How to turn your AudioSource AMP 100 into a real amp. (Paying it forward)

[DCinDC]

Re: How to turn your AudioSource AMP 100 into a real amp. (Paying it forward)

I've fixed several AudioSource amps by replacing the rectifiers. I would put it on the to-do list for any AS amp.

[tyger23]

Re: How to turn your AudioSource AMP 100 into a real amp. (Paying it forward)

I've fixed several AudioSource amps by replacing the rectifiers. I would put it on the to-do list for any AS amp.

I looked over the rectifier circuit on the two boards I've seen. Both used 6A4 rectifiers with snubber caps. Given that they're only 100W amps at best and they're using a 60Hz linear circuit, I'd say that the power supply section on this particular amp is more than good enough.

The layout is not optimal, but I'm not sure spending any money on faster or different rectifiers would buy you anything for this particular amp.

[DCinDC]

Re: How to turn your AudioSource AMP 100 into a real amp. (Paying it forward)

I looked over the rectifier circuit on the two boards I've seen. Both used 6A4 rectifiers with snubber caps. Given that they're only 100W amps at best and they're using a 60Hz linear circuit, I'd say that the power supply section on this particular amp is more than good enough.

The layout is not optimal, but I'm not sure spending any money on faster or different rectifiers would buy you anything for this particular amp.

The stock ones are JUNK. I'm not advocating "better" diodes, I'm saying replace them out of hand. Out of 3 that were broken that I fixed, ALL of them were the rectifiers. Replace them.

[tyger23]

Re: How to turn your AudioSource AMP 100 into a real amp. (Paying it forward)

All,

I just wanted to highlight one thing:

In step 5 of the Main Board reworks, I'm increasing the gain through the non-inverting volume control buffer amp. Basically, the stock values for R103/203 and R104/204 provided a gain level of +16.5dB. This gain level means that your audio source must be able to produce +1.5V RMS or higher in order to get the full power out of this AMP-100.

Unfortunately, most consumer audio devices these days (PC's, iDevices, etc) only produce 750mV RMS to 1V RMS. Therefore, my changes boosted the gain through this amplifier to +19.75dB. This allowed for a much better volume control usage when using one of these lower powered sources.

However, I've been working with Firefox and he is experiencing an "ultra sensitive" volume control. His source is an Adcom tuner, which has much higher output than an iDevice. Therefore, his volume control was only limited to about 0 to 1/4 turn. So, I guess I would caveat my changes with:

KNOW YOUR AUDIO SOURCE.

If you're going to be using an ultra-high powered audio source, you may want to actually lower the gain levels. Here's my recommendation:

• If your audio source is rated to produce 750mV RMS - 1V RMS (most modern day consumer devices do this), then R103/203 should be 34K. This produces 19.75dB of gain.
• If your audio source is rated to produce 1.5V RMS to 2V RMS, then R103/203 should be 22.6K (Mouser part number 271-22.6K-RC). This produces +16.64dB of gain. This is 3dB less than original (about 1/2 the power).
• If your audio source is rated to produce >2.5V RMS, then R103/203 should be 15.4K (Mouser part number 271-15.4K-RC). This produces +13.89dB of gain. This is about 6dB less than original (about 1/4 the power).

Thanks Firefox for finding this "improvement" for us!

[randyw]

Re: How to turn your AudioSource AMP 100 into a real amp. (Paying it forward)

Sir,are you doing these mods for money, if I send you my amp?Thanks, randyw from Chicagoland.

[dareblue]

Re: How to turn your AudioSource AMP 100 into a real amp. (Paying it forward)

I have an AudioSource Amp One/A. I don't know how different it is from the Amp 100. I am having trouble with the audio cutting out on the right channel. To verify the problem is in the amp, I've changed sources, cables, speakers, etc. Just the other day however, something happened. We recently got new couches in our home theater. For some reason they tend to generate a lot of static electricity. We were listening to some music, and within a minute of starting, the amp cut out as usual. I got up to turn the volume knob to try and get it to come back on. As soon as I got close to the knob I got a jolt of static electricity and the audio came back on in the channel momentarily. It went out and again, a slight static charge would cause the channel to operate normally for a moment. Yet, if I turn or jiggle the volume knob without and static charge, there seems to be no affect. Other than the channel not working, the amp is like new. I would hate to do the mods and still have the channel cut out. Any help or suggestions on what I should do next would be appreciated. Tyger23, do you do amp repair for a fee?

[tyger23]

Re: How to turn your AudioSource AMP 100 into a real amp. (Paying it forward)

The Amp One is a very different beast than the AMP-100. The Amp One uses a discrete topology (meaning independent FETs driving the audio signal to the speakers rather than an integrated circuit like the AMP-100 uses).

