124 replies to this topic

[rickh]

Folks,

 

I started this topic to discuss audio amplifiers, specifically amplifiers used for virtual pinball cabinets. In addition, I desire to include exciters and speakers, as they pertain to a virtual cabinet.  During my one and half years of building three VP cabinets I have become fascinated on how a well designed cabinet can create a rich experience that rivals the real thing.  During the course of my cabinet designs I have reviewed over a dozen audio amplifiers and several speakers.  In addition to these reviews, I have researched countless other systems and now I wish to share this knowledge.  My first install on this thread discusses my current first choice of amplifier.  I shall continue this very soon......

 

 

Rick

[mjr]

I look forward to seeing your ideas.  It seems surprisingly difficult to find an ideal pin cab audio amp solution.

[Slydog43]

I have contactors in both of my pincabs, but have recently purchased some emitters to play around with and I'm a little confused on if I need a 7.1 sound card and not sure at all about an amp. Very curious to test this stuff out and maybe make another cab.

[rickh]

I forgot to mention that I am currently on travel and do not have my research material on hand.  So I will dive into the subject concerning the amplifier I selected for my mini cabinet, as it was this discussion that gave me the idea to start this new thread.  Please be advised that my recommendations were intended to be at the end of my amplifier primer, so some of the stuff I will be talking about will require a bit of 'splaining'.

 

I was impressed by the audio quality of my first cabinet build.  The jolts of the bumpers, slingshots, and flipper felt realistic.  I used a pair of coaxial 4-1/2" car speakers for the left and right and a 6" sub woofer which had a dual voice coil so that it could be driven by the same channels driving the car speakers.   The amplifier of choice was a cheap 12VDC dual channel amplifier Lapei LP 808.  This amplifier was based upon the Sanyo LA4636 amplifier chip.   The amplifier is rated at 11 Watts @10%THD (true harmonic distortion).  A 10% THD is not impressive, but at 8 watts this amp give a respectful 1% THD.  I tried designing a cross-over circuit so that the amplifier wouldn't waste high to midrange power to the subwoofer.  However this didn't work.  So my next experiment was to get a similar amplifier with a separate subwoofer amplifier(commonly referred to as a 2.1 system) .  I tried the Lapei LP838, as it was being sold as an improved version of the LP-808 and was being used as a reference for the 'Poor Man's DOF'.  This amplifier was a turd.  Real power was a paltry 2.5W @ .5%THD for L/R channels and 8W@1%THD for the subwoofer (4 ohms).  Anything beyond this power was just pure garbage.   Allow me to repeat: the Lapei LP838 and all variants of this type were at the bottom of my list for 12VDC systems.  Raise the supply to 16V and this amplifier (along with all others) raised the power ceiling without raising distortion.

 

I tried several other amplifiers until I settled on the TPA3116D2.  This is a 2.1 class D amp capable of producing clean and powerful audio.  At 12VDC it can easily produce 15W per channel at .3% for L/R and 25W for the subwoofer (4 ohm loads).  Bump the supply voltage to 24VDC@4 amps and you have a mighty amplifier capable of at least 25W @ <.2% THD for the L/R channels and 50W for the subwoofer. At ~$20 it is a bargain. Limitation- The amplifier I purchased used toroidal coils which prevent it from driving loads lower than 4 ohms.  Since this is a reference design from TI, several manufacturers produces them with better components, hence giving them slightly better loading performance.

   

After answering questions/comments, my next subject will be 'Amplifiers, bad, good to great'    

Edited by rickh, 23 August 2017 - 08:04 PM.

[RustyCardores]

Poor Man's DOF (Surround Sound Driven Tactile Feedback) (PMD)

 

Many of us have been using the LP838 for driving the tactile exciters with great success. Yes they are too cheap and nasty for the main backglass sound, but for the bumps and knocks through tactile exciters they work really well.

I have contactors in both of my pincabs, but have recently purchased some emitters to play around with and I'm a little confused on if I need a 7.1 sound card and not sure at all about an amp. Very curious to test this stuff out and maybe make another cab.

