JBL 705P / 708P

[Sal1950]

It seems like they didn't go with an all-one-chip for the amplification part. There are 6 chips on the signal side of the board that have heat sinks, 2 are FREDs (FCU20A40) and 4 are switching FETs (IRFR4615).

Brand new and your taking it apart already?

That's what my folks used to say to me all the time.

 

[Thomas savage]

Whenever Dirac releases Unison, I think it will change a lot of things. I use a similar approach with opposing out of phase subs to control length modes. There is no comparable other bass management technique or room treatment. If it's implemented, it will be a fundamental shift in home audio, IMO.

It's what Iv been wanting for some time, It makes perfect sense. A seismic shift in home audio and looks even more effective in the relatively crap acoustical environment of a automobile.

 

[12B4A]

Brand new and your taking it apart already?

That's what my folks used to say to me all the time.

I'm just doing what I'd want someone else to do if they were in my situation. I often have to take apart cockpit avionics in the lab that are significantly more costly so I've built up enough confidence and steady hands to do it with my own significant chunk of money. Through doing so, I discovered that if the amp/dsp module totally goes, it's really simple mechanically to replace it. They designed the whole speaker/amp to be assembled simply. Also, the front LEDs can be easily disconnected as long as you have a star driver bit.

 

[Thomas savage]

I'm just doing what I'd want someone else to do if they were in my situation. I often have to take apart cockpit avionics in the lab that are significantly more costly so I've built up enough confidence and steady hands to do it with my own significant chunk of money. Through doing so, I discovered that if the amp/dsp module totally goes, it's really simple mechanically to replace it. They designed the whole speaker/amp to be assembled simply. Also, the front LEDs can be easily disconnected as long as you have a star driver bit.

Good to know

Might well disconnect the LEDs myself.

 

[Sal1950]

I'm just doing what I'd want someone else to do if they were in my situation. I often have to take apart cockpit avionics in the lab that are significantly more costly so I've built up enough confidence and steady hands to do it with my own significant chunk of money. Through doing so, I discovered that if the amp/dsp module totally goes, it's really simple mechanically to replace it. They designed the whole speaker/amp to be assembled simply. Also, the front LEDs can be easily disconnected as long as you have a star driver bit.

Just razzin ya,
Your insight has brought valuable info to the forum.
Thanks!

 

[Sal1950]

Good to know

Might well disconnect the LEDs myself.

Better give that a second thought.
The last time you opened up a amp, you had components breaking off the circuit board and more.

 

[watchnerd]

I'm just doing what I'd want someone else to do if they were in my situation. I often have to take apart cockpit avionics in the lab that are significantly more costly so I've built up enough confidence and steady hands to do it with my own significant chunk of money. Through doing so, I discovered that if the amp/dsp module totally goes, it's really simple mechanically to replace it. They designed the whole speaker/amp to be assembled simply. Also, the front LEDs can be easily disconnected as long as you have a star driver bit.

How do you have the 705p mounted?

 

[Thomas savage]

Better give that a second thought.
The last time you opened up a amp, you had components breaking off the circuit board and more.

It's ok sal, the JBL's were not built in the USA so should be solid

 

[watchnerd]

Hypothetical question:

For active speakers with DSP crossovers, is there any point in having a luxury DAC if it's all just going to get converted to digital at the speaker input, anyway?

 

[12B4A]

Hypothetical question:

For active speakers with DSP crossovers, is there any point in having a luxury DAC if it's all just going to get converted to digital at the speaker input, anyway?

Yes, at least here anyway. The analog signal is used in the comparator input of the IRS20957S chip to modulate the pulse widths to the output FETs.

Edit: Oh wait, you're talking at the system level. If the DAC has volume control and source switching, yes.

The 705ps are just sitting on stands out in the room a bit. Within the speaker cavity itself, there's a metal plate that joins the mounting holes that are on the top and bottom of the speaker so it's a pretty robust mounting.

 

[Purité Audio]

Hypothetical question:

For active speakers with DSP crossovers, is there any point in having a luxury DAC if it's all just going to get converted to digital at the speaker input, anyway?

