Yo Dacz! \m/
Welcome to the thread.
The design of your peeceebee is just incredible!
All the best for the tests. May it bring pure sonic pleasure to you.
Thanks for sharing.
shaan
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thanks LC and Shaan... hoping to finish it this weekend.. how much transformer amperage for stereo?
i have stock of MJE340-350.. can i use it for VAS?
i have stock of MJE340-350.. can i use it for VAS?
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Hi dacz.
Please note that the peeceebee thread focuses on the simplest VSSA config.
Please read the first post of this thread carefully. The thread topic and rules are described there.
Best to post your progress in the VSSA thread. You can find the link in the first post of this thread.
This is not a rejection, just a suggestion indicating the best place for your posts.
Thanks.
shaan
Please note that the peeceebee thread focuses on the simplest VSSA config.
Please read the first post of this thread carefully. The thread topic and rules are described there.
Best to post your progress in the VSSA thread. You can find the link in the first post of this thread.
This is not a rejection, just a suggestion indicating the best place for your posts.
Thanks.
shaan
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it is pure peeceebee.. all values are from your first post.. i just don't have bd's thats why i ask if i can use mje's.
Nice layout, I like it! Not sure if you can get 60W/channel w. +/-35V DC rails,
LC may have been thinking of the max voltage as specified on his schematics.I expect to get about 40W/channel, with a transformer 25V AC (rms) secondary winding, and I am using a 250 VA transformer, which is plenty of power for my version of this amp.
I am using heatsinks rated at 0.65C/watt, which would give me a 25C worst case temperature rise at the heatsink, averaged over the surface of the heatsink, assuming good air flow over vertical fins.
In normal use, 2 8-ohm speakers, and single-room listening, 20-25W per channel is plenty, and most of that power is used for dynamic range, and not average power anyway...
That's not the problem.
The amplifier is named VSSA(Very Simple Symmetrical Amplifier). "PeeCeeBee" is what we call our lovely boards built around the simplest version of the amplifier.
Your board is awesome and yes you can use MJEs without any problems. However, it contains parallel capacitors in the feedback node, not matching the schematic in the first post.
Please post your future progress and enquiries in the original VSSA thread. The link is in the first post of this thread. Please read it carefully.
Thank you.
Member
Joined 2009
Paid Member
I also offer my insights here: http://www.diyaudio.com/forums/solid-state/196973-tgm5-all-bjt-simple-symmetric-amplifier.html
you will find some information on current-stable Vbe multiplier and use of surface-mount with pcb layout. It is not the simplest design, but after reading about the nice sound of the simplest design I am thinking of making another 😀
I bet my 15-year-old Tektronix bench supply is as stable as your SMPS... just not as new and shiny, I bet! 😀
Unfortunately, my output seems to clip well before I get that close to the rail... 🙁 ...hmmm...
PMI,
Rookie question: what gain are you getting and can it be adjusted without affecting stability?
Thanks,
Freeman
Rookie question: what gain are you getting and can it be adjusted without affecting stability?
Thanks,
Freeman
Yes, one of the two sets of boards I am using is set for a gain of 10, by replacing the 2.2K feedback resistor with 1K. By design, gain is 22x, or ~27db. If you do that, you will get different readings for bias current, but everything is set up the same way, just the numbers will vary.
Both sets of boards are completely stable, to the best of my ability to judge that (oscilloscope readings).
edit:
I should probably add that several people here have built LC's VSSA from Shaan's version of the schematic, plus 4 or 5 using my through-hole version of the board, often with very different component selections, layouts, with and w/o comp caps, with and without Zobel... all seem to be stable and work fine.
One of the two sets of boards I kept for myself has been through a lot - sine wave, square wave, frequencies well beyond hearing range. Always stable.
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31 Vp (62 Vpp) of output amplitude is 4 V below 35 V, it should clip at 32 Vp so 3 V below 35 V. Output current at this point is 4 Ap (2,83 Aeff), that is realy not so high for PSU to withstand. 🙄I bet my 15-year-old Tektronix bench supply is as stable as your SMPS... just not as new and shiny, I bet! 😀
Unfortunately, my output seems to clip well before I get that close to the rail... 🙁 ...hmmm...
😱
Bigun hasn't built a vssa? That's un-possible
(juzz kiddin').
Will be waitin' for his peeceebee...
Bigun hasn't built a vssa? That's un-possible
(juzz kiddin').Will be waitin' for his peeceebee...
U R correct, I looked up my notes, and I must have forgot to divide one reading by 2... 😡
(I was probably too excited it was clipping so cleanly... yeah, that's it, and I am sticking to that story... 😀)
So, corrections: the signal clipped 4.5V below the DC rails, which at that time was set at ~30 +/- on the supply. Most of the time I use the diff. measurement on the scope, so the observed voltage was 51.2 Vp-p with the supply set @ +/-30, 60.1 Vp-p actual.
Wow, think of what I can do with the power I did not know I had...
Hi PMI.
I think I have (finally) found something for you and others here to test.
I was wondering what would be the minimum quiescent bias of the FETs where crossover distortion becomes detectable, by ear and scope. If possible then please test it and tell us the story.
Thanks in advance.
I think I have (finally) found something for you and others here to test.
I was wondering what would be the minimum quiescent bias of the FETs where crossover distortion becomes detectable, by ear and scope. If possible then please test it and tell us the story.
Thanks in advance.
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I will give it a shot by Mon~Tue. Busy weekend, otherwise I would do it today.
If you have any particular test conditions in mind, please post them.