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Old 29th May 2004, 08:28 AM   #21
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Default It is impossible to recognize.

When we construct some, our own self defensive system prepare us tu defend ourselves against frustrations.

Look that, if you spent some hundred bucks and some hundred minutes or hours constructing some equipment.... and if you deduce that it is awfull, you will be giving you a Degrée of Stupid....this way..... our inconscience... sub conscience.... treat to change whole things... and block this real analyses.

If you perceive a loose in bass, normally you will say that is because bass is precise!.... or because no harmonics, the sound is not so big and thunder because theres only fundamental frequencies on there.... or you think that others makes a damn mass in bass frequencies.... and the one you make is the only one on earth that is making good sounds.

Same way we cannot see that our children is bad!....cannot see our wife is awfull.... cannot see when we are stupid..... cannot perceive we were guilty and we are collecting whole we planted in past.

This way, i can not trust in the constructor opinnions, because may be modified by defensive systems.

How can a man that passes his entire life thinking that avoid sex is the best way to find God!.... and someday he discovered that his god do not exists..... look, the way he think god is....good!, and he perceive someday some bad things on his god....he will never believe in that!... he will think demon is taking his mind.... he will be defended, if not, he will see that he was, whole life, completely, no doubts, truly, with sure, a completely fool, idiot, ignorant and brainwashed!...who can support that without suicide... this way our system defend ourselves.

Ask americans if they are bad..... they will say NO!... WE FIGTH FOR WHOLE WORLD FREEDOM!.. DEMOCRACY FOR ALL... and money for them. Cannot see true.... TELL NORDISH THEY ARE COLD, THEY SAY NO!...YOU ARE CRAZY... TELL BRAZILIAN HIS COUNTRY IS A MASS, WE SAY NO!... WE ARE HAPPY! TELL JAPANESE THEY WORK TOO MUCH, WHEN YOU HAVE TIME TO YOURSELF?...THEY WILL ANSWER YOU, YOU ARE POOR BECAUSE YOU DO NOT WORK, YOU LAZY!

This way, other people evaluations, the ones that construct, evaluates in comparisons and keep them can be better, also the ones that construct and dismount because do not like are more precise, because no defended.

And the more crazy ones, that only likes really death of zen, are difficult to satisfy.(me)

Carlos
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Power supply; ripple, filter, noise, stability and the use of capacitance multiplier... Portuguese and English; https://www.youtube.com/watch?v=sSm0ku1eIgg
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Old 29th May 2004, 09:29 AM   #22
djk is offline djk
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"TELL BRAZILIAN HIS COUNTRY IS A MASS, WE SAY NO!... WE ARE HAPPY!"

My sister lived in Belim, Para, for 15 years.

A nice place to visit, but I wouldn't want to live there.
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Old 29th May 2004, 09:54 AM   #23
djss is offline djss  United States
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I will agree with the statement that this amp is silent when idle. The only place I can hear it is within 2" of the direct center of my Morel MDT-33 tweeters.

A couple things to note from someone who's beat the hell out of these amps:

My 2-channel (1 channel when bridged) leach amp has a 1500VA toroid from Plitron, followed by 4x 37,000uF caps.

The amp hardly warms up at all when pushing an 8 ohm load.

Make sure your preamp can push the juice this amp needs. This amp needs a pretty high level input to really bring it to life. I plan to include a small preamp in the chassis with the amp for my new v4.5 amps.

- The amp WILL drive low impedence loads to full power. I've tested this with a 2 ohm load, driven with a sine wave to clipping on a scope, and I've driven a 4ohm speaker to full power with the amp bridged. However, be prepared for the following:

- If you use the 5 amp fuses on the rails like he mentions, they'll melt instantly.
- MAKE SURE YOU CAN KEEP IT COOL. The cooling of the amps is designed for an 8ohm load, not a 2 ohm load. To cross 1000W output you'll be dissipating a lot of heat inside the chassis. Active, ducted cooling on the main heatsinks works well, but problem for me keeps happening on the board itself. The transistors degrade rapidly when you don't put anything on them to dissipate heat. In the amp I'm building right now, I have heatsinks on all of the transistors, including little metal tabs that are glued to the small transistors (forget the package style now). Each amp board will have a duct pushing air from a 120mm fan across it to stop me troubles.
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Old 30th May 2004, 07:15 AM   #24
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I have a stereo Low Tim II from the late 70's and a quad mono Leach 4.5. They are great amps. Just today I picked up a clean Hafler DH200 at a local electronics swap meet. Ultimately I will do some form of Pooging on the Hafler, but after replacing bad input caps with some polypropalenes and the stock RCA jacks with some decent glod plated ones, I did a shoot out between it and 2 channels of the Leach 4.5. The Leach wins hands down. It is not subtle at all. The Leach has far more definition. Cymbals have that sheen that was completely missing in the Hafler. Massed vocals are are an assembly of individual voices in the Leach. They are a blur with the Hafler. The Leach handles all complex passages much better.

