Adding pre outs to Teac AH 300 amplifier

[lockstock]

Hi all,
As the title suggests. I would like to added RCA pre outs to my TEAC reference 300 amplifier.

I have a set of Alesis mk2 active mk1 Monitors I want to use with my set up.

I found this old thread:
http://theartofsound.net/forum/showthread.php?10342-Adding-pre-out-to-Teac-A-H300-possible

Sadly the two guys who knew their stuff on the thread haven't posted for a while, and a lot of the pictures have dropped off due to the age of the posts.


Essentially I know what I need to do in broad terms:

1. Identify the ground and right & left channel outs from the pre-amp stage.
2. Identify the input sensitivity of my power amps in my alesis active speakers
3. If MORE sensitive than the impedance capable of the teac amplifier, I should be able to use the gain control on the alesis to balance the set up (still not sure how i do this right, without risking damaging the pre amp)
4. Assuming 3 is done, I need to cut two holes in my 300 backplate and mount the R & L RCA sockets.
5. Solder from the contacts identified in 1. using some kind of screened audio cable to my mounted RCA sockets.

6. If 3. cannot be done using existing power amp gain controls, then 5. should be modified to include a potentiometer in series, to balance in sensitivity of the power amp and the pre amp out.


I can follow instructions well, but my technical knowledge is limited. So some pictures advising what to solder, where, is basically what I will need. Also, how to approach balancing the system whilst minimising risk of blowing my speakers or teac amp.

Thanks in advance guys.

Jake

[mikmas]

Basically a lot of the information you need is still there in the thread you linked to...

Post 3 has pictures of the points you need to solder your connections to for the RCA out sockets and then further on is detail of how you could set up a potmeter to tame the signal if needed before it gets to your power amp.

I have the same Teac amp in a box somewhere and if I have a moment I'll open it up, have a look and make a couple of photos once I locate the pins in the pic. Once I've seen them I will have a better idea of how difficult the solder job would be .... Won't be til Monday though ;)

[lockstock]

Thanks that would be really helpful. I think I identifies the connector with the pins in the PCB diagram. The diagram is of the amplifier board (bottom of case) these connect to another connector on a daughter board at the top of the case, much easier to access. So I'm hoping I can splice into the connector on the daughter board at top of case. Looks like I won't be able to use my active speakers for a while now so the urgency to mod my teac has reduced, so please don't rush. I will bump the thread in a couple of weeks when I can make progress and will post some pics to confirm what I'm doing. You will probs get a pm! Cheers man

[Mao70]

Hello
you can have photos of the pre out edit
thanks

[Shovel_Knight]

CN14 on the preamp PCB:

pin 1 = L out
pins 2 & 3 = GND
pin 4 = R out

I would add 2.2 uF film caps to the outputs as a precaution to eliminate possible DC offset.

[Mao70]

Thanks for the reply
but connected how?:scratch:

[Shovel_Knight]

https://i.imgur.com/rBt1xhhh.jpg#OL5qy

[Mao70]

perfect!
capacitors any technical specification?

[Shovel_Knight]

2.2uF/50V film capacitors, e.g. Wima etc.

[Mao70]

perfect!
capacitors any technical specification?

[Mao70]

thanks!!