Looking for help with an Akai Terecorder Conversion :-)

[vandoog]

Hi all first amp conversion over here so go easy on me. Looking to convert this Akai Terecorder Reel to Reel that is quite similar to those roberts/akai monoblocks people like. Lots of posts out there but not a clear guide. Right now I'm a little uncertain how to hook up my speaker.

Looking at the schematic I am able to tell that the + of my speaker should go to the yellow wire (#3 on the amp side of the 6 pin plug)

I am a little confused about where the - speaker wire should go. If you look at the "mechanism" diagram it appears that pins 2 and 1 are connected by switch 3 and that the - of the speakers also connects there.

Since I've removed that "mechanism" side of the amp would it make sense to just connect my - speaker wire to pins 1 and 2 of the amplifier side of that plug?

Thanks for the help!

Also my transformer says 100v on it but the schematic says 110 or 117. I don't see any 117v taps but I'm assuing I can just use the 110 taps?

[The Dude]

Connect speaker to pins 1&3 of the plug, pin 1 being ground and pin 3 being the other side of the OT (through what looks to be J3- a switching jack). And yes, you shouldn't have problems using the 110V tap on the PT. It's really your only choice.

[vandoog]

Connect speaker to pins 1&3 of the plug, pin 1 being ground and pin 3 being the other side of the OT (through what looks to be J3- a switching jack). And yes, you shouldn't have problems using the 110V tap on the PT. It's really your only choice.

Thank you! any thoughts on pin 2? I see it ties in with pin 1 on the side I removed. Should I tie that in on the side I am connecting thus sending one side of the speaker over to that part of the schematic labeled "recording bias"?

[The Dude]

I'm not able to study the schematic right now (in the middle of an amp repair), so take this with a grain of salt. AT A QUICK GLANCE, pin 2 is switched to ground to cut bias oscillator signal. If you're turning this into a guitar amp, you won't want the oscillator circuit and would probably remove V4 anyway. If you remove the oscillator, connector pin 2 really serves no purpose. Again, that is just a very quick look at the circuit.

[vandoog]

Thanks for the help The Dude! It definitely plays but has wayyyy to much gain. Kinda sounds nice if I roll down the volume and turn it up but has this kinda sputtery sounds if your turned up and below 4 on the volume. I'm gonna do some research and see if I can turn the gain down or maybe utilize the transformers and sockets for a clone of some sort

[g1]

Have you tried using the Line instead of Mic input? It looks to me like those are standard switching type jacks like Switchcraft 12A, just drawn a little different than we are used to.
If line is too weak, and mic too hot, some compromise between the 2 should get you where you want.

[vandoog]

Have you tried using the Line instead of Mic input? It looks to me like those are standard switching type jacks like Switchcraft 12A, just drawn a little different than we are used to.
If line is too weak, and mic too hot, some compromise between the 2 should get you where you want.

Interesting idea! Line is pretty much silent, i think I hear just a lil bit coming in and mic is tooo hot for sure. Fairly new to this, would it be a matter of experimenting with different resistor values where r2 is?

[g1]

Neither R1 or R2 are in circuit when using Mic input. When you use line input, it puts R1 in series off the tip, then R2 from there to ground (parallel to R3).
Assuming the jacks are working right, I would try approximating the standard Fender lo input and put 100K in both the R1 and R2 positions.

[vandoog]

Neither R1 or R2 are in circuit when using Mic input. When you use line input, it puts R1 in series off the tip, then R2 from there to ground (parallel to R3).
Assuming the jacks are working right, I would try approximating the standard Fender lo input and put 100K in both the R1 and R2 positions.

Interesting idea, I will definitely try this. I assume replacing R1 and R2 might get the line input closer to "instrument level" for a guitar?

Also

Am I right to interpret R4 as being the cathode resistor of the first 6au6? I've been reading up and while I am new to this it appears increasing R4's value could lower the gain?