Thanks, Tiki.
I have played a little bit with RMAA thinking on using it for testing amplifiers. It is quite nice for that! Although my soundcard is more limited and has no balanced i/o.
Of course results should be better using an alluminium power resistor and then a couple of small resistors or a good potentiometer as the voltage divider. This way you can test it to higher powers as well.
The "good" way to do tests is using a quite complex lowpass filter to avoid getting hf transients into the soundcard input, that could deteriorate results.
Please read AudioPrecision's app.note on how to do these measurements. However, I think that you can get quite approx. results without that filter, as you did.
Best regards,
Pierre
I have played a little bit with RMAA thinking on using it for testing amplifiers. It is quite nice for that! Although my soundcard is more limited and has no balanced i/o.
Of course results should be better using an alluminium power resistor and then a couple of small resistors or a good potentiometer as the voltage divider. This way you can test it to higher powers as well.
The "good" way to do tests is using a quite complex lowpass filter to avoid getting hf transients into the soundcard input, that could deteriorate results.
Please read AudioPrecision's app.note on how to do these measurements. However, I think that you can get quite approx. results without that filter, as you did.
Best regards,
Pierre
more re AD8620
What function does the 8620 perform? Does it provide voltage gain? Can it be bypassed with a step-up transformer?
What function does the 8620 perform? Does it provide voltage gain? Can it be bypassed with a step-up transformer?
Well there's two of em, they buffer the inputs and provide some gain... 4.5 I think.
That goes through the coupling caps and connects right to the comparator differentially. Think of a three op amp instrumentation amp with the third amp being the comparator, that's it.
Transformer?? Interesting.. it works in my simulation. Wonder what it would do to EMI, and what EMI would do to it? Might not work well if the feedback isn't mirror like.
That goes through the coupling caps and connects right to the comparator differentially. Think of a three op amp instrumentation amp with the third amp being the comparator, that's it.
Transformer?? Interesting.. it works in my simulation. Wonder what it would do to EMI, and what EMI would do to it? Might not work well if the feedback isn't mirror like.
Hi Chris, I'm not sure what you mean by your reference to feedback. Transformers tend to do well with EMI, at least the higher frequency variety as they have a limited (almost audio-only, ahem) bandpass. If the comparator is at ground potential, a transformer could replace the two op amps, the coupling caps both before and after the op amps, and give *true* differential drive while blocking DC at the same time. The transformer, in fact, could be a transformer volume control to give level attenuation. Very elegant. And sound quality? Excellent, if you ask me. Ask Rowland, even.
serengetiplains said:
But the input impedance could be a problem. The input impedance of the negative UcD input (so after the input opamps) is only about 1kOhm when driven pure symmetrically. When you use a transformer to get gain, the input impedance that you see at the input of the transformer would be less than that, with a factor 5 gain, input impedance would go down to 200Ohm or so, can your preamp drive that?
Gertjan
Hi,
Yeh, seems like a bright idea. I mentioned feedback because if the differential feedback loops aren't identical (I don't know if they are or not) I thought it might introduce an offset, and wouldn't be entirely common mode? Just a thought, not gospel, good for provoking discussion🙂
There's only coupling caps after the buffers/amps, at the comparator inputs, to prevent DC offset being amplified.
Anyway, I simulated it with mirror image feedback loops and inputs, an ideal transformer with secondary grounded center tap, .99 coupling, and at 1:1, 1:2, 1:100...
I can tell you it worked great, but what I have would differ from the real thing, also from non ideal simulator land, by a great deal in this case I would think.
The transformers for this kind of app change impedance with gain right, by an order of magnitude for the one I looked at. At some point it might load down the amp.
At the input of the comparator portion I also don't think the impedance is the same, the old pdf say's ~1.8k inverting input, ~10k non inverting. I'm sure Jan-Peter will fill us in if it can work or not.
Yeh, seems like a bright idea. I mentioned feedback because if the differential feedback loops aren't identical (I don't know if they are or not) I thought it might introduce an offset, and wouldn't be entirely common mode? Just a thought, not gospel, good for provoking discussion🙂
There's only coupling caps after the buffers/amps, at the comparator inputs, to prevent DC offset being amplified.
