Has anybody ever tried this?
For the life of me I can't seem to find on the schematic where the center channel output is coming from. I am assuming it will have a high output impedance so I might need a buffer?
I don't know the specs of the subwoofer that will be given to me but I am sure the input impedance is around 10k.
For the life of me I can't seem to find on the schematic where the center channel output is coming from. I am assuming it will have a high output impedance so I might need a buffer?
I don't know the specs of the subwoofer that will be given to me but I am sure the input impedance is around 10k.
I found it 
Thank you that schematic was easier to read.
Looks like the center out comes off the output transformers 16 ohm taps through a -20db voltage divider.
Would the output impedance be 1.8k?
If yes then that might be low enough to drive a sub's input?
Thank you that schematic was easier to read.Looks like the center out comes off the output transformers 16 ohm taps through a -20db voltage divider.
Would the output impedance be 1.8k?
If yes then that might be low enough to drive a sub's input?
Should be roughly 1.5K source impedance. I think the main concern would be the potential for hum pick up, but a well shielded cable should take care of that concern.
You can also change those resistors to provide more or less output signal and at a considerably lower source impedance if you need to.
I do have one other concern and that is how much LF noise (hum, ripple) is present at the output of the amp?
You can also change those resistors to provide more or less output signal and at a considerably lower source impedance if you need to.
I do have one other concern and that is how much LF noise (hum, ripple) is present at the output of the amp?
I believe your concern is that whatever noise on the output will get amplified by the sub. I haven't measured the noise floor but with high efficient speakers there is no audible 120Hz ripple or 60Hz heater hum even when sticking my ear up to the drivers, the amp is dead quiet.
I guess a better way is to get the signal for the sub before the Scott. Maybe a source buffer that will also sum the left and right channel and send it through a low pass filter and off to the sub?
If you are running high efficiency speakers with decent response down to 60Hz and hear no significant noise then you would probably be fine.
This is all assuming good low end response from the amplifier.
Taking the signal at the source is probably less convenient, and results in two knobs to adjust unless the source is doing volume control, but it may work better if there is only one source.
This is all assuming good low end response from the amplifier.
Taking the signal at the source is probably less convenient, and results in two knobs to adjust unless the source is doing volume control, but it may work better if there is only one source.
You sparked my curiosity so I looked up the specs and my speakers are rated 63Hz-20kHz.
I restored the amp myself a few years ago and from memory remember it had a decently flat bandwidth. I don't remember where the 3db cutoff is in the low end so maybe I will hook it back up to some test equipment and see exactly what I get.
At lower listening levels the low end is just fine to my ears, the reason for the sub is for louder listening levels and watching movies. Now that I know my speakers only go down to 63Hz reinforces why I want to add a sub, depending where the 3db cutoff is from the amps output will determine where I will take the signal for the sub, either from the center channel out or after the source. It doesn't really bother me if I have to turn two volume controls, one for the sub and one for the main speakers.
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Just wanted to update this thread by saying that using the center out into the subwoofer works great. If I want a little extra "thump" while listening to certain styles of music I just turn on the sub and leave the Scott tone controls flat. There is no audible hum present from using the center out either which was a concern.
I do have one other concern with the amplifier I am seeking advice on. I recently installed a fresh quad of 1989 Reflektor 6P14P-EV tubes and re biased and AC balanced the amp....she sounds great! Anyway it's been bothering me for a while now that I think the phase switch is wired backwards. Meaning on "normal" phase I have to put the + speaker wire on the "0" connection on the back of amplifier and the - speaker wire on the "high" connection for channel B. If the phase switch is set to "reverse" the speaker connections for channel B are all properly phased.
Should I bother rewiring the switch? Should I hook the speaker wires up backwards for channel B and leave the switch on normal? Or should I hook the speakers up normal and just set the phase switch to "reverse"?
My personal lazy attitude is telling me to not rewire it and it doesn't matter if I reverse the speaker connections and leave the switch in "normal" or hook the speakers up normally and put the phase switch to "reverse". My OCD side is saying rewire it so it is correct and be done with it. Please help
I do have one other concern with the amplifier I am seeking advice on. I recently installed a fresh quad of 1989 Reflektor 6P14P-EV tubes and re biased and AC balanced the amp....she sounds great! Anyway it's been bothering me for a while now that I think the phase switch is wired backwards. Meaning on "normal" phase I have to put the + speaker wire on the "0" connection on the back of amplifier and the - speaker wire on the "high" connection for channel B. If the phase switch is set to "reverse" the speaker connections for channel B are all properly phased.
