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Gear / Technical Help => Battery Boxes, Preamps, Mixers, ADCs, and Processors => Topic started by: audBall on April 10, 2019, 10:31:53 PM

Title: E.A.A. PSP-2 Preamplifier Thread - Specifications / Photos / Powering
Post by: audBall on April 10, 2019, 10:31:53 PM
I was searching the site for a dedicated PSP-2 thread and found a number of really informative posts placed all around. Since there doesn't appear to be a central thread I have compiled relevant info here.


Preamp Specifications (see Information Sheet links below for additional detailed specs):
 - XLR in/out
 - 1/8-inch (3.55mm) stereo in/out
 - 12V, 24V (internal switching), and 48V phantom powering
 - Mic/Line input
 - 5-9 (max) VDC powered by external battery
 - 6xAA batteries internal power
 - Approximate runtime (with 48V phantom power):  10 hours
 - Gain range: see tedyun's post below
 - Dimensions: 3.4 x 1.4 x 5.6 inches (85 x 35 x 147 mm)

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Internal Photos:
Imgur link:  https://imgur.com/a/hvGokFL

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Link to Manual:
http://www.taperssection.com/reference/pdf/Manual_EAAPSP2.pdf

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Information Sheet:
Imgur link:  https://imgur.com/a/BxF48dj
Page 1:  https://i.imgur.com/rcLgDwr.jpg
Page 2:  https://i.imgur.com/L2DxLjv.jpg

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Gain Ranges:
The gain ranges I estimated were pretty close.

I set up my computer to generate a steady tone, then from my DAC (Headamp Pico), I fed an unbalanced signal to my V3, and then SPDIF out to my PMD-661. I adjusted the signal to a specific level on the meter using the gain and the trim on the V3. Then I placed the PSP-2 between the DAC and V3 and measured the signal increase. I used the balanced outs on the PSP-2.

Mic sens "-35": gain of +28 (ie., the meter increased from -40 dB to -12)
Gain switches +6 and +12 add +6 dB and +12 dB respectively.

Mic sens "-55": gain of +48 (the meter increased from -60 to -12)
Gain switches +6 and +12 add +6 dB and +12 dB respectively.

Mic sens "-70": gain of >+60 (the meter increased from -60 to "over"; I adjusted the trim on the V3 downwards by 4 dB, and it was right around 0, so I estimate that it adds about +65 dB)

That's the best I can do with my equipment I have on hand.

So the revised gain range for the PSP-2 is:

+28 (Mic sens: "-35"; Gain "0")
+34 (Mic sens: "-35"; Gain "+6")
+40 (Mic sens: "-35"; Gain "+12")
+48 (Mic sens: "-55"; Gain "0")
+54 (Mic sens: "-55"; Gain "+6")
+60 (Mic sens: "-55"; Gain "+12")
+65 (Mic sens: "-70"; Gain "0")
+71 (Mic sens: "-70"; Gain "+6")
+77 (Mic sens: "-70"; Gain "+12")

So there probably is a pretty big margin of error and it would be nice to get an actual number for the peak value instead of estimating it by eye. I would say +/- 5 dB. I tried feeding the signal to another computer but couldn't really get the digital in or line in to work.

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Powering / Battery Sleds
Powering via 5V USB rechargeable battery:
http://taperssection.com/index.php?topic=87410.msg2159638#msg2159638

Powering via internal NiMH batteries:
http://taperssection.com/index.php?topic=163699.msg2051946#msg2051946

Replacement battery sled:
https://www.amazon.com/Philmore-Battery-Holder-Standard-Connector/dp/B000LFVFU8

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Bench Tests and Repairs
Bench tests performed by Vark:
http://taperssection.com/index.php?topic=153128.msg1938497#msg1938497

Information regarding repairs:
http://taperssection.com/index.php?topic=167656.msg2088213#msg2088213

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Potential Source of Audio Transformers
Palmer Germany (currently under the Adam Hall Group) was the original manufacturer of the transformers. The PMT05 or PMT09 models located on page 92 of PDF linked below may be suitable replacements, although I am not certain of this.

https://webcontent.adamhall.com/media/online_catalogue/index.html?catalog=Palmer_Catalogue#page_92
Title: Re: E.A.A. PSP-2 - Brochure / Specifications
Post by: fobstl on April 11, 2019, 11:02:37 AM
As someone who has used a PSP2 for over 20 years, thanks for starting a thread.
Title: Re: E.A.A. PSP-2 - Brochure / Specifications
Post by: MakersMarc on April 11, 2019, 01:59:02 PM
I loved mine wish so still had it. But I moved to an Oade m148 so hard to complain. 😀
Title: Re: E.A.A. PSP-2 - Brochure / Specifications
Post by: audBall on April 13, 2019, 01:52:36 PM
Bump for internal photos link in the top post.

Second photo, on the left, the red/blue switch is one of two (the other is out of view below).  These are for switching between 24 and 48 volts phantom powering.

In the top left of the board, what are those trimpots for?  Would these be for input (or output) finer gain adjustments?

