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Old 18th November 2012, 08:27 PM   #1381
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Decreasing the stop resistor would go on the opposite side of the solution I want to apply.

The first issue I had is explained in post 1172.
Bonfis had similar issues in his post 1241. He solved it his by increasing the stop resistor to 56 Ohms (post 1291).
In the simulator, I get instability as soon as I reach 3/4 the power with the 22 Ohms resistor. Increasing the stop resistor solves it, decreasing it to 10 Ohms get things worse.

Of course increasing Cdom a bit won't hurt.

There's a screenshot if simulator oscillations with stop resistor to 10 Ohms.
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Old 18th November 2012, 08:43 PM   #1382
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Default I see...your main targed is stability (more) and my primary targed

is audio quality (more)...then we are going in different directions, but both are very nice.

Go ahead man..do it and come here and say what you have perceived.

I will say something in advance...lifeless sound will be the result...loss of bright and realism.

Let's see what you will observe while listening....but do it one channel to make comparison..because if you do both channels you will be fooled.... and will think/believe/imagine the modification had improved..but this is more connected to our own psychological self than to sound reproduction.

Believe me...we are masters of fooling ourselves.... we humans delirate a lot...we do think we are beautifull when we are not...we do think we are more intelligent than some others..when we are not...we do think our wife is the best...when we have not tested all others to be sure about that...so...all is a matter of belief... something fanatic and non rational..be aware you already decided to evaluate your result as better...and i am sure it will not be better.

We humans, we are all fundamentalists.

regards,

Carlos
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Last edited by destroyer X; 18th November 2012 at 08:49 PM.
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Old 18th November 2012, 09:44 PM   #1383
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Yes I will post my observations.

What will make it sound dull, the increase of the miller cap, or the increase of stop resistor value?

In Self's documentation, the stop resistors are 100 Ohms in value. When I try such values in the simulator, I can lower significantly the value of Cdom without compromising stability.

My question is, If I go to a high value for the stop resistor, and a lower value for Cdom... What could be the result, sonically?
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Old 19th November 2012, 06:02 AM   #1384
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Default Try yourself and simulate...i am too much busy to return

to this thread into full time attention...i cannot.... too much busy.... the 24 hours day is not enougth to me so much i have to do.

So, give it a try.

regards,

Carlos
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Old 25th November 2012, 10:28 AM   #1385
wiljj78 is offline wiljj78  Philippines
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Default Home Made MKIII

Uncle Charlie,

I would like to thank you for this Dx MKIII, been setup and tested this amp last night and bias was set on .23mV, Wow I really like the quality and very punchy amp... i'll take more update photo tonight and post it here.

Many thanks....

Regards,
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Old 25th November 2012, 10:35 AM   #1386
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Default Thank you dear friend....yes...it is very good

I like it too..... was tuned for sonics, but mainly into the simulator...i have made small touches into the workbench searching for more and more stability because some novices have decided to build..then i was very carefull.

People, these old days, where addicted to simulators and numbers...some came to me because of small distortion numbers...this way i have made for them...with good numbers and special stability...at least i could find any issue in my home.

This last amplifiers was made mainly for sonics.....more close to the threshold of oscilation, tuned sharp as a razor's edge

Your pictures are very good...is it a Sony Camera?

regards,

Carlos
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Last edited by destroyer X; 25th November 2012 at 10:40 AM.
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Old 25th November 2012, 10:45 AM   #1387
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Thank you uncle charlie..I'm using Nikon DSLR camera and that pics was taken last week when i assemble the amp. tonight i will take more pictures for the update works when i reach home after work.

Regards,
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Old 25th November 2012, 10:49 AM   #1388
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Default Oh!... this one is good...the Nikon

Yes...post pictures...many pictures please.

regards,

Carlos
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Old 25th November 2012, 12:34 PM   #1389
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How many mv maximal can the bias up with this amplifier?
And if the bias quickly goes up (example from 30mv to 70 mv or higher) how many mv I must stay under the 30mv, so that the amplifier remains stable, is 20mv than a good choise to test the amplifier with music.
What are the benefits if if the bias go upwards, I mean is there also a difference in sound quality if the bias go upwards?
And no, I test with the bias not myself, first I need answers

Regards,
Rudy
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Old 25th November 2012, 01:22 PM   #1390
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Default Yes...yes and no and yes

It is good to increase bias...but it is bad because of heat.... also it is very good because we guarantee all transistor are "on"...but as you have a lot of transistors you gonna have a lot of waste in heat.

To know exactly the "point" you should simulate...i do not have this schematic in my simulator (this computer) and the job computer was formated last thursday...so, i cannot answer you this question...how much you should increase i do not know.

I have strong suspection by the work i have made in the Dx Super A, that you will have to increase a lot...and the point will be forcing power transistors to dissipate 5 watts each one..... i do not remember, but it seems you have 4 or 5 pairs.... so.... multiply and imagine the hell heat...if you are in Siberia...well..this gonna be great for you..but this heat in Brasil may cook my low countries and sterilise uncle charlie for ever.

So, the answer is yes, is no, is more or less and i do not know...also a suggestion, put it into simulator and give it a try to see the point.

I know and i knew this amplifier is a hell hot.... this way i have suggested people to just check if all transistors are conducting...less than 1 milivolt measured over the power emitter resistors.

Guarantee is void if you increase.

Good luck...has fire extinguisher?

regards,

Carlos


............................................

By the way dear BMW, it is so hot today here, that i am nude and going to the shower to cool down my body.... you see over the sofa the water...it is a hell hot....i will buy Air conditioning machine next monday...and you thinking in increase heat..... oh pain!
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File Type: jpg Too much hot.jpg (602.0 KB, 35 views)
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Last edited by destroyer X; 25th November 2012 at 01:32 PM.
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