100W Ultimate Fidelity Amplifier

[keantoken]

Those Sankens you mention look incredible from the datasheet. If they are a little slower than the 1837/4793, they will still have a linear gain region 10 times larger and a larger SOA. I really want to try some of those, it would be nice to do a group buy from Ten Four LTD.

The MJE parts may be comparable but they will be much slower, with much higher capacitance. The 4883/1859 would be very difficult to substitute.

Speaking of which, here are some SPICE models I created for them. I can't say how accurate they really are because I guess on a lot of parameters. But I think Cje and Cjc are accurate as I used them to fit Ft data. Hfe is an approximation as the model seems incapable of producing the curves on the datasheet - whether this is the fault of the datasheet or the model I do not know. I am hoping that my VAF estimates are very pessimistic.

.MODEL 2SC4883A_k npn (IS=725f BF=114 NF=1
+ VAF=40 IKF=2.25 ISE=7e-11 NE=10 BR=1.97064 NR=1.50008
+ VAR=22.902 IKR=35.9467 ISC=4.75e-12 NC=3.59375 RB=7.5 IRB=0.1
+ RBM=0.1 RE=0.0001 RC=0.130733 XTB=0.337319 XTI=1.40625
+ EG=1.31 CJE=1n VJE=0.651779 MJE=0.35303
+ TF=1.2n XTF=1.35721 VTF=0.995654 ITF=1 CJC=90p
+ VJC=0.429208 MJC=0.35114 XCJC=0.803125 FC=0.533449 CJS=0
+ VJS=0.75 MJS=0.5 TR=85n PTF=0 KF=0 AF=1)
.MODEL 2SA1859A_k pnp (IS=600f BF=148 NF=1
+ VAF=30 IKF=6 ISE=4.79702e-14 NE=4 BR=1.96197 NR=1.29503
+ VAR=23.2874 IKR=9.99625 ISC=4.79702e-14 NC=3.59375 RB=6.5
+ IRB=0.108633 RBM=0.101928 RE=0.000100027 RC=0.122304
+ XTB=0.137608 XTI=1.0316 EG=1.32 CJE=1.495n VJE=0.651747
+ MJE=0.353069 TF=1.7n XTF=1.35721 VTF=0.99569 ITF=0.999994
+ CJC=68p VJC=0.42654 MJC=0.24282 XCJC=0.803125 FC=0.533457
+ CJS=0 VJS=0.75 MJS=0.5 TR=188.8n PTF=0 KF=0 AF=1)

- keantoken

 

[Kei]

Good to know that those sanken parts should be ok. I've had a slight redesign of the PCB so that it matches the schematic for the AX-20 protection circuit. I've also noticed that there is a PA protection circuit called the H900 that may also be used. There are too many options and i lack the knowledge/experience to know which is best.

anyway this is how the pcb design looks now. (should be an exact match for the schematic now)

 

[mihailo]

With +/-50V you can use: MJE15030/MJE15031; MJE15032/MJE15033; 2SC2073/2SA940 I had use 2SC2073/2SA940 and it works perfect.
Regards

 

[apexaudio]

AX14P

AX14 with DC and overload protect

 

[Kei]

If i incorporate the changes you've made to that AX14 design into the AX20 will that negate the need for the extra protection board like the H900/PSU-7?

Been looking at suitable transformers today, what would the maximum input voltage be for the AX20? I've been looking at 50-60Vx2, 500-1000VA transformers. (or potentially running a 25-30V transformer with the outputs in series to double the voltage.) Would it be better to use the 50-60V transformer and have 2 separate rectifying/filtration boards or a single board using the series wiring of the secondary windings? (I reckon the separated supplies myself just want to be sure)

 

[apexaudio]

If i incorporate the changes you've made to that AX14 design into the AX20 will that negate the need for the extra protection board like the H900/PSU-7?

Been looking at suitable transformers today, what would the maximum input voltage be for the AX20? I've been looking at 50-60Vx2, 500-1000VA transformers. (or potentially running a 25-30V transformer with the outputs in series to double the voltage.) Would it be better to use the 50-60V transformer and have 2 separate rectifying/filtration boards or a single board using the series wiring of the secondary windings? (I reckon the separated supplies myself just want to be sure)

If you incorporate the changes into AX20 PSU (+/-60V) is only that you need.

 

[Kei]

OK, greatly appreciate the guidance here. This is how the schematic has come out.

I've got so far with a rough construction of the pcb but got lost at the relay. I've circled the two bits that have got me slightly lost.

 

[apexaudio]

Schematic of AX20P is OK, but you have lot of work on pcb, maybie 'alex mm' can help you 🙂

 

[smartx21]

Schematic of AX20P is OK, but you have lot of work on pcb, maybie 'alex mm' can help you 🙂

Oh! That would be great!!!😛

 

[Kei]

Yes I think a more experienced PCB designer is needed here. I've got the AX20P schematic drawn up in Livewire and the basic version without protection drawn up in ExpressSCH if it helps.

 

[emmi]

To Mile

Can i use 2n3773 for the output stage(quasi-complementary) for this ax-14 amp

then voltage will be limited to how many volts for two pairs??

 

[emmi]

Can i use 2n3773 for the output stage(quasi-complementary) for this ax-14 amp

then voltage will be limited to how many volts for two pairs??

Can i use 2n3773 for the output stage(quasi-complementary) for this ax-14 amp

 

[apexaudio]

Can i use 2n3773 for the output stage(quasi-complementary) for this ax-14 amp

I suggest http://www.diyaudio.com/forums/solid-state/167394-quasi-amplifier-beginners-56.html for 2N3773

 

[mihailo]

Finally pictures of my AX-14.

 

[mihailo]

Also AX-14 with 2 pair of output transistors. Can I use this on 80w/4ohm speaker, for PA or I need to add more outputs? It is working on +/-35V DC and bias is 60mA.

 

[44250]

What output transistors are those in AX14 (with two pair of output transistors)?

 

[jacco vermeulen]

BD911/912

 

[mihailo]

Those transistors are BD249C/BD250C (100V, 25A, 125W)

 

[apexaudio]

Also AX-14 with 2 pair of output transistors. Can I use this on 80w/4ohm speaker, for PA or I need to add more outputs? It is working on +/-35V DC and bias is 60mA.

AX14 working on +/-35V can be use with 4 ohm speaker with single pair of output transistors, with 2 pair can be use on 2 ohm speaker but need fan cooling.

 

[44250]

What would be benefit of using two pair of output transistors (mjl21193/21194) and +/-50VDC supply? No doubt in sound quality,what power could be reached with 4 and 8 Ohm load?