Hi Gaborbela,
We just did another listening session, this time also to compare the Cubie2 with the F5.
In short: choose the Cubie2 to build
First we listened with some test tracks to the Cubie2, everything sounded very good: holographic, detailed, very good bass, everything sounded correct, it started us foot tapping
After the Cubie2 the same test tracks with the F5 and immediately we heard that the bass/lower end was lacking/slow, it sounded like there was something missing, it was less involving.
So now I have to make a Juma amp
The Cubie2 went home with Berny
Regards,
Danny
Thank you Danny! Really appreciated!
A big thank you for JUMA also for the design and sharing with us!
Greetings gabor
Hi Danny,
I f you already have k2013/j313 it would be a shame not to use them, and that amp really sounds great. OTOH Cubie2 sounds great too, but it's simpler and easier to build - it needs less heatsinking and uses just one output pair. If you are not lazy about mechanical work (drilling, tapping, etc.) go for k2013/j313 and stick to sch. given in the first post of that thread.
500R is better, although numerous options are possible: 220R fixed resistor + 200R trimmer or 2 red 3mm LEDs in series, or green 3mm LED + 200R trimmer - anything that will set the Vgs of MOSFETs to a value needed to achieve the target current through the output stage (0.5-0.7A, depending on your heatsinking, speakers' impedance, PS voltage...)
Thanks Juma,
it will be the k2013/j313, I have the mosfets and plenty of heatsinking 0.23°c/w
Because my speakers have a 3 ohm dip, I'm thinking of using 4 pairs instead of 3 pairs. Good idea ?
Thanks Juma, 3 pairs will do the job very fine
A side benefit is that it's easier to find triplets than quads.
Dennis
Juma, what size coupling capacitors did you use in your finished example(last photo) in post 1?
I see a couple of large Wimas along with other caps in parallel with them.
Also, what size resistors are on top of the 15KuF caps in photo 4? Are they in series with the capacitors like in a CRC arrangement?
Thanks...
I see a couple of large Wimas along with other caps in parallel with them.
Also, what size resistors are on top of the 15KuF caps in photo 4? Are they in series with the capacitors like in a CRC arrangement?
Thanks...
100nF Wima-MKP10 (red ones) and 1uF Philips MKC (blue ones). The yellow one is there just to couple them mechanically. Now I took them all out because the preamp has the coupling cap at the output.
Yes, they are 0R1 2W in CRC arrangement. I used them as a part of a testing setup - they just make the current draw measurement easier. The actual amp doesn't have them, its PS is built with capacitance multiplier.
Somehow, I overlooked this question...
There is no VAS as such in this amp - Q1, Q4, Q6, Q7 form a gain cell similar to one presented by Mr. Pass at BAF 2013 (preamp project with LSK JFETs). It's just that I used current mirror instead of current source (a big resistor originally) and introduced R7/R16 feedback loop.
The only degeneration used is in JFETs' sources and I'm sure that leaving it out won't improve anything here. Of course, that's just my experience with this circuit...
You are correct, this is my mistake since I have overlooked this current mirror...
Sorry.
Thus, I may look again to see the potential of this circuit....
Fab
I've been listening to Cubie 2 for a couple of weeks. Today I replaced it with my F5, and found I suffered from Cubie 2 withdrawal. It is a great amplifier. For whatever reason, it is able to drive the Maggies much better than Cubie. I'm building a power supply that can run Cubie and Cubie 2 at the same time. I will then try bi-amping the Maggies. I think Cubie will make a great tweeter amp, with Cubie 2 handling the mid/bass. Cubie is precise, but tending toward leanness. Cubie 2 is dynamic and full, punchy. I can't wait to hear the two in tandem. Thanks, everyone!
My Cubie 2 is better than my F5. Is any Cubie 2 better than any F5? I don't know.
The F5 is a darn fine amp. The Cubie 2 is three-dimensional with an uncanny way of presenting music so one can listen into the mix, with drums sounding like drums and lyrics more easily understood. It's fun to listen to music with it. It is so simple and affordable, if you can find the jfets and the latfets, there is no reason not to build one!
The F5 is a darn fine amp. The Cubie 2 is three-dimensional with an uncanny way of presenting music so one can listen into the mix, with drums sounding like drums and lyrics more easily understood. It's fun to listen to music with it. It is so simple and affordable, if you can find the jfets and the latfets, there is no reason not to build one!