output devices on X -X.5 and XA.5

[Zen Mod]

those ones are probably only commercial speakers I coulda/woulda use , but preferably with same outdoor in package

even those strictly from sentimental reasons

An externally hosted image should be here but it was not working when we last tested it.

my reference is , comparing to yours, big and ugly - 15" and coaxial , MLTL box , just one cap as xover

my toys ( so lesser than reference ) are some other coaxial 15" , 12" ER's and some 8" FR's

so - completely different approach - big cones and flea watts

 

[Zen Mod]

it's probably written , on your amp's pcbs :

"X250P
Pass Labs
2004"

?

 

[Stefanoo]

I will check that.....

what would that stand for?


What brend and model of speakers are those?

 

[Zen Mod]

...
what would that stand for?
.........

nothing what you already don't know - transitional model between X250 and X250.5

( at least according to my spy bird in PL )

.....


What brend and model of speakers are those?

what else than SR-1 - Passlabs

 

[5th element]

The 800Signature and the lateat 800 Diamond are simply the most neutral and transparent speaker you can buy.

This is absolute rubbish. For starters, the frequency response of said speakers is far too away from flat to be considered neutral by anyone.

The 800 series is an obviously coloured loudspeaker and engineered to sound a particular way, neutral it ain't.

 

[Stefanoo]

transitional model means that they are the same?

These speakers look very nice..never heard them though and I am sure they sound pretty good too especially with his power amps.
The only observation being that impedance is a little low and efficiency too for big speakers like this.

 

[Stefanoo]

This is absolute rubbish. For starters, the frequency response of said speakers is far too away from flat to be considered neutral by anyone.

The 800 series is an obviously coloured loudspeaker and engineered to sound a particular way, neutral it ain't.

ahahah there are a lot of consideration to make that will certainly go beyond yours and mine understanding.
Would you say that an amplifier with 1MHz BW and 0.00001% distortion from the 80s with a ton of NFB would be more neutral than a Pass?
SIMPLY NOT.
Now understand that these speakers again are used by professionals who mix up your favourite recordings, is that enough to assur top quality with that? you tell me!

 

[Zen Mod]

transitional model means that they are the same?

.....

gimme some pics of your amp, to keep my attention alive

especially what's written on pcbs

.....

These speakers look very nice..never heard them though and I am sure they sound pretty good too especially with his power amps.
The only observation being that impedance is a little low and efficiency too for big speakers like this.

yup - spks with which you can sleep easily ........ and that's important , at lest in my book

impedance and eff. - construction related choice .

 

[Stefanoo]

gimme some pics of your amp, to keep my attention alive

especially what's written on pcbs



yup - spks with which you can sleep easily ........ and that's important , at lest in my book

impedance and eff. - construction related choice .

No I get that i.e. that are construction related choice

I would be really happy to listen to those one day and perhaps make a comparison.

sounds good I will take some pics and keep your attention alive

 

[Stefanoo]

here the pics. Hopefully it explain why I was saying it is exactly like the X250.5
As far as I can see is on the UGS module and there are 3 power resistors instead of 2 at the front.

 

[Zen Mod]

transitional model means that they are the same?

.........

here the pics. Hopefully it explain why I was saying it is exactly like the X250.5
As far as I can see is on the UGS module and there are 3 power resistors instead of 2 at the front.

so - conclusion - they aren't the same

your X250P is mix between X250 and X250.5

newish hardware and pcb organization but - X250.5 is having newer UGS module , along with newer bias gene , and some SE bias , while yours is having older UGS , mosfet bias gene , no SE bias

bummer - if you're going to search another one to buy , you must look for exactly the same (transitional ) specimen

 

[Stefanoo]

yeah I know, it is a bummer and I was thinking of that yesterday .
I am going to buy another one a little later and I have to make sure it is the same late production.

Just thought aside: at first you thought they had different number of MosFets, but now you can see it is not the case.
Also, boards look identical BUT if you look at the first generation they are different not just in layout, but it is missing some BJTs and other little stuff.

I agree, the UGS module is different, but if you look closely the only difference I can see is that it is using the dual Toshiba instead of single lower quality FET.
Strangely, Pass uses the same UGS module on the 250.5 and 350.5 but then the 160.5 100.5 and other models use the UGS with TO220 instead of SOT BJTs which is marked as UGS5.0 (note that on my revision the UGS is marked as 6.0).

Speaking of SE Bias, if the X.5 has a shunt Bias, it means, please correct me if I am wrong, that it has one or more Mosfets from the output to the Negative Rail in constant current configuration.
If that is true, then the number of Output device should differ.
However this is not the case.

