James Freeman
Rock Star
- Messages
- 3,175
I plugged my Hi-Fi single-ended EL34 amp to my guitar cab running Helix into one channel, got a very impressive juicy round sound that gradually compresses to a smooth growl as I turn the volume higher.
Aside from lack of a Tone knob it is identical in topology to an early Class A Fender Princeton but with slightly more preamp headroom and power, both are basically a textbook implementation of a 40's radio amp.
I got a good taste of Single-Ended Class A and I have to say I understand now, it sounds rounder, smoother, and compresses more gracefully to crunch, very different than Class AB guitar amps.
If I needed a wider range of edge-of-breakup or clean-to-crunch sound controllable with the guitar volume I would definitely go Class A like Princeton.
It also works very nicely with full range speakers for some cork sniffing hifi music listening.
Some technical info:
Topology is as simple as it gets, clean 6SN7 preamp tube that doesn't distort (7v cathode bias voltage) into a cathode biased EL34 (25v cathode bias voltage), no negative feedback, no tonestack, flat frequency response (measured with a resistive load) when operating in the linear range.
6SN7 preamp swing is 45Vp with 3Vp (2Vrms 0dBFS standard) on RCA inputs, so the power tubes grids get full swing and output full power or can be pushed to clip.
Aside from lack of a Tone knob it is identical in topology to an early Class A Fender Princeton but with slightly more preamp headroom and power, both are basically a textbook implementation of a 40's radio amp.
I got a good taste of Single-Ended Class A and I have to say I understand now, it sounds rounder, smoother, and compresses more gracefully to crunch, very different than Class AB guitar amps.
If I needed a wider range of edge-of-breakup or clean-to-crunch sound controllable with the guitar volume I would definitely go Class A like Princeton.
It also works very nicely with full range speakers for some cork sniffing hifi music listening.
Some technical info:
Topology is as simple as it gets, clean 6SN7 preamp tube that doesn't distort (7v cathode bias voltage) into a cathode biased EL34 (25v cathode bias voltage), no negative feedback, no tonestack, flat frequency response (measured with a resistive load) when operating in the linear range.
6SN7 preamp swing is 45Vp with 3Vp (2Vrms 0dBFS standard) on RCA inputs, so the power tubes grids get full swing and output full power or can be pushed to clip.
Last edited:
