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rhing

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About rhing

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    South Carolina
  • My System
    Denon DJ VL12 Prime direct drive turntable, Talisman Alchemist IIB MC cartridge, Sony ES NS999ES DVD/SACD/CD player, Audio Research PH5 vacuum tube phono stage preamp, Audio Research LS7 vacuum tube line stage preamp, rebuilt McIntosh MC240 vacuum tube power amplifier, rebuilt and modified Dynakit Stereo 35 vacuum tube amplifier, Wiener 2.0 TI TPA3118 PBTL (dual mono) Class D amplifier (diyAudio.com group buy), TI TPA3255EVM BTL Class D amplifier, rebuilt and modified Klipsch Forte II floorstanding speakers, KEF LS50 bookshelf speakers

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  1. The OPA627AU op amps are shown in the top photo. The OPA1622 op amps are shown in the bottom photo. I have not tried the LME49720 op amps yet.
  2. I have had a chance to roll op amps in this little, yet powerful, amp: Texas Instruments OPA1622 Burr-Brown OPA627AU In comparison to the stock Texas Instruments NE5532 dual op amps, both significantly improved the sound quality in terms of creating a larger, deeper soundstage, better frequency response at the extremes, and improved detail. Both sets of op amps required 2-3 hours to really settle in. Since both types were mounted on DIP8 adapters, they were very easy to plug into the DIP8 sockets. On the other hand, removing the stock TI NE5532 op amps with their soft metal legs was more challenging and I ended up mangling the legs of one of them that would not come out of the socket easily. After much listening, I prefer the Burr-Brown OPA627AU op amps. The presentation is tonally rich and the bass energy was equal to my Pass DIY Sony VFET Class A SS amp and rebuilt McIntosh MC240 tube amp. The soundstage is life-size with really good separation of performers. The midrange and treble are very smooth with no brightness sometimes associated with Class D amps. In all, a very high quality amp, power supply, and optional op amps can be had for less than $100 to power Klipsch speakers.
  3. Yes. There is an output pot on the Mean Well to make that adjustment.
  4. For your setup with the balanced connections to the Pono Player, you are set with the best solution in the Texas Instruments TPA-32xx Class D amplification. I prefer the Aiyima for its compact simplicity and the very dead silent background. It has a built-in protection against the thumps/pops on power-up and power-down. I no longer have to be concerned with using the reset switch on the TI TPA3255EVM to mute and unmute the amp. I also wanted to roll op amps to see the effects on sound quality. The amp as-is is a keeper, at less than $50 sans power supply, it is quite a bargain for an amp capable of powering low-medium to high sensitivity speakers.
  5. Hey All, I wanted to purchase an Aiyima TPA3255 2.0 amp through eBay, but the seller in China could not ship the amp due to the COVID-19 virus outbreak. They were great about it and promptly refunded my payment. That left me with the choice to purchase the Aiyima TPA3251 2.0 amp through Amazon.com who had some inventory of these amps in the US. I had to purchase a Mean Well LRS-200-36 switching power supply to power this amp since it does not come with a power supply. I had to dial down the power supply's output to 30VDC since the power rail capacitors on the Aiyima amp are rated at 35V. I've had great results with a Mean Well LRS-350-48 switching power supply powering my Texas Instruments TPA3255EVM Class D amplifier. I connected this amp to my main system using my Audio Research LS7 tube line stage preamp and modified Klipsch Forte II speakers. This is where I started my critical music listening and discovered that the right and left channels are reversed, so I switched my right and left hand RCA interconnect connections. My reference power amplifiers are a rebuilt McIntosh MC240 vacuum tube amp and Pass DIY Sony VFET Class A solid state amp I built with the diyAudio.com store kit offered several years ago. Both of my reference amps are excellent and I am quite pleased with the low distortion and highly musical performances of both amps in my system. I connected the Aiyima Class D amp to the Audio Research preamp and my speakers, and I have to say this little amp is impressive. First of all, it is very quiet with no music playing through it. I held my ear close to my efficient Klipsch speakers and didn't hear any hiss or other noise. Unlike the Texas Instruments TPA3255EVM amplifier, this amp only supports the use of single ended inputs. I'm sure the amp could be modified to accept balanced inputs, but XLR and TRS balanced connectors are too large to fit inside the compact enclosure. All that said, I like this Aiyima amp so much, I am now considering selling my Texas Instruments TPA3255EVM amp.
  6. The Pass Labs and First Watt amplifiers are built with different design philosophies. Pass Labs amps are built to work with a wide range of high end audio speaker systems—some which represent very difficult loads, while most First Watt amplifiers are designed for high sensitivity speaker systems like horns and full range single driver systems with minimal crossovers. Not sure if meaningful apples-to-apples comparisons can be made since they are designed for different purposes. Having attended several Burning Amplifier Festivals in San Francisco including the last one a month ago, I can tell you that Nelson Pass’ passions are with the First Watt and Pass DIY crowds.
