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View Full Version : Crown PSA-2X - What the H???



toddalin
08-10-2006, 03:31 PM
I finally picked up an amplifier to replace my ailing subwoofer amp. I got a Crown PSA-2XH from Craigs list for $230 (and a 4 hour drive). Other than "rack rash" and surface dirt, the amp played OK when demonstrated it through 4312s. (The guy also had some L46s and 4425s so can't be half bad. ;) ) (He even offered me a free set of Blose 501s that needed new foams that I politely refused.:p )

I figured that with a damping factor >700, a slewing rate of 60 v/us in mono, and a very low noise floor, this would be a good amp to drive my W15GTI. Plus, it can drive the 5 ohm load in mono on those occasions when both the W15GTI and 2235 in the center channel are wired in parallel (e.g., listening to the Yamaha in the Roxy Theater setting that doesn't use the center channel).

Anyways, the front of the amp clearly says PSA-2XH and I can find no mention of the "H" on the Crown web site. The amp does have the optional balanced input.

Can anyone shed some light on this so I know what the "H" I got?

Thanks,

Todd

allen mueller
08-10-2006, 03:49 PM
From the service manual.

"The PSA-2AX provides the same high quality performance and display as the PSA-2, but does not include the balanced input module for those who do not require it, the features or for those who wish to design an imput module of their own. This model with accept the standard PSA-2 balanced imput module (PSA-2MOD) if so desired."

Its an awsome amp for subs. I piced one up from another forum member and am very happy with it.

Allen

toddalin
08-10-2006, 04:07 PM
From the service manual.

"The PSA-2AX provides the same high quality performance and display as the PSA-2, but does not include the balanced input module for those who do not require it, the features or for those who wish to design an imput module of their own. This model with accept the standard PSA-2 balanced imput module (PSA-2MOD) if so desired."

Its an awsome amp for subs. I piced one up from another forum member and am very happy with it.

Allen

This one says PSA-2XH. It is the "H" that I can find no reference too.

I did note that the optional balanced module may be a little different in that it appears to have cover stickers where the gains should be. Glad they make good sub amps. Figured they would.

Thanks

scott fitlin
08-10-2006, 05:15 PM
They had different letter designations back then to indicate which options the amp had.

The fully loaded PSA-2 had the ladder type LED display on the front, instead of the three sets of LED,s and the other letter would indicate whether it had the balanced input module on the back.

All of mine have the balanced input modules, its a very useful thing, it offers gain control, hi pass filtering, and totally adjustable compression, with variable threshold and release.

Most of mine have the stock three LED fcront panel display, and 2 have the ladder display. The ladder display is nice, but adds nothing to the amp sonically.

What you got is a PSA-2. They kick, and sound clean on subs. Durable amp. As for the gain trims on the balanced input card being removed, seems like that might have been an aftermarket mod, some companies took them out, and replaced them with a fixed resistor. Ive seen Showco modded amps this way. I prefer having the gain pot, and being able to do whatever I need to.

But, it is a PSA-2, a great amp for subwoofer duty.

:D

allen mueller
08-10-2006, 05:41 PM
Sorry missed the H part. Like scott said its just the different options. Again you'll like this amp on subs.

Allen

scott fitlin
08-10-2006, 07:37 PM
Something i had posted on another forum sometime ago>>>>


OK, its really simple! All the amps are basically PSA-2,s!

The letters only indicate extra options.

1. SA-2. Consumer hi fi version with RCA inputs, ladder led display, and milled aluminum knobs.

2. PSA-2. The amp. 1/4in inputs, no bal input module.

3. PSA-2X. Amp with balanced input module.

4. PSA-2DX. Amp with both balanced input module and ladder led display.

They all say PSA-2, and if they have the options you will be able to see them.
__________________
Scott Fitlin


I had forgot about this, some others had asked way back when.........

:)

johnaec
08-10-2006, 07:51 PM
That "H" isn't one of those "Hospital" amps, is it?

John

toddalin
08-11-2006, 09:29 AM
Something i had posted on another forum sometime ago>>>>


OK, its really simple! All the amps are basically PSA-2,s!