 

If you want to use DJRobX's new surround sound feature of 10.4 to create directional sound and feedback ....trust me you do!   Then yes you need a 7.1 sound card. ( btw, tables are already being released to take advantage of the surround. Dozer's Indy500 and my mod of Tom's MedMad for example)

 

You don't need to run a 7.1 amp however (these are often large and expensive), instead you can run dual 2.1 mini amps for the tactile feedback, while continuing to use your existing sound system for backglass sounds.  Each of these amps plug into a separate output channel on the 7.1 card.

 

Edited by RustyCardores, 23 August 2017 - 09:21 PM.

[Brer Frog]

Rick -

Thank you for starting this thread.

Comparing this TPA3116D2 to the one you used.
http://www.ebay.com/...DUAAOSweW5VNSJU

You mentioned in your Micro-Cabinet Build thread “Those black square things are inductors and they look nicer than mine which were huge toroids that get hot because they have so much loss.”

Wouldn’t the inductors also get hot? And how do they affect driving loads lower than 4 ohms?

[rickh]

I have contactors in both of my pincabs, but have recently purchased some emitters to play around with and I'm a little confused on if I need a 7.1 sound card and not sure at all about an amp. Very curious to test this stuff out and maybe make another cab.

A standard stereo sound system should suffice.  Most 2.1 power amplifiers use a cross-over filters that direct L/R channels of low frequency audio to the sub woofer and the mid to highs to the stereo L/R speakers.  A 2.1 pre-amp system uses signal processing to create L/R Subwoofer content so that these signals can drive 3 separate amplifiers.  A 5.1 dolby digital system takes this to a whole new level by creating a center channel and two surround rear channels.  To the best of my knowledge visual pinball is simply stereo output, not 5.1 surround audio output, but I could be wrong.

Edited by rickh, 23 August 2017 - 08:27 PM.

[RustyCardores]

 

I have contactors in both of my pincabs, but have recently purchased some emitters to play around with and I'm a little confused on if I need a 7.1 sound card and not sure at all about an amp. Very curious to test this stuff out and maybe make another cab.

A standard stereo sound system should suffice.  Most 2.1 power amplifiers use a cross-over filters that direct L/R channels of low frequency audio to the sub woofer and the mid to highs to the stereo L/R speakers.  A 2.1 pre-amp system uses signal processing to create L/R Subwoofer content so that these signals can drive 3 separate amplifiers.  A 5.1 dolby digital system takes this to a whole new level by creating a center channel and two surround rear channels.  To the best of my knowledge visual pinball is simply stereo output, not 5.1 surround audio output.  Consequently, there is no benefit in paying extra for 5.1 or 7.1 audio system.

 

 

10.4 Beta now supports 7.1 output.

[rickh]

Rick -

Thank you for starting this thread.

Comparing this TPA3116D2 to the one you used.
http://www.ebay.com/...DUAAOSweW5VNSJU

You mentioned in your Micro-Cabinet Build thread “Those black square things are inductors and they look nicer than mine which were huge toroids that get hot because they have so much loss.”
Wouldn’t the inductors also get hot? And how do they affect driving loads lower than 4 ohms?

Mike,

 

No, the inductors get warm meaning that they are wasting some power.  However, the bonus is that the amplifier chips are so efficient that they remaining relatively cool under the most demanding circumstances.  As for driving low impedence loads under 4 ohms, linear amplifiers are better suited.  Regardless, I'm easily driving 2 ohms with my amp, as I'm not cranking it up beyond 15W. 

 

 

I have contactors in both of my pincabs, but have recently purchased some emitters to play around with and I'm a little confused on if I need a 7.1 sound card and not sure at all about an amp. Very curious to test this stuff out and maybe make another cab.

