Thanks Thiago and Prasi!!
Getting any product to look good is an obsession but making it sound good seems to have taken years....
However I am pleased. I have worked hard and now it's up to the market and particularly how the customers like it.
In this cut-throat amp market a western maker cannot compete with $20 Ebay products... but he can sweep the floor with a brand new concept exploited by no-one else.
I've tried to differentiate my products with fresh thinking and inpeccable presentation and build quality. We shall see!
Hugh
Getting any product to look good is an obsession but making it sound good seems to have taken years....
However I am pleased. I have worked hard and now it's up to the market and particularly how the customers like it.
In this cut-throat amp market a western maker cannot compete with $20 Ebay products... but he can sweep the floor with a brand new concept exploited by no-one else.
I've tried to differentiate my products with fresh thinking and inpeccable presentation and build quality. We shall see!
Hugh
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That's a terrific looking amplifier, Hugh - very similar in appearance to the NAKSA 70 & 80. I gather that by now you're happy with this general layout? Will you release the SAKSA as a kit, like the original AKSA, as a built module, or both?
Hi Christian,
Yes, the layout is ideal, thermally and physically. It's evolved and is now very sophisticated. The four large mosfets are spaced along the pcb, and the beefy power supply is bifurcated, one for each channel. Same for rectifiers.
I will sell as modules with optional enclosure (3mm Al single piece, uses the box as the heatsink, fully drilled, threaded and stamp for this amp), and a few will be fully built here for plug 'n play, but most of these will be local rather than o'seas because of the shipping issues.
Hi Geirin,
Close. It is LTP input stage, and the rest is very like the NAKSA 80. The VAS drive is different, and the outputs are double the size, but yes, similar. It's actually a replacement for the N80, but I have a few still in inventory - same price.
I did not mention but this amp has a clip indicator, a red led, and it works very, very well. But very hard to get it to clip!
Now, we should get back to Thimios' QUASI. How is it with a 47pF on the C to B of the phase inverter? Fix it?
Ciao,
Hugh
Yes, the layout is ideal, thermally and physically. It's evolved and is now very sophisticated. The four large mosfets are spaced along the pcb, and the beefy power supply is bifurcated, one for each channel. Same for rectifiers.
I will sell as modules with optional enclosure (3mm Al single piece, uses the box as the heatsink, fully drilled, threaded and stamp for this amp), and a few will be fully built here for plug 'n play, but most of these will be local rather than o'seas because of the shipping issues.
Hi Geirin,
Close. It is LTP input stage, and the rest is very like the NAKSA 80. The VAS drive is different, and the outputs are double the size, but yes, similar. It's actually a replacement for the N80, but I have a few still in inventory - same price.
I did not mention but this amp has a clip indicator, a red led, and it works very, very well. But very hard to get it to clip!
Now, we should get back to Thimios' QUASI. How is it with a 47pF on the C to B of the phase inverter? Fix it?
Ciao,
Hugh
Hugh, so its an LTP input stage... now you've got me wondering what that second trimmer is for.
Hugh,i wish you all of the best for your new amplifier,i wish to be best seller!
Testing this amplifier again i can't see the instability.
Can you advice me to a stability test? What is the maximum capacitance pareallel to dummy load where amplifier must be stable?
I prefer not to instal this capacitor yet.
I want to repeat test and see scopes.Something is strange with this amplifier.
Did you had the time to look this in Ltspice?
Go through a range of capacitor from 1nF to 1uF. Remember that ringing of the cap loading through the output inductor is a necessary and unavoidable result.
This test either needs to ignore that ringing or omit the inductor from the test.
It is the amplifier stability margins that you are wanting to examine not the ringing of a C+L load.
You also need a fairly fast, but not instantaneous, step in current/voltage as the test signal. This usually requires that the input filter needs to be crippled/removed/adjusted to pass a fast transient. I typically change the 0.7us input filter to 70ns time constant to see the effect of fast transients. The generator has a 50ohm output and the 1k0 input resistor gets changed to 51r//1k for an effective 100ohms of total RC impedance, giving a 10times faster signal step.
