No worries Stretch, we all need to do what’s best for our own goals. You did mention that you have very sensitive speakers. Perhaps a 20w, 35w or 40w super sounding pure Class A (Aksa Lender front end and P-channel Aleph output stage). Look for Alpha 20 (35w with 28v rails) or Alpha Nirvana (40w) amps in the GB forum. They are simple to build and very very nice sounding.
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Hi xrk971 - or anyone who has tried/ measured this use
Some questions please, re
- multiple channels? “SE mode”
- the output into loads around 4 (possibly a little less)
- minimum prudent impedance
In standard/ default configuration.
… And in particular whatever other options there are. Four channels/ presumably two could also be an option. I apologise if I missed it but I‘ve only seen a sentence or two on other configurations
At this stage, I’m looking for an amplifier for the bass on the Linkwitz LX521. Though I could well use them in one or two other projects: I've got a number of drivers that I’d get going on sooner if I had knew of an excellent amp to have the whole active system plan solid. I know a reasonable amount about speaker design, but little about amplification and “optimising”
Exact situation -
The LX521 (I’ve the kit for) crosses actively to its bass at 120 Hz. Linkwitz says 60 watts is sufficient, the drivers are 87 dB so 60 watts should yield c 105 dB.… enough
But impedance presented to the amplifier …
Nominally, 4 ohms
Voice Coil Resistance is specced at 3.3 ohms. I don’t know how good an indicator that 3.3 ohms might be of the load to the amp?? (And it’d be measured on a standard IEC baffle. These are in an unusual dipole baffle)
Being dipole, there is a lot of EQ to keep them flat almost down to 30 Hz, so there are two woofers a side
If only two channels of bass amplification were used, and the drivers were wired in series, it could be only c 1.7 ohms. Few owners do that
(I am a fan of the sound of both Nelson Pass and Hugh, and simultaneously looking at using the ABBB for their midrange) - with their bass possibly driven by this.
A description said TPA3255 when operated in SE mode provides for 4 channels of output.
When it’s used that way, what is the output per channel, at 8 and at 4 ohms?
http://www.seas.no/images/stories/extreme/pdf_datasheet/L26ROY-XM001-04_Datasheet_v2.pdf
While the real amplifier load could be/ appears is likely to be a little below 4 ohms, as it’s only being used over only two or three octaves, I’m guessing that even though it’s limited bandwidth, being the bass it doesn’t make it any easier.
So, would this be a good choice?
Thank you !!!
Some questions please, re
- multiple channels? “SE mode”
- the output into loads around 4 (possibly a little less)
- minimum prudent impedance
In standard/ default configuration.
… And in particular whatever other options there are. Four channels/ presumably two could also be an option. I apologise if I missed it but I‘ve only seen a sentence or two on other configurations
At this stage, I’m looking for an amplifier for the bass on the Linkwitz LX521. Though I could well use them in one or two other projects: I've got a number of drivers that I’d get going on sooner if I had knew of an excellent amp to have the whole active system plan solid. I know a reasonable amount about speaker design, but little about amplification and “optimising”
Exact situation -
The LX521 (I’ve the kit for) crosses actively to its bass at 120 Hz. Linkwitz says 60 watts is sufficient, the drivers are 87 dB so 60 watts should yield c 105 dB.… enough
But impedance presented to the amplifier …
Nominally, 4 ohms
Voice Coil Resistance is specced at 3.3 ohms. I don’t know how good an indicator that 3.3 ohms might be of the load to the amp?? (And it’d be measured on a standard IEC baffle. These are in an unusual dipole baffle)
Being dipole, there is a lot of EQ to keep them flat almost down to 30 Hz, so there are two woofers a side
If only two channels of bass amplification were used, and the drivers were wired in series, it could be only c 1.7 ohms. Few owners do that
(I am a fan of the sound of both Nelson Pass and Hugh, and simultaneously looking at using the ABBB for their midrange) - with their bass possibly driven by this.
A description said TPA3255 when operated in SE mode provides for 4 channels of output.
When it’s used that way, what is the output per channel, at 8 and at 4 ohms?
http://www.seas.no/images/stories/extreme/pdf_datasheet/L26ROY-XM001-04_Datasheet_v2.pdf
While the real amplifier load could be/ appears is likely to be a little below 4 ohms, as it’s only being used over only two or three octaves, I’m guessing that even though it’s limited bandwidth, being the bass it doesn’t make it any easier.
