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Delacroix,If you can pry these amps from dimfer's warm living fingers, I submit it should be a candidate for review at affordableaudio.com. That is if affordable audio accepts reviews of commissioned rather than lot or mass produced products. I've heard these amps driving LSA2 towers and I can attest to their very high value (performance/price ratio). These amps use tubes in the driver stage that are readily available but not commonly used. For the record I am in no way associated with Trodt audio.
Tube Newbie, how do you like the Memory Player? Stand alone transport or w/dac? Jack B
Hi, I've never heard of these amps but they do sound and look interesting. I'd love to take them on for a review for A$$Audio but many times companies that build in small batches just don't have the capacity to send pieces out, there's a paying customer waiting impatiently. Certainly the magazine would welcome them, I'll see what I can find out.Best
This is my first post here. I just found about this forum which is great news.I own a VR-4SR Mark II speakers and they are powered by a pair of NAGRA Pyramids Monoblocks Amplifiers (200 watts each). the speakers sound great but at high volumes the amplifiers clip and shut down (no distortion though). I believe the low impedance of the bass drivers is too much for the NAGRA amps to handle.I am thinking of getting a more powerful amp/amps for the bass modules and use the NAGRAs for the midrange/tweeters. I just can't figure what kind of amp i need and what would be a good impedance match for the NAGRA. The pre-amp is an Audio Research LS-26.
Quote from: Dr. M on 23 Mar 2009, 05:54 pmThis is my first post here. I just found about this forum which is great news.I own a VR-4SR Mark II speakers and they are powered by a pair of NAGRA Pyramids Monoblocks Amplifiers (200 watts each). the speakers sound great but at high volumes the amplifiers clip and shut down (no distortion though). I believe the low impedance of the bass drivers is too much for the NAGRA amps to handle.I am thinking of getting a more powerful amp/amps for the bass modules and use the NAGRAs for the midrange/tweeters. I just can't figure what kind of amp i need and what would be a good impedance match for the NAGRA. The pre-amp is an Audio Research LS-26.Hi Dr.M,The Nagras should be able to drive anything louder than anybody would actually want including loudspeakers that dip briefly below 2 ohms which your SRs do not. The most common problems between tube preamps and solid state amps in general are potential impedance mismatches. This may not be your problem but I have a nagging feeling that there might be an impedance mismatch between your LS-26 which has an output impedance of 700ohms (XLR) and your Nagra which has a 100kohm input impedance. Out of curiosity, are you running balanced or single -ended? If you are running balanced then there is a chance you are experiencing a mismatch. The single ended outputs rated at 350ohms should be a better match. I haven't used Nagra's high-fi gear but have worked countless hours with Nagra recorders. Their inputs are "picky" for lack of a better word.As far as I know the Nagra's protection circuit is activated when there is DC leakage (could be a bad tube or tubes are not yet in a state of thermal stability) or when they are running too hot (overdriven either by an input signal too hot or too heavy a speaker load). There are some things you might want to verify. I'll put it in a list just so it's neater.1. The Nagra is internally switchable between 1v and 2v inputs. If you listen primarily to Digital then 2V should be the default setting.2. The ARC LS-26 has adjustable Gain settings from 6db to the mid twenties. If you're maxed out or close to maxed out it could make your amp's input stage clip especially if your amps are set at 1V. You might want to throttle back the gain before cranking them back up. Never mind if the volume numerical display will show a much higher number than you're accustomed to since it is just a relative number. For as long as there's no distortion you're golden.3. Try the single ended inputs in case the problem is in the impedance matching which could also clip the amp's input stage.4. Wait at least 45 minutes before cranking the preamp to avoid the risk or DC leakage due to thermal instability.5. It could also be a thermal problem. Your amps might be better off in a cooler location (away from heaters) or in spots with better ventilation.6. I saved this for last. According to friends that design amplifiers, extending bass lower than 20Hz in amplifiers takes a power penalty. In this case the amps might really find the speakers a difficult load as you suspect.In the end If you have another preamp around (preferably a solid state one) you might want to check if the amps protect at the same SPL. If they do then we can rule out the preamp as the problem. If they don't then we might have found the right starting point and run through Nos 1 to 4.Good Luck!JackD
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