New Stasis front end

[Zen Mod]

you don't need deep A Class with Stasis type of amp

[email protected] means 60Vdc-ish rails

with xformers you have - your'e short with voltage for non-bridged amp

for bridged amp - their voltage is too high, you're short with amps

 

[Kicman]

you don't need deep A Class with Stasis type of amp

[email protected] means 60Vdc-ish rails

with xformers you have - your'e short with voltage for non-bridged amp

for bridged amp - their voltage is too high, you're short with amps

Sorry but i don't quite understand what you wrote. If the transformers have symetrical 37V so it goes for about +/-52V with no load.
So all the voltages that been posted in this topic, called "per rail" are the sum of symmetrical voltage? Not the 37-0-37 Volts for example?
You mean that I can't go with my 37-0-37 Volts transformers to run the normal Stasis FE + OS8 per channel?

 

[TungstenAudio]

Personally, I am planning for 40V rails derived from a pair of 400VA, 32V transformers. And as much bias current as can be withstood by a set of 8 deep OS boards in 2 pico’s 500mm deep chassis. I have ways of extending the thermal capacity beyond the norm for these heatsinks.
I will be pretty happy with 75 Watts in deep class A. We will see.

 

[Zen Mod]

Sorry but i don't quite understand what you wrote. If the transformers have symetrical 37V so it goes for about +/-52V with no load.
So all the voltages that been posted in this topic, called "per rail" are the sum of symmetrical voltage? Not the 37-0-37 Volts for example?
You mean that I can't go with my 37-0-37 Volts transformers to run the normal Stasis FE + OS8 per channel?

you'll get +/-52Vdc , without load
I just said that for 150w you need more than that with non - bridged amp .... and way less than that with bridged amp

 

[Kicman]

OK Zen Mod, everything is clear, I was a bit confused after your post. So I can go with this transformers but are they not a bit too weak, it is only 2x320VA. I know that I will have a little less power, but when buying a transformer for SUSY, it will have too little voltage to the normal one and vice versa. Unfortunately, the purchase of such a powerfull transformer (1200-1500VA) is quite expensive...

 

[Zen Mod]

you know how saying goes - put up or shut up

you want to build it, you need to invest

but - you need higher voltage and really stronger xformer for non bridged amp, than you have with your xformers

for SUSY Stasis - not just that you need different xformers ( with lower voltage than you have but also higher VA), you also need either to wait that someone more experienced tackle that nt, or you to tackle it by your self

as I said - SUSY Stasis need development

 

[Kicman]

I see that the topic died a bit but I was not idle and instead of building a power amplifier, I just became the owner of the stasis topology. I did some research on auction sites that are popular in my country and bought an Usher R-1.5 in perfect condition.
Unfortunately, I cannot say that I am the happy owner of this design because this power amplifier sounds terrible. Surprised?
Because my surprise after connecting it to the source that I use all the time, which is the DAC with adjustable output, was huge. I do not have any preamplifier, so this is the only way I can drive the power amplifier or from a CD player, which also has an adjustable output level.
The sound presented by this power amplifier is rather flat, expressionless with lacks in the lower and upper range. It sounds completely without energy, as if I had connected something with very low power, there is almost no bass, the treble is so low quality, it sounds mainly in the midrange. When there are many sounds at the same time, they simply merge, a tragic separation.
At this point, I started to wonder why people are so delighted and praised these power amplifiers, maybe they just didn't hear anything else, better or simply never had the opportunity to compare directly with an amplifier, 3-4 times cheaper.
Unfortunately my Marantz PM7200 kills this power amp with sound quality after the first few seconds of any track, believe me, it doesn't take more time to find out.
This is such a big difference in sound quality that I can't believe it, can the lack of a preamp make such a difference? Could this be the main reason for such a poor sound? I am so disappointed that the power amplifier is disconnected and pretends to be a monument, it should be added that quite an expensive monument and plugging it in does not make any sense.

 

[johnhenryharris]

Maybe you can rebuilt that Usher Amp with the new Stasis front end board.
One thing to check is the amps temp, if the bias is low it might have that effect on the sound, don't know though.
A real Threshold Stasis amp has deep bass, sweet and extended highs, and a dynamic sound.

 

[Zen Mod]

Usher is not Pass

who knows what of differences are there, vs. origin?

attached supposedly R2.5 schematic I collected from somewhere

that's far enough from efficient simplicity of anything Pass drew

 

[Kicman]

The Usher R-2.5 is a completely different amplifier than the R-1.5, which is practically a 100% replica of the cascode based Threshold Stasis 2 (3). I talked to a guy on the Polish forum who has such a power amplifier and he drew a diagram of the final stage and confirmed that it was Stasis 2 (3) on cascodes and not, as many forum threads say, that it is S300, the values of emitter resistors also prove it. He disassembled it almost into parts and made a lot of modifications to the factory version. I will attach the photos he shared and you can see everything perfectly on them. For him, the layout on the cascades is not as clear as the traditional one, and I'm joining it. I know at the moment that it sounds tragic.

 

[Zen Mod]

well, what can I say ...... except that I believe Pa did learn trick or two in years after Stasis 2

present FE is certainly cleaner than that one of Yore

anyway, I'm way above my level there, really never played extensively with these exact Front Ends, so can't say that I'm familiar with most critical points

probably sole person able to give you proper comment (regarding old FE vs. new one) is Pa himself

 

[Nelson Pass]

It seems that Usher was the OEM for Threshold for a period of time before making something that looked much the same under their own name. However I have no specific information and none of the parties involved have communicated with me.

 

[Kicman]

Thank you Mr. Nelson Pass for the answer and you, Zen Mod, for including the master himself in the conversation.
However, since there is such a possibility, I would like to ask Mr Pass, what could be the reason for such a weak sound in this case? The lack of a preamplifier itself? Or maybe something worth improving here? The use of new, improved FE boards as proposed by Zen Mod?
I would like to add that in the coming week I will get the Pass Aleph P preamplifier for testing, probably the 1.7 model, but I do not know it exactly.

 

[Zen Mod]

it could be helpful that you have exact schmtc of your Usher

I didn't say anything about changing your FE with new ones; we are still in the dark, without needed facts

 

[Kicman]

Unfortunately, the schematic for Usher R-1.5 is not available even by calling Usher, as it would not exist. Nobody has been able to obtain it so far. As I wrote earlier, when drawing a schematic from a PCB, it coincides with the one from Stasis 2 (3).
I will try to write to the Usher company personally regarding the schematic, we will see what they write back.

 

[Zen Mod]

as long schematic is correct, we don't care is it from Usher directly or you took it from existing amp

 

[Kicman]

I wrote directly to Usher regarding the service documentation or at least the schematic itself. Let's wait for their answer.

 

[Gladiator33]

Hi. Sorry if my question was answered earlier in the thread, but where can I buy front end circuit boards for my original Stasis 3? Is it possible to buy a fully tested circuit board? Thanks for reply.

 

[Zen Mod]

maybe someone who made his own from published Gerber files is having some leftovers

 

[Nelson Pass]

I generated artwork for one not too long ago. I will dig it up later today.