"New" preamp, but I got a problem...

Early B.

My Audio Experience Symphonies Plus preamp arrived today. I hooked it up and it sounds great. However, the problem is that my amplifier (Marsh A200S) keeps cutting off. I believe the amp is going into protection mode, possibly because it detects a DC voltage leak from the preamplifier outputs. My amplifier does not cut off unless it is connected to the Symphonies Plus. I also checked my connections twice for potential shorts, but didn't see any.

The reason I think it's a DC voltage leak is because, upon reading reviews on this unit on audiogon, the DC voltage leak is a known issue and was fixed by the manufacturer late in 2004. However, my preamp was built in 2004 (based on the serial number), so it may not have been fixed before it left the factory.

What can I do to fix this problem? Is it an easy fix?

Thanks.

ND13

Sell all of it, it's all crap and a never-ending saga of frustrastion:p

Systems

First if you have a multimeter I would check the output of the preamp for any large amount DC present.It should be in the millivolts range or zero.If their is a large amount of DC the fix would be to add a capacitor to output of the preamp or the input of the amp.Another possible cause of the amp shut down is an oscillation in the preamp.How long does it take to shut down?does it get hot ?

Ricardo

If it was me, I would sell that preamp right away (I am assuming no return possible..)

W WALDECKER

Early B. wrote:

My Audio Experience Symphonies Plus preamp arrived today. I hooked it up and it sounds great. However, the problem is that my amplifier (Marsh A200S) keeps cutting off. I believe the amp is going into protection mode, possibly because it detects a DC voltage leak from the preamplifier outputs. My amplifier does not cut off unless it is connected to the Symphonies Plus. I also checked my connections twice for potential shorts, but didn't see any.

The reason I think it's a DC voltage leak is because, upon reading reviews on this unit on audiogon, the DC voltage leak is a known issue and was fixed by the manufacturer late in 2004. However, my preamp was built in 2004 (based on the serial number), so it may not have been fixed before it left the factory.

What can I do to fix this problem? Is it an easy fix?

Thanks.

Hey Early B, i am sorry to hear that you are having Preamplifier problems.some of the first runs of the Balanced Audio Technology VK 3i also had problems with DC leakage . i would contact the manufacturer to find out what action you should take to rectify this unfortunate situation. if you bought it on Audiogon maybe you could ask the seller for a refund.good luck....WCW III

Early B.

GV#27 wrote:

First if you have a multimeter I would check the output of the preamp for any large amount DC present.It should be in the millivolts range or zero.If their is a large amount of DC the fix would be to add a capacitor to output of the preamp or the input of the amp.Another possible cause of the amp shut down is an oscillation in the preamp.How long does it take to shut down?does it get hot ?

I have a multimeter, but I don't know even know how use it to check the output of the preamp.

Oscillation? Please explain what that is.
I used the preamp very briefly before I removed it from my system, but didn't notice any heat and it appeared to shut down quickly.

I don't know if this is related, but when I turn on the preamp and CDP, there's static coming from the speakers even though the amp is off. WTF? That may be normal, I dunno, because the manual says to turn the preamp on first, wait 30 seconds, then turn on the amp.

Early B.

W WALDECKER wrote:

Hey Early B, i am sorry to hear that you are having Preamplifier problems.some of the first runs of the Balanced Audio Technology VK 3i also had problems with DC leakage . i would contact the manufacturer to find out what action you should take to rectify this unfortunate situation. if you bought it on Audiogon maybe you could ask the seller for a refund.good luck....WCW III

I bought it off ebay.
If it's a simple fix, such as adding a capacitor, I'd prefer to keep it. Sounds too good to let it go. Besides, I'd like to tweak it anyways, which is one of the reasons I bought it.

danger boy

personally, i'd write the company.. and see how much they charge for the fix.

that way they it may not void any kind of warranty. which there prob isn't one since it's a few years old. I'm a big believer of the manufactuer doing the work.

but that's just me.

Early B.

danger boy wrote:

personally, i'd write the company.. and see how much they charge for the fix.

that way they it may not void any kind of warranty. which there prob isn't one since it's a few years old. I'm a big believer of the manufactuer doing the work.

The manufacturer is in Hong Kong, so I probably would not even bother sending the unit back to them to fix it.

I wrote the manufacturer, so hopefully I'll get a response. However, I already know his English ain't too good. You ought to read the manual.:eek:

Systems

Early B,to check for DC set the multi meter to the lowest DC volts setting.Connect the black lead to the outer ground on the Preamps output RCA jack,and touch the red lead to the inner part of the connector.Then read the value on the meter.

Refefer

Early B. wrote:

The manufacturer is in Hong Kong, so I probably would not even bother sending the unit back to them to fix it.

I wrote the manufacturer, so hopefully I'll get a response. However, I already know his English ain't too good. You ought to read the manual.:eek:

If nothing else, maybe he'll send you a diagram of how to fix it internally and you can do the work yourself. Since you want to tinker with it anyways, you could take a look around inside and figure out what to replace while you're waiting for his response and if it's a go, heck, kill two birds with one stone.

Early B.

Refefer wrote:

If nothing else, maybe he'll send you a diagram of how to fix it internally and you can do the work yourself. Since you want to tinker with it anyways, you could take a look around inside and figure out what to replace while you're waiting for his response and if it's a go, heck, kill two birds with one stone.

