Quad 303 triple cascade

[tiefbassuebertr]

This I have archived in my own file system:

[hahfran]

Originally Posted by tiefbassuebertr

Only truly experienced (and unfortunately very few) developers (like Quad) achieve a design of such triple stages without any oscillation under any load condition.



I want to have basic articles about such three stage super ß quasi complementary stages. Who knows more about this?

.

Check out the thread Class B w/o crossover distortion.
The Vish topology discussed is a derivate of the Quad 303 and has very nice properties but also some catastrophic disadvantages.
These are avoided in Quad 303 as the Rush cascode has current feedback to the emitter but at the expense of crossover distortion.
However each Quad triple cascade can be made always conducting and be still class B if one places a fast switching phase splitter in front of the two triples. If the switch switches at exactly zero-cross of the signal that would yield a perfectly stable crossover-distortion free class B amp.

[tiefbassuebertr]

Originally Posted by tiefbassuebertr

About this address perhaps there is a complete Equa schematic available:
Audioclub Oost Brabant, clubavonden

I want to have basic articles about such three stage super ß quasi complementary stages. Who knows more about this?

I know too few English keywords therefore. I recall, that I have read some years ago a JAES article. But I don't know if it was the main topic.

In the meantime I have find this:
QuadTriple, Harman's T-Circuit, Triple Cascade, Elektor's EQUIN
Class B w/o crossover distortion (1975)
Harmans T-Circuit: "An Ultra-Low Distortion Direct-Current Amplifier" from the author
BART N. LOCANTHI (James B. Lansing Sound, Inc.)
http://www.harman.com/EN-US/OurCompa...tions/1091.pdf
Quad 303 triple cascade (post #21)
EQUA-Verstaerker HiFi Verstaerker bis 100W - 1972, december, page 1216
Von DIN zur EQUA-Norm Normen fuer HiFi Anlagen - 1972 december, page 1215
but actually there must be more - thank you for additional advices.

[hahfran]

Attached find an interesting amp which I designed with LTSpice.
The design objectives were:
1.) the harmonics spectrum should stay constant ( that is the relations of the amplitudes of h2 to h3...h9, h3 to h4..h9 etc) in db independent of frequency from 20 hz to 6000 hz
2. the harmonics spectrum should be constant from 1% to 90 % of full power
3. the harmonics spectrum should be independent of reactive ( i.e. complex) load

This amp has little overall feedback. The thd is not at all low, in fact it is about 0.3% but objectives 1 to 3 are met. I have been testing with various speaker models, also 4 way with complicated crossover, and electrostatic midrange/tweeter. In simulation, it works.
The really built amp, tested with a spectrum analyzer , matches the Spice sim
closely but has in fact less thd about 0.15% . The sonic quality reminds vividly of good to very good tube / triode amps.

Hans Dieter

[tiefbassuebertr]

Originally Posted by hahfran

Attached find an interesting amp which I designed with LTSpice.
The design objectives were:
1.) the harmonics spectrum should stay constant ( that is the relations of the amplitudes of h2 to h3...h9, h3 to h4..h9 etc) in db independent of frequency from 20 hz to 6000 hz
2. the harmonics spectrum should be constant from 1% to 90 % of full power
3. the harmonics spectrum should be independent of reactive ( i.e. complex) load

This amp has little overall feedback. The thd is not at all low, in fact it is about 0.3% but objectives 1 to 3 are met. I have been testing with various speaker models, also 4 way with complicated crossover, and electrostatic midrange/tweeter. In simulation, it works.
The really built amp, tested with a spectrum analyzer , matches the Spice sim
closely but has in fact less thd about 0.15% . The sonic quality reminds vividly of good to very good tube / triode amps.

Hans Dieter

The VAS stage looks like Lender's circuit
The most linear stage for large voltage swings - Lender's Circuit
What about R26/28? Why are this connect to the supply rails instead the output line?

In general there is no justify to make such complicated topology (my experience). My favorite design is that one from the links by post #13 about
Anybody have scan of AN-483B (Motorola)?
in an optimized version
If you have build both topologies in high quality standart you will not able to say, which of them is clearly better - for this I am quite sure.
A great disadvantage of your topology is the DC coupling of the speaker and therefore an relais contact in series to the speaker wire for DC protect.

[hahfran]

Connecting R26/28 to output has negative influence on OLG as well as on open loop cutoff frequency and thus violates design objective.

Btw the insensitivity to reactive load comes at the expense of damping factor
which is independent of frequency but quite low about 100.

Also btw with a symmetric input the design objectives are not met. The 2N5196
has two jFET on one chip and hence low temperature drift and almost identical
charcteristics there is no pFET available with such properties.

[tiefbassuebertr]

Originally Posted by tiefbassuebertr

In the meantime I have find this:
QuadTriple, Harman's T-Circuit, Triple Cascade, Elektor's EQUIN
Class B w/o crossover distortion (1975)
Harmans T-Circuit: "An Ultra-Low Distortion Direct-Current Amplifier" from the author
BART N. LOCANTHI (James B. Lansing Sound, Inc.)
http://www.harman.com/EN-US/OurCompa...tions/1091.pdf
Quad 303 triple cascade (post #21)
EQUA-Verstaerker HiFi Verstaerker bis 100W - 1972, december, page 1216
Von DIN zur EQUA-Norm Normen fuer HiFi Anlagen - 1972 december, page 1215
but actually there must be more - thank you for additional advices.

The URL about Harmans T-Circuit: "An Ultra-Low Distortion Direct-Current Amplifier" from the author
BART N. LOCANTHI (James B. Lansing Sound, Inc.)
http://www.harman.com/EN-US/OurCompa...tions/1091.pdf
is death. Here the currently URL:
http://www.aes.org/tmpFiles/elib/20110325/1091.pdf

[WuYit]

The author would have tremendous difficulty explaining the purpose of R23 in post #12.

[tiefbassuebertr]

in this case this thread is also of interest:
Groner Triple

[tiefbassuebertr]

The URL fom post #27 (Harmans T-Circuit) is death again. Here the currently URL:
http://www.aes.org/tmpFiles/elib/20120704/1091.pdf