if you interested to see the website is here but in Russian lol
http://схема-авто.рф/сабвуфер-и-усилитель-своими-руками-ча.html
Regards
Juan
new layout Russian style "I'm just joking lol"
what about have the option to use also TO-3 encapsulate metal transistors ? I like the way they look you know how I'm I like "vintage style pcb" see image it has two options of transistors.
Regards Juan
What happened is that i have assembled an unit to amplify satelite receiver from my cable TV...and even without any modification (Dx Super A - 42V) i found the sound very nice, even operating 20 volts using series pass regulator.
Then i have simulated and what a surprise!.... even lower THD...... because of that surprise i have checked using Scope and found the slew rate wonderfull, also nice the harmonic distribution.
I have decided to tweak a little to see if could result even better and then the distortion fell down to 0.00009123%...and this is much better THD compared with the 0.002 to 0.003% i was having.
that is fantastic! I will then make a layout from the file you send me I hope I can make it nice style,Russian style lol
Regards
Juan
The need to tweak is because a Brazilian forum folks asked me a deep comparison review in between the LM1875 compared with the Invincible Dx Super A model...same supply..... same conditions...same load.... same speaker...same sensitivity.
Because of that i have published the results...this does not mean the Dx Super A standard is not good...it is awesome...but this one, i have perceived, since first time i have listened, the sound is even better..... the treble is special....i use to be under strong emotions while listening...it is really awesome.
You do the layout you want dear Juan....i set you free to try whatever you want....i would ask you to test the layout...to assemble, to listen and to inspect it using scope........OR....if do not want to test, or if cannot do that, then tell folks the layout was untested...just that...to be transparent...the way we use to be.
regards,
Carlos
what about have the option to use also TO-3 encapsulate metal transistors ? I like the way they look you know how I'm I like "vintage style pcb" see image it has two options of transistors.
Regards Juan
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It is better to be out of the heatsink
Because some guys may use small heatsink.
If using small heatsink, then the drivers will overheat and will cause thermal drift...this is dangerous because people usually select small heatsinks..or smaller than the needed size...so..considering this kind of error from the builders due to high cost of heatsinks and lack of space inside the enclosure..it is better to install the driver transistors out of the main heatsink.... they can use small heatsinks.
Russian language you copy and paste the text into google translator... then you gonna have it translated to your language.
regards,
Carlos
Because some guys may use small heatsink.
If using small heatsink, then the drivers will overheat and will cause thermal drift...this is dangerous because people usually select small heatsinks..or smaller than the needed size...so..considering this kind of error from the builders due to high cost of heatsinks and lack of space inside the enclosure..it is better to install the driver transistors out of the main heatsink.... they can use small heatsinks.
Russian language you copy and paste the text into google translator... then you gonna have it translated to your language.
regards,
Carlos
Ok I'm in the progress this is just a "draft" I still moving stuff around, yes I did that paste it to Google translator
ok I will continue tomorrow I spend a couple of hours today Regards
Juan
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The power variation in the drivers can be enormous.
If the temperature of the drivers varies a lot from start up, or during varied audio reproduction, then that WILL CHANGE the output bias.
Either provide large enough heatsinks to minimise the temperature variation, or change the driver quiescent current to reduce the power variation.
If the temperature of the drivers varies a lot from start up, or during varied audio reproduction, then that WILL CHANGE the output bias.
Either provide large enough heatsinks to minimise the temperature variation, or change the driver quiescent current to reduce the power variation.
I've got a question about the standard Super A. Mine sounds fine but the scope shows an over shoot. Recently I built a Slewmaster that showed a similar wave pattern and it turned out to be that the gain was too high. My Super A has very high gain. I'd like to try lowering it to see if that helps reduce the over shoot but I'm not sure what the best way is to do that. Can one of you tell me what to change to lower the gain some?
