Hi Terry,my test was with one channel only and star ground as ground position.
Hum was clearly heard. Tested amplifier was Shaan PeeCeeBee.
I believe that a separate power supply is necessary. You can have the main power supply under control using an opto isolator.
Mile, can you modify the circuit in this way?
That is not true. I thoroughly testest it today using an FX8. I tried using a separate supply as well. The only setup that was silent was with a ground wire directly from the star to the center ground lug on the protection. I only used one wire from the transformer secondary to the ac in on the protection. I have zero hum. If you like I could check it tomorrow with a peeceebee. I have one handy. I will take a picture in the morning of how I have it routed.
Blessings, Terry
Beautiful work guys. I knew that something had to give, but didn't know enough to know that the real-estate-eating caps could be downsized, I simply noticed that dragging all the tracks to T1 and T2 up to the heatsink was using a lot of area....
Also, while I fully understood that T1 and T2 still NEEDED heatsinks, I was probably overly-optimistic to think that the heatsink(s) wouldn't need real estate of their own. Nice to put them together. Do they need to be thermally-coupled?
Again, beautiful work.
Ben Franklin
Sprint files of FX8 with and without (zener and 1N4148).
47uF/50V used instead of 22uF/63V, some manufactures have 56uF/50V with 6.3mm diameter and 2.5mm lead spacing.
1000uF/16V can be used instead of 100/63V as Mr. Miles suggested but only 1000uF/16V with 8mm diameter and 3.5mm lead spacing will fit.
47uF/50V used instead of 22uF/63V, some manufactures have 56uF/50V with 6.3mm diameter and 2.5mm lead spacing.
1000uF/16V can be used instead of 100/63V as Mr. Miles suggested but only 1000uF/16V with 8mm diameter and 3.5mm lead spacing will fit.
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Hi Bimo,
You seem have have done many modifications (for improvements). Did you make a simulation as per Mr. Mile's sch? How are its results?
reg
Prasi
No. It only to make me busy
And it can be improvements or just different point of view about how to design an amplifier.
I like an amplifier with high slew rate, because I like "airy" sound. Sometime I compromise THD for H2 dominant. Sometime I use transistors that widely available in my country so the result is not optimum.
I mean, sometime I choose MJE340/MJE350 instead 2SC3503/2SA1831 for VAS or use 2N5551/2N5401 instead 2SC1845/2SA992 for LTP, etc. It difficult to find good transistors for VAS.
In my country, many people still using 2N3055, TIP3055, TIP41 on their amplifier. Many store still selling kit amplifiers that designed many long...long time ago (1970's ?), those kits still very popular. You will surprise if I tell you, that a kit amplifier have full power bandwidth around 10 kHz is very popular
Yes, very often an ordinary circuit with better transistors and better overall implementation just sounds better than better circuit with ordinary transistors (and implementation)...
I'm suggesting every DIYer to purchase more than you need when you have access to purchasing high quality transistors...
Because in my experience, there's no way you can hear the "high-end" sound with ordinary transistors, especially at the front end (and VAS!). It doesn't mean that using top transistors will automatically improve the sound, but using ordinary transistor will just LIMIT the possibility.
For input, you want low noise transistors (hfe is also important, but high hfe to drive Cdom is easily achievable). FX8 and P3A for example, is designed/specified with BC546 (preferably BC546B which has higher hfe). This transistor has Vce=60V, which I believe can work in probably all amp circuits rated at 100W or below (without cascode of course). This is at least what you have to use.
A1015/C1815 GR is slightly better in noise figure, slightly worse in Cob, but I prefer this one (in my comparison, using transistors I have on hands, which may differ with other production batches), only limitation is Vce=50V. But so far I have no problem using it in LTP of amps with +/-35V rail voltage.
There are better transistors in Vce=35V (I think the popular low noise BC549C is also in this category) and Vce=15V categories... That's when you want to build low wattage amplifiers...
My favorite is the 5-leg vintage dual transistors (there are 2 categories/levels here). When I purchased them more than 10 years ago, the seller didn't even want to sell many of them (it was already rare and hard to find).
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An externally hosted image should be here but it was not working when we last tested it.
Don't! This looks better!
Cheers!
Tnx!Sprint file for FX9.
Your makros helped me a lot.
Regards
Sonal Kunal
Nice compact design. Are the two 47uF's on left flipped polarity as drawn? Does this system not need emitter resistors?
Oops, I missed that.
Since only sprint files are shared every one can correct it.
Regards,
Sonal Kunal
Hi,
If you match the hfe of i/p pair (both are same sex, so should be very easy), and thermally couple them , there would not be any issues with DC offset. If I remember correctly, I measured around 5mV . And I tested this at different times.
reg
Prasi
PS I used a DMM
Hi,
If you match the hfe of i/p pair (both are same sex, so should be very easy), and thermally couple them , there would not be any issues with DC offset. If I remember correctly, I measured around 5mV . And I tested this at different times.
reg
Prasi
PS I used a DMM
You mean the two BC546's sitting next to each other? My DMM's also have the hfe measurement holes on the top deck. How closely does it need to be matched? Should be easy as you say as they are made in the same batch probably when delivered (especially if bought on tape reel). I am new at making my own PCB's - for fabricating the PCB's with typical low cost Chinese suppliers (10 5cmx5cm boards for $10), do they accept the Sprint file directly? I have mostly heard that they want Gerber files.