Anyway, I simulated it with mirror image feedback loops and inputs, an ideal transformer with secondary grounded center tap, .99 coupling, and at 1:1, 1:2, 1:100...
I can tell you it worked great, but what I have would differ from the real thing, also from non ideal simulator land, by a great deal in this case I would think.
The transformers for this kind of app change impedance with gain right, by an order of magnitude for the one I looked at. At some point it might load down the amp.
At the input of the comparator portion I also don't think the impedance is the same, the old pdf say's ~1.8k inverting input, ~10k non inverting. I'm sure Jan-Peter will fill us in if it can work or not.
1K-ohm is a lowish impedance. My DAC outputs a 24dBu signal, so I think it could drive the comparator via a 1:1 line-level coupling transformer.
Jan-Peter, would appreciate any comments. If the UCD sounds as good as some say it does, the opamp and coupling capacitors would seem to be the weak links in this amplifier---ridding the amp of them should provide a healthy upgrade. For those of you who have not heard a high quality coupling transformer, it can be a jaw-dropping experience.
Jan-Peter, would appreciate any comments. If the UCD sounds as good as some say it does, the opamp and coupling capacitors would seem to be the weak links in this amplifier---ridding the amp of them should provide a healthy upgrade. For those of you who have not heard a high quality coupling transformer, it can be a jaw-dropping experience.
Chris, thanks for your simulations. A good transformer provides precisely-mirrored opposite-phase signals the precision of which is unobtainable by active devices, which tend to bounce around, even if accurately matched.
Jensen Transformers probably sells a 600ohm:600ohm transformer that would work in this circumstance.
By the way, a transformer would also offer galvanic isolation, reducing ground-carried noise from the oh so sensitive input circuitry.
Jensen Transformers probably sells a 600ohm:600ohm transformer that would work in this circumstance.
By the way, a transformer would also offer galvanic isolation, reducing ground-carried noise from the oh so sensitive input circuitry.
Jan-Peter, to be a little more clear about the information we're needing, if you could indulge us we need the drive requirements and input impedance of the comparator (can the comparator be driven either single-ended or differentially---if so, we need drive requirements for both drive modes), and on a related question the gain provided by the opamps.
Thanks! 😀
Thanks! 😀
FuriousD, any comments re the transformer suggestion? It was your posts re the opamp that got me thinking of a solution.
parts list needed
alright. reading all of the posts on this thread took me a week. wow, that was a lot. altho, I am still confused what I have to buy and hook them up. can anyone post parts list & schematic so that I can get some idea and start buying stuffs?
btw, I found a aluminum box company in us. take a look.
http://www.action-electronics.com/
alright. reading all of the posts on this thread took me a week. wow, that was a lot. altho, I am still confused what I have to buy and hook them up. can anyone post parts list & schematic so that I can get some idea and start buying stuffs?
btw, I found a aluminum box company in us. take a look.
http://www.action-electronics.com/
If you have read the thread, sorry it's already quite long 😀 . You found the answers.....
The input of the modulator has the following input impedance;
Inv - 1.8k
Noniv - 10k
Regards,
Jan-Peter
new batch of UCD180 modules
Hi Jan-Peter,
When will the new modules be available?
Ciao,
Valter
Hi Jan-Peter,
When will the new modules be available?
Ciao,
Valter
Next week we reeive the new batch from our subcontractor, so in about a week we can again deliver UcD180 ( UcD400 comes 2 weeks later).
Sorry for the delays!
Regards,
Jan-Peter
Sorry for the delays!
Regards,
Jan-Peter
Wahoo, finished all 110 pages in 3 days!
Hi All-
First I need to say WOW to JP and Bruno for the support and timely feedback they provided in this thread. It is quite extensive. I hope this is an example of the support Hypex customer receive. Bravo to the two of you!
