I just got (ebay) for a steal of ~ USD2K a brand-new Crown XTI 6002 to power my 2 pcs of 18G50 in my garden-house discotheque (no more need for building that cumbersome UCD2K setup!). All info on Crown's website is, that it has "class I circuit", which means basically interleaved class D. There is no detailed info on control loop/feedback design, bus voltage (clip level per channel), PSU topology, schematic, etc.. Does anybody know the details?
I understand that 2 x 1200W is burst RMS power, but what is long-term RMS power at 8 / 4 Ohms? Good Ole Macro-tech series did have a more detailed power specification sheet in the manual...
I understand that 2 x 1200W is burst RMS power, but what is long-term RMS power at 8 / 4 Ohms? Good Ole Macro-tech series did have a more detailed power specification sheet in the manual...
Just got the amp - still no idea what operational DSP mode to set up. I just want full range stereo amplification for my 2 18" subs - 2 inputs -> 2 outputs. Signal for inputs is already lowpassed by my Digitech DSP. Would be nice to have some subsynth signal added (just out of curiousity).
Yeah finally I found out its Band Manager needed to configure....
nice tool, nice amp, btw... takes the word "pro" to seriously
nice tool, nice amp, btw... takes the word "pro" to seriously
"Its a Crown Balanced Current Amplifier, search for BCA whitepaper, old school technology."
I ve just done some researching. BCA is obviously US005657219. Very clever topology. No body diode reverse rec. issues. The Crown's do generally have low damping factor / mediocre performance at hi frequencies, though - right? Not that I would care - I 'm gonna using this amp only for the subs and good old class AB for Mid-Hi....
I ve just done some researching. BCA is obviously US005657219. Very clever topology. No body diode reverse rec. issues. The Crown's do generally have low damping factor / mediocre performance at hi frequencies, though - right? Not that I would care - I 'm gonna using this amp only for the subs and good old class AB for Mid-Hi....
So, out of curiousity I am just starting to put together some simulation of the BCA circuit of US005657219 (also called Opposed current amplifier), together with control loop.
I understand that overlap (summed duty cycle > 100%) will increase bias current through the 2 coils, while underlap will decrease it. 100% total duty will hold it constant at the current value forever (theoretically). In other words, bias current is an integral of triangle wave`s DC bias (which relates to under -/ overlap). There must be some additional control loop to ensure proper bias current. To put together such a loop, I need to find some conditions (based I guess on audio input signal) to define the desired bias current and so to properly modulate triangle wave's DC bias. The patent says "The bias control can be responsive to dynamic conditions,...such as a temporary demand for power...". Hm, quite undefinded, isn't it?...Does anybody here know how to best modulate triangle DC bias? Has anybody done simulations / designs using this topology? Also, this directly relates to load impedance, since bias current is related to load current.... So generally, at 4 Ohms, higher bias current levels would be desirable / sensible than at 8 Ohms. So the audio signal cannot be the sole condition for desired bias current.
I understand that overlap (summed duty cycle > 100%) will increase bias current through the 2 coils, while underlap will decrease it. 100% total duty will hold it constant at the current value forever (theoretically). In other words, bias current is an integral of triangle wave`s DC bias (which relates to under -/ overlap). There must be some additional control loop to ensure proper bias current. To put together such a loop, I need to find some conditions (based I guess on audio input signal) to define the desired bias current and so to properly modulate triangle wave's DC bias. The patent says "The bias control can be responsive to dynamic conditions,...such as a temporary demand for power...". Hm, quite undefinded, isn't it?...Does anybody here know how to best modulate triangle DC bias? Has anybody done simulations / designs using this topology? Also, this directly relates to load impedance, since bias current is related to load current.... So generally, at 4 Ohms, higher bias current levels would be desirable / sensible than at 8 Ohms. So the audio signal cannot be the sole condition for desired bias current.
So about the bias current: I can not find any significant change in performance with different bias currents. The topology works well also w/o any bias current (each part of the converter is conducting only for one current half-wave, while the other one is going discontinuous). Nevertheless, I think there lies some deeper secret in the way how bias current is controlled.