The letters only indicate extra options.

1. SA-2. Consumer hi fi version with RCA inputs, ladder led display, and milled aluminum knobs.

2. PSA-2. The amp. 1/4in inputs, no bal input module.

3. PSA-2X. Amp with balanced input module.

4. PSA-2DX. Amp with both balanced input module and ladder led display.

They all say PSA-2, and if they have the options you will be able to see them.
__________________
Scott Fitlin


I had forgot about this, some others had asked way back when.........

:)

And the "H"...?

scott fitlin
08-11-2006, 10:33 AM
I wasnt able to find "H" suffix listing, but there was an H!

It isnt a hospital or industrial model though. Amps made for medical and industrial applications used the Techron, and Gradient names.

scott fitlin
08-11-2006, 12:49 PM
So, Todd, have you hooked it up to your subs yet? If so, how is it thus far?

mech986
08-11-2006, 03:48 PM
Hey Toddalin,

I left a message asking the ID question to Crown Tech Support. Hopefully they can clear this up, if there is an answer. I went through the Crown Audio website and technical literature about the PSA-2 series amps and couldn't find any -H reference either. Interesting.

Regards,

Bart

toddalin
08-11-2006, 03:53 PM
So, Todd, have you hooked it up to your subs yet? If so, how is it thus far?

Not yet.

First thing I did was to take off the face and take the front apart for a thourough cleaning and I painted the top bar in black (from its anodized aluminum color) to help with the rack rash.

Of course in replacing the front panel circuit board, there is a glass diode (Lucky D113) right next to the nut that holds the board and simply touching it with the wrench was enough to break the glass. :banghead: I replaced it with a regular 1-amp 50 volt diode (schematic shows that the diode is used in the indicator LED and only carries 15 volts). I'll reassemble it after the paint hardens and probably try it out later today.

Taking our equipment cabinet apart to replace the existing amp is a two person operation.:blink:

scott fitlin
08-11-2006, 04:13 PM
I`m thinking the "H" suffix may indicate high power version, as Crown knew very well of mods done by Showco, Clair Bros, and Walter Boho of Boho Labs NJ. Back when, if you called crown, and asked them about these mods, they would recommend Boho,s high power mods to you.

At some point, Crown may have even began to offer this as an option, I`m not sure, but, somehow, I seem to remember vaguely, the H designation for high power.

latteboy
05-11-2009, 01:31 PM
I just picked up a psa-2xh out of someone's trash. It doesn't work but its incredibly simple inside so I would like to fix it. A small transformer was loose inside and the shield for the balanced input section had come off but everything else looks fine. It powers up and all that but the red lights (IOC lights) turn on whether there's input or not and there isn't any output. It does this for both channels. What can I do to fix this?

Thanks
Taylor

toddalin
05-11-2009, 02:27 PM
I just picked up a psa-2xh out of someone's trash. It doesn't work but its incredibly simple inside so I would like to fix it. A small transformer was loose inside and the shield for the balanced input section had come off but everything else looks fine. It powers up and all that but the red lights (IOC lights) turn on whether there's input or not and there isn't any output. It does this for both channels. What can I do to fix this?

Thanks
Taylor

The schematics are available on-line through Crown. Follow the link:

http://www.crownaudio.com/pdf/legacy/psa2schematics.pdf

Service manuals are also available at:
http://www.crownaudio.com/gen_htm/legacy/legacamp.htm

The XH (eXtended Headroom) series was made especially for ShowCo and has a beefier power supply and cord to reduce losses due to long power runs (so I've been told). These XH models must really be special and somewhat rare as I can find no literature on this specific model at the Crown site.

If you are having a problem, there is someone on this web site who repairs these models and has an appreciation for the fine product that they are.

subwoof
05-11-2009, 04:08 PM
Scott - stop guessing...:o)

The H version is the showco mod - search using the word showco and you will find my posts explaining the differences.

and put the right diode in there - there are differences. IN914 or IN4148

sub

toddalin
05-12-2009, 10:21 AM
and put the right diode in there - there are differences. IN914 or IN4148

sub

Agreed there must be differences because the channel with the replacement diode shows the "overload" light on occasion whereas the channel with the original diode doesn't. I actually went though a few diodes when doing the replacment and saw differences in when the overload light comes on with the different diodes.