This test either needs to ignore that ringing or omit the inductor from the test.
It is the amplifier stability margins that you are wanting to examine not the ringing of a C+L load.
You also need a fairly fast, but not instantaneous, step in current/voltage as the test signal. This usually requires that the input filter needs to be crippled/removed/adjusted to pass a fast transient. I typically change the 0.7us input filter to 70ns time constant to see the effect of fast transients. The generator has a 50ohm output and the 1k0 input resistor gets changed to 51r//1k for an effective 100ohms of total RC impedance, giving a 10times faster signal step.
If you have time then you should do the following 6x sine wave tests:
1. 1kHz into 10n || 8R
2. 1kHz into 100n || 8R
3. 1kHz into 1u || 8R
4. 20kHz into 10n || 8R
5. 20kHz into 100n || 8R
6. 20kHz into 1u || 8R
This is what I normally do when I'm feeling diligent and when I'm not I just grab a 1uF and test at 1kHz and 20kHz.
1. 1kHz into 10n || 8R
2. 1kHz into 100n || 8R
3. 1kHz into 1u || 8R
4. 20kHz into 10n || 8R
5. 20kHz into 100n || 8R
6. 20kHz into 1u || 8R
This is what I normally do when I'm feeling diligent and when I'm not I just grab a 1uF and test at 1kHz and 20kHz.
Thimios,
Christian's suggested regime is very good; I found most amps tend to lose it at 100nF to 220nF. 2uF I the value of an ELS63, particularly at 20KHz, it's a severe test for ESLs.
The instability is clearly coming from the inverter. I conclude that trying to keep them equal is probably not possible; I always see them different, with the Bax resistor lower than the base to rail on the quasi. Seems to me to be best at 120R Bax, and 150R quasi. I have seen 82R and 120R too.
The 22nF Bax cap is not critical and has now effect on stability. It supposedly simulates the junction capacitance of a driver, but in fact it damps any ringing on the diode as it turns on and off. The stability is always created at the collector of the inverter, and this is why a small miller cap is recommended from C to B.
Thank you for your comments about my new amp. Yes, I hope it will sell well too! I've put a lot of time and effort into it....... but products success or fail on marketing, not so much on excellence!
Ciao,
Hugh
Christian's suggested regime is very good; I found most amps tend to lose it at 100nF to 220nF. 2uF I the value of an ELS63, particularly at 20KHz, it's a severe test for ESLs.
The instability is clearly coming from the inverter. I conclude that trying to keep them equal is probably not possible; I always see them different, with the Bax resistor lower than the base to rail on the quasi. Seems to me to be best at 120R Bax, and 150R quasi. I have seen 82R and 120R too.
The 22nF Bax cap is not critical and has now effect on stability. It supposedly simulates the junction capacitance of a driver, but in fact it damps any ringing on the diode as it turns on and off. The stability is always created at the collector of the inverter, and this is why a small miller cap is recommended from C to B.
Thank you for your comments about my new amp. Yes, I hope it will sell well too! I've put a lot of time and effort into it....... but products success or fail on marketing, not so much on excellence!
Ciao,
Hugh
Hi
There is another way to stabilize the inverter who is not using miller cap C-B.
Bax capacitor could be 390 pf?
There is another way to stabilize the inverter who is not using miller cap C-B.
Bax capacitor could be 390 pf?
Hi, can i build this version ? is it functionally
can i replace IRF840 with irfz44n ?
i want to try an power amp with mosfets, and i own irfz44n ( it is used in power supply i dont know if it's good in audio )
can i replace IRF840 with irfz44n ?
i want to try an power amp with mosfets, and i own irfz44n ( it is used in power supply i dont know if it's good in audio )