So it's on to modding the Hafler to see if it can beat the Leach 4.5. Hopefully I will be able to determine if it is the topological differences or the details of the execution that differentiate the two.
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Old 30th May 2004, 08:07 AM   #25
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Quote:
Originally posted by Greg B.
I have a stereo Low Tim II from the late 70's and a quad mono Leach 4.5. They are great amps. Just today I picked up a clean Hafler DH200 at a local electronics swap meet. Ultimately I will do some form of Pooging on the Hafler, but after replacing bad input caps with some polypropalenes and the stock RCA jacks with some decent glod plated ones, I did a shoot out between it and 2 channels of the Leach 4.5. The Leach wins hands down. It is not subtle at all. The Leach has far more definition. Cymbals have that sheen that was completely missing in the Hafler. Massed vocals are are an assembly of individual voices in the Leach. They are a blur with the Hafler. The Leach handles all complex passages much better.

So it's on to modding the Hafler to see if it can beat the Leach 4.5. Hopefully I will be able to determine if it is the topological differences or the details of the execution that differentiate the two.
That was somewhat my experience with my upgrade to 4.5
boards; more depth of field and focus, and individual instruments
and many sounds of all sorts had more 'character' rather
than being, well, generic.

I can still fault massed orchestral works and other complex
music for lacking focus, but I really need better speakers. I
hope to audition my Leach amp on an electrostatic system
some day and see how it does in the definition department.

I am wondering what else could be done to further update
Leach's design, such as Toshiba 2SA1943/2SC5200 output
transistors, current mirrors or whatever. But I'm saving that
sort of tinkering for my 'finished' version with suitable
heatsinks for flatpack output transistors. I don't think much
elaboration on the existing design would be worthwhile; its
relative simplicity may be elegant enough and just some
'voicing' with selected components might be tweak enough.

I'd be interested in hearing your progress with the Hafler.
Two aspects of the Leach design that I've always liked are
the mirror symmetry of the circuitry, and the two stages
of RC filtering in the power supply rails to the input
section.
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Old 31st May 2004, 07:09 PM   #26
pooge is offline pooge  United States
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Quote:
Originally posted by Damon Hill
One modification: a 1 uF film cap between the driver
emitters, as per Self and Sloan. Supposed to help
turn off the outputs and improve high frequency
distortion.
Quote:
Originally posted by Charles Hansen
If you listen you will see that the capacitor here improves the sound quality. It doesn't matter that it's a triple emitter follower. When it comes to making something sound better, thinking is good but listening is better.
Well, I haven't yet listened to this mod. As far as thinking goes, Leach's thinking on this issue has been added to his web site at that bottom of this page:

Leach's output stage
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Old 31st May 2004, 07:54 PM   #27
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I don't think Leach has listened to it yet, either. Why don't you try listening to it? It will take about 5 minutes. I'm not sure why you want to debate about the reasoning instead of just listening to it.

"When it comes to making something sound better, thinking is good but listening is better."
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Old 31st May 2004, 09:04 PM   #28
pooge is offline pooge  United States
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Quote:
Originally posted by Charles Hansen
I don't think Leach has listened to it yet, either. Why don't you try listening to it? It will take about 5 minutes. I'm not sure why you want to debate about the reasoning instead of just listening to it.

"When it comes to making something sound better, thinking is good but listening is better."

I haven't had time yet, alright?
In the meantime, why do you have a problem with me trying to learn something, instead of just criticizing me for having the audacitiy to "debate" this issue? If you can hear a difference with capacitor, maybe it's not for the reason given. If there is a difference, I'd like to know why. Can you handle that?
Perhaps it has nothing to do with charge depletion. Maybe it has to do with bias voltage stability or something else.
BTW, it will take a LOT longer than 5 minutes!
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Old 31st May 2004, 11:15 PM   #29
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Quote:
Originally posted by pooge
Perhaps it has nothing to do with charge depletion. Maybe it has to do with bias voltage stability or something else.
That is exactly my point. Leach is (erroneously) drawing a conclusion that it will make no difference because he performed a "thought experiment" considering only one factor (transistor switching time).

But it does make an audible difference. And that is why listening is more important than thinking. If a circuit change makes an audible difference, then if one wishes, one can spend time to understand why. This is a one-to-many mapping.

But simply thinking about the problem (as Leach has done) can give the wrong answer, as there are too many factors to consider appropriately. He is trying to do a many-to-one mapping, but choosing the wrong starting point and so reaching the wrong conclusion.
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Old 31st May 2004, 11:21 PM   #30
fab is offline fab  Canada
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Quote:
Originally posted by Greg B.
I have a stereo Low Tim II from the late 70's and a quad mono Leach 4.5. They are great amps. Just today I picked up a clean Hafler DH200 at a local electronics swap meet. Ultimately I will do some form of Pooging on the Hafler, but after replacing bad input caps with some polypropalenes and the stock RCA jacks with some decent glod plated ones, I did a shoot out between it and 2 channels of the Leach 4.5. The Leach wins hands down. It is not subtle at all. The Leach has far more definition. Cymbals have that sheen that was completely missing in the Hafler. Massed vocals are are an assembly of individual voices in the Leach. They are a blur with the Hafler. The Leach handles all complex passages much better.

So it's on to modding the Hafler to see if it can beat the Leach 4.5. Hopefully I will be able to determine if it is the topological differences or the details of the execution that differentiate the two.
Greg

Before you quit on modifying the DH-200, please consult this thread
http://www.diyaudio.com/forums/showt...323#post359323

On my side, I am sad that I have not heard the Leach amp but what I can say is that the mods I have done on the DH-200 amp resulted in having the good characteristics on sound that you mention about the Leach. It is true that the original stock DH-200 sound is clean but not as detailed as the modified one. So, since you want to pooge the DH-200 and you have a Leach, keep us posted on your results.

Fab
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