Incredible quality amplifier by Graham, prepare your ears for it - Page 51 - diyAudio
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Old 6th November 2005, 11:14 PM   #501
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very well said Carlos

cheers
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Old 6th November 2005, 11:17 PM   #502
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Graham is no1 as carlos has said over and over we cant affort to lose members, we need more

cheers
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Old 1st May 2006, 02:53 PM   #503
GEirin is offline GEirin  Argentina
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HI.

What happened with this amplifier?

GEirin
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Old 1st May 2006, 07:16 PM   #504
Stocker is offline Stocker  United States
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Those who built it, loved it

He who designed it, took his marbles and went home

Without his support, the thread has died

Graham may still help individuals by email or have a webpage elsewhere for this project
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Old 30th July 2006, 02:55 PM   #505
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Hello I am looking for the circuit page for the 200w gem. Could anyone point me in the right direction?
Thanks Steve
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Old 31st July 2006, 01:02 PM   #506
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Default I am sorry, i could not find the home page

It may be somewhere inside my PC.

But i have his new schematic, and a lot of informs are written there

He continues with research...but has any intention to return to our forum.... what a pitty!.

Problem is that people can be unkind....can bother all time long.... cannot only broke rules...and rules do not say that we cannot bother...this is the problem.

People goes disturbing..you say Yes and them the guy say NO..you say red, people say green...always bothering...you will holding your patience...but things have some limit.

Graham Limit exploded...he thinks, the same way i think, that forum cooperators , the ones work for forum, the ones that help forum with money or any kind of help, deserves some support.

But Democracy say that everyone of us is the same in the front of the law..... in the reality this is not true....happens only between people that are not famous, not rich and not influent.

hehe

regards,

Carlos
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File Type: gif gem200.gif (71.1 KB, 693 views)
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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 31st July 2006, 06:53 PM   #507
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Default In the reality folks...i want Graham back

I think it is selfish to me to have his attention only to me.

He wants me to construct, in the reality he want people constructing and having fun with his amplifiers.

And they are good as a hell...they are incredible good, they are really, really, really, really very good.

But also has problems that i have asked Graham to fix...if you advance bias trimpots you will burn output unit, as you can drain all the possible current that your supply can send to your boards, at least you will have to buy many fuses.

I have asked Graham limiting resistors in series with the adjustment trimpots to avoid us to go into danger ranges of current during the class A setting of current

This Graham circuit is two in one...it has two amplifiers driven by the same input differential, one is a class A amplifier, single ended, the lower transistor will produce audio amplification, giving us guaranteed top quality single ended class A audio to low power reproduction.... around 2.5 watts, and you do not imagine how long we listen in this power range...i think some of you do not imagine that 2.5 watts each channel is much more than enougth, and average music power, without peaks, use to be adjusted inside this power range.

The GEM amplifier works in class A all time long.... wasting, lets say this way, 50 watts of energy that is transformed in heat, to produce those 2.5 watts....... but here you can find the real advantage...as it will be driving current all time long, if you have, as usually we have, some small crossover distortions in the second amplifier, the standard 100 watts unit superimposed in the schematic...included in the schematic as another power output,..well..the current beeing driven will not allow those unlinear pulses of crossover to appear...mufling them, let`s say this way.

The class B amplifier is something very standard, efficient and i do not know why produces so big dinamics...it is a bootstrapped traditional version with enormous electrolitic condenser to avoid the use of zener to stabilization, to make them simple to diy, and to avoid noises that usually are generated by the zener...well..he prefered this way...but include a interesting circuit into the input that seems to me a ccs, ...also some resistors are use to cancel phase errors, or to correct them.

Graham send me many technical details and description, but i cannot talk too much, as some friend will arrive here to make a question and it is possible that i cannot be able to answer...them i will run to Graham, and them i will run here once again...and this is not something interesting...it is not practical, not well organized and not fair with you all and not fair with me too.

I am proposing Mr. Graham Maynard to land in our forum once again, and face the problems that we have here from time to time...giving a chance to moderator to fix, to control, to act if they were needed and asked to do it.

