thank you a lot. blue resistor I mean metal film resistor because they are coated with blue paint and have 5 color strips. I am quite experiences on make pcb, ground line I allway solder an extra copper wire to the ground and line track to make it thicker many time.
Might my transistor low quality so they have higher distortion and noise than some tubes made by Sony???
Don't laugh at me but my electronic group made a FUNNY RULE for some months in the end this year : "Avoid to use opamps in your circuit, just use dicretr transistors or tubes"
Hi Nikolai,
Sorry if I was preaching about something you already know and have experience with. That's one of the problems I have on ETO, especially being a newbee. Good that you are generous with copper tracks and earths. I expect you are familiar with skin effect. It happens at surprisingly low frequencies.
You make me feel guilty; I wouldn't laugh; besides which your friends are right. The very best amplifiers are made with discrete transistors, the Burson discrete opamp is a good example:
https://www.bursonaudio.com/products/ss-discrete-opamp-v4/
The thing about tubes is that they inherently seem have a smooth open sound which many people like, including me. Up until about 2000 what your group said was pretty much true and a good rule. Having said that, the phono stage in my son's amp did sound nice and it used an NE5534 but it did have a a pair of matched discrete transistors at the front. Also, the NE5534 was specially selected.
So where is all this leading. It's this. Your friends are right but even with the best valves or transistors you, or anyone else would have a real job doing all the development work to realise the potential of them. I would guess in a year's time you would still be working at it. The reason is that every little thing makes a difference that's why the top end gear is built on cast and machined chassis and the circuits have all sorts of little bits here and there to make them work to the last knockings. Don't forget the pro designers have masses of specialist gear to help them too. The other thing is that many amps don't just use components off the shelf. Very often they are custom made or selected .Many of the components simply are not available to the public
On the other hand, if you went with an audiophile opamp you would have a massive head start along the development path. I would suggest that, in practical terms, you would end up with 99.9% of the perfection you are chasing and you would have an amp that isn't too twitchy either. I hate to say this, but in practical terms I suspect that you would end up with a far better performing amp than one you tried to make with discrete transistors.
I speak from long experience. I'm just like you always chasing the last knockings. It's a good way to be and I admire your enthusiasm but you need to add a touch of practicality. If you treat it as a development/learning programme without necessarily any end product, that's fine. You may not have anything to show for your efforts but you will learn a lot along the way- I did.
One thing I haven't mentioned is frequency stability. That's what you will get you unless you are very lucky. The circuits you will be developing will have open loop voltage gains of around a 100K, possibly 1M. So work it out 1uV differential signal on the input of your amp will produce 100mV output or if the open loop gain is 1M, 1V. You may look at the circuit and think, the open loop gain might be high but I have negative feedback which reduces that to say 100. That is sort of true but the trouble is that there is no such thing as an opamp like you see on the schematic, there is no such thing as a resistor, capacitor, or inductor either. In fact, it is so bad that there is no such thing as a simple piece of wire. Even air isn't a perfect insulator. You will see on ETO that myschematics are splattered wit 100nF capacitors. That's partly a prcaution against the parasistcs and strays that you dont see on shematics.
Just to give you a clue, typical tin oxide resistors become an inductor at 200MHz and capacitors have the weirdest models you could imagine. Many turn into inductors even at relatively low frequencies. This is why often the most wonderful amplifier you design on paper with 0% distortion just oscillates. And it is not simple oscillations either. The amp may sit there at 0V input quite happily, but when it gets a signal it might oscillate say from 2mV and stop again at 3mV (just to illustrate). It will probably sound pretty good but there will always be something not quite right when you listen to it for long periods. There are many many more insipid problems that will catch you out. You could do it, but time is your enemy and with too many problems it stops being fun.
And if I haven't completely put you off yet, be very careful about connecting you latest wonder amp to your precious and expensive speakers. The tell-tale sign is a puff of smoke from the centre pf the speaker chassis and an acrid smell- more of a danger with power amps, but can happen with preamps also. Always put around 16 Ohm resistor in series with the speaker until you are sure that the output offset is around 0V and the amp is copletely stable (oscillations).
I will stop now but take my and others advice: go for an op amp. You will have plenty enough problems doing an audiophile amp with those! And all things being equal, you should end up with a pretty good phono amp. Alternatively get a part time job and buy the amp you want. It will be much less effort.