A standard stereo sound system should suffice.  Most 2.1 power amplifiers use a cross-over filters that direct L/R channels of low frequency audio to the sub woofer and the mid to highs to the stereo L/R speakers.  A 2.1 pre-amp system uses signal processing to create L/R Subwoofer content so that these signals can drive 3 separate amplifiers.  A 5.1 dolby digital system takes this to a whole new level by creating a center channel and two surround rear channels.  To the best of my knowledge visual pinball is simply stereo output, not 5.1 surround audio output.  Consequently, there is no benefit in paying extra for 5.1 or 7.1 audio system.

 

 

10.4 Beta now supports 7.1 output.

 

Rusty, After I submitted my first hack I read your remark and changed it accordingly.  I need to research this a bit deeper, as many of the sound samples for VP have been recorded in stereo. This means that 10.4 will have a new sound library, this is exciting.

[DJRobX]

Rusty, After I submitted my first hack I read your remark and changed it accordingly.  I need to research this a bit deeper, as many of the sound samples for VP have been recorded in stereo. This means that 10.4 will have a new sound library, this is exciting.

The way it works is the samples are mono, but VP places the sounds based on x and y locations. Microsoft takes care of the placement in the virtual "room" depending on how you've configured your speakers in the control panel.

[rickh]

 

Rusty, After I submitted my first hack I read your remark and changed it accordingly.  I need to research this a bit deeper, as many of the sound samples for VP have been recorded in stereo. This means that 10.4 will have a new sound library, this is exciting.

The way it works is the samples are mono, but VP places the sounds based on x and y locations. Microsoft takes care of the placement in the virtual "room" depending on how you've configured your speakers in the control panel.

 

Thanks DJRob-  I'll relegate my audio expertise to the hardware side of things ;-)

 

Rick

[RustyCardores]

 

 

Rusty, After I submitted my first hack I read your remark and changed it accordingly.  I need to research this a bit deeper, as many of the sound samples for VP have been recorded in stereo. This means that 10.4 will have a new sound library, this is exciting.

The way it works is the samples are mono, but VP places the sounds based on x and y locations. Microsoft takes care of the placement in the virtual "room" depending on how you've configured your speakers in the control panel.

 

Thanks DJRob-  I'll relegate my audio expertise to the hardware side of things ;-)

 

Rick

 

 

Rob's "da man!" as he wrote the VPX audio code.

[Brer Frog]

Let's say you start with a pair of stereo speakers. Then add a woofer. Then add exciters.

 

Should the woofer be powered by the 2.1 amp that drives the stereo speakers? Or a 2.1 amp that drives the exciters?

 

If the woofer is added at the same time as the stereo speakers it's probably already powered by the same 2.1 amp. But should it be changed over to the 2.1 amp powering the exciters when they are added?

 

Would it depend on the signal driving things? IIRC you can split the sound & send the mechanicals to secondary audio device.

 

IOW do you want the woofer enhancing the audio sounds from the backbox or adding haptic feedback along with the exciters?

[rickh]

Mike,

 

Based on a stereo output and not 5.1 Dolby surround :

 

The exciters do not have the volume of the regular speakers, so I would place them on their own separate amplifier (same audio source), provided that it has a volume control.  try a Pam8610 Audio Stereo amplifier.  They are ~$5 USD and provide >10 watts at <1%THD @12V (4 ohms) and a volume pot.  I would like to know what Rusty's recommendation is on this too, as I know that he has done lots of experimentation on this also.

 

Regards,

 

Rick

Edited by rickh, 24 August 2017 - 12:30 AM.

[RustyCardores]

Let's say you start with a pair of stereo speakers. Then add a woofer. Then add exciters.

 

Should the woofer be powered by the 2.1 amp that drives the stereo speakers? Or a 2.1 amp that drives the exciters?

 

If the woofer is added at the same time as the stereo speakers it's probably already powered by the same 2.1 amp. But should it be changed over to the 2.1 amp powering the exciters when they are added?

 

Would it depend on the signal driving things? IIRC you can split the sound & send the mechanicals to secondary audio device.

 

IOW do you want the woofer enhancing the audio sounds from the backbox or adding haptic feedback along with the exciters?

