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Old 4th June 2009, 05:00 PM   #11
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Quote:
By DX - Some were original, others not...but do not worry with parts..they do not sound...topologie sounds
Carlos... , You of all people should know it is ALL about the parts !!!

They do not design the circuit and THEN make the transistors to fit the design!! The boring people in their man caves (cubicles) are given the latest, greatest parts from the factory and told to design the best consumer Ceeearrrp... as to sell more factory parts.

(bird before egg / egg before bird?? )
OS

Quote:
Oh!...is this amplifier oscilating?.... was you that made it?
Nope... no oscillator .. even with 25' speaker cable and NO zoble.
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Old 4th June 2009, 05:07 PM   #12
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Default No...it is none about the parts

enjoy your learning... have room to that.

bye..till Christmas..... have a Merry Christmas and a happy new year.

ahahahahah!


Carlos
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Old 4th June 2009, 05:17 PM   #13
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By DX -No...it is none about the parts
Then , as YOU said ..(MJ- XX ,higher Ft, etc) would oscillate in the DX. If it was only topology , ANY transistor would work..
The one above does NOT oscillate , the evil 22R and extra miller C allowed the high Ft KSA to work. Topology follows the device.
( Bird before egg?? )
OS
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Old 4th June 2009, 05:28 PM   #14
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Default Listen this amplifier sound..you will recognize the Dx Amplifier sound


Because this one is using absolutelly the same schematic..some resistances are different, some small differences into the bias current.... i have discovered that schematic monthes ago... a friend has sent it to me.

I have the schematic, but the one gave me (I have asked him please to give me copy) said that he will not be happy watching the schematic published.

So...i have not used this one as reference..but sounds the same..because topologie sounds...the RCA can sound the same if you remove some strange things it has, alike that diode.

I see, Ostripper, that we have strong differences in points of view..so... will let you conduct your thread without my interferences..be happy and enjoy your beliefs.

Bye...next Christmas i will visit you to wish you a happy new year.

Will not waste my time discussing..i have work to do, to people that are tuned with my ideas..you are not.

Parts does not sound..topologie sounds, adjustment of bias, vbe voltages and currents (operation points) sounds..the rest is myth... but a lot of good people use to say parts sounds...i do not use to discuss beliefs, as this is alike religion..no good result.


http://www.youtube.com/watch?v=warJLziW6gkregards,

I hope you recognize the Dx sonics... i think you have assemble one as a toy to your kids to play music, or into the kitchen or somewere into the house... maybe you remember the sonic characteristics of the Dx amplifier..characteristic of this topologie... observe the slew rate, the attack speed into the tones when guitar is playing..awsome!... the topologie...was not me, nor the parts....it uses low speed transistors into some places as drivers and VAS.

Carlos
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Old 4th June 2009, 05:45 PM   #15
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Default Sorry, i forgot to show you the topologie


I cannot publish the schematic, but partial and without values i think my friend will not be mad with me....the one sent me the schematic.

This is the Scott model you saw into the youtube video..same topologie, same nice sound.

regards,

Carlos
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Old 4th June 2009, 06:07 PM   #16
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by DX-I cannot publish the schematic
Thank you, my friend. I see (learned)2 things from your schema (the diodes on the VAS and Vbe).

They seem to be "insurance" to make the design foolproof (2 are thermal for cfp OP - better than P3A).
Actually , both of us are right. A smaller amount of the sound is the part , the topology is dominant. BUT , unless the topology takes the devices into account , you will have less OPTIMAL sound and a possible burnt pile/oscillator (unreliable).

BTW , I am not a blackgate capacitor "believer" , the sounds quality is the LTP balance + compensation. While the local feedback of the bootstrap is also a MAJOR effect , A high quality standard cap will give you 95% satisfaction.

OS
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Old 4th June 2009, 06:30 PM   #17
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Quote:
Originally posted by ostripper


Just a few changes from the DX,TGM. The "trick" is the devices , since it is RCA's design for those devices.

BTW ,On your TGM, what is the LTP current. I did notice , depending on device , the bootstrap/RCA amp has a "window" (.9 to 1ma -2sa992) where the differential becomes balanced , offset goes low, and distortion really drops). This is not the case with the blameless or symasym topologies. Also , I noticed that this amp can keep its low output distortion up to about 2/3rd's peak to peak of the rail voltages , then a big increase in THD (another bootstrap effect)??
Have you seen this errata ?
OS
The TGM amplifier will work fine with a range of LTP currents, down below 0.9mA for example. The issue is not to allow it to be so unbalanced that you destroy the waveform, you see this quickly even in a dc operating point simulation. The current at which the LTP is well balanced depends on the collector load resistor of the input device, which we are free to adjust over a certain range; it also depends a bit on the device models. I think the 'window' you suggest is a good starting point for this thread.
I haven't looked at distortion with output close to the rails, we will try this in the sims to start. TGM with +/-15V p-p output swing looks nice and clean distortion wise.


Here's the schematic into spice, please check for errors. Then I will post the actual file.
It doesn't work as-is because it uses default library for the active devices and so it isn't going to balance. Check it first - but I think the LTP is so out of balance that this must be fixed.
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Old 4th June 2009, 06:35 PM   #18
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Quote:
Originally posted by ostripper
BTW , I am not a blackgate capacitor "believer" , the sounds quality is the LTP balance + compensation. While the local feedback of the bootstrap is also a MAJOR effect , A high quality standard cap will give you 95% satisfaction.
OS
There should be some compromises on parts selection. As with most things in life, you pay a bit more and you get something better but at some point you have to pay a helluva lot more to get not much extra. It's the care in which all the parts are selected, some parts are not so critical and others can make a difference. Listening tests can help, not the simulations.
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Old 4th June 2009, 06:53 PM   #19
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By Bigun -Here's the schematic into spice, please check for errors. Then I will post the actual file.
Looks correct , Gareth.
I will find the closest devices to the RCA's that I can and post a .ZIP with their models.

On the topic of high output distortion , after that 2/3rd's "point" THD
stays .1% all the way up to actual clipping and is almost exclusively H2 in content. I suspect this is the reason for the pleasant bass or the perception of "better bass" , especially at high levels.

I "looked" into the bootstrap cap as I increased the level and saw both phase and level changes within. It should be cool to see the plot of this while stepping the input. (next)
OS
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Old 4th June 2009, 09:33 PM   #20
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Let's see if this works... attaching the spice file
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