None whatsoever, unless your 'luxury' DAC colours the sound .
Keith

 

[watchnerd]

None whatsoever, unless your 'luxury' DAC colours the sound .
Keith

That's what I'm thinking.

Put most of the money into the speakers. Put the next budget allocation into a decent analog preamp with XLR out. Use a modestly priced but well-measuring no-frills DAC.

Or perhaps just a Parasound P5 (~$1095 with built-in DAC and phono) and call it done.

 

[Sal1950]

None whatsoever, unless your 'luxury' DAC colours the sound .
Keith

I would absolutely agree, accept for the fact that I don't see a remote listed for control of volume, levels, etc.
What am I missing?

 

[Sal1950]

That's what I'm thinking.

I've always been a proponent of the KISS principle and being able to accomplish a mission with the minimal required introductions.
I believe the Kii 3s have gone in this direction with the addition of their remote?
Since the abilities to handle all a systems needs are available within the speaker, it makes no sense to me to be inserting anything else between them and the sources.

 

[Purité Audio]

Just look for a DAC with attenuation, variable analogue output is useful for matching overall gain, and it means you don't use too much digital attenuation.
Keith

 

[watchnerd]

I have analog sources, so I have to go the other route: a preamp for source switching and volume, and a 'dumb DAC' with fixed output.

 

[Blumlein 88]

I have analog sources, so I have to go the other route: a preamp for source switching and volume, and a 'dumb DAC' with fixed output.

The various Tact units did do variable digital out on AES EBU or SPDIF. Their stand alone amps only had digital input as they were made so the ADC was done in the power output stage. Early units used 40 bit calculation for volume control and later units 56 bit if I recall rightly. Early units were good up to 96 khz and later units up to 192 khz. Another unit I had that would do what you want if you only need 48 khz or 44 khz is the Meridian 518. It was digital in, digital out. It could supply various dither schemes and alter bit depth. It also could be a straight pass thru and do variable digital volume control. Not up on Meridians latest offerings, but as they make speakers that are active and DSP controlled with digital inputs I would think they make a digital preamp that would fit your needs.

Another option is digital volume in playback software and simply have that feed a USB to SPDIF converter.

I would think there might be various pro gear that has variable digital out though it likely has no remote control.

 

[watchnerd]

The various Tact units did do variable digital out on AES EBU or SPDIF. Their stand alone amps only had digital input as they were made so the ADC was done in the power output stage. Early units used 40 bit calculation for volume control and later units 56 bit if I recall rightly. Early units were good up to 96 khz and later units up to 192 khz. Another unit I had that would do what you want if you only need 48 khz or 44 khz is the Meridian 518. It was digital in, digital out. It could supply various dither schemes and alter bit depth. It also could be a straight pass thru and do variable digital volume control. Not up on Meridians latest offerings, but as they make speakers that are active and DSP controlled with digital inputs I would think they make a digital preamp that would fit your needs.

Another option is digital volume in playback software and simply have that feed a USB to SPDIF converter.

I would think there might be various pro gear that has variable digital out though it likely has no remote control.

Yep, there are lots of pro ADDAs with AES out but, as you said, no remotes.

Merdian appears to use their proprietary Speaker Link Ethernet-based connector for digital out:

The $16k Meridian 818V3 has one output labeled S/PDIF which might be variable, but the price point rules it out.

The NAD 50.2 does offer analog in / AES out and a remote...but no volume control...

 

[NWCgrad]

I am thinking of getting a set of 708P's. I want to stay digital all the way to the speaker.

The best options I have found so far for a digital preamp (digital to digital conversion, volume control, switching) are the Grace Design M905, Lynx Hilo, and Weiss Engineering INT204. All are remote controlled.

Potential system: Aurender N100H -> Grace Design M905 -> JBL Pro 708P. Simple, yet powerful. May need subs at some point, the Grace Design has sub outputs so not a problem.

 

[amirm]

That Grace Design M905 sounds cool: https://www.sweetwater.com/store/de...exWlW-usk4DKS35ewnYn4CH9b2ke6KVsaAjGVEALw_wcB

Welcome aboard by the way.