I have never been comfortable with this connection scheme as a result of the separation of input and output modules/stages.
Hmm... 104.2 MHz is one of the standard radio-broadcasting frequencies (FM band). Coincidence? 😕
No, what I meant is I'm used to the "shortest track" idea/concept, so I have always looked with suspicious at the idea of separating input from output, even with slow amps.
Of course the modular idea has certain objectives, such as ease of debugging etc., but does it not have price to pay??? Even tho I don't know exactly the answer, I will not do things like this except maybe in prototypes. But even in prototypes I don't do things like that.
I don't want to do a detailed experiment to prove my assumption, but right or wrong I have assumed that better track means better sound. So why not go with the best track possible, I said to myself.
It is a distinct possibility that the infidel's IP/VAS could oscillate at RF (FM !).
ksa/c devices are >100mhz Ft .
The OPS would be attenuating this with <35mhz Ft.
Not to be funny , but have I created an FM X-mitter ? Let's modulate it -
and broadcast. 😀
Infidel did not do this with regulated diamonds and CCS's , but had thermal
instability.
One more idea ! (below) ditch the hawksford ....
OS
Attachments
With a shorted input?
I will search with a scanner.
BTW, strange is that zobel is absolutely cold even when amplifier plays square waves at high frequencies
Slower ksa to lower ft 75 mhz or local feedback,inductors at input to to ksc is bad solution,i think.
to get stages more stable,
to get stages more stable,
HF unstability can be caused also by improper PCB routing, ground traces are too thin and too long , more as parasitic inductance than proper ground connection. For such "speedy" amp will be inevitable to use ground plane, poured copper(double sided PCB), or make ground traces much wider, to use all free space..
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Have we gotten Terry to try his version of the Infidel with different components to see if he see the same oscillations? How about it Terry, can you see if you have the same problems as Thimios?
I populated a pair but have issues with them and didn't have time to troubleshoot at the time I have too many projects going at one time. I will try to make time today to get them working.
Thanks Terry. It would be interesting to see if you have the same oscillation frequency as Thimios with different components.
Hi Guys,
I got the Infidel working. It plays music fine but square waves look a little funny and I can hear a sizzling sound if I push them more than about 15vac from 20khz up. I'm attaching some pictures. These are with an 8 ohm dummy load
I got the Infidel working. It plays music fine but square waves look a little funny and I can hear a sizzling sound if I push them more than about 15vac from 20khz up. I'm attaching some pictures. These are with an 8 ohm dummy load
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You have a bit ringing on the rising and falling edges. Can be your generator or simply weak oscillation. Try reduce open loop gain bandwitdh by 10% and see if it dissapears ..
Terry,
I know nothing but that doesn't look terrible, but not what you want I know. Thimios did a sine wave test, could you show a similar scope output and sine so we can see the difference? Perhaps Thimios would have to tell you what he did?
Thanks for doing all the work and getting it to run, great work again Terry.
I know nothing but that doesn't look terrible, but not what you want I know. Thimios did a sine wave test, could you show a similar scope output and sine so we can see the difference? Perhaps Thimios would have to tell you what he did?
Thanks for doing all the work and getting it to run, great work again Terry.
Series Resistor between the two diamond buffers x1.1 times bigger
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