So here is an update from my todays measurements on my new XTI6002:
Clip level @ 8Ohms: 145Vpk (102.5Vrms) per channel
Clip level @ 4Ohms: 138Vpk ( 97.5Vrms) per channel
Clip level indicators seem to not work (!) since even deep into clipping they don't light (firmware bug?)
Input Clip level: >5Vpk (not possible to clip with my signal generator)
Vu = 142 (43dB) per channel - DSP OFF mode
In my setup, Crown's statement, that 1.4Vrms is needed for full rated 4Ohms output, is wrong -> to reach 2100W (92Vrms), only about 0.65Vrms input voltage is needed. That is about half the level - maybe there is some connection to the fact that I am using Cinch-XLR unbalanced-balanced adapters for testing....
Slew rate can reach up to >20V/us if fully kicked by a square wave input.
Frequency response (-3dB): 7.5Hz - 23kHz
The amp has obviously a steep and slightly oscillating anti-aliasing filter at 23kHz even in DSP OFF mode.
(For Comparison my class AB Sony SRP-P450 today showed an awesome 3dB-response of 1.3Hz- 290kHz (!!!), but has no DSP and far less power / efficiency......
Summary: It is a very good amp and Crown is laudably not falling for the seduction of overstating output juice, but: the clipping indicators don't work.
Clip level @ 8Ohms: 145Vpk (102.5Vrms) per channel
Clip level @ 4Ohms: 138Vpk ( 97.5Vrms) per channel
Clip level indicators seem to not work (!) since even deep into clipping they don't light (firmware bug?)
Input Clip level: >5Vpk (not possible to clip with my signal generator)
Vu = 142 (43dB) per channel - DSP OFF mode
In my setup, Crown's statement, that 1.4Vrms is needed for full rated 4Ohms output, is wrong -> to reach 2100W (92Vrms), only about 0.65Vrms input voltage is needed. That is about half the level - maybe there is some connection to the fact that I am using Cinch-XLR unbalanced-balanced adapters for testing....
Slew rate can reach up to >20V/us if fully kicked by a square wave input.
Frequency response (-3dB): 7.5Hz - 23kHz
The amp has obviously a steep and slightly oscillating anti-aliasing filter at 23kHz even in DSP OFF mode.
(For Comparison my class AB Sony SRP-P450 today showed an awesome 3dB-response of 1.3Hz- 290kHz (!!!), but has no DSP and far less power / efficiency......
Summary: It is a very good amp and Crown is laudably not falling for the seduction of overstating output juice, but: the clipping indicators don't work.
So update again:
I found out that my Tek AFG3022B signal generator puts out exactly twice the voltage that its display shows, if it is not loaded by 50Ohms. So the generator's display is actually telling lies instead of measuring the signal correctly. That is why all the input levels were wrong by a factor of 2, and gain also.
Again here my results corrected:
Clip level @ 8Ohms: 145Vpk (102.5Vrms) per channel
Clip level @ 4Ohms: 138Vpk ( 97.5Vrms) per channel
Clip level indicators seem to not work (!) since even deep into clipping they don't light (firmware bug?)
Input Clip level: >10Vpk (not possible to clip with my signal generator)
Vu = 71 (37dB) per channel - DSP OFF mode
In my setup, Crown's statement, that 1.4Vrms is needed for full rated 4Ohms output, is verified:-> to reach 2100W (92Vrms), about 1.3Vrms input voltage is needed.
Slew rate can reach up to >20V/us if fully kicked by a square wave input.
Frequency response (-3dB): 7.5Hz - 23kHz
The amp has obviously a steep and slightly oscillating anti-aliasing filter at 23kHz even in DSP OFF mode.
Summary: Like above
I found out that my Tek AFG3022B signal generator puts out exactly twice the voltage that its display shows, if it is not loaded by 50Ohms. So the generator's display is actually telling lies instead of measuring the signal correctly. That is why all the input levels were wrong by a factor of 2, and gain also.
