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Old 6th October 2005, 03:47 PM   #1031
Byrd is offline Byrd  South Africa
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By any chance - has anybody compared this amp to a Leach amp? I am buzy trying to complete 12 of the new Leaches atm but am interested in this as a future project.

Impressions compared to any commercial equipment?

I know you all you builders have been waiting for somebody to ask this question. Give me a reason to build it
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Old 6th October 2005, 03:51 PM   #1032
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Quote:
Originally posted by rudi
the "class a" trick. well i did not think that it robbed it of any headroom.

Oh yes, I actually think that biasing the 318 to class A has the best chance of anything of making a very appreciable change.

Whenever you bias an opamp class A you trade output current for the current you force it compensate to get class A.

I am actually going to try it this afternon I will start with 5ma and work up and see how it sounds.
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Old 6th October 2005, 04:16 PM   #1033
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Quote:
Originally posted by Byrd
By any chance - has anybody compared this amp to a Leach amp? I am buzy trying to complete 12 of the new Leaches atm but am interested in this as a future project.

Impressions compared to any commercial equipment?

I know you all you builders have been waiting for somebody to ask this question. Give me a reason to build it

Hi Ross

I can't say that i can compare it to a Leach amp. seeing that i never heard one. I never really liked the Idea of parralel devices and never found them to sound better than using one (obviously do not have the same power) the Leach amp is regarded as a very good amp.

I can do this comparison for you. I compare it to fine tuned JLH. and the digital.

the JLH have a very rich tonal quality and full of pace. but it does have a bit of a veil to it. (you discover this only once you hear the digital) My digital we compared in a AB test with a TACT . from everybody listning to the two (even the owner) mine sounded better that is the tripath tech.

then with all the mods that have been done to my current amp . i have to say that it has the tonal quality of the JLH, the preciseness of the digital and then some. the bass is not exactly up to par with the digital.

so according to this it is better than a TACT 2150. with would set you back R 36 000 in SA

cheers
Rudi
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Old 6th October 2005, 04:22 PM   #1034
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Rudi,

I think you hit on something.

Increasing the supply voltage of the LM318 also increases its slew rate. I was reading the datasheet to see what sane values would be and decided to perform some experiments.

I actually like the shunt regulators better than the LM78xx/LM79xx as they are actually more quiet(noise wise, if you use a good quiet resistor) and let less AC ripple through to the LM318 (check it with a scope, if you have good zeners you will see there is less ripple).

So what I did, was I took two 18V zeners and popped em in, and then biased the LM318 class A with 7ma with an adjustable current source. I also tried a resistor for kick(3.3K as suggested) but the current source is better.

All I have to say is wow.

This amp has always been excellent, but now I think I am in heaven.



This is on my REV C monoblocs with no other mods at all.

Now keep in mind I have a 300Va toroid on each channel, so my supplies are stiff and clean.

Cheers!
Russ
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Old 6th October 2005, 04:38 PM   #1035
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Well Russ I am glad you like it.
I agree with you the current source is better.

I just used the 3k3 to test the theory.. (Ryan was bugging me the whole day to try it)

the biggest win is the 18V the other stuff is just to have a cleaner supply (esoteric and very audiophile like ) and it does contribute to that last bit of tweaking that was left to be done and it does have a effect but you do get into the 80/20 ratio here as far as return on effort and money goes)

but as i said in the beginning this is.............
My audiophile aproach to the ( My "audiophile" LM3886 approach)
I started out as just experimenting seeing that i was very happy with my setup and i asked "what if...." and this is the fianl product. thry the other changes just for interrest sake but try them all together

cheers
Rudi
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Old 6th October 2005, 04:41 PM   #1036
troystg is offline troystg  United States
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So to clarify...

After I burn in (not up) my beta brds I can just drop in 18 volt Zeners?

Edit:

And also rebias the LM318 to class A via a 3K3 resistor or ccs...
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Old 6th October 2005, 04:44 PM   #1037
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Quote:
Originally posted by rabstg
So to clarify...

After I burn in (not up) my beta brds I can just drop in 18 volt Zeners?
Yep, no problem.
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Old 6th October 2005, 04:55 PM   #1038
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Default REF A experiment

Rev-A only

Well now that we have established that 18 V does a nice trick here is the next one for you.

in the beginning we established that the OPA627 does not make a difference in the amp. (but we have reason to believe that it was under powered and therefore no change)

with 18V you might just get the performance you are looking for out of a OPA627

just a thought. try it and give us your findings

cheers
Rudi
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Old 6th October 2005, 04:55 PM   #1039
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Default PDFs for single side PCB

I just wanted to humbly make available my single side "REV C" monobloc design which is suitable for REV-A/B/C (with a little simple re-arrangement).

PDFs

The PDFs are suitable for the toner transfer method as the copper side is not mirrored, and the component side is.

Please enjoy it if you are capable of etching your own boards.

If anyone makes a good amp with it then this journey has been worth it for me.

Thanks to everyone who has made this a lot of fun (and very educational) for me. The results are largely thanks to you. Thank you Mauro most of all.

Cheers!
Russ

EDIT: fixed the link.
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Old 6th October 2005, 04:59 PM   #1040
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Default Re: PDFs for single side PCB

Quote:
Originally posted by Russ White

If anyone makes a good amp with it then this journey has been worth it for me.

Thanks to everyone who has made this a lot of fun (and very educational) for me. The results are largely thanks to you. Thank you Mauro most of all.



it sounds as if you are retiring now that you are in heaven
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