Revisiting some "old" ideas from 1970's - IPS, OPS

[vzaichenko]

Back to the amplifier please.
I wonder if any improvement expected using a separate power supply for the vas stage.

To be honest, I don't expect any noticeable improvement.
I would add a 2-pole CCS to R24 || R95 - I already have it designed, based on LM317 regulator - see attached.

 

[jwilhelm]

The antek transformers have a 12volt and 18 volt tap for a second vas supply.
AN-6450 - 600VA 50V Transformer - AnTek Products Corp

Their AS series have dual 15VAC windings. That's what I'm using.

 

[evanc]

as comes in 400VA ans smaller. I suppose this is big enough for one channel.

 

[jwilhelm]

400VA is good for sine wave testing a 200W channel all day.

 

[thimios]

Testing vz-x4 using a 2R dummy load.

 

[vzaichenko]

Yep - pretty much as expected )
Luckily, the speaker's impedance falls down to that low level (if it does at all) at the low frequencies (below some 200-300Hz).
A good example is Thiel cs5i - a sophisticated five-way, six–drive-unit, having two 4-ohm drivers in parallel in the sub section (below 50Hz). So, we see the 2-ohm load in the range, where low-impedance-load performance is the best. Nice 😎

P.S. Thiel cs5 impedance curve is taken from Stereophile test measurements.
Bottom line is impedance, top (dashed) line is phase.
Serious stuff, demanding a "tank" amplifier 😉

 

[thimios]

EsiJulia on Asus Mobo

A little more clear results using an Asus motherboard.

 

[thimios]

VZ-X4 Distortion from 1 to 57W RMS.

Here is what MY sound card can measure using Arta Steps.

 

[thimios]

vz-x4 vs cfa

Here is a comparision between vz and cfa

 

[vzaichenko]

Here is a comparision between vz and cfa

Interesting... looks like there is some grounding issue with CFA front-end.
Because of the low-impedance feedback network, CFA has got no ground lifting - maybe this is the reason for such a big 50 /100 Hz components difference.

 

[thimios]

VZ-X4 distortion at different frequencies

Using ARTA.

 

[thimios]

NS FRANKENSTEIN!

Ns OPS together with the Verical IPS.

 

[vzaichenko]

Ns OPS together with the Verical IPS.

Huh! )) 1-st generation IPS with last generation OPS ))

 

[jwilhelm]

It'll be interesting to see if the open input noise is still present.

 

[thimios]

A little test.

 

[thimios]

Using RMAA

 

[thimios]

It'll be interesting to see if the open input noise is still present.

Jeff, please can you explain further this?
What you want to test?

 

[jwilhelm]

The first version of the Vertical CFA boards with the big NS OPS board had a 50/60hZ noise when the input was left open. Is that noise still there with this output board?

 

[thimios]

The first version of the Vertical CFA boards with the big NS OPS board had a 50/60hZ noise when the input was left open. Is that noise still there with this output board?

So you want an fft test leaving the inp open, or you mean a test by ears?

 

[jwilhelm]

Just a quick listening test would tell if the noise is still there. Mine had a quite noticeable 60hZ hum when the input was disconnected, but went away as soon as anything was hooked to it.