The Frugalamp by OS

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danielwritesbac

danielwritesbac

Member
Joined 2007
startfetch.com
ostripper said:
. . .
I would like to go the "quasi" route and just use 6-8 NPN
IRF 250's to get my 300W.. it might even stay "frugal" with
that arrangement..
OS
Click to expand...

Oh, yes. On the same "station" here!

Most heavy duty speaker drivers get facefirst on fidelity at 400w@8R or 800w@4R, so that sort of scale represents something that's more significant than an increment.

It looks like FA1 will have as much power as I need for personal use. My speakers don't scale farther. Its simpler to stack more speakers and amps when needed.

Will let you know how it does, after the shopping is done. I found everything except that LED. Isn't that silly? Can't find it. ;)
 
G

GK

Disabled Account
Joined 2006
Those junk SPICE models for the ON Semi driver transistors make any attempt to sim a high power BJT output stage a waste of time. Don't trust that a real circuit will oscillate with these MJE150XX's just because the simulator say so.

Cheers,
Glen
 
jaycee

jaycee

Member
Joined 2004
What about the Fairchild FJP5200/FJP1943 transistor? This is a TO-220 version of their FJL4315/FJL4215 (2SC5200/2SA1943 clones). It looks suitable for driver use.

My experience is that Fairchild's models are generally pretty good, so maybe it is worth simming with their driver and outputs.
 
ostripper

ostripper

Member
Joined 2008
Yes ,JC, they look good ,but WTF:mad: no models. Fairchild
sucks in this way, they have good models for some but are
very incomplete in their listing. They want us to buy their
$#$T ,but don't even supply us with adequate design
resources...ARggg:mad:

Maybe I could just use the FJL4315/FJL4215 models,
but those junctions are way larger with more Cob
so that would put me off the mark for starters.:(

OS
 
MJL21193

MJL21193

Disabled Account
Joined 2007
ostripper said:
Is there better.. please advise...

I haven't made my next order yet..
so I have no problem going japanese..:D
OS
Click to expand...


Hi OS,
I recommended the 2SC4793/2SA1837 before. These are fast and cheap Toshibas. Andy_C did a model pair for these.

Also, I use these models for the MJE15030/31. They seem to work well:

.MODEL MJE15031 pnp
+IS=7.17489e-11 BF=457.169 NF=1.11376 VAF=6.01557
+IKF=0.345808 ISE=1e-08 NE=2.18567 BR=0.247882
+NR=1.39549 VAR=60.1557 IKR=0.0263893 ISC=1e-16
+NC=2.89486 RB=2.29208 IRB=0.0114006 RBM=0.000102795
+RE=0.00815557 RC=0.0407779 XTB=0.1 XTI=0.1
+EG=1.05 CJE=1.64037e-09 VJE=0.819491 MJE=0.537987
+TF=1.60991e-09 XTF=180.82 VTF=1.16561 ITF=6.50499
+CJC=4.82516e-10 VJC=0.4 MJC=0.374287 XCJC=0.786653
+FC=0.712788 CJS=0 VJS=0.75 MJS=0.5
+TR=3.32795e-08 PTF=0 KF=0 AF=1


.MODEL MJE15030 npn
+IS=3.894e-11 BF=312.524 NF=1.0979 VAF=9.9963
+IKF=0.796201 ISE=2.37397e-09 NE=1.94897 BR=0.14246
+NR=1.64791 VAR=99.9749 IKR=0.00539895 ISC=2.33175e-09
+NC=2.79024 RB=267.202 IRB=9.99994e-13 RBM=0.299835
+RE=3.04316e-05 RC=0.252928 XTB=0.1 XTI=3.92812
+EG=1.05 CJE=2.42998e-09 VJE=0.794171 MJE=0.569313
+TF=1.87986e-09 XTF=1000 VTF=1835.34 ITF=270.188
+CJC=2.43127e-10 VJC=0.4 MJC=0.361453 XCJC=0.802892
+FC=0.8 CJS=0 VJS=0.75 MJS=0.5
+TR=9.86194e-06 PTF=0 KF=0 AF=1


I can't remember where I got them from.
 
ostripper

ostripper

Member
Joined 2008
By MJL - I recommended the 2SC4793/2SA1837 before
Click to expand...