I will have to reverse engineer later on when I have more time to understand the details of how it works.

 

[Zen Mod]

you know - even if I know answer to your questions ( except why particular UGS generation is used where ) , it's really up to Pa to reply
btw - no odd number of mosfets , so no SE bias based on Mosfet CCS

generally - one can make SE bias establishing CCS in several ways - using either simple resistor , or mosfet or BJT based CCS

if your UGS is marked as 6.0 ....... then you don't have any reason to worry ... except need to triple check potential amp you'll gonna buy

how is your amp having UGS generation , which is chronologically later than amp itself , is puzzle for me

disclaimer - even if I know some things for sure - as facts - only Pa is able to give all answers ......

just one thing more - single Jfets aren't so inferior to dual ones ; there are differences , but nothing to cry at loud

 

[Stefanoo]

yeah I agree.
single Jfets are not worse than duals unless you are using lower quality Jfet in purpose to make the desing a little scaled down.
I don't know about the 6.0 this is the same thought I have and the explanation I can find is that maybe it doesn' go by numbers that are purely random...which would be bad practice.
Or maybe this specific unit was refurbish (which it was) and Nelson put a newer module inside because the onld was bad!! I don't know.
For the SE Bias:
Resistors would work but then you would deal with a variable SE with the level.
If BJTs or Fets or whatever are used, unless the level of current is really, really low and SE power is on the oder of 100mW or so, then no need for heatsink, but if logic assists me, if there is a SE bias that would make sense, let's say, 5-10W then it's gotta be on the main heatsink

Yeah I will need to check then next amp, but either way all I need is the same Hardware i.e. caps, Mosfets transformers and Chassis and of course heatsinks, then I will re-do the boards and take the parts off on the final one, which means that if I want to put back the old X250 I can still do it.
In this regard the specific UGS model used doesn't matter to me as I think they are pretty much all similar

 

[5th element]

ahahah there are a lot of consideration to make that will certainly go beyond yours and mine understanding.

That's quite an assumption to make.

Would you say that an amplifier with 1MHz BW and 0.00001% distortion from the 80s with a ton of NFB would be more neutral than a Pass?
SIMPLY NOT.

I'd say that the first amplifier is probably more neutral then the pass device. I would argue that the reason why you like the Pass amplifier so much is because of the subtle way they modify the sound.

Now understand that these speakers again are used by professionals who mix up your favourite recordings, is that enough to assur top quality with that? you tell me!

As far as I understand Abbey Road use some B&W speakers in one of their mixing/listening rooms, but most do NOT use B&W speakers.

With regards to neutrality in speaker design the first fundamental parameter that you must get right is having a flat frequency response. If you don't have this then all other bets are off, it doesn't matter what else the design does, it will not be neutral. Who says you like listening to neutral anyway?

 

[Zen Mod]

5th

you're living in same fantasy world , as Stefanoo

 

[Stefanoo]

and I am not alone....so far we are in three...me 5th and Zen...who else is going to join us here?

 

[Stefanoo]

That's quite an assumption to make.



I'd say that the first amplifier is probably more neutral then the pass device. I would argue that the reason why you like the Pass amplifier so much is because of the subtle way they modify the sound.



As far as I understand Abbey Road use some B&W speakers in one of their mixing/listening rooms, but most do NOT use B&W speakers.

With regards to neutrality in speaker design the first fundamental parameter that you must get right is having a flat frequency response. If you don't have this then all other bets are off, it doesn't matter what else the design does, it will not be neutral. Who says you like listening to neutral anyway?

Fifth you should check your facts:
analogue production, StockFish Recording and another one that I can't remember of use it...plus Abbey Road and other Studios, plus important theater decided to power their room up with B&W800 as well.

As far as frequency response I can't say anything, I would tend to agree with you....however just listen to them and let me know how close they get to the live music and then we can talk about.

 

[Stefanoo]

5th

you're living in same fantasy world , as Stefanoo

And by the way, you haven't answered to my point about the Biasing in SE nor have a reason as to why they both have the same number of Output Devices while you were stating as a "fact" that it had to be different no matter how much I would say otherwise!!
So you tell me if you are not in the same fantasy world dude!!

 

[Zen Mod]

while you're throwing questions in my direction , and I'm trying to address them all (without going really too much in details - Pa's IP ) , there is sometimes glitch in understanding

to cut a log story short .....

according to info I have :
- your X250P is not having SE bias
- X250.5 is having SE bias ; it isn't made with Mosfet ;

.... enough regarding that issue from me

off course - you are in situation to look by your self ; who knows which iteration is that .....