KR ST70 build and First Watt F8 listening experiences

It's interesting to listen to the sound signatures of different amplifiers and I think this really has a good deal to do with matching amps to speakers more than just blanket statements that one amp is necessarily superior to another. I'd like to thank my friend Justin for being kind enough to loan his First Watt F8. For this comparison I used the Erhard Audio Aretha tube preamp.

I've had the opportunity to listen to the First Watt F3, SIT3, F6 and F8 and the two that really stood out for me were the F8 and F3. The F3 just tends to run hotter than the F8, but in my opinion I'm surprised at how similar they sound. I think the thicker sound signature of the SIT3 is a nicer match for open baffle speakers. It provides a darker, thicker, meaty sound signature that isn't quite as nice a match for the Forte I's in my opinion because jazz tends to sound less sweet and refined, particularly while hearing horn instruments.

The First Watt amplifiers are still the only solid state amplifiers I've listened to that can trick listeners into thinking they were listening to tubes. I have always struggled with solid state amplifiers, however, the First Watt's are the exception. 

While playing various LP's listening to jazz, 70's type pop and Frank Sinatra, the F8 delivered solid bass, a big soundstage and a balanced presentation. By balanced, I mean that certain instruments didn't jump out at you too forward or too far in the background. I was very impressed with the F8 and told Justin it's my favorite version of the First Watt's. It also produced huge volume levels without any signs of clipping or distortion to speak of.

After finishing up, I played the same songs with a newly modified Dynakit ST70 that Kenny Russell constructed using very high quality components along with the original David Hafler circuit design. There were several things that stood out for me while using this amplifier.

The first thing was the way it images with a the "phantom image" that I personally found quite remarkable. This effect gives the listener the impression that there's a 3rd speaker between the stereo image. Instruments like horns and piano's for example often sound like they are coming from the center of the soundstage while other instruments are exhibited in the stereo image and this was truly remarkable to me.

It added an additional element of three dimensionality to the soundstage and it does this with more consistency than I expected while providing incredible balance at the same time. The space around instruments is beautiful to hear. 

Another feature that struck me about this particular ST70 build was the bass. I could not distinguish any differences in the speed or impact compared to the F8. This may have something to do with the solid state rectifier Kenny Russell uses in his build. Even at the highest volume levels while playing Tom Sawyer by Rush, Neil Peart's drum solo was tight and perfectly controlled with startling impact while using the Forte I's. The bass was nothing short of sensational in both the F8 and this ST70.

Another thing I noticed about this build was the warm, sweet sound that simply flowed like silk. It sounded exactly like a single ended Decware Zen but with more power and weight to it with even greater balance and far greater bass. Jazz instruments take on a very refined sound with this unit while the F8 has a slightly thicker sound. This refined sound the ST70 produces is one of the reasons I really enjoy listening to this amplifier so much with the Forte's as well as my Heresy II's. It has a very sweet and pretty tone but can deliver serious impact and incredible volume when called upon.

I have listened to other ST70 builds which were also nice, but they didn't sound as balanced and they took on a more grainy, brighter sound signature that's less like that vintage sound signature from of the original circuit David Hafler designed. Kenny Russell's version of the ST70 is without question, one of the most remarkable amplifiers I've ever heard in my listening space ever. 

I'm hoping to hear these two wonderful amplifiers again very soon using Justin's custom Tannoy speakers to hear how each respond.  

Happy listening,

---daniel