[Occam]

I'd like to know if anyone is using unbalanced inputs and a "ground cheater plug" to eliminate noise..

I would hope that no one, who cares about the safety of others, would publically admit to such.
You might well minimize ground loop induced noise/hum, but give up whatever benefits you accrue via balanced inputs. It is an unnecessary choice. It it also a substantial violation of US/Canada electrical codes. There is no such thing as a 'cheater' plug, There ARE plugs whose intended use is to provide a grounded outlet to a nominally ungrounded receptacle, via the receptacle's center center screw which is tied via the receptacles strap to a grounded box.
This might be appropriate for alternative solutions -
http://www.jensen-transformers.com/an/an003.pdf

FWIW,
Paul

[jhm731]

I'd like to know if anyone is using unbalanced inputs and a "ground cheater plug" to eliminate noise..

I would hope that no one, who cares about the safety of others, would publically admit to such.
You might well minimize ground loop induced noise/hum, but give up whatever benefits you accrue via balanced inputs. It is an unnecessary choice. It it also a substantial violation of US/Canada electrical codes. There is no such thing as a 'cheater' plug, There ARE plugs whose intended use is to provide a grounded outlet to a nominally ungrounded receptacle, via the receptacle's center center screw which is tied via the receptacles strap to a grounded box.
This might be appropriate for alternative solutions -
http://www.jensen-transformers.com/an/an003.pdf

FWIW,
Paul

"Ground Loop Hum - Sooner or later every sound person encounters a 'ground loop hum' in their sound system. Most people think that adding a transformer module to the power amplifier rack will eliminate the problem, but this is not always the case.

In professional audio, the audio signal path should only be grounded at a single point. This single point grounding is circumvented when 2 pieces of AC powered gear are connected to each other. (Our USA National Electrical Code (NEC) specifies that all electrical equipment that draws potentially harmful amounts of current from the AC Mains must have its metal chassis grounded to the electrical systems 'earth' ground) With this being the case, any AC powered piece of gear with a 3-prong AC plug will more than likely have it's signal grounds at "earth ground" potential. This usually gives the quietest operation for the equipment. Now, if we connect 2 or more pieces of AC powered audio gear together via signal cables, we now have the sound system's audio signal path connected to ground at two points, creating paths that also connect the audio signal to the electrical 'earth' ground. The resultant hum is directly related to the differences in current that flow in the respective electrical circuits, which all share the same earth ground.

If the audio signal path is only connected to ground at a single point, the differences in ground currents will not induce any interference from the power line, so the sound system will not hum.

Using the little gray three pin to two pin electrical AC adapter on the end of the power cord of (1) of the AC powered devices will usually solve the problem, but is not the recommended solution.

The most common problem lies in the fact that the balanced (XLR) audio connections between the mixer and amplifier have a common audio signal ground that finds its way to the electrical ground via multiple chassis ground connections. The solution is to lift the audio signal ground or pin #1 of the balanced connector at the source of the balanced audio signal line. In this case, pin #1 should be lifted at the mixer position. This can be done with an XLR Ground Lift adapter, or if you're adept at electronics, you can lift pin #1 from ground on one end of the balanced cable, this will eliminate the ground loop hum but you may then experience 'RFI' (radio frequency interference) in the system. The solution is this case is to add a small capacitor (such as a .001 mFd) from the shield or ground wire to pin #1. Adding the capacitor allows the balanced line to be lifted (open) from ground at audio frequencies, while acting as a closed circuit for radio frequencies.

The real cause of the ground loops has to do with the way that our electrical power is distributed. In order to explain in any further detail would require a thorough discussion of electrical power distribution. The foundation of the above tip is: Not allowing the audio signal path to go ground in more than one place."

[AmpDesigner333]

We received a question about damping factor this week.  Both the DAC4800A and Cherry were tested for this at 1KHz, which is higher than normal for a damping factor test.  Into 8 ohms, it measures around 200 (Rload/Rout).  We plan to test at 100Hz and post the result here...

