350 is often substituted but they are a different package and not easy to use with Leach's PCB.
duekfx
If you have a spare 33.00 Advanced Circuits will make you a couple of proto boards in a couple of days. Kind of like a special for small orders.
Then you can download the gerbers from Delta-Audio.com ie, the Jens Rasmussen boards in either the 6 or 10 output devices and send them to Advanced Circuits. These boards use modern devices and are VERY well layed out and constructed.
I have built 2 fantastic Leach amps from these boards and can personally attest to how well they sound. I am currently running 1 amp bias per rail with 70 volt rails. The sound is amazing.
Just something for you to think about. They really turned out nice. Tad
If you have a spare 33.00 Advanced Circuits will make you a couple of proto boards in a couple of days. Kind of like a special for small orders.
Then you can download the gerbers from Delta-Audio.com ie, the Jens Rasmussen boards in either the 6 or 10 output devices and send them to Advanced Circuits. These boards use modern devices and are VERY well layed out and constructed.
I have built 2 fantastic Leach amps from these boards and can personally attest to how well they sound. I am currently running 1 amp bias per rail with 70 volt rails. The sound is amazing.
Just something for you to think about. They really turned out nice. Tad
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