IcePower ASP1000 - Tweaking/Mods/Upgrades
I've just got my hands on a pair of ASP1000, and I would like to know what could I do to take the most of it.
I already know all the limitations these modules, and I'm also going to give a try with Hypex's UcD with SMPS and HxR, and maybe Coldfire.
Anyway for now I want to take the most of them.
I've read that Bel Canto uses this module in a straight forward implementation, that is, looks like they simply put the ASP100O on a case, add some ferrite chokes, add a small Led that's connected to the connector P3 with maybe some kind of resistor on the pins:
1 PGND Power supply Ground GND
2 Vp2 (80V) Power supply 80V Output
And that they fit a RCA socket and a XLR socket and the only thing they do is to put a switch (supposedly to switch between inputs) that I haven't figured out what exactly is it doing... And that's it!?!?
Wired4 Sound for example as a different approach, looks like they do some kind of component modding (superior grade caps and resistors, and add a input buffer board to solve the low impedance problems of this amps.
JRDG, is the one that I'm most curious about what mods to they do. I've been unable to found out what they do.
Looks like they add a lundahl Line Input and Repeat Coil Transformers and that's all I know..
So all n all, I would like to know your opinions on what could I do to improve this amp (maybe except for components upgrade since this is a 4 layer board full of smd's and I don't think it should be easy to change stuff on it. But if anyone as a good proposition I'm an open minded person, so....)?
One thing I tough to apply on my case was an input transformer, like a Jensen or a lundahl Line Input and Repeat Coil Transformers for galvanic isolation a RF protection on the input signal, and I was also thinking on putting some ferrite chokes, on output to speakers and power supply, also to avoid RF interference.
I've read that the ASPs have very low input impedance, 7kOhms, so that could be a problem when hooking it up with a pre-amplifier.
Especially if you are using a tube pre-amp.
I think, and I'm really not an expert on electronics, that it should have at least a 100kOmh input. No?
One way to solve this problem, at least that is what I've heard, is to use a direct-coupled, balanced, dual FET input stage (input buffer).
The problem is that my electronic knowledge is limited since the stuff that I studied a few years ago (7+ Years) at the university when i was tanking my masters in electrical engineering (Electrical Power systems field) was minimum.
Maybe if I go into my books I might be able to find some kind of literature on input buffers, but I think I would have to study again and remind stuff that I don't usually work with.
I saw a post once @ DIYAudio regarding a project for a balanced dual FET input stage... Do you have any knowledge on the subject? Would anybody recommend the use of such a input stage on ASP 1000?
At the moment I will be using my pre-amp that as the following specs (It's a Electrocompaniet EC 4.5):
Single ended operation (gain)0 dB
Balanced operation (gain)6 dB
Input impedance50 kOhm
THD single ended (1.5 V output)< 0.003 %
THD balanced (1.5 V output)< 0.0015 %
Max. input> 10 V RMS
Channel separation (1 V output, 1 kHz)> 90 dB
Output impedance100 Ohm
Max. output Single ended8 V RMS
Max output Balanced16 V RMS
Output noise400 Hz - 30 kHz input shorted
Single ended : 6 µV
Balanced :11 µV
I'll have to check whether it's a good option or not for this power amp...
But I would like to upgrade my pre-amp for, one (DIY or Not) let's say, in the league of a JRDG Capri or Concerto... or let's say a passive pre-amp (like Pass labs B1).... Preferably balanced and with bypass possibility... But for now I'm stuck with my EC4.5 (And I could get easily a CJ PV12)..
By the way, does anybody know where does Krell get from those speaker binding posts? On "low end" krell models they use WBT but on top levels they use binding posts that you usually see on soldering machines!
If only I could find out who makes those Hi-Tech connectors like for example on those evolution 900 series...
Also an other thing, Where could I get good looking cases in rugged aluminum? Like Alcoa Alloy 6061-T6? Preferably In Europe
Does Anyone have the schematics of this power supply module that Bel Canto have fitted on their revision of the Ref-1000 (MKII)
Looks like a small bank of capacitor a a few diodes....
Should this be some thing like the PFC (Power Factor Correction) PC1 from Jeff Rowland??
To me the PFC (And I'm not an Expert) sould bean AC-DC converter feeding the ASP1000 SMPS with DC (384VDC) if that correct?
Anybody can comment?
From the picture, it sure looks like that PSU on the right side is exclusively powering the low level input board in the top left corner.