 

If not using 7.1, leave the woofer on the existing backglass sound amp and add a second 2.1 amp for the front exciters positioned near the flippers.  Split the mechanical sound to the second amp in VP audio prefs.

 

This will give you the basic starting point for you to "dip your toes" in.

 

If you like what you hear and feel, then you can add a rear position "audio" sub to that amp, or add yet another amp for rear exciters and rear audio sub (see my diagram above, or in the thread that I linked if the diagram does not display here). These will all work off the second sound device output from your computer, provided that you split the output to feed the two amps.  Once you balance all the amp volume levels, the effect is quite amazing..... This is how I played for over a year and it was absolutely fantastic, but it was only Left/Right positional and not true "surround" sound.  Any surround effect front / back was just as illusion of balance between amps and visual input of the ball.

 

If using 7.1 in VPX Beta, then you can use the same setup as above and each of your your three amps plugs into a different channel output from the 7.1 card. In this case, your subs are all working independently.  

 

OR.....

 

as Rob has done, use the Bass routing feature of your system and the surround will feed ALL bass via just the one main sub.  This negates the need for the purchase and install of the additional sub(s) as seen in my diagram.

 

It's a very configurable system and it's a system that you can start small and build on. That said, it's my recommendation that you jump right into 10.4 beta and 7.1, as directional sound & feedback is a game changer and can be used in place of DOF, or to at least minimise DOF installs to just blowers & LEDs. (although I have my LEDs sound driven too, but that's another thread on its own) 

Mike,

 

Based on a stereo output and not 5.1 Dolby surround :

 

The exciters do not have the volume of the regular speakers, so I would place them on their own separate amplifier (same audio source), provided that it has a volume control.  try a Pam8610 Audio Stereo amplifier.  They are ~$5 USD and provide >10 watts at <1%THD @12V (4 ohms) and a volume pot.  I would like to know what Rusty's recommendation is on this too, as I know that he has done lots of experimentation on this also.

 

Regards,

 

Rick

 

Re volume... the exciters that I am using are loud! I live on acreage with my closest neighbour is about 150m away.... but if I lived in the suburbs, I'm pretty sure that I would get complaints from the neighbours lol

[rickh]

Re volume... the exciters that I am using are loud! I live on acreage with my closest neighbour is about 150m away.... but if I lived in the suburbs, I'm pretty sure that I would get complaints from the neighbours lol

 

 

Rusty,

 

Interesting.   Here are the Exciters I am currently using: 

Dayton Audio DAEX25VT-4 Vented 25mm Exciter 20W 4 Ohm

Dayton Audio DAEX25 Pair of Sound Exciters (Black)

 

I am comparing both these exciters to:ANy 

BOSS AUDIO CH4230 Chaos Exxtreme 4" 3-way 225-watt Full Range Speakers

 

Have you used these components?

 

Thanks,

 

Rick

[RustyCardores]

I'm using these... https://www.jaycar.c...peaker/p/AS3039

[Onevox]

Mine: https://www.amazon.c...-6L&ref=plSrch.

I would be interested in knowing if surface area makes a difference in vibration.


Sent from my iPhone using Tapatalk

[RustyCardores]

Mine: https://www.amazon.c...-6L&ref=plSrch.

I would be interested in knowing if surface area makes a difference in vibration.


Sent from my iPhone using Tapatalk

I've ground the sides off my lockdown one so that I could fit it between mame buttons. It still works great.

I think the most important thing is the mass of the driver coil itself. The more mass that gets chucked around the better.


Sent from my iPhone using Tapatalk

[Brer Frog]

I'm doing a budget build so 7.1 will have to wait.

 

Rick -
In your 27" mini-pin build you mention about install another amp dedicated to the exciters. Would you use the Pam8610 or the TDA7377 since they're both 10W per channel?

Since the Dayton DAEX25VT-4 Exciters can handle 20W why not use a more powerful amp? Or is that really not needed? Since these are attached with adhesive how would you ever reposition them?

Rusty -
Do you think your exciters are louder because they're larger or maybe because they have a flat surface that attaches to the cabinet?

 

Mike