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  1. #1
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    SB and Low Volume on Klipsch Promedia Setup

    I have a SB Classic hooked to a Klipsch Promedia 2.1 setup. This has provided good quality sound for a long time but the amp in the subwoofer burned up. This is typical failure mode for the Promedia system. Rather that replace/repair the Klipsch amp I thought to replace it with a Lepai LP210PA 2x30W + 60W 2.1 plate amp.

    To power the Lepai I used a 20vdc HP laptop charger which should provide plenty of power. I converted the charger (3 wire cord) to a dc power supply (2 wire cord). The power plug on the charger has red (+), black (-), and blue (sense) – the blue wire is meant to send the laptop’s battery state back to the charger. I isolated the blue wire and just connected the remain + and – wires to a new power plug that fits the Lepai.

    The switchover to the Lepai was quick and easy. When I turned it on the sound quality was excellent but with very little volume. The SB is set to 100% output.

    I’m confused because this Lepai conversion has been done by others and it should have plenty of juice to produce more volume than this. Not sure though if others were feeding a signal from a SB Classic.

    Is there any way to up the gain on the SB?

    I do have a spare Sony receiver I could try and a DC power supply to see my 20vdc hacked power brick is just not delivering enough power.
    Thoughts?

  2. #2
    Senior Member Heuer's Avatar
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    Could be the output capacitors have failed which causes volume loss. Easy DIY fix if you search on the Forum for instructions.

  3. #3
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    Quote Originally Posted by traderyoda View Post
    I have a SB Classic hooked to a Klipsch Promedia 2.1 setup. This has provided good quality sound for a long time but the amp in the subwoofer burned up. This is typical failure mode for the Promedia system. Rather that replace/repair the Klipsch amp I thought to replace it with a Lepai LP210PA 2x30W + 60W 2.1 plate amp.

    To power the Lepai I used a 20vdc HP laptop charger which should provide plenty of power. I converted the charger (3 wire cord) to a dc power supply (2 wire cord). The power plug on the charger has red (+), black (-), and blue (sense) – the blue wire is meant to send the laptop’s battery state back to the charger. I isolated the blue wire and just connected the remain + and – wires to a new power plug that fits the Lepai.

    The switchover to the Lepai was quick and easy. When I turned it on the sound quality was excellent but with very little volume. The SB is set to 100% output.

    I’m confused because this Lepai conversion has been done by others and it should have plenty of juice to produce more volume than this. Not sure though if others were feeding a signal from a SB Classic.

    Is there any way to up the gain on the SB?

    I do have a spare Sony receiver I could try and a DC power supply to see my 20vdc hacked power brick is just not delivering enough power.
    Thoughts?
    Try using another source to feed the amplifier to rule that out.

    Sent from my Pixel 3a using Tapatalk

  4. #4
    Senior Member Heuer's Avatar
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    Here is the capacitor repair thread: https://forums.slimdevices.com/showt...ults-over-time

    if you don't want to mess with the caps then you can use the digital output via a DAC to the amp. I use a Topping E30 but others have used the Behringer DAC https://www.amazon.co.uk/Behringer-U..._t1_B0023BYDHK

  5. #5
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    Quote Originally Posted by Heuer View Post
    Here is the capacitor repair thread: https://forums.slimdevices.com/showt...ults-over-time

    if you don't want to mess with the caps then you can use the digital output via a DAC to the amp. I use a Topping E30 but others have used the Behringer DAC https://www.amazon.co.uk/Behringer-U..._t1_B0023BYDHK
    Great tips. I actually have two Lepai unit. I'll try hooking my DC power supply up first set at 22vdc and let the amp draw whatever amps it needs - that should eliminate my hacked power supply as the culprit. If power isn't the issue I'll swap out the Lepai with another and see if it's a cap or other discrete component issue on the amp. It's possible that this little plate amp needs more gain to work with - is should have plenty of power to crank the Promedia equipment to at least comfortable levels.

    My bet is power supply - converting a charger to a DC power supply is an iffy business as I have no clue how the control circuitry does and what happens when you isolate the sense wire.

    Will report back!