The input board i most likely some kind of buffer and/or single enden to ballanced converter that takes care of the low impedance problem you mention.
Maybe you shold try to understand the connections between the two boards (look at the conector description in the ASP1000 manuals)
The PCB on the right side is either adding more storage capacitance on the mains side of the SMPS or is a PFC.
And what's the ideia with the other input board before the SMPS? Is it a so called PFC board (Isn't really a PCF only an AC-DC circuit with a bank of capacitor on the AC side? Does any one have an example of schematics of a PFC circuit, or this board on BC's MKII or JRDG's PC1?
JRDG has a comercial product called the PC1 that is suposed to be a power factor correction circuit. It seems that on the MKII version of Bel Canto's Ref 1000, they use a similiar circuit.
Every body says that for example Jeff Rowlands's Model 501 uses a Lundahl transformer, some claim that is a Lundahl LL 7902, but isn't that only uses if I want to convert for example e non balanced signal into a balanced one? Since model 501 has only available a XLR connector, if my assumption is correct then why would Jeff use a Input transformer that will only alter the signal?
Would it only be for galvanic Isolation? Or should it be to raise the input impedance of the ASP 1000? But in that case IMHO it could not be this model of lundahl since to acheive a higher input impedance witha line transformer it should be necessary to use a step down trafo and then use some kind of gain stage with amp op's, correct?
Look at this pic fo example:
Could it also be possible that JRDG uses a input trafo, to provide the possibility to convert an unbalanced signal to a balanced signal should a customer use a RCA - XLR converter in the case that the person as only available a pre-amplifier stage with RCA connections?
Of the shematics examples that are available at Jensen's site, in case you found that the use of a Line trafo would improve the ASP 1000 sound, wich of the examples would you recommend?
By the way does anyone know what is the brand or supplier of the binding posts that Krell uses like :
Here are some interesting pictures:
So it's a confirmation that JRDG uses a Lundahl 7902 input transformer and it seems that there is some kind of gain stage also.
What is that metalic box that is near the IEC connector?
Does anyone have schematics for such a circuit using the LL 7902?
Look here another interesting pictures of the JRDG PC-1 PFC:
Looks like JRDG uses a OPS 500-U-100-385C Power factor correction front-end power supply for the PC-1 product and inside of the 312 Model Also.
I've been unaible to found out where could I get such a Power supply.
Here are some details of the OPS:
Three years of research,development and testing have been put into the OPS-U-500-385 to provide tightly regulated, Power Factor Corrected DC power. The OPS-U-500-385 delivers full output performance with no forced air (heat sinking required). Other features include compact size with all necessary components internal, high MTBF, thermal protection and no thermal derating.
OPS-U-500-385 Product Benefits:
* Unity power factor
* High efficiency
* Universal input voltage
* 85 degree Celsius baseplate operation temperature
* High reliablility
* No thermal derating
* "Class B" EMI
* EMI filter and hold up caps including internally
* Compact size
* Thermal protection
* Over current protection side filtering
Online Power Supply, Inc., 6909 South Holly Circle, Suite 200, Englewood, CO 80112. Tel: 303-741-5641; Fax: 303-741-5679.
I think I've found an similar font-end from an other suplier:
Pardon my ignorance but wouldn't it be better if I used a 1000W PS?
Bu the way, this OPS Front end uses on JRDG PC-1 as an output of 385VDC, so does the other option that I've found, but isn't 385V above the limit setting of overvoltage protection of the ASP 1000 ?
Look like on JRDG Model 201 the input trafo is diferent,might be because the input impedance of the ASP1000 is diferent from the ASC250.
I've found a various DIY projects where the person uses the LL7902 also, some of them without any external circuits, tohers use some kind of circuit board with op'amps.
Is icepower 1000ASP or 500ASP accept 385V DC?
If I used AC to DC 385V PFC, is it directly plug it into icepower AC input? Any problem?
Any tweak can do in icepower modules to improve the sound such as modify input, output and power ?
What are your opinions on using a AC-DC FrontEnd with PFC like this one on the link below?
The OPS Front end that JRDG uses on the PC-1 as an output of 385VDC, so does the other option that I've found, but isn't 385V above the limit setting of overvoltage protection of the ASP 1000 ?
What about the comuting frequency of the asp1000 vs the AC-DC PFC circuit? Do you find any possible issues?
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