[Chadly]

I am thinking about building an RA-1 amp. This will be my first DIY amp but I have been playing around with electronics on a breadboard for years. I printed the schematics for the RA-1 and it looks super simple. I love it!

However, the schematic looks too small. I am inexperienced with amp building. Is the schematic for only one channel? Or is it for both channels? If it is for both channels, why is there only one line in and one line out? If this is only one channel drawn where does the second channel fit in at?

I haven't been able to find a whole lot of information on building the RA-1. If anyone knows where I can find more info please direct me there.

I plan on using this solely for home use so I was wondering if it would be possible to use it with an AC adapter instead of the 9 volt batts. If someone could tell me how to do this I would greatly appreciate it. Do I just wire in a wall wart instead of the 9volt batts?

Thanks for all your help in advance,
Chad

 

[CaptBubba]

If you want to get information about how to build the RA-1, just look for stuff about building the Cmoy amp, they are practically the same thing. People say tangent's webpage is really helpful, so give it a shot:

http://tangentsoft.net

 

[rickcr42]

the schematic is only showing one channel , the other channel being identical other than op-amp pinout this is common practice

I suggest you download the NJM4556A data sheet for the correct pins

rick

 

[Chadly]

Thanks, where do i wire in the second channel? Do I use 2 opamps? Would I use 2 pots too? Also the Grado RA-1 has an LED, where would I wire that into the circuit?

Chad

 

[rickcr42]

the specified op-amp is a dual op-amp (two op-amps in one package)

The volume control would also be a dual or two section device for simultaneous control of both channels

The led would be wired across the battery supply . Not from positive to ground but from positive to negative . Make sure you use a low current led or it will drain your batteries fast !

 

[Chadly]

So where do I connect the second channel too? Am I suppose to connect both channels to the same pot? How do I know where to connect everything on the pot up at?

Chad

Sorry for the densness. For some reason this isn't really sticking very good. The opamp is an 8 pin chip and only 1/2 of the pins are being used, this is confusing me.

 

[rickcr42]

if you download the op-amp data sheet it will become clear when you look at the pin diagram . This shows the op-amp from the top while superimposing the two internal op-amp block diagrams on the case with the pin connections.

yes it is only 8 pins but the pins are
op-amp A = inverting in (-input), non-inverting in (+input),output ---- 3 PINS
op-amp B = inverting in , non-inverting in , output-----3 PINS
the last two pins are the power supply . One for V-plus, one for V-negative -----2 PINS
TOTAL PINS 8
There is no actual ground connection to the op-amp . The configuration indicates the ground contact point .

A dual volume control is two SEPARATE pots ganged together so turning the volume control adjusts both channels at the same time , just like any other stereo equipment with a single volume control .

 

[Chadly]

AAAA, all is clear to me now. Many thanks for your help.

Chad

 

[rickcr42]

glad to be of help , just doingmy job man