Lament for a Tiger
Tiger tiger burning bright,
your output circuit is black as night
Your front end looks great
but its the overall oscillations that we hate
They are, we fear, linked to that Output stage
and that really shows your age
For the culrpit is that common collector
that really screws the transfer vector
We see excess gain and poles galore
and then, just when we thought it safe, even more
no miller capacitor just like Doug told us
this I tell you is why there is a fuss!
So friends, lets ditch this burning design
and go for something a bit more benign.
bonsai
Tiger tiger burning bright,
your output circuit is black as night
Your front end looks great
but its the overall oscillations that we hate
They are, we fear, linked to that Output stage
and that really shows your age
For the culrpit is that common collector
that really screws the transfer vector
We see excess gain and poles galore
and then, just when we thought it safe, even more
no miller capacitor just like Doug told us
this I tell you is why there is a fuss!
So friends, lets ditch this burning design
and go for something a bit more benign.
bonsai
Hi Nordik, have you considered an even older and also simle design on the same page. A single input transistor with quasi output the "Brute 70" design made in 1967
Nice to see the old vintage stuff
http://www.swtpc.com/mholley/PopularElectronics/Feb1967/PE_Feb1967.htm
Nice to see the old vintage stuff
http://www.swtpc.com/mholley/PopularElectronics/Feb1967/PE_Feb1967.htm
CharleyW said:
I've got a 215/A here, yes it is like a Plastic - Tiger .01, dual diff front end, output triple. This amp needs work, anyone have a schematic scanned or know of it online?
Turned out to be one open and one shorted PSU cap, bridge also failed. Fixed all that, it is otherwise fine.
Decided to take a look at the stability and tendency to blow up when the input jacks are inserted or removed hot. Brought it up on a Variac to about half voltage so that the outputs are well within their SOA. Tapped the input terminal with a screwdriver, then with my finger on it. Syncing the scope on the hum, I see about 2 volts of hum on the output, however, there are slivers where the output goes rail to rail. I believe that it is oscillating.
Next drive it with a square wave, then into clipping, the tops and bottom of the square wave become about twice as thick with fuzz on them when in clipping. I believe that it is oscillating here due to the reduced OP stage bandwidth in saturation. I can also see odd behavior on the edges of the square wave, and looking at the VAS I also see bursts of oscillation.
Considering some mods to the circuit to correct this, difficult to do given that there does not seem to be any "normal" method of compensation used in this design.
Anyway, anyone have a schematic scanned to make this a bit easier? I have the Tiger .01 schematic and it is very close, but it would be better to have the actual.
Pete B.
Has anyone fooling with this topology tried the combination of adding the normal Miller compensation and the taking the lead comp from the output of the VAS instead of the outputs? With other high-feedback topologies it has woked well for me resulting in very stable amps. Some of which get used in pro apps where I do swap them hot.
burnedfingers said:
I also have those schematics, thanks anyway.
Have you ever read about the torture tests that Phase Linear used to weed out their design/component issues? Any amp should survive this, it may put out enough noise to fry the speakers, but it should not oscillate or go up in smoke, IMO. I come from Military design where we design for worst case and properly derate parts.
Pete B.
wg_ski said:
hence, the nickname "Flame Linear"...... especially the 700's. i've seen the pc boards after the fact.... not much left........ they were good amps as long as you didn't do anything to them to let the smoke out.....
ever work on an Acoustic Controls 370 bass amp? i rebuilt one 3 times, meticulously replacing EVERY bad component. brought it up s l o w l y on the variac, watching the ammeter for the slightest twitch. at 60V, WHAM!!!, the ammeter slammed, the variac fuse blew, and 4 hours of work went up in smoke. after the third time i told the owner, "sorry, i've rebuilt it 3 times and had it smoke every time". years later i was talking to a tech that specializes in vintage guitar amps, and he made a comment about something being as futile as rebuilding an Acoustic 370. i said "say again?"... he said "ever try to rebuild an Acoustic 370?" i said "yeah, tried to rebuild one 3 times"... he said "i've tried a few times over the years to rebuild them, and i'm convinced there's no way to get one working after it's been smoked".... so i guess i'm not the only one that has had that kind of experience with an amp, where you have to tell somebody it's too far gone to fix....
My bad. Due to some stupid moves I suppose I blew the outputs on one of my amps. I say I suppose because it is blowing the PS fuses. When I measured B to E and B to C the ohmmeter readings were good forward and reverse but as a further measure I checked E to C forward and reverse and found low resistance. Weird. BTW NTE180 and 181 are direct replacements. Mouser has them.
Hi Alfa88 - so do you have an Alfa Romeo? I've had a few.
Please don't use those replacements, the MJ802/MJ4502 are still in
production, why would you use subs? I commented here on the poor
SOA as compared to modern devices:
http://www.diyaudio.com/forums/showpost.php?p=574726&postcount=84
Let me find that schematic and I'll try to scan it for you.
Pete B.
Please don't use those replacements, the MJ802/MJ4502 are still in
production, why would you use subs? I commented here on the poor
SOA as compared to modern devices:
http://www.diyaudio.com/forums/showpost.php?p=574726&postcount=84
Let me find that schematic and I'll try to scan it for you.
Pete B.
I started a new thread with a link to the schematic here: http://www.diyaudio.com/forums/showthread.php?p=1913712#post1913712
Plastic Tiger substitutions
The MPS6566 part is now listed in Ebay for $1.29 ea. plus $3.99 shipping. If you're building 2 channels, you'll need 6. That will be $7.74 + shipping. Hopefully, they will combine shipping for you.
I wonder if the 1122,1123 need to be matched PNP, NPN pairs. If they are then we (yes, I want to try my hand at this too) need to check the specs of the substitutes to be sure that they are well matched.
Have you completed the amps? How did they work? I haven't started on mine yet.
The MPS6566 part is now listed in Ebay for $1.29 ea. plus $3.99 shipping. If you're building 2 channels, you'll need 6. That will be $7.74 + shipping. Hopefully, they will combine shipping for you.
I wonder if the 1122,1123 need to be matched PNP, NPN pairs. If they are then we (yes, I want to try my hand at this too) need to check the specs of the substitutes to be sure that they are well matched.
Have you completed the amps? How did they work? I haven't started on mine yet.
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