Should I bother rewiring the switch? Should I hook the speaker wires up backwards for channel B and leave the switch on normal? Or should I hook the speakers up normal and just set the phase switch to "reverse"?
My personal lazy attitude is telling me to not rewire it and it doesn't matter if I reverse the speaker connections and leave the switch in "normal" or hook the speakers up normally and put the phase switch to "reverse". My OCD side is saying rewire it so it is correct and be done with it. Please help
I think your rational side is probably the right one here, I'd leave it as is.. I assume you have checked to make sure the speaker itself is not wired incorrectly (It happens) or that the speaker cable itself is swapped at the other end. (I've done that... lol)
The problem was confirmed on my oscilloscope......and yea I will probably just leave it as is for now anyway.
"Rational" side, I like the sound of that better than lazy
Thanks
-bird
I wonder if they're all like that.. The 299A I remember was a pretty nice amp. I had a NIB 299B that I picked up at Hoss Traders in 1989 for $45 - it was pretty nice. Now heavily modified it lives with a friend.
It is pretty nice, I really like it. I am also curious if they are all like that or I just got a duff. The only other mistake I found was that the 6BL8 pentode's cathode resistors were marked blue, grey, and brown which is correct for 680R but they both measured 680k. Needless to say they both got replaced.
Wow that's a great deal for a NIB! I thought I did well for picking up mine for around $150 if I remember correctly, but this was only about 5 years ago.
You mentioned you heavily modded yours, what was done? If you can remember the deetz that would be great. I think mine sounds fine but I am a tinkerer by nature so I wouldn't mind experimenting. I did the usual replacement of selenium rectifier to silicon and increased the filter caps too.
I can probably dig up the details if you are really interested. I basically gutted the whole thing and built an entirely new amplifier on the chassis. These days I would probably not recommend going that route, and particularly with the A version which I think sounded significantly nicer than the B which is why I modified it so extensively. I did not much care for the C, but the D I had was also really nice stock.
The 296 if you can find one is pretty amazing. (It was not terribly common)
The 296 if you can find one is pretty amazing. (It was not terribly common)
Wow! Did you follow the 299A topology or design your own? I probably wouldn't gut this amplifier because it is an antique and to be honest really like the sound. So I guess don't go out of your way to dig up the details but I am interested in what you did.
I have only heard one other 299 and it was a 299D but it needed work and wasn't driving the best speakers. It's funny I was actually looking for the 296 because of the higher output power but got tired of looking for one at a price I was willing to pay. I am happy I pulled the trigger and picked up the 299A.
Any idea how I can connect a REL subwoofer to my 299?
I have ZU Audio 13 ohm speakers connected. The amp is set to 16 ohms and all is well.
The center channel seems to be the way to go but I am baffled at the labels on the 3 RCA jacks on the rear, a blank top spot with 2 underneath labeled "recorder a-" and "recorder b-"
Here is what REL has to say:
Hi Daniel,
Using the Neutrik high level cable, the T/9i should be connected to the 8 ohm taps for optimal output even if your speakers are on a different load--RED to right and YELLOW to left. The BLACK wire should be connected to a common ground terminal.
Let us know if you have any other questions about integrating a REL into this setup.
Best Regards,
Rachel
REL Customer Service
I have ZU Audio 13 ohm speakers connected. The amp is set to 16 ohms and all is well.
The center channel seems to be the way to go but I am baffled at the labels on the 3 RCA jacks on the rear, a blank top spot with 2 underneath labeled "recorder a-" and "recorder b-"
Here is what REL has to say:
Hi Daniel,
Using the Neutrik high level cable, the T/9i should be connected to the 8 ohm taps for optimal output even if your speakers are on a different load--RED to right and YELLOW to left. The BLACK wire should be connected to a common ground terminal.
Let us know if you have any other questions about integrating a REL into this setup.
Best Regards,
Rachel
REL Customer Service