Sound Quality Vs. Measurements

[tvrgeek]

What do folks think about KSA916/ for drivers, KSA992/ for IPS ?
I saw both listed as obsolete, but the Farichild site says full production.

[ThorstenL]

Hi,

Originally Posted by tvrgeek

Matched single die pairs seem to be smt and very low power.

Why not a LSK389 with zenners (to extend voltage rating) in the drain leads?

Originally Posted by tvrgeek

Is it considered safe to use 40V transistors in the IPS CM and input pair with 55V rails?

The current mirror is clamped. The input pair in it's own way too. It cannot see more than the positive rail voltage.

Ciao T

[SoNic_real_one]

Originally Posted by tvrgeek

Confusing, a BC550 is rated at 45V, a BC559 at 30, a BF469 is 250. Don't see a trend.

IThose BC are different families (doping levels). They start as different processes (same line).
Family is: http://www.datasheetcatalog.org/data...hild/BC547.pdf
BF family are definetelly different geometry...

[dvv]

Originally Posted by SoNic_real_one

All the BC family is selected in the same way, starting with BC107,108,109 continuing with 171,172,173... etc. Numbers for voltage, letters (A, B, C) for NF.
You can test non-destructive the inverse Base-Collector voltage with one 2-4 Mohm resistor series...

With BC types, A, B and C refers to gain group, not voltage, as it does on some BD types, e.g BD 249/250 - A=60V , B=80V, C=100V, D=120V, etc.

[dvv]

Originally Posted by tvrgeek

Not tried CSD on the amp yet. SoundEasy has this. Very powerful, but he uses the first law of Madison Av. "Take your worst attribute and advertise it" Easy it is not. I too have the emu-1616. It's input impedance on line is very low, so I had to build a buffer for the voltage divider type probes.

I was scanning through a few hundred pages of comments looking for favorite transistors that can still be bought. BC5550, 2SC970 etc. I have quite a list of low power I gleaned off various catalogs and forum comments, but not much on medium or output types, and almost nothing of FET's. A few comments of favorites and why would be helpful as a jump start.

Matched single die pairs seem to be smt and very low power. THAT has a few but they don't seem to be very tightly matched, more a packaging advantage.

A lot of the "prefered" parts are lower voltage. Most of the parts in the DH-120 for example, don't see very high voltage in operation, but I am not sure about power up and down. Is it considered safe to use 40V transistors in the IPS CM and input pair with 55V rails? Do you just figure to lose them if a rail fuse blows or some other hic-up? There seem to be very few in the 120 V range as that pushes you to the higher power devices, i.e. larger die and all that entails. KSA916 maybe?

For low power but high voltage, consider BC 639/640 - not unlike MPSA 56/06, only higer Ft.

For even more voltage, think of 2N5551/5401 from Philips, these are rated at 150 Mhz, 160 V.

For high voltage and medium power, look at BF 471/472.

For high voltage and linearity like you wouldn't believe, take alook at medium powered BF 720/721 (they sell them at Farnell); the only caveat is the SOT-223 packaging, which si for SMT, so soldering tehm manually is a little more difficult than normal, but WELL WORTH the trouble. You could find that your open loop full power gain THD at 20 kHZ suddenly halves.

For medium power, the venerable old BD 139/140 set is still hard to beat, and you may want to look for them with extensions, like "-10" and "-16", indicating higher gain classes.

In the 30-50W class, it's no contest - Motorola's MJE 15030/15032 take the first prize. They are 160V, but there are lower and higher voltage versions.

[ThorstenL]

Dejan,

Originally Posted by dvv

For low power but high voltage, consider BC 639/640 - not unlike MPSA 56/06, only higer Ft.

For even more voltage, think of 2N5551/5401 from Philips, these are rated at 150 Mhz, 160 V.

For high voltage and medium power, look at BF 471/472.

For medium power, the venerable old BD 139/140 set is still hard to beat.

