SRPP vs. plate loaded, musicality and details

[MrCurwen]

I've heard a lot of good about SRPP - it's supposed to have very low distortion and (depending on where you take the output) low output impedance. However as many of you probably agree, figures don't mean good sound necessarily.

What I'm asking is how would you describe the overall musicality, detail levels, transparency and so fort (insert your favourite mojowords here) of SRPP, and how would you compare it to the traditional common cathode plate loaded topology. Is the SE magic still there in SRPP?

[SY]

I've heard a lot of good about SRPP - it's supposed to have very low distortion

Fashionable, it is. Low distortion, not so much.

[Merlinb]

A topology does not have a characteristic sound. An SRPP built with one particular valve, with particular component values and voltages, in a particular system, will not have the same "musicility" (whatever that means) as another SRPP using a different valve under different conditions. The question has no answer.

[DF96]

Do you want low distortion or musicality? As you mention SE magic I assume the latter.

The SRPP does not have low impedance output, unless by low impedance you mean lower than a common cathode but much higher than a cathode follower. Typically, SRPP output impedance is about 0.3-0.5 times the impedance of the same valve used in common cathode. This is why it also has a reputation for being fussy about what follows. Too much load pushes up distortion.

I find the current popularity of the SRPP rather puzzling. In many cases a common cathode followed by a cathode follower would work much better, yet some people don't like cathode followers. Maybe this is because there are too many poorly designed ones, using the wrong valve type.

[levelfive]

Agree with Merlinb:

SRPP built with one particular valve, with particular component values and voltages, in a particular system, will not have the same "musicility" (whatever that means) as another SRPP using a different valve under different conditions.

[ThorstenL]

Sy,

Originally Posted by SY

Low distortion, not so much.

Surely Sir, you jest?

Set up correctly an SRPP stage has lower distortion than ANY other form (including Mu-Follower or CCS load) of Gainstage (not follower) that can be realised using the same double triode.

Of course, not all SRPP's are set up correctly for low distortion.

Ciao T

[jamj]

Srpp to me always sounds more brightish more towards mids & highs
especially in dac out or preamp duties

[ThorstenL]

Hi,

Originally Posted by DF96

Typically, SRPP output impedance is about 0.3-0.5 times the impedance of the same valve used in common cathode. This is why it also has a reputation for being fussy about what follows. Too much load pushes up distortion.

Yes. This can be fixed though, by adding another tube set up as a modified white follower. If you do that you end with something called after it's inventor the "Gomes" stage. Others have called it supertotempole.

John Broskie did an expensive expose of the Gomes stage and (as usual) found that in theory the Aikido is better at suppressing power supply noise* while the Gomes stage did rather well on other accounts.

I personally like this stage as it can be optimised for lowest distortion with no recourse to load impedance, while retaining a classic "SE" spectrum and also sounding quite "single-ended", subjectively speaking. I agree with John Broskie that it does not have a lot of power supply noise rejection, but I like to make powersupplies very quiet anyway, so I never found this an issue.

A Linestage from diyhifisupply used a 6CG7 & 5687 Gomes Stage (yes, I had a small part in the design). This in practice measured better than the Aikido version on all counts and more critically, it sounds quite extraordinarily good.

My personal biggest complaint about it was that I have absolutely no use for a linestage with 20dB Gain.

Ciao T

* I still fail to understand this quest for ultra-high power supply rejection to the exclusion and even detriment of other performance attributes, including sound quality. I always feel it is much easier to design a competent powersupply to start with, instead of trying to fix noise later with all sorts of circuit tricks that react unfavourably to non-ideally matched tubes, non-ideal capacitors and resistors with tolerance...

[SY]

Originally Posted by ThorstenL

Sy,

Surely Sir, you jest?

Not in the slightest.

[ThorstenL]

Hi Sy,

Originally Posted by SY

Not in the slightest.

Care then to support your blanket assertion with some actual data?

Which Tube gainstage (as stage with gain) topology using a dual triode and no looped feedback can you present to illustrate that it offers lower distortion than an SRPP optimised for lowerst distortion?

Ciao T