It's truly amazing how compact and tightly put together this preamp is.  I would have taken a picture of the other side, but it's basically just a metal wall that extends beyond the battery compartment.  It appears there are three total boards, all facing in towards one another in a sandwich.   
Title: Re: E.A.A. PSP-2 - Brochure / Specifications
Post by: inoutoffocus on April 13, 2019, 04:59:02 PM
Thanks for starting thread and posting pics. Anyone running there's on a 5v usb battery? When I set mine up that way with fresh charge, low level battery light flashes  as soon as you power the unit on. Haven't run any tests this way. Any thoughts? The usb battery can do 5-12v but it senses voltage automatically, no way to set voltage you want. Weirdness
Title: Re: E.A.A. PSP-2 - Brochure / Specifications
Post by: tedyun on April 14, 2019, 04:15:08 PM
I've been using a USB battery to power my PSP2 for the longest time. I've used a variety of packs, from the older ones that supply 5V, 500 mA, to the newer ones that supply around 2 A per port.

Check if it's your battery. Try powering the PSP2 by using the same cable plugged into your computer. If your battery is fine (ie., it can charge other devices like a phone), it might also be the cable too. Worst case scenario is if it's the preamp. Then you'll have to send it in to get checked out.

Do you have any way to measure if the PSP2 is supplying the correct voltage to your mics (ie., a multimeter?)


Thanks for starting thread and posting pics. Anyone running there's on a 5v usb battery? When I set mine up that way with fresh charge, low level battery light flashes  as soon as you power the unit on. Haven't run any tests this way. Any thoughts? The usb battery can do 5-12v but it senses voltage automatically, no way to set voltage you want. Weirdness
Title: Re: E.A.A. PSP-2 - Brochure / Specifications
Post by: audBall on April 17, 2019, 12:18:03 PM
In addition to my trim pot question above, has anyone ever experienced a difference in output levels (via XLR and 1/8” stereo outs)?  This occurs with both mic and line-in sources, with output gains set to 0 dB.
Title: Re: E.A.A. PSP-2 - Brochure / Specifications / Photos / Information
Post by: inoutoffocus on April 17, 2019, 05:21:24 PM
I'm not 100% sure, but I think the mini out isn't as hot as the xlr outputs. And I checked my usb battery output. It was 5.2v. Light still flashes on psp2. Talked to VARK audio and they didn't really have an answer for me. Cable I'm using is a short right angle usb to power cable. Seems they designed to pre to run at 9v optimally thus the 6aa battery sled. Might hook up rig tonight and record to see if there's any audible noise with low batt light flashing. Wish I could find a tiny 9v usb battery or one that you can adjust output manually. Mine senses voltage automatically and adjusts.
Title: Re: E.A.A. PSP-2 - Brochure / Specifications / Photos / Information
Post by: audBall on April 17, 2019, 05:38:19 PM
Woops, I should clarify. I meant a difference in levels between channels L and R. This difference in channel outputs is reflected on both XLR and 1/8” outputs. My right channels are significantly hotter.

You are correct that an overall difference would be expected between the 1/8” (unbalanced) and XLR (balanced) outputs.
Title: Re: E.A.A. PSP-2 - Brochure / Specifications / Photos / Information
Post by: perks on April 17, 2019, 06:55:48 PM
Woops, I should clarify. I meant a difference in levels between channels L and R. This difference in channel outputs is reflected on both XLR and 1/8” outputs. My right channels are significantly hotter.

You are correct that an overall difference would be expected between the 1/8” (unbalanced) and XLR (balanced) outputs.

I have a set of 48V PFA's that output L/R differently by a very noticeable amount but not my PSP2. They seem pretty even to me. I love this pre too. My new favorite thing about it is running the XLR outs to the AD2K+ and also running a M10 off the 1/8 out. Just so easy to have a backup now that takes up virtually no additional bag space.
Title: Re: E.A.A. PSP-2 - Brochure / Specifications / Photos / Information
Post by: fobstl on April 17, 2019, 07:24:13 PM
I like to run the 1/8" out into an M10 as backup also. No brainer to do.
Title: Re: E.A.A. PSP-2 - Brochure / Specifications / Photos / Information
Post by: audBall on November 16, 2021, 08:08:15 AM
Regarding my previous posts above, I have this PSP-2 that has some sort of channel mismatching going on. For whatever reason, the right channel (regardless of input source XLR or 1/8") is much higher than the left channel (by ~12-15dB), which appears to function normally via gain settings and adjustments. The right channel also responds to the gain adjustments, but there is something causing the input signal to be very high/overloaded.

I have reached out to a couple technicians over the years (Vark and Oade), with little to no response (no surprise), but have not had anyone look over the unit. I suspect few would even want to look under the hood. I recognize that the ability to repair these preamps, due to the compactness of their construction and lack of parts availability, renders them potential dust collectors.

Although, I was able to find a source for what appears to be similar transformers that were originally used, possibly still in construction by Palmer Germany (see link HERE (https://webcontent.adamhall.com/media/online_catalogue/index.html?catalog=Palmer_Catalogue#page_92)). The transformers inside the preamp are stamped with "Palmer". The unit can be almost completely disassembled; however there is point-to-point wiring for two separate chip boards that keeps them tightly packed together - it's quite impressive.

The reason for this post is to gauge if there is any interest out there for this thing in its current state - otherwise it will be a nice display piece for the foreseeable future.  ;)