Do you have those,since you use them, already have the mje's
I'm moving on to MOSFET's ,they are killer...:cool:
But I still want the fast drivers...

Now I will do the "Beast"... (attached)
OS
 

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MJL21193

MJL21193

Disabled Account
Joined 2007
ostripper said:


Do you have those,since you use them, already have the mje's
Click to expand...


Those are the same models for the MJE's you have Carlo...er, I mean OS? :D

The models for the 4793/1837 are:

.MODEL 2SC4793 NPN
+ IS=1.8E-09 NF=1.43 BF=146.38 VAF=273 IKF=2.6
+ ISE=6.286997E-10 NE=2.223629 BR=4 NR=1
+ VAR=20 IKR=1.05 NK=0.95
+ RE=0 RB=1.7 RC=1.25 CJE=5.96964E-10 VJE=1.1 MJE=0.5
+ CJC=5.78E-11 VJC=0.3 MJC=0.3 TF=1.22678E-09 FC=0.5
+ ITF=10 XTF=99.52253015 TR=.983e-06

.MODEL 2SA1847 PNP
+ IS=2.39372559E-10 NF=1.304015937 BF=300 VAF=273
+ IKF=2.087725944 NK=0.94719458 ISE=1.46829699E-11
+ NE=1.526663542 BR=4 NR=1 VAR=20 IKR=1.05
+ RE=0 RB=1.8 RC=1.65 CJE=4.7407E-10
+ VJE=1.1 MJE=0.5 CJC=8.6700E-11 VJC=0.3 MJC=0.3
+ TF=1.642191E-09 FC=0.5 ITF=1.076260106
+ XTF=5.868994022 TR=1.38e-06
 
jaycee

jaycee

Member
Joined 2004
ostripper said:
Yes ,JC, they look good ,but WTF:mad: no models. Fairchild
sucks in this way, they have good models for some but are
very incomplete in their listing. They want us to buy their
$#$T ,but don't even supply us with adequate design
resources...ARggg:mad:
Click to expand...

They do have models... they will only email them to you instead of download, but they have them.

AS they stand, they're a subcircuit which models both the transistor and the thermal parameters, but it is trivial to change it to a straight transistor model. Here you go:

.MODEL FJP5200 npn (
+ IS = 1.24896E-10 BF = 220.2 NF = 1
+ BR = 1.025 NR = 1.0 ISE = 2.04807E-8
+ NE = 2.0 ISC = 2.01764E-9 NC = 1.5
+ VAF = 188.7 VAR = 100 IKF = 5.2182
+ IKR = 1.39087 RB = 22.1 RBM = 0.00011
+ IRB = 1.51189E-6 RE = 0.0032 RC = 0.0183
+ CJE = 1.132025E-10 VJE = 0.711 MJE = 0.304
+ FC = 0.5 CJC = 6.88229E-10 VJC = 0.84
+ MJC = 0.25 TF = 5.1703E-9 TR = 3.342E-7
+ XTB = 1.72 EG = 0.78 XTI = 3)

.MODEL FJP1943 pnp (
+ IS = 6.04896E-11 BF = 200.2 NF = 1
+ BR = 8.805 NR = 1.0 ISE = 8.24807E-9
+ NE = 2.0 ISC = 4.01764E-10 NC = 1.5
+ VAF = 18.7 VAR = 20 IKF = 2.2182
+ IKR = 0.19087 RB = 1.1 RBM = 0.000011
+ IRB = 1.51189E-9 RE = 0.00611 RC = 0.0103
+ CJE = 1.132025E-10 VJE = 0.711 MJE = 0.304
+ FC = 0.5 CJC = 6.88229E-10 VJC = 0.84
+ MJC = 0.25 TF = 5.3703E-9 TR = 3.342E-7
+ XTB = 2.28 EG = 0.81 XTI = 3)
 
ostripper

ostripper

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Joined 2008

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jaycee

jaycee

Member
Joined 2004
Go to the actual product page for the device in question. If they have a model for the device, there will be a link "Models" in the Contents section of the page.