Exactly. I e-mailed the manufacturer for a schematic. I'd like to upgrade a few caps. Based on what other owners have said, replacing caps improves the performance of the preamp.

Systems

To answer your question ,If the preamp had an oscillation(instability) it would send a nasty hi freqency signal to the amp triggering it's protection circuit.But I doubt this is the problem.
BTW Do you have any capacitors laying around in the 3-10uf 50volt range that you can quickly try?
If not I can send you a couple.

Early B.

Thanks, GV, but I took out my multimeter and I'm not ashamed to tell you, but I don't know a damn thing about how it works, so I don't even know how to perform a simple DC test as you described. And I damn sure wouldn't know what to do with capacitors in the 3-10uf 50volt range.

I think I'll take it to a technician and have them fix it. Based on the faint odor and quantity of dust accumulation inside the unit, it appears to have been sitting around in a basement or garage for the past couple of years, so I'd like to get it checked out anyway. But first, I want to hear back from the manufacturer.

Systems

No problem Early,good luck with the unit and let us know what the manufacturer has to say.

pearsall001

Duct tape my man, duct tape. It'll stop any leak. All joking aside, good luck on finding a fix. It sounds like you really like the piece & want to hang on to it. Sorry I can't be of better service to you but I know squat about electronic's except how to plug 'em in.

RuSsMaN

If you are getting static, (with the unit off), wiggle the tubes around in a circular motion in the sockets, you could have some oxidation, esp with used or nos tubes.

Early B.

RuSsMaN wrote:

If you are getting static, (with the unit off), wiggle the tubes around in a circular motion in the sockets, you could have some oxidation, esp with used or nos tubes.

I pulled out the 3 of the 4 stock tubes and replaced them with Groove Tube 12ax7M's. The fourth tube is a Phillips NOS 6x4 tube. Did some wiggling with that one. Thanks.

BTW -- am I OK with the Phillips, or should I replace it? If so, with what?

Early B.

A couple pics of the guts exposed...

RuSsMaN

I have the same preamp in my whole-house rig, and the preamp actually has a solid state rectification stage - the 6x4 is almost acting like a buffer on the power supply.

Bottom line, it's not in the signal path, so as long as its working, that's all you need.

Curious, was the preamp recently upgraded (caps)? I've had several preamps, Audcom, Anthem - new caps needed a while to break in - they were stable in a 'new' state, and sent various amps into protection, even blew a fuse on some Maggies a couple of times.

Cheers,
Russ

Early B.

Here's the response I just received from the manufacturer:

Dear Sir, I try replace all 47uf / 450 cap ( in power supply ). thank , Chui Chi Wai.

Huh?

RuSsMaN

Get the dust out of it, and off the boards. Try again sans tube shields (I don't use mine, never have). You are also missing a plate that covers the circuit behind the tubes, not that it should make a difference, it's just not there.

Early B.

RuSsMaN wrote:

Get the dust out of it, and off the boards. Try again sans tube shields (I don't use mine, never have). You are also missing a plate that covers the circuit behind the tubes, not that it should make a difference, it's just not there.

I'll remove the dust and the tube shields. Thanks, Russ.

To remove the dust, should I use a can of compressed air?

BTW -- I have the plate that covers the curcuit behind the tubes; I removed it to snap the pics.

Early B.

Early B. wrote:

Here's the response I just received from the manufacturer:

Dear Sir, I try replace all 47uf / 450 cap ( in power supply ). thank , Chui Chi Wai.

Huh?

There are four of these caps on the power supply board. Is Mr. Wai suggesting that I may have a bad capacitor?

RuSsMaN

Do any of them look 'swollen' on the top, buldging? I don't see anything to suggest a bad cap on the board.

Compressed air, and with it unplugged, get in there with a dustrag / qtips and get it clean.

Early B.

No, all of the caps look normal.

I put a dust rag on it, but I'll buy some compressed air tomorrow and break out the q-tips.

Systems

Humm,a bad filter cap would mean you would have some hum at the output but that should not cause the Marsh to shut down.Also if the unit is only a few years old the caps should have lots of life left in them.

Dennis Gardner

I would try running a single channel at a time into your amp (disconnect one RCA cable) and see if a certain "side" is causing the cutoff issue, then swap the outer 12ax7s to see if it moves from "side to side". If the problem moves "sides" you have a bad tube.

BTW, I have noticed on my AE preamp, the outer tube on the left controls the right channel and right controls the left. Just FYI.

Early B.

I wiggled the tubes, removed the tube covers, and cleaned her up a little, then I hooked it up again and here's what happened:

-- there was no static at all upon powering up (great!!)

-- I still have the problem with the Marsh amp wanting to go into protect mode. Specifically, every few minutes, the power light on the Marsh turns off for several seconds, the music output decreases, and there's static. Then the light comes back on and everything returns to normal.

Systems

Does the amp work OK with another preamp?

Early B.

Oh, I should also mention that seller shipped the preamp with the tubes installed and the unit was not packed well (single box, 1/2 inch of styrofoam around the bottom and sides, virtually nothing on top.:eek:

I replaced 3 out of 4 tubes, so maybe the 6x4 tube is bad??? I dunno.