Again here my results corrected:
Clip level @ 8Ohms: 145Vpk (102.5Vrms) per channel
Clip level @ 4Ohms: 138Vpk ( 97.5Vrms) per channel
Clip level indicators seem to not work (!) since even deep into clipping they don't light (firmware bug?)
Input Clip level: >10Vpk (not possible to clip with my signal generator)
Vu = 71 (37dB) per channel - DSP OFF mode
In my setup, Crown's statement, that 1.4Vrms is needed for full rated 4Ohms output, is verified:-> to reach 2100W (92Vrms), about 1.3Vrms input voltage is needed.
Slew rate can reach up to >20V/us if fully kicked by a square wave input.
Frequency response (-3dB): 7.5Hz - 23kHz
The amp has obviously a steep and slightly oscillating anti-aliasing filter at 23kHz even in DSP OFF mode.
Summary: Like above
So again I am here. Does anybody know how to setup a "soft clipping" with XTI2 series? I do not want a compressor or limiter or the like, just soft clipping mode.
You probably need to go where more people have Xti6002 amps. ProSoundWeb maybe.
By the way, the Xti6xxx series amps have more in common with Crown's iTech amps than it's Xti1xxx, Xti2xxx and Xti4xxx brethren.
By the way, the Xti6xxx series amps have more in common with Crown's iTech amps than it's Xti1xxx, Xti2xxx and Xti4xxx brethren.
Could not find any thread on XTI series there.
Anyway, here is a picture of the current setup - The XTI 6002 plus I choose a linear amp 2 x 450W for the 2 Event 4000 speakers.
The ohmic-inductive voltage divider with -50dB output can be seen on top of the rack - it can absorb up to ~4kW for short time. It is working fine besides some small audible noise.
Thy system is up and running although I am still working to find the optimized level for the DSP input.
Also, I am currently playing around with the Crown's limiter and the subsynth.
I want the subsynth to add low bass if the record does not contain very low frequencies. If it already does have low frequencies included, I don' want the subsynth to further halve the frequency. So in effect I would like to filter out of the signal side chain that is going to the subsynth, lower frequencies up to a certain corner frequency.
Anyway, here is a picture of the current setup - The XTI 6002 plus I choose a linear amp 2 x 450W for the 2 Event 4000 speakers.
The ohmic-inductive voltage divider with -50dB output can be seen on top of the rack - it can absorb up to ~4kW for short time. It is working fine besides some small audible noise.
Thy system is up and running although I am still working to find the optimized level for the DSP input.
Also, I am currently playing around with the Crown's limiter and the subsynth.
I want the subsynth to add low bass if the record does not contain very low frequencies. If it already does have low frequencies included, I don' want the subsynth to further halve the frequency. So in effect I would like to filter out of the signal side chain that is going to the subsynth, lower frequencies up to a certain corner frequency.
Attachments
So now I have set up the Crown "PeakX plus Limiter" to 50Vrms to limit the o/p to 100Vrms for bridge mode (verified with static sine waves and ohmic load). It is obviously a rms limiter. Attack = 1 sec to have short pulses unlimited, release 300msec. I hope this is a somewhat good "foolproof" setup to fully protect the voice coils of my 18G50s while not sacrifying too much of the fun. I addition, for monitoring I have an analogue AC-Vrms meter in parallel to the woofers.
Sony srp
....Hello, I'm new on the site, and looking for old studio amplifiers. I"m looking fo sony srp amplifiers for sale... May be you want to sale yours ?
....Hello, I'm new on the site, and looking for old studio amplifiers. I"m looking fo sony srp amplifiers for sale... May be you want to sale yours ?
"....Hello, I'm new on the site, and looking for old studio amplifiers. I"m looking fo sony srp amplifiers for sale... "May be you want to sale yours ?"
lol.. you found the Sony amp in my picture right?
