I would like to try an ICEpower amplifier.
My speakers are MarkAudio fullrange, and I listen at low-to-moderate volume levels.
My DAC is a Quanghao ES9018 with Lundahl LL1684 transformer output stage, which is pin-configurable for unbalanced or balanced output. This DAC also has software-controlled attenuation.
Q1. Even if I don't need the extra power of the 125ASX2, is it sonically any better than the 50ASX2?
Q2. Although I could feed balanced outputs from my DAC to dual BTL ICEpower amps, I'm thinking just to go unbalanced into a single amp board, unless anyone can say that dual BTL amps will sound better?
3. Compatibility of DAC output with ICEpower input:
I understand the 50ASX2 and 125ASX2 have relatively low input impedance - 8k or so.
My DAC's output transformer apparently does not like being connected to low impedance amps. But the DAC's circuit board has provision for an optional R-C network at the transformer secondaries, intended to suitably dampen the transformer's resonance in cases such as this.
Q3a. will the addition of this R-C network be a (good) solution to connecting my DAC directly to a 50ASX2 or 125ASX2 ?
Q3b. or should I use a buffer between the DAC and ICEpower? If op-amp buffer, are we talking about the often-discussed NE5532 / LME49860 / OPA1622 / MUSES02 etc, or some other?
Q3c. or a solid state buffer, such as -
JFET cascode buffer
JFET input Cascode buffer board assembled ! | eBay
or diamond buffer
Diamond buffer board stereo broadband strong driving capability assembled ! | eBay
My speakers are MarkAudio fullrange, and I listen at low-to-moderate volume levels.
My DAC is a Quanghao ES9018 with Lundahl LL1684 transformer output stage, which is pin-configurable for unbalanced or balanced output. This DAC also has software-controlled attenuation.
Q1. Even if I don't need the extra power of the 125ASX2, is it sonically any better than the 50ASX2?
Q2. Although I could feed balanced outputs from my DAC to dual BTL ICEpower amps, I'm thinking just to go unbalanced into a single amp board, unless anyone can say that dual BTL amps will sound better?
3. Compatibility of DAC output with ICEpower input:
I understand the 50ASX2 and 125ASX2 have relatively low input impedance - 8k or so.
My DAC's output transformer apparently does not like being connected to low impedance amps. But the DAC's circuit board has provision for an optional R-C network at the transformer secondaries, intended to suitably dampen the transformer's resonance in cases such as this.
Q3a. will the addition of this R-C network be a (good) solution to connecting my DAC directly to a 50ASX2 or 125ASX2 ?
Q3b. or should I use a buffer between the DAC and ICEpower? If op-amp buffer, are we talking about the often-discussed NE5532 / LME49860 / OPA1622 / MUSES02 etc, or some other?
Q3c. or a solid state buffer, such as -
JFET cascode buffer
JFET input Cascode buffer board assembled ! | eBay
or diamond buffer
Diamond buffer board stereo broadband strong driving capability assembled ! | eBay
On your point 3, an RC network on the output of a transformer is to provide damping at higher frequencies. If you put an 8k load on your transformer's output its highly likely that load will overdamp the transformer meaning you'll get premature HF roll-off even without the RC in-circuit. Adding the RC will just make matters worse.
Whether the overdamped response from the trafo is livable with depends on the recommended R in the RC network. If that's below 8k you're fine and can just adjust it so the parallel combination is the same with the 8k in place. If its much higher than 8k then you're going to lose HF anyway so shouldn't fit the RC.
Whether the overdamped response from the trafo is livable with depends on the recommended R in the RC network. If that's below 8k you're fine and can just adjust it so the parallel combination is the same with the 8k in place. If its much higher than 8k then you're going to lose HF anyway so shouldn't fit the RC.
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They are different, but "better" is very subjective. To my ears, the 50ASX is warmer and the 125ASX is more neutral, but YMMV.
I think a single board would be fine for what you describe.
8k doesn't seem to be an outrageous load for the Lundahls, but the RC network doesn't seem like a bad idea for transformers in general?. EDIT: Scratch this, based on Abraxalito's answer above.
I would start without the buffer but make space for it in your chosen chassis and then you can more easily experiment once you know which part of the sound you are not happy with.
Thank you both.
The recommended R-C values are 1k-3nF.
Yes, it sounds like I may need to experiment with/without buffer. And I'm leaning towards the idea of a solid state buffer.
I also like the idea of a tube buffer - I've had nice results with the (cheap) FX-Audio TUBE-01 preamp in combination with a TPA3116 amp ...
but I read that tube preamps don't like to be connected to power amps with low input impedance??
The recommended R-C values are 1k-3nF.
Yes, it sounds like I may need to experiment with/without buffer. And I'm leaning towards the idea of a solid state buffer.
I also like the idea of a tube buffer - I've had nice results with the (cheap) FX-Audio TUBE-01 preamp in combination with a TPA3116 amp ...
but I read that tube preamps don't like to be connected to power amps with low input impedance??
With 1k/3nF for the recommended damping network you should be OK driving an 8k load. Just increase the 1k to 1k1.
Well after a false start - buying a fake/faulty ICEpower module from eBay - I now have a genuine 50ASX2 module up and running.
Initially I connected it directly to my DAC, and it sounded quite good, perhaps a notch better than the TPA325x amps that I had been playing with previously. But I had a suspicion that a buffer would yield even better results, so I pulled out a Joachim Gerhard jfet buffer board that I had sitting amongst my collection of unfinished projects, soldered all those damn tiny SMD resistors, and gave it a good +/-15V power supply in the form of an LT3045/LT3094 regulator from ldovr.
Wow, the sound now has more authority and attack, and the soundstage is better defined. This combination is sounding great.
Initially I connected it directly to my DAC, and it sounded quite good, perhaps a notch better than the TPA325x amps that I had been playing with previously. But I had a suspicion that a buffer would yield even better results, so I pulled out a Joachim Gerhard jfet buffer board that I had sitting amongst my collection of unfinished projects, soldered all those damn tiny SMD resistors, and gave it a good +/-15V power supply in the form of an LT3045/LT3094 regulator from ldovr.
Wow, the sound now has more authority and attack, and the soundstage is better defined. This combination is sounding great.
Here is my build, which includes the jfet buffer and associated regulator and transformer, all in the same chassis. I thought I was being clever to buy a Ghent Audio chassis one size larger than what they usually supply for a 50ASX2, but it ended up still being a tight fit, and I always seem to forget that wiring takes up space as well! For neatness and safety I made up some brackets which raised all power cables above the height of the main boards, while still keeping them sufficiently clear of the sides of the chassis.
In hindsight I should probably have given the buffer a separate chassis.
In hindsight I should probably have given the buffer a separate chassis.
