Destroyer x Amplifier...Dx amp...my amplifier

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Also a tip for checking tansistors.

Put your meter leads over the base and emitter leads. After you have the normal forward bias voltage reading use the probe on the base lead to short against the collector lead so that you are reading biased transistor action.

If you have 600mV between base and emitter, you could read only 520mV between base+collector and emitter.
The lower the second figure the higher the gain, and you can match transistors for low voltage operation doing this.

Actually I have found that match gain holds good for higher voltages with small signal devices, but would not trust this method with power devices.


Cheers .......... Graham.
 
The cheap solder sucker i use comes with a pin in the center,
that pushes out the solder every time you push the piston forward.
Well, at least that's the idea :(

Had to check the calendar to see it's thursday, it's what working in shifts does to a person.

Loek, about possible hum-pickup in my amp: The picture is distorting, in reality there's about 6 cm distance between inputs and ac-mains plug.
Hum is undetectable in my DX, both by ear and by scope.
Temprarily bypassing the 10r groundlifting-resistors was a great way for me to find a good wiring/grounding-layout.
Worst-case setup i tried had a hum that was influenced in amplitude by gently pushing the cone of the attached loudspeaker inward :xeye:

Feeling a bit sad with you Carlos about the plane-crash in Sao Paolo. A horrible accident. Well, not entirely i think.
You can only call it an accident when there's nobody to blame.

Thanks for your help regarding the layout of the Gem Graham, i must admit i was a bit lost.

Best regards,

Klaas
 
AKSA said:
Vbe matching means that parallel pairs pass identical quiescent. If their betas vary, then providing they are driven from the same driver it is of no consequence, and in any event gnfb will equalise, precisely as Graham says.

I use 0.47R emitter resistors, rather large, so as to reduce quiescent to just 60mA or so and to force current sharing AT HIGH CURRENT. Also means you can leave my amps on all day and still feel green. These resistors are within the nfb loop anyway, so they have little impact on Zout. They do cost rail efficiency, but at high current help to iron out the non-ohmic Ic v. Vbe discrepancies, pushing the distortion spectrum lower by flattening the transfer function - if that makes any sense......

Cheers,

Hugh

Hello

If I understand correctly (after reading lot of threads in the forum), and applied that to power transistors choices, since the 0.47 ohm emitter resistors force current sharing, helping for better linearity, and since the VAS are more important than the output stage, wen we used a schematic with those 0.47 ohm emitter resistors the output transistors choices are less critical, if I push a bit that ideas we can even use those old 2N3055 and MJ2955 without big sonic differences, even with high end diy amps like Dx, Aksa, Gem, etc, if we used the 0.47 ohm emitter resistors on all of them.. . But I may be wrong... ??

Gaetan
 
Man! oh man!!!!!!!! Charlie, this thing sounds good... such a nice romantic sound...felt a little cold after the chipamp, until my ears adjusted... wow... all sounds liberated from each other, no more of that boundary layer of sound between similar voices and instruments.... all running effortless and individual...

Bass kicks you solid in the chest without sounding bass heavy... its just one massive accousitcal air coupling between the bass drum and your body... and it pics up the bass in female voices so much better... giveing a much more liflelike sound...

Was planning to integrate a subwoofer, but it seems pointless now, this thing take my speakers as low as they can go, very convinceingly.... while the chipamp always felt like it was overdriveing the tweeters...

My wife and I ended up playing dominoes infront of the amp last night... just listening t music.

I have an incredibily wide musical selection... and it is good on all material tested so far... First song was Georgia, by Van the man.

First CD so far this morning is Kings of Leon... going to work my way up the The Wall... can't wait for that track with the stukka bomber plane...

I still have a little hum on one side... likely due to my sloppy wireing inside the case... just wanted to hear the damn, thing once it looked like it couldn't fry speakers by looking at it...

Still have to take it to a local forum member with a scope to help me set it up optimaly
 
Hi Andrew everything is standard as per the schematics (www link below), except for 10uf on the input, which I may reduce a bit to 4.7

PSU as per schematic, only with higher wattage rateings on components...

The song is In The Flesh?, by Pink Floyd, its is at the transistion between this song (first one on cd one) and the next one... the CD is basicaly recorded like the movie, without breaks between songs.

Wow, that CD is sounding better than ever before... all the tracks!!

I'm at Another Brick In The Wall Part 1 now, and that drum solo before the fist We don't need no education, is awesome, very 3d.

DX amp loves drums, for those of you not familiar with my history... my dad was a drummer from the age of 12 and I was born into this world of music... I have babyphotos of me navigateing my way between band equipment while still in my walking ring.... I KNOW the sound of drums very intimately.
 
I use to listen Pink Floyd too.... good recording to testings

You are right, the unit is very good to drums and bass.

Also reproduce a beautiful voices and treble.

My speaker is naturally mufled Nordic.... reason why i use some boost of treble into the amplifier.....472 capacitor in parallel with R10.

My input capacitor, now a days, in use, is 0.5 uF

Be happy.

regards,

Carlos
 
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