My guess is they maintain the models page by hand, and they havent updated it - a stupid thing to do, but well there you go :)
 
jaycee

jaycee

Member
Joined 2004
Got a few ideas after looking at your FA3:

Q8/Q11 dont have to dissipate much power - you could use KSA992/KSC1845 there instead. Then make Q9/Q10 the KSA1220/KSC2690's instead.

How about changing the mirror Q6/Q7 into a Wilson mirror ? Normally Q6 dissipates about 2mW and Q7 around 200mW which could unbalance it.. in a Wilson mirror the power would be dissipated in the 3rd transistor but this wouldn't affect the mirror's balance.

Personally I'm still diddling with my Cyrus input stage affair. The KSC1845/KSA992 have actually improved things a lot. My guess is speed is important in the input stage, the Cyrus One used very fast small signal devices (200MHz fT) here and in the VAS.

Who knows what i'll end up with though!
 
jaycee

jaycee

Member
Joined 2004
Hehe yeah I saw that and wonder if you'd seen the Marantz 300DC schematic like I have :)

I'm wondering if the diamond buffer would be better applied as a predriver stage - see this for example:

http://home.no.net/andiha/articles/audio/claclassa.htm

He calls the amplifier "Classical Class A" but really it's Class AB heavily biased. Incidentally the designer of that amp is using the same 2SA872/2SC1775 as the Cyrus 1 does.
 
A

AndrewT

R.I.P.
Joined 2004
jaycee said:


I'm wondering if the diamond buffer would be better applied as a predriver stage - see this for example:

http://home.no.net/andiha/articles/audio/claclassa.htm

He calls the amplifier "Classical Class A" but really it's Class AB heavily biased. Incidentally the designer of that amp is using the same 2SA872/2SC1775 as the Cyrus 1 does.
Click to expand...
this is a real ClassA amplifier.
25W into 8r0 if biased to >=1.25A
and 30W into 6r0 if biased to >=1.6A

He does explain that it goes into ClassAB if the ClassA output current is exceeded and quotes 2r0 use to support his reliability claims of the design.
 
ostripper

ostripper

Member
Joined 2008
By JC - I'm wondering if the diamond buffer would be better applied as a predriver stage - see this for example
Click to expand...

Yes,yes ,yes...a wonderful predriver stage.. :D
After reading about the diamond buffer,dissecting the "krill"
i have been won over to this technique. Steve dunlap explained
it to me very good but after playing with it, I wanted to
go solo (more like the marantz dc300).
An externally hosted image should be here but it was not working when we last tested it.


This arrangement differs from the krill in 3 ways , 1. use of
a standard Vbe and 2 diodes bootstrapped (like the marantz)
2. Full global NFB instead of VAS only (eliminates CCS's
for the diamond (also like the marantz) 3. Use of the wonderful
input stage of the FA3.

This one has been fun to Simulate :) :cool: and performs better
than any I've done yet.. Very strange loopgain ,flat with
no "hump" at the end like a blameless or P3A type topology.

I first tweaked an isolated "krill" type current stage
to get rid of oscillations (fast newer devices) then
realized any VAS could be attached (used mine).
The only question that remains is feedback.. Does the
original Current stage without feedback or associated
influence from the dynamic speaker load make for a
better sound than a global NFB arrangement.

Even with steve's current sources improved with IC's(lm234z)
the global feedback version (above) does better
distortion wise. The marantz (more like mine is highly regarded
for it's sound..so I guess I'll have to build it to find out..
OS
 
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