So, would this be a good choice?
Thank you !!!
My application was also planned to be LX521.
https://www.ti.com/lit/ds/symlink/tpa3255.pdf?ts=1601901865237&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FTPA3255
Page 6 - looking at this looks like the minmum impedance in SE config is 1.7 ohms. Should cope fine with LX521, single channel per woofer.
XRK's RTR solution is only in bridged config though, you'd need to modify or building from PCB to use it single ended.
https://www.ti.com/lit/ds/symlink/tpa3255.pdf?ts=1601901865237&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FTPA3255
Page 6 - looking at this looks like the minmum impedance in SE config is 1.7 ohms. Should cope fine with LX521, single channel per woofer.
XRK's RTR solution is only in bridged config though, you'd need to modify or building from PCB to use it single ended.
Thanks again
in SE mode, if it can handle a minimum of 1.7 ohms - and can output 4 channels, of only 60 W into about 2 ohms … then only one amplifier module should seem enough ?
under Audio Characteristics - SE (on p 9) it states that at 1%THD+N, eg at 3 ohms “TYP” is 98. In this context, I would have thought that TYP is now a measure of watts.
But
- it doesn’t state how many channels are being used. Which seems to me “incomplete“ as a purpose of SE is multi-channel ?
- and “ PVDD = 53.5V “ … does that mean for SC mode a slightly higher rated transformer would be more appropriate?
as I said earlier, I’m primarily interested in the LX521 bass, but I’m also exploring its flexibility, how well it could work in other situations. And looking into that now, because if it works well in other situations it would be good to add numbers to help get the group buy threshold up
in SE mode, if it can handle a minimum of 1.7 ohms - and can output 4 channels, of only 60 W into about 2 ohms … then only one amplifier module should seem enough ?
under Audio Characteristics - SE (on p 9) it states that at 1%THD+N, eg at 3 ohms “TYP” is 98. In this context, I would have thought that TYP is now a measure of watts.
But
- it doesn’t state how many channels are being used. Which seems to me “incomplete“ as a purpose of SE is multi-channel ?
- and “ PVDD = 53.5V “ … does that mean for SC mode a slightly higher rated transformer would be more appropriate?
as I said earlier, I’m primarily interested in the LX521 bass, but I’m also exploring its flexibility, how well it could work in other situations. And looking into that now, because if it works well in other situations it would be good to add numbers to help get the group buy threshold up
Also - anyone -
At least as important - what I think of in layman’s terms from the amplifier’s point of as “bass grip”
I once swapped a Byston amplifier into a system, and the amount of tightness and extension it added to the bass was amazing. it seemed almost as though another octave of extension was added, probably because what was there before the Byston was just kind of loose. It really took control of the woofers. Drums had more punch.…
partly I think, because of “generous” capacitance.
(It was a long time ago but) I also recall it was “high current”, but I have no idea what is considered “high”. It’s not a common spec. (If money and space were less important I might be a bit tempted to “play safe” on this premium hopefully “speaker for life” and wait for 4 channels of Byston to come up second hand.
But, Active bass, class D seems particularly suited to.
How do you think this amplifier would compare with a similar rated Hypex UCD - or Bryston - re bass tightness?
At least as important - what I think of in layman’s terms from the amplifier’s point of as “bass grip”
I once swapped a Byston amplifier into a system, and the amount of tightness and extension it added to the bass was amazing. it seemed almost as though another octave of extension was added, probably because what was there before the Byston was just kind of loose. It really took control of the woofers. Drums had more punch.…
partly I think, because of “generous” capacitance.
(It was a long time ago but) I also recall it was “high current”, but I have no idea what is considered “high”. It’s not a common spec. (If money and space were less important I might be a bit tempted to “play safe” on this premium hopefully “speaker for life” and wait for 4 channels of Byston to come up second hand.
But, Active bass, class D seems particularly suited to.
How do you think this amplifier would compare with a similar rated Hypex UCD - or Bryston - re bass tightness?