  6. #6
    Senior Member chill's Avatar
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    In the past I've made the mistake of assuming that more power equals more gain. I'm no expert, but my understanding is that although more power would be needed to drive an amplifier that has more gain, for an amplifier that has a certain gain, more power simply allows for less distortion. Too little power for an amplifier with a given gain will lead to distortion. So if you're hearing clean, undistorted sound but at a low volume, I doubt that would be because of the power supply. It points more to the input signal being too low (which is what the output caps thread is about).

    I'm happy to be corrected by those with more knowledge.

  7. #7
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    Quote Originally Posted by chill View Post
    In the past I've made the mistake of assuming that more power equals more gain. I'm no expert, but my understanding is that although more power would be needed to drive an amplifier that has more gain, for an amplifier that has a certain gain, more power simply allows for less distortion. Too little power for an amplifier with a given gain will lead to distortion. So if you're hearing clean, undistorted sound but at a low volume, I doubt that would be because of the power supply. It points more to the input signal being too low (which is what the output caps thread is about).

    I'm happy to be corrected by those with more knowledge.
    I read this thread, went away, thought about it, then return, and @chill had replied. My thoughts exactly. No distortion is the key. It sounds like a gain issue, or more specifically, and impedance mismatch. I am not familiar with your klipsh 2.1 speaker setup, but it looks like the typical "computer speaker system". I had an altec lansing system back in the day. I remember trying to use the subwoofer for something else and gave up because there seemed to be additional control wiring that I didn't know what to do with. I never got it to work right. I just could never figure out what do do with the extra wires

    It seems like your klipsch system takes the line in signal into the satellites, which have a volume and bass attenuator, then the signal is fed to the sub. The sub (on the kilpsch) has no attenuation? But now the lipa does. How do you have it hooked up? If you have the sb3 into the sattelites then the attenuated signal into the sub, that could be your problem, even if one of the two volumes is turned up full, it is still a possible impedence mismatch.

    I think your extra receiver experiment might be revealing

    Jim

  8. #8
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    one other thought....

    would be to run the sb into the lipa (which will control the sub as intended) and try to run the "speaker out" of the lipa into the satellites, or, if you have another speaker(s) handy, just to test. Then control the volume from the lipa.

    Continuing to think, you might have three gain stages in the signal path, the sb volume (if not 100%), the sat, and the lipa

    Jim

  9. #9
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    Here's what I've done so far. I'm using the following hookups. Signal is Analog RCA from the SB Classic to the Lepai. Klipsch satellites are RCA connected to the Lepai using its volume control. The SB is set to 100%. The Klipsch sub is 5.7 ohm and the each satellite is showing around 4.3 ohm.

    This is what I did so far:

    - Switched out the Lepai - no difference; both Lepai amps perform the same.
    - Hooked up another dc power supply (not my hacked laptop charger) rated at 19vdc and 3.9amps - no difference
    - Hooked up a digital DC power supply fixed at 22vdc (the max rated voltage for the Lepai) with floating current so the amp could draw what it needed - no difference
    - Took the SB out of the system and replaced it with a Yamaha radio for the source - music was louder but still not much more so - maxed out it about a background comfortable level.
    - Hooked the Klipsch satellites to a Sony AVR along with the subwoofer (using the mono sub output to one sub RCA input - tried both right and left) with input from the SB to the CD in channel - I can crank up the volume but the sounds is simply awful (muffled and distorted and the woofer just chuffs along incoherently.

    Here's what I think I've learned.

    - No issue with my SB Classic - it seems to be working fine.
    - No issue with my hacked laptop charger - it's putting out precisely 19vdc and will ramp up current when demanded (I hooked it to a light strip to check).
    - I can't test anything with the Sony AVR since it wants at least 8 ohms and can't do anything with these low ohm speakers.
    - The Lepai needs more gain to work with - when the setup was connected to my digital power supply it never pulled more than .4 amps. When you turn the Lepai's volume knob from zero it will amplify about half way up the dial and beyond that there's no increase in sound.

    Here's where I think this is headed - two options:

    1 - Buy a good DAC with a pre-amp stage to boost the gain.
    2 - Pitch the whole Klipsch system and replace it with 8 ohm satellites and a real sub.
    3 - Just buy another K. Promedia setup and stop getting fancy.

    By the way, the reason I went through all of this is because I made the fundamental mistake of wiring the Klipsch system into my walls. That was a great strategy until it failed. It's in a small reading/listening room which is a great place to chill but doesn't need a lot of punch. I just didn't want to tear everything out and was looking for a quick fix I could pull off with the existing wiring. Lesson learned.