There has been some controversy regarding the real meaning of damping factor, however.  Tube amps are known for their sweet sound but usually have a low damping factor due to high output impedance.  We believe the natural open loop performance of the amp comes into play as damping factor lowers.  In most cases this occurs as frequency rises.  With good power supply design and strong output stages, damping factor can mean less to the sound of an amp.  Once again, the proof is in the pudding, so there's no substitute for listening.

Looking for some commentary about this subject...

[AmpDesigner333]

copied from the Google Chrome thread:

on this page there is a picture with the link "http://www.digitalamp.com/Picture%203619.jpg". This picture does not show up. Also if I click on the link to go to that product page http://www.digitalamp.com/4800a_amp1.htm the same picture does not show up, while the other one (of the two pics) does.  This happens on both the Chrome and Firefox browsers so I think it's safe to say the file is missing.  If you delete the cache in your browser (under options) you will probably see the same thing I am seeing.

I would recommend you pay someone who knows how to setup a "Joomla" website.  Very professional and less expensive than having one built from scratch.  You may be able to buy a Joomla Template and set it up yourself.

Good luck with your biz.

cheers, -Brad-

update: I downloaded one of your "small" pics. It was 1600x1200 pixels and 700K bytes in size!  This would be OK for an expanded display after clicking on the small image.  But you can reduce these images to 12% (to 20K in size) for the initial pic on your products page.

The "this page" above is our products page.

Is anyone out there having similar problems with our site?  If you are having speed problems, are you using dial-up?

Also, anyone have feedback regarding "Joomla"?  I never heard of it before, but like I said on the other thread, we're much better at making amplifiers than we are at making websites!  Thanks.

[jman66]

Tommy,

No problems accessing your website site using IE7...

[AmpDesigner333]

We received a question about damping factor this week.  Both the DAC4800A and Cherry were tested for this at 1KHz, which is higher than normal for a damping factor test.  Into 8 ohms, it measures around 200 (Rload/Rout).  We plan to test at 100Hz and post the result here...

There has been some controversy regarding the real meaning of damping factor, however.  Tube amps are known for their sweet sound but usually have a low damping factor due to high output impedance.  We believe the natural open loop performance of the amp comes into play as damping factor lowers.  In most cases this occurs as frequency rises.  With good power supply design and strong output stages, damping factor can mean less to the sound of an amp.  Once again, the proof is in the pudding, so there's no substitute for listening.

Looking for some commentary about this subject...

A bold statement from Wikipedia:
"For audio power amplifiers this source impedance Zsource (also: output impedance) is generally smaller than 0.1 Ω (ohms), and, from the point of view of the driver voice coil, is a near short-circuit."

Here's the link:
http://en.wikipedia.org/wiki/Damping_factor

I took some more measurements and will report the results soon...

[AmpDesigner333]

At 1KHz I got a damping factor of more than 180, and the same for 100Hz, both with an 8 ohm load.

Here's an easy measurement trick to find output resistance, but you need an accurate audio analyzer to use it:
Load the amp with 24 ohms and change the input voltage (sine wave) until you get exactly 24 volts out of the amp.  Remove the load and subtract 24 from the new output voltage measurement.  This is the output resistance in ohms!  24 ohms was picked to increase accuracy, but you can do the same thing with 8 ohms and 8 volts.  The voltage measurement should have 3 digits after the decimal point for this to yield an accurate measurement.

Any comments???

[AmpDesigner333]

We received some questions outside AC about DAC4800A (and Cherry) input impedance, which is 10K...

It's simple...  You get more noise with higher input impedance.  Going from 10K to 100K might cost as much as 3dB, but since stock SNR is over 114dB, there's room.  We don't do this stock because most preamps have a 600 ohm or lower output impedance, more than 10:1 (the typical "rule of thumb") to drive the amp.  We opted for better SNR.  The current of the preamp's output driving 10K is VERY low (microamps), so that's not really a significant factor.  We can modify amps for 100K input impedance when requested, but there is some rework required.