Hi Otto,
I would recommend BTL config for the woofers on the Lx521. The other channels probably fine with SE output. Ideally the woofers would be 4ohms nominal (two 8ohms parallel) would be best impedance fit for the TPA3255 in BTL. If 2ohms then use parallel BTL monoblock. The bass grip on this amp is impressive as good as my best Class AB. It has huge (for class D chip amp) 4700uF rail caps as close to power rail pins as possible. The indicators have a massive cross section of flat copper wire and can handle 27A I think. That’s the max current rating of the TPA3255.
If the impedance is 1.7ohms as you indicate above, you should run PBTL mode - one amp per woofer channel. That will give you probably 250 clean watts. The datasheet says 480w 2ohms PBTL at 1% THD. But with PFFB, the power will be reduced due to lower gain. You could easily disable PFFB (not needed for a sub amp) and get your 480w for 2ohms.
I would recommend BTL config for the woofers on the Lx521. The other channels probably fine with SE output. Ideally the woofers would be 4ohms nominal (two 8ohms parallel) would be best impedance fit for the TPA3255 in BTL. If 2ohms then use parallel BTL monoblock. The bass grip on this amp is impressive as good as my best Class AB. It has huge (for class D chip amp) 4700uF rail caps as close to power rail pins as possible. The indicators have a massive cross section of flat copper wire and can handle 27A I think. That’s the max current rating of the TPA3255.
If the impedance is 1.7ohms as you indicate above, you should run PBTL mode - one amp per woofer channel. That will give you probably 250 clean watts. The datasheet says 480w 2ohms PBTL at 1% THD. But with PFFB, the power will be reduced due to lower gain. You could easily disable PFFB (not needed for a sub amp) and get your 480w for 2ohms.
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Thanks, XRK
“Hi Otto
I would recommend BTL config for the woofers …
The other channels probably fine with SE output
… …
If the impedance is 1.7 ohms you should run PBTL mode - one amp per woofer channel”
I just re-read stretchneck mentioning that the RTR solution is “only in bridged config, you'd need to modify or building from PCB to use it single ended”
How easy or not is it to change the RTR for another purpose, eg from the default BTL to SE?
“Hi Otto
I would recommend BTL config for the woofers …
The other channels probably fine with SE output
… …
If the impedance is 1.7 ohms you should run PBTL mode - one amp per woofer channel”
I just re-read stretchneck mentioning that the RTR solution is “only in bridged config, you'd need to modify or building from PCB to use it single ended”
How easy or not is it to change the RTR for another purpose, eg from the default BTL to SE?
QUOTE=xrk971;6365231] … The indicators have a massive cross section of flat copper wire and can handle 27A I think.
That’s the max current rating of the TPA3255. [/QUOTE]
Thank you
There’s a lot of specs in the data sheet, but I didn’t see that. … Or the Zout, if you know that ?
Which class AB was it?
Cheers
That’s the max current rating of the TPA3255. [/QUOTE]
Thank you
There’s a lot of specs in the data sheet, but I didn’t see that. … Or the Zout, if you know that ?
Which class AB was it?
Cheers
Conversion to PBTL or SE requires changing several zero ohm resistor jumpers on the bottom side, and flipping a few of the DIP switches on the top. For SE mode you need to add 1500uF AC coupling caps on the output. I have not personally done it but look at the EVM document from Texas Instruments.
In the data sheet look under OC_current limit setting. There is a resistor that is set to 22k that sets the maximum current. Its 17A, not 27A - sorry, my mistake.
My Class AB is the FH9HVX.
FH9HVX - Budget Conscious 100w Class AB for Lean Times
In the data sheet look under OC_current limit setting. There is a resistor that is set to 22k that sets the maximum current. Its 17A, not 27A - sorry, my mistake.
My Class AB is the FH9HVX.
FH9HVX - Budget Conscious 100w Class AB for Lean Times
Here is perhaps the best example of my TPA3255 paired with an XRK audio Yarra preamplifier that member Redjr made with a remote controlled volume. Beautiful work!
The YARRA Preamplifier/HPA for Melbourne DB Group Buy
The YARRA Preamplifier/HPA for Melbourne DB Group Buy
Just tested the new SMT BTSB Buffer with the TPA3255. Works great. Super quiet and provides choice of selectable 0dB, 6dB, 14dB, 20dB gain.
BTSB Buffer - SE/Bal to SE/Bal Buffer GB
BTSB Buffer - SE/Bal to SE/Bal Buffer GB