    The SB is a fantastic device - anyone with a Classic or Touch that has a nice, small-area solution I'm all ears.

  10. #10
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    Quote Originally Posted by traderyoda View Post
    Here's what I've done so far. I'm using the following hookups. Signal is Analog RCA from the SB Classic to the Lepai. Klipsch satellites are RCA connected to the Lepai using its volume control. The SB is set to 100%. The Klipsch sub is 5.7 ohm and the each satellite is showing around 4.3 ohm.

    This is what I did so far:

    - Switched out the Lepai - no difference; both Lepai amps perform the same.
    - Hooked up another dc power supply (not my hacked laptop charger) rated at 19vdc and 3.9amps - no difference
    - Hooked up a digital DC power supply fixed at 22vdc (the max rated voltage for the Lepai) with floating current so the amp could draw what it needed - no difference
    - Took the SB out of the system and replaced it with a Yamaha radio for the source - music was louder but still not much more so - maxed out it about a background comfortable level.
    - Hooked the Klipsch satellites to a Sony AVR along with the subwoofer (using the mono sub output to one sub RCA input - tried both right and left) with input from the SB to the CD in channel - I can crank up the volume but the sounds is simply awful (muffled and distorted and the woofer just chuffs along incoherently.

    Here's what I think I've learned.

    - No issue with my SB Classic - it seems to be working fine.
    - No issue with my hacked laptop charger - it's putting out precisely 19vdc and will ramp up current when demanded (I hooked it to a light strip to check).
    - I can't test anything with the Sony AVR since it wants at least 8 ohms and can't do anything with these low ohm speakers.
    - The Lepai needs more gain to work with - when the setup was connected to my digital power supply it never pulled more than .4 amps. When you turn the Lepai's volume knob from zero it will amplify about half way up the dial and beyond that there's no increase in sound.

    Here's where I think this is headed - two options:

    1 - Buy a good DAC with a pre-amp stage to boost the gain.
    2 - Pitch the whole Klipsch system and replace it with 8 ohm satellites and a real sub.
    3 - Just buy another K. Promedia setup and stop getting fancy.

    By the way, the reason I went through all of this is because I made the fundamental mistake of wiring the Klipsch system into my walls. That was a great strategy until it failed. It's in a small reading/listening room which is a great place to chill but doesn't need a lot of punch. I just didn't want to tear everything out and was looking for a quick fix I could pull off with the existing wiring. Lesson learned.

    The SB is a fantastic device - anyone with a Classic or Touch that has a nice, small-area solution I'm all ears.
    when you mention that the sats are "showing around 4.3 ohm" are you measuring them? Speaker impedance is frequency dependent, you can't measure it with an ohm meter. In fact, a speaker on it's own is practically a DC short circuit, as it is just a coil of wire. It is true that the wire has a resistance per unit length.

    I wouldn't worry about the receiver wanting 8 ohms, and you giving it, say 4. You will just be making it work harder. In fact if you use the A+B speaker setting with 2 pair of 8 ohm speakers, the receiver is seeing 4 ohms.

    It still sounds to me that there is an active circuit in the satellites in between the lepai and the actual speaker itself (if its a single mid/high driver). If it is a little two way (separate high and mid) and there is some sort of active circuit in between the sat "in" and the actual sat speaker drivers. The fact that the klipsch system accepted the audio source into the sattelites (which have a volume control) and then sent the bass signal to the old sub, makes me think this is the case.

    Name:  2021-02-06 16_34_15-ProMedia21OwnersManualRev2012_635042122162050000.pdf.png
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    ok, I just found the manual. This is different from the altec lansing system I messed up. I can see why you would think this would work. each satelite has actual speaker hookups, and one of the sats has a preamp. We are assuming that a 2.1 amp is in the sub box. with your hookup you are assuming that you don't need the path through the sat preamp.

    When you say low volume, it is both the sub and the sat volumes that are low? Is there any difference in the sound between the sat with the preamp and the one without? Have you completely disconnected the sat preamp cables (only speaker wires hooked to sats)?

    If you hookup the sb3 to just the lirpa, do you get good clean bass volume with the gain turned up? In other words, the klisch out of the picture)

    Jim

    Jim

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