Most of my changes mentioned in the AMP-100 were to the pre-amp phase, so some of those changes *could* be useful, but I doubt that the two amps would look anything similar and it would require hours of debug and re-engineering work to get it done.

I recently changed jobs and I now work out of my home, so I don't have access to a full lab yet (until I get off my arse and finish cleaning out that room that's supposed to be my office/lab), so I'm afraid I can't really help you at this moment. For the money, I'm willing to bet that you'd come out cheaper (and happier) by just purchasing a new AMP-100 from PE or something similar.

Good luck!

[dareblue]

Re: How to turn your AudioSource AMP 100 into a real amp. (Paying it forward)

Is it safe to say the volume pots are the same between the two amps? And could a faulty pot cause the audio to cut out? If so, I could just replace the pots with the model you spec'd for the 100. What do you think? Thanks.

[audioengr]

Re: How to turn your AudioSource AMP 100 into a real amp. (Paying it forward)

I have an AudioSource Amp One/A. I don't know how different it is from the Amp 100. I am having trouble with the audio cutting out on the right channel. To verify the problem is in the amp, I've changed sources, cables, speakers, etc. Just the other day however, something happened. We recently got new couches in our home theater. For some reason they tend to generate a lot of static electricity. We were listening to some music, and within a minute of starting, the amp cut out as usual. I got up to turn the volume knob to try and get it to come back on. As soon as I got close to the knob I got a jolt of static electricity and the audio came back on in the channel momentarily. It went out and again, a slight static charge would cause the channel to operate normally for a moment. Yet, if I turn or jiggle the volume knob without and static charge, there seems to be no affect. Other than the channel not working, the amp is like new. I would hate to do the mods and still have the channel cut out. Any help or suggestions on what I should do next would be appreciated. Tyger23, do you do amp repair for a fee?

I think the AudioSource Amp One/A has a speaker relay which oxidizes over time causing your speakers to cut out or sound distorted due to the diode effect. The static shock may be sending a brief pulse of energy through the amplifier which jumps the oxide and allows the signal to play through. The relay is often serviceable or replaceable.

[dareblue]

Re: How to turn your AudioSource AMP 100 into a real amp. (Paying it forward)

Unfortunately I can't find a schematic for this amp online. How do I know where the relay is, what it looks like?

[danvee]

Re: How to turn your AudioSource AMP 100 into a real amp. (Paying it forward)

It may be easier to post a photo of your amp's board and someone could spot and highlight it for you...

[tyger23]

Re: How to turn your AudioSource AMP 100 into a real amp. (Paying it forward)

The relay is a big black rectangle sitting dead in the middle of the unit. There are wires leading from the speaker connectors at the back of the unit to an area on the motherboard very close to this relay. The pots appear to be similar to the ones used in the AMP-100, but without seeing the construction and part number, I can't tell for certain. I'd recommend checking your fuses (one near the AC cord input and two near the big capacitors) and checking all the wires for loose connections.

Also, look at all of your capacitors to see if any are bulging or open. If you can get the main board out, you may want to try and wiggle different caps and other components to see if anything has a cold-solder joint (looks like it's soldered, but when you wiggle it you can see that a crack has developed and the part needs to be re-soldered). Good luck!

[dareblue]

Re: How to turn your AudioSource AMP 100 into a real amp. (Paying it forward)

I opened the amp tonight to take a photo of it and it looks very similar to the 100. My relay appears to be clear and looks to be in good condition, but I doubt I would be able to see any corrosion anyhow. I haven't taken the board out to look for cold solder joints, but the components look in good shape. Should I be suspect of the volume pots? Fuses test good on a volt meter.

[tyger23]

Re: How to turn your AudioSource AMP 100 into a real amp. (Paying it forward)

FYI - the picture I posted with descriptors was of an Amp One, not an Amp 100. If you can, try and get the amp to momentarily play music. If you hear the relay clicking on and off when the music comes and goes, then the relay (or the relay's control circuit) is likely to blame. That one pot looks similar to the Amp-100's volume pot. It's a 100K-ohm pot with an "A" taper. However, I'd need to see the bottom to know for sure.

If you can wiggle the volume or balance knob and hear the music come and go, then you can suspect the pots. One other trick is to (with the power off) quickly cycle the pots from min to max to min to max, etc. over and over again for about 40-50 times. This would free up any dust lodged in the contacts that could be causing an issue.

[dareblue]

How to turn your AudioSource AMP 100 into a real amp. (Paying it forward)

I just did some testing and if I touch the relay I can make both channels cut in and out. I'm suspecting bad solder joints and am going to remove the board to get access to the bottom. Do you think it's just solder and the relay is fine? But after touching solder joints, it seems to be really sensitive and audio cuts out almost anywhere I touch on the board. Still could be a solder joint? I'm gonna touch them up and test again.