Condition of the amp: I recently ('bout 2 months ago) opened it and did a complete dust blowout, then added 4 x 2200uF/125V (actually 16 x 2200uF / 63Vdc plus bleeder resistors) per rail (rail voltage is 2 x 100Vdc, found empty space for several smaller caps next to the big heatsinks) for a total of 26800uF per rail. So even if the original 10 y old caps big caps are good only for 75% of nominal capacity, the amp will still have effectively >22000uF per rail.
"May be you want to sale yours ?"
Everything is for sale - just a matter of price. Give me a million euros and I 'll bring you the amp tomorrow on a tray of pure gold.
Fun aside, the price is the price of a reasonable replacement amp (2 or 3 U in rack hight) with at least the same power and very good sound quality. I ll start some researching for amps of that power level. Meantime you can pn me your offer.
lol.. you found the Sony amp in my picture right?
Condition of the amp: I recently ('bout 2 months ago) opened it and did a complete dust blowout, then added 4 x 2200uF/125V (actually 16 x 2200uF / 63Vdc plus bleeder resistors) per rail (rail voltage is 2 x 100Vdc, found empty space for several smaller caps next to the big heatsinks) for a total of 26800uF per rail. So even if the original 10 y old caps big caps are good only for 75% of nominal capacity, the amp will still have effectively >22000uF per rail.
"May be you want to sale yours ?"
Everything is for sale - just a matter of price. Give me a million euros and I 'll bring you the amp tomorrow on a tray of pure gold.
Fun aside, the price is the price of a reasonable replacement amp (2 or 3 U in rack hight) with at least the same power and very good sound quality. I ll start some researching for amps of that power level. Meantime you can pn me your offer.
Good morning,
I use sony srp for my classic performances. I already have two srp-p300, one srp-p500, one srp-p450 and I need a second for my FOH... and its difficult to found in Europe... may be its more easy ro continue on my mail Thanks for your answer. patrick.leveaux@gmail.com
"
My posting from another thread in april:
"~100 - 130dB for disco evenings...
That was my usual listening habit up to about 2 weeks ago. For the months coming, that will not happen anymore soon ;-(. Since I had an accident with a cotton stick while cleaning my ears as usual (like you should never do!!), my tympanic membrane is torn as well as my middle ear inflammated (on one side). It hurted like hell so I wanted to cut off my head like of but finally decided to not do so.
Hope that I can enjoy listening to music at >100dB in stereo again some 4 - 8 months from now. Not sure if that is possible. Pray for me!"
Update: In the meantine my sony amp exploded (too bad I didn t sell to classicalbrussels before that) and was replaced ba Camco D Power 2. My amps total about 3700W into 8 Ohms. Ear is almost 100% good now, but after some 120+dB sessions, straight forward i ve run into the next problem: Not all of my neighbors seem to like my music. One guy is even complaining about things like car wash in the village alley (officially not allowed by state authorities, but usually accepted), or about mowing the lawn even with an "low noise" electrical mower....oh my god...
My posting from another thread in april:
"~100 - 130dB for disco evenings...
That was my usual listening habit up to about 2 weeks ago. For the months coming, that will not happen anymore soon ;-(. Since I had an accident with a cotton stick while cleaning my ears as usual (like you should never do!!), my tympanic membrane is torn as well as my middle ear inflammated (on one side). It hurted like hell so I wanted to cut off my head like of but finally decided to not do so.
Hope that I can enjoy listening to music at >100dB in stereo again some 4 - 8 months from now. Not sure if that is possible. Pray for me!"
Update: In the meantine my sony amp exploded (too bad I didn t sell to classicalbrussels before that) and was replaced ba Camco D Power 2. My amps total about 3700W into 8 Ohms. Ear is almost 100% good now, but after some 120+dB sessions, straight forward i ve run into the next problem: Not all of my neighbors seem to like my music. One guy is even complaining about things like car wash in the village alley (officially not allowed by state authorities, but usually accepted), or about mowing the lawn even with an "low noise" electrical mower....oh my god...
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Since Crown state that you need only 1.4V to reach the full power, and you say you have reached it at 0.65V, could your measurement be wrong and not Crowns? Since you also state that the amps clip indicators don't work, could you also be clipping the input side of the amp?
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