Winter Weekend Project - Copy of a 1960's Shure Headphone amp circuit

[chuckworkb]

I am thinking about building this headphone amp using the schematic from a 1965 Shure Head phone amp.

Pretty straightforward, not many parts, and looks like something to try out. I have attached the schematic.

I have only one question on the schematic - What size do you think the power transformer should be. ( 120V, not 240V ) It is a center tapped, so I was thinking maybe a 12.6 Volt Center Tap Filament transformer might work. What do you all think?
I would also eliminate the switch on the front end since I would only have one left and right input.

Thank you in advance.

 

[maxhifi]

Few comments.

1. I think you're right on the money about the power transformer. Any small one will work, the capacitor voltage ratings tell me you'd expect about a 12V B+

2. You are aware that this is designed to be used with a moving magnet phono cartridge. Shure has put a reverse RIAA network to make it work with other sources. This isn't the way you'd want to do it if you want a line only headphone preamp, since you're going through two stages of EQ for no reason.

3. It's a really old design - something more modern would likely sound better, due to higher performance modern semiconductors.

 

[chuckworkb]

Thanks for confirming the transformer. i am not goimg to use that phono input. this is really just something to build using mostly parts i have from prior projects,etc just for the sake of seeing how it works out. Keeps me out of trouble I like old stuff since i am too. LOL

 

[chuckworkb]

Few comments.

2. You are aware that this is designed to be used with a moving magnet phono cartridge. Shure has put a reverse RIAA network to make it work with other sources. This isn't the way you'd want to do it if you want a line only headphone preamp, since you're going through two stages of EQ for no reason.
MAXHIFI,

I think I misread your reply - point #2, and responded incorrectly. I re-read it. Thanks, for the info, your right of course. I will look for another design, or like I said just mess around and breadboard some of this, and another one I found. Thanks again. Appreciate the reply.

 

[maxhifi]

This one looks interesting - never tried it but looks cool to me.

https://www.nutsvolts.com/magazine/article/precision_stereo_headphone_amplifier

 

[BinaryMike]

I will look for another design, or like I said just mess around and breadboard some of this...

If you build it, be aware that the output stage transistors are germanium, but the bias diode is silicon. This insures that a few mA of idle current will flow through the output stage at all times, which minimizes crossover distortion.

My personal opinion is that one should never build a headphone amplifier with a push-pull output stage. The amount of power dissipated in single-ended class-A circuits, which have no crossover distortion, is so low in headphone amps that there's no reason to use push-pull unless you're compelled to run on battery power.

 

[DEAFASABAT]

This one looks interesting - never tried it but looks cool to me.

https://www.nutsvolts.com/magazine/article/precision_stereo_headphone_amplifier

That's more like it

 

[Fsatsil]

You might also want to check out the Pass DIY Whammy headphone amp.
https://diyaudiostore.com/products/whammy