I am not about to claim that the Manley Steelhead is the best possible phono stage, but I do own one and enjoy it. I use it as a full function preamplifier to drive the amplifiers of a pair of Beveridge speakers (another topic entirely). I chose the Steelhead because reviews and comments led me to believe it was very good, and because it provides three pairs of phono inputs. I required that because I use two turntables to feed the Steelhead phono stage. FWIW, you don’t say whether you own v1.0 or v2.0 of the Steelhead. I have v2.0. The following describes the modifications I made to my Steelhead that greatly improve its Sound Quality (SQ). You will have to be someone with some electronics savvy and soldering skills:
I could not get a schematic; Manley does not provide a schematic even for professional repair shops. But if you read an interview with Evanna Manley, several years ago in 6 Moons, she describes the output stage. I won’t reiterate her summary (please google it; look for the Steelhead review in 6Moons) but suffice to say that the output of the phono stage, which either drives the volume control if you use it as a full preamplifier or the outboard linestage, if you use it as a phono stage only, uses a 47-ohm resistor in series with the signal followed by a 30uF output coupling capacitor, whichin my opinion is mediocre in quality, at best. This capacitor and what follows are holding back the performance of the Steelhead, IMO. I removed the 47-ohm resistor entirely; it’s not needed for anything, and I replaced the 30uF coupling cap with a much higher quality 10uF capacitor. (Choose whatever you like but spend the $$$ for a very good one.) You need 10uF, I calculate, because the volume control seems to have a 5K ohm input impedance (very low). (10uF driving a 5K ohm load will give you a very low bass cut-off; 30uF is way overkill. Less than 10uF might compromise extreme low bass performance.) OK, then the output from the linestage section (the output side of the attenuator) uses yet another 47 ohm resistor in series with yet another 30uF capacitor of the same type and brand. I removed that 47R resistor and replaced THAT second coupling capacitor with a 4uF film cap that I like very much. Since my amplifier has a 50K input impedance, 4uF is more than adequate to get good bass. Those two coupling capacitors, from phono stage output to attenuator and from attenuator to linestage output have everything to do with the SQ of the Steelhead. Coupling capacitors should be rated for at least 250V, to be safe.
