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Old 10th May 2012, 10:18 AM   #1211
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Default I have tested the Dx Super A into the simulator..to use together the MKIII Hx

I have not approved....too much hot...too many modifications..... i am adapting it to test together the MKIII Hx but with reduced power (41 plus 41V supplies) because easier to me as i have one unit assembled.

The MKIII Hx uses high voltage supply, and some of you are using even more volts than the suggested value..... so, if we try 500 mA as stand by current start up at class A biasing..then we may have too much heat...not a good idea as this amplifier is already hot..... i could see the heatsinks people will use and i do not thing they are good enough even to the standard operation at full power..... if we increase bias till 10 or 20 watts, tracking the operation in class A (high bias)..then we will have much more troubles than we want.

I am uploading a video showing that i have simulated and that worked with some modifications because the VAS current is bigger in this model..... i have to try real life and i gonna do it next week i think...

Will assemble a spider type circuit to connect it to the MKIII Hx reduced power i have already made....to be easier to me.

This stuff is good to lower power units.... the high power amplifiers already have a couple of watts (sometimes one or two) while in class A because of their stand by bias.... the power consumption in stand by mode will be able to generate non switching audio for 1 or 2 watts RMS .

If you want you can try.... i have not succed to adjust this thing to smaller currents than 500 miliamperes....my circuit is not accepting this well.... if you want you can try under your own risk...but put a camera for us to see..sometimes this smokes a lot and you can became an Youtube champion of hits...people loves this stuff exploding.

Ahahahahahah

regards,

Carlos
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Old 26th May 2012, 06:09 PM   #1212
bonfis is offline bonfis  United States
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Default Stability and Gain Issues

Quote:
Originally Posted by canonnica View Post
Nope. Unable to simulate the instability. I even updated transistors SPICE simulation models in my simulator with the ones from the manufacturer's itself (I use OnSemi).

Although the transistors weren't matched, I ordered them from a big well-renowned USA reseller, so I doubt they'Re counterfeit...

Well, even though my "high bias" test were not conclusive, I still like the quality of what I hear at the low bias setting.
I just completed some mods on my first board and thought I'd pass them on to the forum. I had also encountered some odd stability problems on my first build although they were not related to bias. Instead the amp would go into oscillation as soon as I connected an 8 ohm load. With no load it seemed stable. Since I was interested in lowering the gain anyway I experimented with changes to the IPS and feedback factor in Spice. I ended up with the following component changes:

R4 a&b 100
R6 150
R1 and R11 12k4
R9 470
R3 2k7 and C4 470pf (per Cannonica)
No change to Cdom

I should mention that my build has 4 output pairs and 50v rails under load. I also moved the output coil and resistor off the board to the speaker term.

The amp now produces full output at 1.25v in. Lowest measured distortion was achieved with bias set to give 64.7 mv across 2 emitter resistors! I won't quote the number because I don't fully trust my sound card based distortion measurements. However it does reliably show changes up and down.

Stability seems fine. See the attached scope shot of 10Khz sq. wave (vert. scale is actually 10v/division). The main heat sink at this bias is only warm to the touch. The VAS and CCS sinks aren't even warm.

But the best part is the sound. The amp sounds fantastic. I have built and still have a Leach Double Barrel and a Randy Slone 120 watt amp. Although I haven't done an A/B comparison of either to the Blame it sounds every bit as good to my ears.

Thank you Carlos and all contributors to the thread for your work on this project.

Steve
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Old 26th May 2012, 06:59 PM   #1213
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Default Thank you Steve...i am glad you like it.

Your findings are interesting and this is a reference to other builders.

Thank you,

regards,

Carlos
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Old 27th May 2012, 06:32 AM   #1214
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Welcome back Carlos, We appreciate you. Still have my DX board to complete.
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Old 27th May 2012, 07:40 AM   #1215
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Default Hey John.... i remember you!

It is awesome to see you around.... so long time man.

I am glad you still have the audiococus frequenciae inside your blood...the only bacteria penicillin cannot kill.

Audiococus (a kind of sonic addicted staphilococus) frequenciae is the only body invader that is resistant to time, disappointment, it shielded against hatters, also protected against envy, jealousy, evil spirits, karma, bad spirits, vodŰo, hot beer, coke without gaz, cold cheeseburger, big magic, frozzen coffee and melted icecream...... grand positive guys and grand negative guys does not influence it's multiplication and it is active in full spectrum not needing to split the badwidth.

regards,

Carlos
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Last edited by destroyer X; 27th May 2012 at 07:47 AM.
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Old 5th June 2012, 07:34 PM   #1216
BMW850 is offline BMW850  Netherlands
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Hi Steve,

You also have first listened to the original, or have you measured first and then the changes have been made.
I am curious to the differences in sound quality before de changes and after the changes.
Steve, thanks for sharing the information and modifications here on the forum.

Please let me know, are there more people who have made these modifications, after listened to the originaal?

Regards,
Rudy
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Last edited by BMW850; 5th June 2012 at 07:37 PM. Reason: typo
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Old 5th June 2012, 07:54 PM   #1217
a.wayne is offline a.wayne  United States
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Why not do the mods BMW and let us know, since you already have the original done ..?
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Old 5th June 2012, 08:12 PM   #1218
potepuh is offline potepuh  Slovenia
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Any builder tryed the jims audio boards, are they good? They claim to be authorized version.
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Old 6th June 2012, 01:50 AM   #1219
evette is offline evette  Canada
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Authorized by who. Evette
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Old 6th June 2012, 02:08 AM   #1220
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Default Someone have asked me to produce some boards to distribute to the community

I understood what he intended to make using my own references..... i was thinking was for free...or almost no profit...some contribution...... was someone from UK i think.

The guy did it and asked me i i want one board to test.... i said OK and he sent me one board for testing purposes...the same board made by Meanman and the US guy too (sorry, my 61 years old and i forgot the name)

So, there is a man, do not remember the name, from UK i think, that made some boards.... this may be the guy he is talking about.... that guy was authorized by me... was not what i had in mind when i said ok...but it is true that i said OK to someone.

The guy have asked me (circuit design) and i said OK, but he have not asked permission to Alex mm (pcboard design) .... If Alex complain..then the guy should stop.

No problems Joseph..... let it be..... there are thousands of pcboards made in China and being distributed.... i do not care.... i can make much more amplifiers, and faster then they can copy... also i am not making my living from this.

It is all right..all sweet.... all fine.

Be happy..... and healthy my dear friend Evette.

regards,

Carlos
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Last edited by destroyer X; 6th June 2012 at 02:13 AM.
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