Phase Splitters

[acorn]

Hi all

What in the panels view would would be the best phase splitter to use, baring in mind the need to obtain the best possible sound together with a very low distortion figure.

Acorn

[pre65]

Hi Acorn-not an answer as such !

Am i to believe that a phase splitting transformer is preferable to the usual valve solution ?

Philip

[pre65]

Hi- Found this site with a listing of the different types of phase splitter with a list of pros and cons for each type.

http://www.bonavolta.ch/hobby/en/audio/split.htm


Philip

[Ianm2]

very interesting, philip, there is a way of making the top one more linear using capacitors, some american amps used it back in the 50s, but I couldn't find much info. on it. scott I think

its dead easy, same resistors for top and bottom. andy grove used in kel84 where it works a treat.

its also used in dynaco derivatives, driving el34s, kel84 is pretty much dynaco circuit clone.

andy grove, probably for the sake of variety, stopped using long tail pair pretty early and went to the paraphase on the 6550 types, later wad.

the one with the 'crossroads' of 4 resistors, is very commonly used in american amps esp. guitar amps, its probably quite good.

and as we know transformers can and do work superbly.

the fact that there are so many, and all used effectively, means you really can take your pick.

there is another method not so widely seen, simply 2 differential pairs cascaded together, makes a pretty elegant solution.some earlish transistor amps used this, and I think the simpler the transistor amp circuit, and closer to a valve topology, the better the sound. later got more complex and perhaps clinical imo.

[NealG]

Long Tail pair with a CCS as the tail and matched valves.

[acorn]

Hi Neal

Yes, I thought the Long tailed Phase splitter looked good on a circuit I have it uses two ECC88s one for long tailed pair, by the way could you explain what is meant by a CCS in the Tail.

Acorn

[Ianm2]

constant current source, using a transistor for bias instead of a simple resistor, could also be called active bias, then the transistor will need to be biased,perhaps by another transistor, which will need biasing......

you can go a step further, and make the load resistors with transistors, or even valves, and make something called a current mirror, these are getting into opamp techniques, and are the foundation of opamps and complex transistor amps.

in fact, one of the simplest transistor amps just uses 2 differential pairs, you can put a ccs in the tail of the first one, and current mirror the 2nd stage load, many amps have used this classic topology

look familiar? its not too disimilar to this, again not a million miles from some valve amps,

http://www.plexoft.com/SBF/mounted/0tube.html

[NealG]

Ian's covered most of it. Here's a thread I started on the cct I used for K5881...

http://wduk.worldomain.net/forum/sho...ighlight=k5881

Also see post 30 for an alternative to the Gary Pimm cct I used to replace the tail resistor.

[acorn]

Hi All

It now begs the question why do we need the transistor as a current source rather than use a simple resistor IE what is the benefit and will you perseve a better sound.

Acorn

[IslandPink]

Sowter 3575 , with primary driven parafeed .
Surprisingly good transformer phase-splitter for around £35 each .

MJ