What has Dan been up to…?
Hi all, it has been a busy past year and I have been working on finalizing two important integrated amp designs, primarily. Both of which will debut at CAF 2019 on Nov. 1 in WA DC.
The Ai325: 25W 300B PP Tube Integrated Amp is the first of the two.
The notion of the design was born out of a discussion with a customer at last year’s CAF. We brought the HA 300, 8W SET HP/Inegrated amp which we used to drive Fritz Speakers Be Carreras. The entire system was not terribly expensive and defied all odds with 8W driving 87dB mointors. The sound was haunting, beautiful and natural. Reviewer Greg Weaver was stunned when listening to Jeff Beck.
A customer who kept coming back to the room asked me if it could be done with more power? Perhaps parallel 300B outputs in a conventional amp or integrated. I said sure, should be pretty straightforward. Different output transformers, same input stage, etc. He said that he would buy the prototype if I built it. I said great, lets do it! So, it began as a comission.
Well, I looked at parallel 300B and also PP 300B options and I realized that with parallel 300B, I could get at most 15W of power, but other PP (push-pull) designs from the past I noted, achieved 25W to as much as 30W (VAC 30/30 for example), RESPECT!
Thus started, what was expected to be a simple modification of an existing design, turned into something quite different! I determined that PP was the way to go for power and punch. I learned about how to treat 300B grid current for max power and impact and the amount of gain and voltage swing needed to produce 25W of power from PP 300B’s.
The process took most of the year, but the unit comissioned will be received by the customer who suggested it, after the show where it will be used with Fern & Roby Raven speakers!
The KWH 225i is our other integrated, high power (225W), and hybrid. This design takes the controls of the KWI 200 SS integrated, combined with the output stage of ourKWA 150SE Reference power amp, but with more current and power. Lastly, it adds a pure triode tube preamp section.
This too has been a greater challenge than expected. The design is completely modular, with separate PCBs for power supply, preamp, input, output stages, protection, etc. It is a tightly packed and organized enclosure.
Interfacing the tube stage and the SS output stage produced challenges with noise and grounding and this has taken some time to resolve. The sound is excellent and we are in Beta testing stage right now.
This amp will also be used at CAF 2019 with Studio Electric speakers!
The PH 9.0 tube phono stage with on-the-fly loading, gain and MM/MC input has also sold very well this year and garnered many reviews and great customer feedback.
Obviously with Oppo closing its doors, we have had to look for new products to modify and the Pioneer LX 500 has proven to be an excellent choice.
Stay tuned as the new amps move to production and we embrace our next new design challenge!
CEO & Chief Design Engineer
ModWright Instruments Inc.