There are Japanese alternatives in all cases that are MUCH better suited.

I admit also to overusing European discrete's when there better japanese alternatives, but I'm learning. Especially BD139/140 are positively stone-age.

Ciao T

[bcarso]

Originally Posted by abraxalito

Have a look at this and give consideration to where the diode strings of your cascode reference terminate:

http://www.essex.ac.uk/csee/research...%20cascode.pdf

<edit> Also Samuel Groner has things to say about current mirrors:

SG-Acoustics · Samuel Groner · Power Amplifiers

Taking nothing (or at least not much) from MOH, in this case he missed prior art by about 20 years; but his detailed analysis and bringing the bootstrapped cascode and other topologies to the attention of the audio community is still appreciated. The first occurence I've found of the BC is from Aldridge, who applied the basic base current feedback back into the "lower" emitter to telephony amplifiers in 1962, in the first case to common-base stages; right after that an associate applied it to a topology where the first device is operated common-emitter with local feedback, which is now known as the MOH cascode. I discovered this recently and wrote of it in one of the Baxandall super-pair threads in here.

So it properly should be called the Aldridge cascode, not the Hawksford cascode. It is analogous to the other Hawksford topology with the complementary devices, the also-misnamed Larson/Baxandall-Swallow pair, invented and patent-applied-for by Frank Boxall in 1957 when he was an employee of Lenkurt, before he moved to HP.

Of course I am not suggesting that any of the later art was cribbed from the prior. The patent office missed Boxall when they granted Larson his patent (when he was at Tektronix, where it was called the super-alpha, according to John Addis), and Baxandall missed Boxall as well (he couldn't have known of Larson, as his piece applying the folded complementary pair to a current source, which has become eponymous as the Baxandall super-pair, was written while Larson's patent was under examination).

It's hard to do anything new!

Brad

[bcarso]

Originally Posted by ThorstenL

There are Japanese alternatives in all cases that are MUCH better suited.

And how!

[john curl]

T and bcarso are certainly correct.
The Japanese, at least up to now, have had a much better assortment of bipolar transistors and jfets, than either USA or Europe. Unfortunately, many really good devices (for audio) have been discontinued, leaving us to scramble to find nearly equal alternatives from what is still made.
Tvr's questions are virtually 'scary'! Please learn what voltage breakdown means with a bipolar transistor before applying one in a new situation. Learn what Vceo, Vcb, and Veb mean, and memorize their meanings. Remember, you usually don't have a second chance if you avalanche the transistor, and you MUST study the SAFE AREA of each and every power bipolar transistor, and please note that they are often expressed in LOG-LOG and are difficult to interpret casually without 'uncompressing' them by re-graphing or by very close study.
The best way to learn this is to study a series of data sheets (long form) from a major manufacturer, one after the other, to see the tradeoffs that are made for specific tasks. The best that I can personally recommend is to go to a used bookstore or the internet to get a 30-40 year old, or so Motorola Semiconductor Handbook, or one from another major manufacturer from that era, BEFORE home computers became available, and this was the only way to get the information necessary to design with a specific part. For example, you can find the 2N5551 bipolar transistor there with 5 pages of graphs and charts on that part ALONE. What a goldmine! All I can do is to suggest. '-)

[ThorstenL]

Hi,

Originally Posted by bcarso

The first occurence I've found of the BC is from Aldridge, who applied the basic base current feedback back into the "lower" emitter to telephony amplifiers in 1962, in the first case to common-base stages

Pentodes date to the late 1920's IIRC and are basically hawkesford cascodes as their screen grids are (for AC) returned to the cathode in almost all cases (occasionally they are connected like ordinary cascodes, but that was considered bad practice in the 1930...

Cascoded triodes are probably as antique and usually also feature the AC return to the cathode.

Originally Posted by bcarso

It's hard to do anything new!

Indeed.

Ciao T