  7. When I lived in the San Francisco Bay Area, I used to attend the San Francisco Tube Users Group meetings at the small auditorium in the Randall Museum. We used a pair of Klipsch Chorus speakers that were re-capped by one of the members. I hope the group still gets together, because I met some really great people in that group, had the opportunity to learn from others, and hear some great gear. The class should be very educational and the hands-on building experience is priceless. It’s a great way to get into DIY audio.
  8. When I lived in the San Francisco Bay Area, I had the privilege of meeting Roger when he moved his operation from Santa Barbara to El Cerrito to start up a school to teach others about audio electronics. Roger was highly opinionated and eccentric. He was a true genius with designing and building audio electronics, and he was generous in lending me some of his creations. He taught me about A/B testing and showed my friends and me how his amps were both musical and iconoclastic in terms of their design. He was in the process of releasing a fantastic sounding OTL tube amp and a budget-friendly tube preamp. He auditioned a pair of electrostatic speakers with a pair of subs that sounded open and lively with his RM-200 Mk II power amp. He also regularly attended San Francisco Audio Society and Burning Amp DIY Audio events, and shared his opinions about boutique components, exotic cables and point-to-point wiring vs. printed circuits. I will miss him.
  9. The Elekit TU-8600R with upgrades including Lundahl output transformers is high on my list. https://diyaudiostore.com/products/elekit-tu-8600r
  10. Just a little bit with the pots. I still need to set up a distortion analyzer to measure harmonic distortion and phase. Setting the test points, T7 and T8, to 10 VDC works well for my ears.
  11. I just built this kit offered through the diyAudio.com store and Nelson Pass. It is Nelson Pass’ JFET B1 buffer married with a Korg NuTube dual triode. The Korg NuTube dual triode is essentially a vacuum tube built on a Silicon wafer footprint. https://diyaudiostore.com/products/korg-nutube-b1 Having built several DIY projects, I assembled this kit over a weekend and used Duelund DCA20GA Tin-plated Copper wire for all signal connections and Kimber Kable TCSS Copper wire for DC power supply connections. The chassis fits very nicely together to make a very professional-looking preamp. The Korg NuTube provides gain, so this is an active preamp with two line-level inputs. I brought this preamp with me to Northern California recently and tried this preamp in a couple systems at friends’ homes. The preamp was used with a Conrad-Johnson MV75-A1 tube power amp driving KEF Reference 101 monitors, and with a Texas Instruments TPA3255EVM Class D power amp driving a pair of Klipsch Forte II speakers. In both cases, this little gem performed very well creating a deep soundstage with holographic imaging as most tube preamps do. The detail and tonality are excellent and this preamp is really quiet. Even better is that this dual triode runs cool. Nelson Pass has even recommended leaving the preamp powered on all the time with the kit-supplied wall wart power supply. You can read this lengthy forum thread on this preamp where some people have installed film caps instead of the electrolytic caps that fit the PCB, installed stepped attenuators and tweaks for taming tube microphony. https://www.diyaudio.com/forums/pass-labs/313612-b1-korg-triode.html
  12. When I lived in the San Francisco Bay Area several years ago, I had an opportunity to attend the San Francisco Vacuum Tube Users Group where the group had a shootout between several vintage tube amps of varying designs including the Marantz 8B. The group used to meet at the Randall Museum auditorium which sat maybe 100 to 175 people and used a pair of Klipsch Chorus II speakers. Among the amps which included a fine our of Fisher monoblocks (sorry I do not recall which ones), the Marantz 8B was the most musical amp of the group. Like vintage Mac tube amps, you would have to carefully search for a Marantz 8/8B in good shape or properly rebuilt. With careful shopping, you will be rewarded for your efforts.
  13. Wish I could join, but I just moved back to South Carolina from Minnesota. I now have my full complement of amps working with my Klipsch Forte II’s.
  14. When I still lived in California several years ago, Roger Modjeski was generous in coming to my home and joining other friends to try a few of his tube amps including his RM-10 MkII EL84/6BQ5 amp in my system, which includes an upgraded pair of Klipsch Forte II’s. We compared it to my Dave Gillespie EFB-modified, rebuilt Dynakit Stereo 35 tube. Even though I have not heard the Forte III’s, I would think they perform similarly as my Forte II’s based on their specifications. From our listening sessions performing a true blind ABX comparison with matched levels, the RM-10 MkII and Dynakit Stereo 35 were very close in performance. That said, both amps sounded fantastic driving the Klipsch Forte II’s with a wide range of material. You will need an equally great preamp and source to work wonders with the RM-10 MkII and Klipsch Forte III’s. My tube line stage is an Audio Research LS7, and this combination was stellar. The RM-10 MkII is among one of my favorite amps. Roger put a lot into that amp’s design with custom wound transformers, point-to-point wiring and a solid tube biasing system.
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