Secondly, post # 1010 asked a question about a GB for the pwr supply boards and I didn't catch an answer... Bueler, Bueler,... anyone...(now that's a classic)
And lastly, after reading this thread and committing to also building the Krell KSA-50 on another thread I decided to sell my beloved Jeff Rowland Model 2 and try the UcD180's or 400's in its place. The question is, since I don't require much power is there anything to gain by going to the 400 other than watts? Are the circuits similar enough that they sound the same or is one module sonically superior to the other...
I will likely be building a 4-module amp with 2 high passed modules and 2 woofer modules and the LWE feedback controller module. LWE has a new module but not listed yet.. I will NOT be using my current one.
Does either design 180 or 400 invert absolute polarity?
Hi All-
First I need to say WOW to JP and Bruno for the support and timely feedback they provided in this thread. It is quite extensive. I hope this is an example of the support Hypex customer receive. Bravo to the two of you!
Secondly, post # 1010 asked a question about a GB for the pwr supply boards and I didn't catch an answer... Bueler, Bueler,... anyone...(now that's a classic)
And lastly, after reading this thread and committing to also building the Krell KSA-50 on another thread I decided to sell my beloved Jeff Rowland Model 2 and try the UcD180's or 400's in its place. The question is, since I don't require much power is there anything to gain by going to the 400 other than watts? Are the circuits similar enough that they sound the same or is one module sonically superior to the other...
I will likely be building a 4-module amp with 2 high passed modules and 2 woofer modules and the LWE feedback controller module. LWE has a new module but not listed yet.. I will NOT be using my current one.
Does either design 180 or 400 invert absolute polarity?
Attachments
transformer coupling (again)
Jan-Peter or Bruno, I sent an email to Jensen Transformers asking what transformer they might recommend for possible application as an input transformer to your amp module replacing the op-amp input. His response is as below. Are you able to help me regarding his question?
Jan-Peter or Bruno, I sent an email to Jensen Transformers asking what transformer they might recommend for possible application as an input transformer to your amp module replacing the op-amp input. His response is as below. Are you able to help me regarding his question?
input transformer
May I repeat my question from the UcD400 Q & A thread:
The JeffRowland 201 amps use a Lundahl LL 1545 line input transformer right in front of the ICEpower 500ASP module. Does it make sense to try something similar with the UCD modules? Anybody have any experience?...
May I repeat my question from the UcD400 Q & A thread:
The JeffRowland 201 amps use a Lundahl LL 1545 line input transformer right in front of the ICEpower 500ASP module. Does it make sense to try something similar with the UCD modules? Anybody have any experience?...
It is possible to use a balanced input transformer on the UcD.
In this link by point 2.2, is drawn the input section of the UcD amplifiers.
www.hypex.nl/Hypex UcD Intro.doc
I do not see any reason why you should use a transformer, besides a transformer can be a solution when you have very heavy earth ground problems. The inputsection of the UcD amplifiers are build just as an instrumential opamp. When you remove the first opamp stage you have the asymmetrical input resistance of the bare UcD modulator.
The ICEpowers are having a different setup with the powervoltages. They use +12V / GND / -12V, and for the powersection GND and +60V (or so). The output of the amplifier is the half of the powersupply voltage with reference to ground. To avoid higher voltage as 40VDC to ground they are probably using an input transformer and connect the GND with an high impedance.
Jan-Regards
In this link by point 2.2, is drawn the input section of the UcD amplifiers.
www.hypex.nl/Hypex UcD Intro.doc
I do not see any reason why you should use a transformer, besides a transformer can be a solution when you have very heavy earth ground problems. The inputsection of the UcD amplifiers are build just as an instrumential opamp. When you remove the first opamp stage you have the asymmetrical input resistance of the bare UcD modulator.
The ICEpowers are having a different setup with the powervoltages. They use +12V / GND / -12V, and for the powersection GND and +60V (or so). The output of the amplifier is the half of the powersupply voltage with reference to ground. To avoid higher voltage as 40VDC to ground they are probably using an input transformer and connect the GND with an high impedance.
Jan-Regards