I had actually contacted Crown on this in the past, and it was them who said to use an ordinary rectifier diode. :o:

Thanks

subwoof
05-12-2009, 04:33 PM
check the position of the limiter pots on the balanced input module and make sure both are all the way open. And / or the selector switch for it - cycle it a few dozen times.

If one is backed off the light will come on earlier and the channel will not get any louder until another 12db is sent to it. This was kind of handy when I used one of these as a universal "replacement" amp for stage stuff.

The harmonica guys loved it because you could hook up a small 8" POS sears speaker to it without fear if needed.

BTW the correct diode is rated for 100ma - the larger black ones would allow too much current to pass ( like a fuse ) and also the larger the diode, the lower the voltage drop across it.

The black types are about .5v where the little glass ones are .7v

The circuit is a voltage divider so the math is wrong....:)

sub

toddalin
05-12-2009, 04:44 PM
BTW the correct diode is rated for 100ma - the larger black ones would allow too much current to pass ( like a fuse ) and also the larger the diode, the lower the voltage drop across it.

The black types are about .5v where the little glass ones are .7v

The circuit is a voltage divider so the math is wrong....:)

sub

Actually, I think you have it backwards. The drop on the black rectifiers is ~0.7 volts whereas the drop across these is about 0.4 volts. (I pulled and measured the good one when hunting for a replacement.)

Initially, I pulled and checked about every glass diode and lots of black epoxy diodes from every old circuit board I had in the junk box looking for one with a similar ~0.4 volt drop..., to no avail. :(

Coincidence that right now Goldmine Electronics has the 1N4148 at 100/$1. What am I going to do with 98 extra signal diodes???

toddalin
05-12-2009, 04:58 PM
check the position of the limiter pots on the balanced input module and make sure both are all the way open. And / or the selector switch for it - cycle it a few dozen times.

If one is backed off the light will come on earlier and the channel will not get any louder until another 12db is sent to it. This was kind of handy when I used one of these as a universal "replacement" amp for stage stuff.

sub

There are no pots on the PSA-2XH balanced input module. These are factory set using resistors and the holes for the pots have foils over them.

http://www.largescaleonline.com/eimages/lsolpics/Team_Member_Pics/toddalin/Crown_Back.jpg

I run the amp in bridged mode, so the lights should be "tied" together. It is not a matter of one coming one before the other. It is a matter of one coming on, momentarily on occasion when the amp is not clipping, (a false indication of clipping).

The Crown manual notes that the purpose of these diodes is to reduce this incedence of false clipping indication that was noted prior to this addition.

subwoof
05-12-2009, 06:17 PM
could you double check the D113 number?? The service manual says it's a 1N4004 which isn't normally glass...

As a general rule the glass ones *are* higher. A few manufacturers made the 4004 out of glass for the military and for high temp commercial so maybe crown used some of them in that batch...? Wouldn't be the first time...

I don't have a PSA2 opened up here at present to compare.

Another common issue is the 1.2K dropping resistor that feeds both the clip and signal light ( R113,213). They are notorious for opening up or changing value.

remember these amps have had a few hundred thousand miles of use before you got them...:)

sub

toddalin
05-12-2009, 07:29 PM
could you double check the D113 number?? The service manual says it's a 1N4004 which isn't normally glass...


sub



It is a simple glass banded diode with no number on it's case.

I recognize that the manual calls for a simple 1N4004 rectifier and that is what Crown said to use. But that channel shows the false clipping on occasion.

subwoof
05-12-2009, 08:54 PM
I have a box of 10,000 1N4148 diodes and a host of others. send me your address and I will send a sample of them.

There was another diode used ( 1N370 ) that was kinda special but I don't think the diode is the issue in this case.

Most of the time when an LED flashes, it has to be "time stretched" by a circuit using a cap so the human eye can see it.

Maybe a cap is off value - check C100 and C200 and the resistors R104 and 204. My bet is that normal 10 percent tolerance is the culprit.

sub