Comments?

[AmpDesigner333]

Please take a moment and sign up for our newsletter.  We have one coming out very soon (this weekend?).  Here's the link:
http://www.digitalamp.com/news.htm

[AmpDesigner333]

Please take a moment and sign up for our newsletter.  We have one coming out very soon (this weekend?).  Here's the link:
http://www.digitalamp.com/news.htm

The newsletter went out today, so please send me a private message if you signed up but didn't receive it.  Thanks.

[richidoo]

Tommy or jhm731,
Can you post a clear picture of the front and rear? I can't get what it looks like from any online photos. Looks like a lot of LEDs on the front. Can they be shut off?
Thanks!!
Rich

[mcullinan]

Plus post your review Id like to hear your thoughts.
Mike

[AmpDesigner333]

Tommy or jhm731,
Can you post a clear picture of the front and rear? I can't get what it looks like from any online photos. Looks like a lot of LEDs on the front. Can they be shut off?
Thanks!!
Rich

Sorry for the delay, I'll get working on the pics, probably will post tomorrow...

There are 7 LEDs on the front of the DAC4800A, protect, clip, and active for each channel, red, yellow, green respectively.  The LED in the middle is an AC power indicator, blue.  The Cherry has the same LEDs, but they are internal and glow through the vent holes (looks pretty cool, actually).  The LEDs can be disabled prior to shipping if requested.  Opening the chassis voids the warranty unless we authorize it.  The clip LEDs don't ever light because we disable the clip compression these days.  So far, our customers prefer not to enable compression of any sort even though it only happens during extreme conditions.

Thanks for your kind post.

[jman66]

Tommy,

Can you elaborate on this:

This amplifier is also a "green" product since it consumes less than 30W when "quiet" and less than 5W in standby mode.

Is it better to:
     A) Leave the amp powered on 24/7 in "quiet" mode?
     B) Leave the amp powered on 24/7 and switch into standy mode when not listening?
     C) Power on/off for each listening session?

Some amps work fine powered on/off for each session, while others benefit from being left on. Where does your amp fit into this?

-jim

[THE_ANSWERS]

Please take a moment and sign up for our newsletter.  We have one coming out very soon (this weekend?).  Here's the link:
http://www.digitalamp.com/news.htm

The newsletter went out today, so please send me a private message if you signed up but didn't receive it.  Thanks.

got your mass email.......       still pushing the amazon thing, huh????  i just dont get it

[AmpDesigner333]

Tommy,

Can you elaborate on this:

This amplifier is also a "green" product since it consumes less than 30W when "quiet" and less than 5W in standby mode.

Is it better to:
     A) Leave the amp powered on 24/7 in "quiet" mode?
     B) Leave the amp powered on 24/7 and switch into standy mode when not listening?
     C) Power on/off for each listening session?

Some amps work fine powered on/off for each session, while others benefit from being left on. Where does your amp fit into this?

-jim

It's up to you and won't make a difference in the sound either way.  I usually leave them on all the time.  Standby is convenient for changing cables and such if you like to do that.  Some customers have said our amps sound best after a few minutes of warm up.  Thanks.

[jhm731]

Tommy or jhm731,
Can you post a clear picture of the front and rear? I can't get what it looks like from any online photos. Looks like a lot of LEDs on the front. Can they be shut off?
Thanks!!
Rich

[jman66]

Tommy,

How does one operate the DAC4800A in bridged mode?

-jim

[richidoo]

Thanks for the pics jhm 

Looking forward to reading your comments about its sound.
Rich

[AmpDesigner333]

Tommy,

How does one operate the DAC4800A in bridged mode?

-jim

Jim,

You need a "Y bridge cable" (XLR single female to XLR double male) to that has plus and minus straight into the first channel and reversed on the second channel.  We are planning to offer this on our site eventually, but we make them custom on request.  Thanks.

Best Regards,
Tommy