Phono input cap to preamp

You got a plausible explanation for the capacitor from Atmasphere. I wouldn’t second guess him, but I do wonder why Hafler chose to use 10uF there and why he didn’t use a film cap, as well. Is this an MM stage or MC? If MC, what is the value of the load R? (“MC” defined here as moving coil, not the guy you asked for).

I looked up the schematic. C2 is the top half of a capacitative voltage divider network. C1 is the other half. Together these act on AC frequencies delivered to the input transistors. R1 is your phono load resistance. I have never seen this topology before, and I don’t quite get it. But Hafler was one of the greats. Don’t mess with it except maybe to upgrade the capacitors. Do NOT change their values.

Also, C1 and C2 protect the coils of an MC cartridge from any DC offset at the transistor gate. I’d love to have that confirmed or refuted by any pro in the audience. Thx.

There was an informative article in Audio Amateur n4/1980 on modifying the Hafler DH-101 you might want to look at

I couldn’t download the article without paying a fee. However it’s been referred to in several ways at various sites. Seems C1 and C2 are tantalum in the OEM circuit. Tantalum’s are polar and correct orientation is mandatory lest they catch fire. (I know from first hand.) They are ok sounding but a modern electrolytic or a film cap will sound better. However tants  are tiny and there isn’t much room for anything much bigger. Calls for some ingenuity. Suggestion to the OP. Before you remove a tantalum capacitor mark a PCB for polarity, and if you are replacing the tantalum with another polar cap like an electrolytic, conform to the polarity of the tantalum.