If problems faced turn bad again to survive.... he can get out once again.... and i am afraid for ever and ever.

I do not even believe i can convince him to land here...with his enormous airplane of geniality, bring wonderfull things, result of 40 years of researches.

Having conditions to answer everyone, directly, and explaining when the amplifier can oscilate...why it can oscilate, how to avoid this, the construction technique needed, the new anti oscilation circuit.... the care needed in the adjustment and all details.

I am sure that the ones that have good amplifiers in their homes will be happy with this amplifier, it is a GEM, it is not comercial, it is a diy amplifier, free for everyone, and with qualities that may turn you astonished.

I will not face the thread alone...without Graham stand up aside me....i have not enougth knowledge to face this, and this is a very selfish priviledged informations that i have, when all forum can have this GEM.

The upper class A power transistor is holding the entire positive supply voltage and draining current for this positive side...it is able to hold the 50 positive volts to stablish the needed zero at the output line......the upper transistor is not an active device, it represents a resistance only to hold 500 miliamperes of current and 50 volts over it...so you can calculate using ohms law, the equivalent resistor needed there, if you think in this substitution..not a good idea, quality will not be the same, but construction prices will go lower.

Taking a good observations of the 200 watts amplifier you will perceive that it forces some low impedance input that can be arranged differently, also you have a resistor to help to match high impedance inputs....this is very helpfull, a very simple trick.


You may observe that it is very simple, having not too much strange circuits..only enormous electrolitic condenser that can be reduced...and will produce worst results, but still sounding nice.

The problem is that the schematic brings too much detailed informs into frames with letters inside...this turns the amplifier vision very complicated, when it is very standard and very simple...try to separate and recalculate them with resistors and equivalents circuits and you will see how simple it is.

those informations posted there, together the schematic turns it strange and crowdy, when in reality, after those informs removal, it is not complicated..... easy to calculate this amplifier, easy to modify and adapt.... very simple and easy....those more simple ideas use to produce a very nice sound (for the ones apreciate JLH designs i me).

Yes, i know that Samuel and other guy already made criticisms, made comparisons and did not give to GEM the value i believe it has...i do not agree with that evaluation, but i have to respect Samuel, as he made the amplifier and produce a comparison, and this is a very respectable way to support his thougths.

But many reasons can result bad.... parts, boards, construction, comparison technique, environment, speakers and the constructor personal WILL...as when we pay big money for something, we do not feel happy when a free and cheap diy circuit had the capacity to eat our expensive unit in the breakfast.

ahahahahah!..i am sure this amplifier is a big mouth with enormous troat, able to eat several comercial amplifiers...easy, laughing and asking for more!


Mr. Graham Maynard, please, return to our forum, this is your home too, now we have experienced moderators, and much more experienced moderators, they have banned many bad guys from here, we have Weldon, this one is alike a tiger, soflty and fast he jumped over bad guys......we have my friend from Canada...this one will not let people loose respect from you....Pinkmouse has enormous attention with details, a very fast man in the trigger, Stuart Yanniger is my friend, also Planet 10...i will ask them protection if you face problems, also i will stand aside you during the fire.

regards,

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 31st July 2006, 09:57 PM   #508
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Default Here is a link to Graham schematic

http://www.zen22142.zen.co.uk/Circuits/Audio/gem100.htm

I am discussing with him about his amplifier and asking his return.

regards,

Carlos
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Old 31st July 2006, 10:05 PM   #509
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Default Sorry guys...i heard a clear NO!

Graham will not return...what a pitty.

regards,

Carlos
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Old 31st July 2006, 11:01 PM   #510
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I also am sorry that Graham does not grace us with his presents
Thank you Carlos for responding to my inguiry. I have built the JLH 10 watt amp which I love and aquired trannis and heat sinks for the leach 6 transistor amp.
I prefer the JLH and was hoping that the Leach transformers would work on the 200w GEM
Thanks again
steve
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