Thanks, Terry
Thanks, Terry
Install a coil in series with the output
In parallel with 2.2uH coil (not critical value) use 10 ohms 2 to 5 watt resistor.
The Dx Amplifier, the first one....the standard one...does not have output coil if i can remember...not sure about it.... memory not that good anymore.
If you have a coil..then increase the number of turns...having it, make it twice the turns...overlap a coil making two layers.
regards,
Carlos
In parallel with 2.2uH coil (not critical value) use 10 ohms 2 to 5 watt resistor.
The Dx Amplifier, the first one....the standard one...does not have output coil if i can remember...not sure about it.... memory not that good anymore.
If you have a coil..then increase the number of turns...having it, make it twice the turns...overlap a coil making two layers.
regards,
Carlos
The gain is 1+ 56k/1.2k = 47.7times +33.6dB
Reducing the gain by increasing the lower leg feedback resistor is feasible.
BUT !!!!! this increases the feedback and usually requires a different set of compensation to maintain stability.
Using a high gain, which +33.6dB is, may have been a way of hiding the instability due to poorly designed compensation.
Reducing the gain by increasing the lower leg feedback resistor is feasible.
BUT !!!!! this increases the feedback and usually requires a different set of compensation to maintain stability.
Using a high gain, which +33.6dB is, may have been a way of hiding the instability due to poorly designed compensation.
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It's not like you to get wimpy on us Terry
You could reduce the open loop gain before you adjust the feedback resistor by increasing the emitter degeneration on the LTP. Instead of 10R resistors try 100R - increased degeneration in the LTP improves the behaviour of the LTP when subject to peak transients by flattening it's response.
Thanks Gareth, I'll give that a try.
Edit; I just looked back and saw that that two resistors were changed from 39R to 10R back in March 2013. I know Thimios had the same issue with the over shoot and I asked him recently if he found a solution and he said no.
I will try the 100r in there and see what happens.
Edit; I just looked back and saw that that two resistors were changed from 39R to 10R back in March 2013. I know Thimios had the same issue with the over shoot and I asked him recently if he found a solution and he said no.
I will try the 100r in there and see what happens.
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It is very interesting that people is having overshot
I have tested and i could not find overshot...see the video where i have tested Juan Vargas pcboards.
Well.... even if you have overshot you should not worry....you will not listen the overshot.
Some text books even shows the waveform with overshot and is understood as normal or not a problem.
https://www.youtube.com/watch?v=CEgK4l0MH8k
regards,
Carlos
I have tested and i could not find overshot...see the video where i have tested Juan Vargas pcboards.
Well.... even if you have overshot you should not worry....you will not listen the overshot.
Some text books even shows the waveform with overshot and is understood as normal or not a problem.
https://www.youtube.com/watch?v=CEgK4l0MH8k
regards,
Carlos
Hi Carlos,
You are correct of coarse. I cannot hear the overshot. But, I am on a journey to learn and learning how to fix little errors that are seen on the scope is all part of the learning process. As I said earlier, on a different project, I had a similar looking wave form and it turned out to be too much gain in the NFB. Once I lowered it, the overshoot was gone. That made me think of this amp and I wanted to try some things to see if I could get rid of the overshoot. This amp does have the highest gain of all my amps.
Blessings, Terry
You are correct of coarse. I cannot hear the overshot. But, I am on a journey to learn and learning how to fix little errors that are seen on the scope is all part of the learning process. As I said earlier, on a different project, I had a similar looking wave form and it turned out to be too much gain in the NFB. Once I lowered it, the overshoot was gone. That made me think of this amp and I wanted to try some things to see if I could get rid of the overshoot. This amp does have the highest gain of all my amps.
Blessings, Terry
I just want it to show a second draft I didn't like the first one so on this layout a SK12 or SK13 heat sink can be use and there are plenty of those on the net so here is the second draft prototype layout I can like this one let see what happens in a few more days
Regards
Juan
Regards
Juan
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