Hi Salas
Up to now, when I made VSSA compensation scheme calibration, all measurements were done at 2,7 MHz (generator upper limit). OLG was around +80 dB (-3 dB at 50 kHz), CLG +23 dB (0 dB at 2,7 MHz). Sine distortion at 2,7 MHz negligible as a result of proper compensation. At this frequency it is very simple to trimm compensation caps since any wrong value is immediately clearly visible on the scope as a distorted sine waveform. With this latter VSSA channels assembled will do squares test and post scope pics.
I'm getting this 72-6805 - GW INSTEK - OSCILLOSCOPE, 2 CHANNEL, 20MHZ | Farnell United Kingdom for this build and my DIY future. Not sure if I need SMD tweezers too. A small chissel tip would be good enough? Never done SMD before. All good tutorials links are welcomed.
One more info. VSSA is stable no matter the load's capacitance. 10 pF, 100 pF, 1 nF, 4,7 nF, 10 nF, 47 nF, 100 nF, 470 nF, 1 uF capacitors alone clamped the output terminals and nothing, all clear. It looks like 1 uF capacitor was charged a little, so I noted a little spike on the output when VSSA discharged it, later clamping with the same cap was zero response, because it was already discharged.
Also wire clamping was performed, short circuit on the output to be more clear and again nothing on the scope image, zero, nada ...
Also wire clamping was performed, short circuit on the output to be more clear and again nothing on the scope image, zero, nada ...
Good choice. Scope is obligatory in any amp production, so you can clearly "see" what is going on at the output or elsewhere in the amp. SMD tweezers obligatory too.
Here's one very important tip if you want the soldered SMDs looks like in my pics.
Solder one side of the SMD part excessively, small ball of clear solder arise. Next step is to strongly shake off soldering iron (not clean the tip with sponge) so all soldering tin falls off the tip and than reheat the same SMD pin. The tip of the soldering iron will "take" all excessive tin from that pin. Repeat this step until soldered pin looks like the slope of the mountain.
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Exactly and for high speed and large bandwidth amp regulation system via feedback is a peace of cake.
Hi Gabor
At the VSSA project PCB layout is, as I already said once, the last but certainly not the least important part of the game called sound quality. Fair "battle" among the two would be only as each is in its best form, so in this manner I suggest you to go to PCB set from the start, especially if your intention is comparison.
Hello Andrej
What good would do to me to order your PC board (actually to be honest is very nice and supper quality) if I don't use SMD parts???
When I write I want to compare the two amplifier that is for me to learn not to publish the result or any other opinion.
Or promote my amplifier!!!!!!
Only to you in PM if you would interested I promise
!Why I do not use SMD parts?
I do believe in the regular exotic part quality still better and I got used to certain type of resisters like Caddock, PRP and silver solders ( high temp melting because lead free).
I do have at home 4 spool different type ( some of them $65 a spool) solder.
PLEASE DO NOT SAY SOLDER IS SOLDER because we tested!
Even so called non "audiophile" guy can her the difference when we did A-B test.
Please guys again I do not want to argue over the parts quality etc... That is another topic...
I do have my own experience, you have your own and I respect that!
Andrej please help me so I can get a pair power mosfet (may be they do not sell only 2PC to me)!
Here I ask a favour with a lot of respect to your result about these amplifier!
Just remember when someone posted here some circuit from my thread I did ask for the removal, again I do respect your achievement, your project!!!
Greetings Gabor
https://dcc.ligo.org/public/0002/T0900200/001/current_noise.pdf
This paper shows Vishay TNPW on par with the infamous s102K. It also shows Caddock power resistors and how poorly they fare vs something like the Isabellenhuette PBH. It doesnt speak of teh sound, but the Vishay TNPW sound very wonderful in the RIAA where the currently reside. I use all 1206 except in power resistor spot where 2W Vishay SMD is used. Youwant to get real exotic, look at Vishay PLT. 5ppm, good lord.
This paper shows Vishay TNPW on par with the infamous s102K. It also shows Caddock power resistors and how poorly they fare vs something like the Isabellenhuette PBH. It doesnt speak of teh sound, but the Vishay TNPW sound very wonderful in the RIAA where the currently reside. I use all 1206 except in power resistor spot where 2W Vishay SMD is used. Youwant to get real exotic, look at Vishay PLT. 5ppm, good lord.
Thank you very much! Really a great information..
The Caddock and other resisters I mentioned as an example.
Caddock I used for only one project called ProFet..
Usually I use PRP or DALE.
Shinkoth are not bad if I can get the right value.
Many people forget the fact some resister need 100 hours burn in, some sound smooth right away.
Noise level is not everything.
Those AB carbon resisters or other carbon type how nosy and people still love it and use them!
Again I want to do a A-B test with the same resisters , solders etc I got used to it.
That would be the only fair game to me.
Here I want to get some idea about LC how much he improved these topology, that is all.
After I can test your resister , PC boards etc!
I hope you understand my point.
Greetings Gabor
No.
And i do not wanted to introduce any "audiophile" (plz, read my signature) controversy about "component's sound" or fashionable component providers.
Correct engineering is calculating, measuring and using the right component in the right place. Not tasting things like wine.
"Silver solders" is an example of things that i avoid: It heat too much components and nobody is able to provide evidence of the slightest difference.
It is used in Industry to comply with RoHS and audiophile loves-it because there is the magic word "silver" inside.
Anyway, it is not the right place to argue about this. My link was to help VSSA builders to take care of a critical part.
well, you might have a problem
I have heard that one of those amps sound much better with a certain kind of solder
and the other one cannot use that special solder because of SMD
so for optimal result you need to use two different kinds of solder as well....gets tricky now
and one amp sounds better with one certain resistor
and the other amp does not like this resistor, but sounds optimal with a completely different component
and so it goes on and on...quite impossible comparison if you ask me :
I have heard that one of those amps sound much better with a certain kind of solder
and the other one cannot use that special solder because of SMD
so for optimal result you need to use two different kinds of solder as well....gets tricky now
and one amp sounds better with one certain resistor
and the other amp does not like this resistor, but sounds optimal with a completely different component
and so it goes on and on...quite impossible comparison if you ask me :
I think you went to far with the final conclusion about PBH in comparition with Caddock MP series.
Take a look on the fig 8 , and huge spike around 7kHz with PBH resistor,
it can be a resonans frequency due to resistor construction
I did a JFET input version of this amp few years ago when I wanted to incorporate LATFETs into F5 (adding them as a Source Follower output stage to F5 topology).
Input stage biasing is easier (JFETs being depletion mode devices) and input impedance is much higher.
It sounded OK but I liked this one more...
Anyway, here is the JFET input, BJT VAS and LATFET output version (the forum member "fab" built something similar before me) of this amp:
Attachments
Eutectic solder with silver AND lead has no significantly higher melting temp (something like 185 vs 175°C is nothing).
Lead-free is the devil.