My plan is to make an amplifier without a servo circuit (cut off part of the plate or leave it blank without parts).
I ordered this board because it provides the ability to build 2 or 3 pairs of output transistors into the amplifier, which according to Ultima Legione is a pretty big improvement in bass. I couldn't find bare PCB without parts that only have 2 pairs of transistors.
My first question is why instead of input transistors 2N5401 and 2N5501, low-noise matched paired transistors in a common housing with similar characteristics are not used.
Such as MAT or MPSA transistor?
I ordered this board because it provides the ability to build 2 or 3 pairs of output transistors into the amplifier, which according to Ultima Legione is a pretty big improvement in bass. I couldn't find bare PCB without parts that only have 2 pairs of transistors.
My first question is why instead of input transistors 2N5401 and 2N5501, low-noise matched paired transistors in a common housing with similar characteristics are not used.
Such as MAT or MPSA transistor?
Much earlier in this thread Domenico mentioned using HN1B04F. Perhaps the original designer is partial to the sound of devices used.
Welcome aboard dmarget5 🙂
I will order the same board today, but I will try to keep servo and find a way to switch it on and off, just like new versions of NHB-108 do. Perhaps this is the best way to evaluate servo which I never tried but I will. I am reluctant however to test it at full power - my neighbours might lynch me on a tree in front of my house. 🙄
Here is link for this PCB: Imitation Swiss darTZeel 1 channel post amplifier board|Amplifier| - AliExpress
Thanks.
If the things go like now with China transports, I will get it in august. 😉And, please, don't cut-of the servo. There must be a way to switch it off and on.
No I won't cut it, after all the tile PCB didn't even arrive I ordered them a month ago.
I have some more projects and drafts so I’m in no hurry.
I would be grateful if someone would put in one place all the most important things that should be adhered to when building so that I would not accidentally skip something.
Is it good enough if I pair the input transistors with a universal instrument that has an HFE meter?
I have some more projects and drafts so I’m in no hurry.
I would be grateful if someone would put in one place all the most important things that should be adhered to when building so that I would not accidentally skip something.
Is it good enough if I pair the input transistors with a universal instrument that has an HFE meter?
Could you be a bit more explicit? Link? Quote? Picture? To the best of my knowledge no version has ever had a servo.
Sorry fellas I will slightly necropost here 🙂.
It is quite simple. Select pairs within 1% of h21 and thermo-couple them. I selected quads in 1%-2% range and couple snugly pressing them together via small plate of copper (26-28 awg) with thermal compound and thermoshrink.
If you can use matched pair/quads entry transistors there is no need in any other stabilizing circuits.Your problem you do not have either the supercapacitor either the offset stabilized. Like that you can not use the amplifier!
It will remain unstable!
You need to do something to stabilize the offset.
See the picture for the capacitor or the extra stabilizer circuit, you need one of those. 🙂🙂
Greetings
Original uses stab circuits to avoid matching input transistors. It is fully understandable as matching transistors to any sizable amount of sets is a pain)
It is very nice of you to try to warn people. I spent countless hours on one of the largest russian forums trying to explain extent of fake electronic parts production in China, mostly in wain I think 🙂. But thank you for trying. Paraoxod4 one of the few who could hear the voice of reason. A lot of buyers don't understand that what you get with the aliexpress assembled clones is workable version of the amp built solely on fake/(chinese analogue) parts.
I get interested to built it when a lot of discussions about this amp sparked on one of forums couple of years ago. Didn't like any of chinese cloned pcb's and also didn't get exited about layout of original. One of the old acquaintances from same forum well known for analog pcb design skills had pcb version for this amp and kindly sent me lay files to use at my discretion. I have slightly adjusted the layout to suit my needs (replaces few parts with cmd versions split 5w resistor in 2x2W as it is appears quite difficult to find 5W metalfilm resistors. The board on the picture paroxod4 posted here, is one of mine.
You right not an issue particularly if input transistors matched. I had one pcb set running with 5k pots 🙂 499k-5k-499k. And higher resolution to adjust offset is quite nice I found 50k 21 turn pots a bit rough.
According to a lot of russian builders multi-pair versions lack in resolution
That could be related that most of builders apart just a few built it out of aliexpress sourced parts.
I think multiple reasons. I looked into it at some point but didn't find this idea particularly compelling. One of reasons, couple hundred 5401/5551 in my desk drawer to select from.
That, was my second reason.
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This is always the case when paralleling devices, whether triode valves at MC input stages or output transistors. It cannot be cured by matching, there is always a reduction in focus and resolution. At the same time there is a substantial improvement in other areas: bass, solidity, dynamics and technically the ability to drive low impedance loads.
What a pity that black board isn't commercially available. I wanted to purchase it and already have named it:
"Black Widdow T-34" 😎
Well, not all wishes come true.🙂
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I do have several almost completed sets. First set of ordered boards somehow got sold, I ordered second small batch as there was/is some people asked me for completed sets and also I have urge to try to juggle parts a bit. ANd managed to order them on existing gerbers without tooling charge second time, not sure if this option still available.
The board have 105um copper
If you have one left I am in. We can settle details by PM.
Lookong forward to hearing from you. 🙂
Perhaps I get mine T-34 in the end. Looking forward to put it in a beautiful chassis and feed her from good power supply.
Cheers dear garrbage. 🙂 (you deserve a better nick).
Not in my experience, unless you need to drive some difficult loads with quite low impedance overall or extremely uneven when at certain points it drops very low by example impedance drops to 2.3Ohm for almost 1/8 of an octave around 800Hz for 8Ohm speaker.
For speakers without such issues in crossover, sufficient power supply, properly designed amp layout, and as a matter of opinion 🙂 I don't find that claim justified enough but again it just IMO
My post contains two claims. Perhaps you should make it clear which of the two you disagree with 🙂
I have an idea that on the copper foil with ( which the input transistors spook and wrapped over the thermal paste), a line is soldered and connected to ground, would reduce the noise of the transistors?
Perhaps this would also reduce the DC output voltage?
I applied this on my phono preamp on 2sk170 and BF 245 with very good result much more hum and noise.
I also wrapped the adhesive copper foil in several layers and made a foil cap on top so that the transistors were completely shielded with foil. I soldered a short wire to the foil and connected it to ground.
Could that little tweak be useful on NHB-108?
Perhaps this would also reduce the DC output voltage?
I applied this on my phono preamp on 2sk170 and BF 245 with very good result much more hum and noise.
I also wrapped the adhesive copper foil in several layers and made a foil cap on top so that the transistors were completely shielded with foil. I soldered a short wire to the foil and connected it to ground.
Could that little tweak be useful on NHB-108?