Hi, I've been trying to find a good transistor set, for old Pass's design, http://www.firstwatt.com/pdf/art_classa_20.pdf.
And I've gotten somewhere with it in my simulation but it seems that my configuration is either doesn't have proper substitute transistors, there could be a design flaw or unreliable simulation setting.
I could use some help getting further with the design but I'm stuck figuring out where to go next.
MPSL01 = 2N5550
RCA1A16, RCA1A15 = MJE15030G, MJE15031G
2N5877 = 2N6341G
PS.
If anyone knows where to get 2n5877 SPICE model somewhere that would be great, but at the moment I don't know how to make one for it my self.
And I've gotten somewhere with it in my simulation but it seems that my configuration is either doesn't have proper substitute transistors, there could be a design flaw or unreliable simulation setting.
I could use some help getting further with the design but I'm stuck figuring out where to go next.
MPSL01 = 2N5550
RCA1A16, RCA1A15 = MJE15030G, MJE15031G
2N5877 = 2N6341G
PS.
If anyone knows where to get 2n5877 SPICE model somewhere that would be great, but at the moment I don't know how to make one for it my self.
If you are using LTspice then if you fancy posting what you have (the .asc file) then we could take a look using other devices.
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Unfortunately its in multisim file. I should probably use other simulation tool than multisim? Or is it just a preference.
Unfortunately its in multisim file. I should probably use other simulation tool than multisim? Or is it just a preference.
I suppose its just a preference, what you have got used to using really. I'm afraid I've never used Multisim but perhaps someone who has can help out. The basic circuit doesn't look as though it should be critical on semiconductor models.
What is it doing, not doing?
The plan is straightforward. For simulation, the exact transistors are probably not critical. It sure should come to a DC solution even if the huge POWER transistors are faked with tiny 2N2222. (My sim does not complain when I put 50 Watts in a quarter-Watt part...)
The plan is straightforward. For simulation, the exact transistors are probably not critical. It sure should come to a DC solution even if the huge POWER transistors are faked with tiny 2N2222. (My sim does not complain when I put 50 Watts in a quarter-Watt part...)
Attachments
How would one advance in faking a power transistor in LTspice from 2n2222 or any other transistor for that matter. Damn I gotta get a hold on this program more.
Bob Cordells excellent book 'Designing Audio Power Amplifiers' has several chapters devoted to LTSpice and there is a detailed description on creating basic spice models.
This (attached) list of Bobs own models will cover 95% of generic audio circuits such as yours. The MJL21194/3C complementary pair seem suitable candidates.
Also search for Ian Hegglun's excellent lateral FET models.
This (attached) list of Bobs own models will cover 95% of generic audio circuits such as yours. The MJL21194/3C complementary pair seem suitable candidates.
Also search for Ian Hegglun's excellent lateral FET models.
Well, technically doing fine and dandy but after Q5 the signal is incoherent mess.
I've been trying using
Q4 is a MJE15031G and Q5,6,7 MJE15030G.
If these don't lead me forward I'm checking next
D44H11 / D45H11.
So I'm not stuck on getting the signal to pass from the OPamp to end-stage to be finally amped up.
I've been trying using
Q4 is a MJE15031G and Q5,6,7 MJE15030G.
If these don't lead me forward I'm checking next
D44H11 / D45H11.
So I'm not stuck on getting the signal to pass from the OPamp to end-stage to be finally amped up.
Oh jeez..
Well firstly I've been using wrong voltage apparently. I had been using 14V volts, instead of 20V, that figures.
One transistor was not oriented correctly...
Well firstly I've been using wrong voltage apparently. I had been using 14V volts, instead of 20V, that figures.
One transistor was not oriented correctly...
I'm just reading Nelsons write up on this and that shows a 14-0-14 volt transformer which would actually give around -/+20 volts dc if we ran it at near to its continuous VA output rating.
I've set the preset as per the instruction and that gives a current of just over 800ma in each output pair. Driver current is nearly 500ma giving around 10 watts dissipation in the little drivers
but hey, this is LTspice with the indestructible transistors.
This is where using more suitable (hi beta) devices for drivers and outputs would pay dividends.
Also the bias preset is incredible critical in simulation. This shows the result of going from 1k45 to 1k47. I wonder if the real build is as critical and behaves like this ?
I've set the preset as per the instruction and that gives a current of just over 800ma in each output pair. Driver current is nearly 500ma giving around 10 watts dissipation in the little drivers
but hey, this is LTspice with the indestructible transistors.This is where using more suitable (hi beta) devices for drivers and outputs would pay dividends.
Also the bias preset is incredible critical in simulation. This shows the result of going from 1k45 to 1k47. I wonder if the real build is as critical and behaves like this ?
Attachments
Yes, that is how it works out. This amp simulation seemed to clip at around 15 volts peak into 8 ohms so DC=AC x 1.25 holds true.
what I meant is for PSU
example - classic FW PSU is 18Vac secondaries , giving approx. 22V5dc at caps
example - classic FW PSU is 18Vac secondaries , giving approx. 22V5dc at caps
Try it for current as well 😉
15 volts, 8 ohms is approx. 1.9 amps peak. Multiply by 1.25 and we get 2.375 amps.
Bias current adjusted as per Nelsons method worked out at a shade under 800ma per pair. So 3 pairs equals 2.4 amps.
Near enough for Jazz 😉
15 volts peak into 4 ohms is around 3.8 amps peak. Bias now 1.42 amp per pair.
So 3.8*1.25 is 4.75 and 1.42 * 3 is 4.26.
Its sort of in the right ball park.
15 volts, 8 ohms is approx. 1.9 amps peak. Multiply by 1.25 and we get 2.375 amps.
Bias current adjusted as per Nelsons method worked out at a shade under 800ma per pair. So 3 pairs equals 2.4 amps.
Near enough for Jazz 😉
15 volts peak into 4 ohms is around 3.8 amps peak. Bias now 1.42 amp per pair.
So 3.8*1.25 is 4.75 and 1.42 * 3 is 4.26.
Its sort of in the right ball park.
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