Revox C36 output

[Bo Deadly]

What I meant was to have an 8ohm load wired to the the speaker output all the time, so with the speaker in the machine I would have two 8 ohm loads in parallel, 4ohms total.

I don't understand why you would do that. If you have the speaker in, why do you need a load? No, you probably don't want to make the load 4 ohms. That could stress the output tube.

 

[remsouille]

I don't understand why you would do that. If you have the speaker in, why do you need a load? No, you probably don't want to make the load 4 ohms. That could stress the output tube.

So I can use the output as a line out without having to use an external dummy load! Pluging something in the speaker output disconnects the internal speaker, and I wan't to keep it that way.
I'll have to use an external  load, then.

 

[Bo Deadly]

No, I would not do that. You could burn out the EL84 output tube. If you're going to keep it stock (which is wise) then just use it as intended. Like I said, the manual specifically mentions that you can run that output into an external amp.

You could change the jack to 1/4" TRS with a normalling contact on T and then put the load between T and R. When you plug in a standard TS plug, the normalling contact disconnects the speaker just like in the unmodified unit but then R becomes connected to S and the load is switched in.

 

[remsouille]

You could change the jack to 1/4" TRS with a normalling contact on T and then put the load between T and R. When you plug in a standard TS plug, the normalling contact disconnects the speaker just like in the unmodified unit but then R becomes connected to S and the load is switched in.

Now, THAT is smart! Thank you!

 

[remsouille]

Like I said, the manual specifically mentions that you can run that output into an external amp.

Ugh, I didn't know the manual was available in english.... It's all in there... I feel like a total twat... You can even plug headphones in that output.... So it means that, as long as you're not plugging that output in thin air, any input would be a sufficient load?
Thank you so much, squarewave!

 

[Bo Deadly]

Headphones would work great and load it plenty. But a line input is usually 10K which is basically no load at all in place of a speaker. You might notice a difference 100R or lower. Try running it into a DAW input with and without the extra load, listen for a difference, look at an FFT for differences in frequency response, noise floor, etc.

 

[PRR]

> don't want to make the load 4 ohms. That could stress the output tube.

It is safe to short the output of a self-bias single-ended tube amp. Note that this product does just that. And nominal load is safe. And a "low Z load" is safe. This is not some overexcited transistor amp!

As you say, the thing you do NOT do is drive to clipping with infinite load. Sparks jump out and the OT dies.

 

[remsouille]

> don't want to make the load 4 ohms. That could stress the output tube.

It is safe to short the output of a self-bias single-ended tube amp. Note that this product does just that. And nominal load is safe. And a "low Z load" is safe. This is not some overexcited transistor amp!

As you say, the thing you do NOT do is drive to clipping with infinite load. Sparks jump out and the OT dies.

Well that's great! This settles the output matter! Thank you all!
Two issues, now:
-There is quite a bit of 50/60Hz hum when you monitor from the playback head, that is even if the machine is on stop or there is no tape loaded. The hum is not present when monitoring the input, So I guess it's coming from between the reproduce head and the monitoring switch. I've already tried swapping tubes, without success. 
-The other issue could be related: Again, when monitoring from the playback head, if I turn the output control past around 2 o'clock, some weird low frequency oscillation happens on the output. Once again, it is totally absent when monitoring the input, and the oscillation is there whether you're listening from the internal speaker or plugged into an external device.
Here is a little video I made, so you can see what's going on:
https://youtu.be/QN1pLYSJ_vg

 

[ruffrecords]

Both symptoms could be caused by poor power supply smoothing. Probably time to recap the PSU.

Cheers

Ian