D
Deleted member 537430
I picked up two Quad 303 amps recently and am considering using them as “monos” into my ESL’57’s. I’m not going to strap them for more power, but thinking of using a single channel per amp. I guess all I would need to do is remove one of the output boards of each amp.
I don’t think anything else would need to be done. Would there?
I don’t think anything else would need to be done. Would there?
Why? No need to remove anything. Just don't use one channel. But then why not just use one 303 and sell the other, pocketing the change?
Or else bridge the channels in each, either in series or parallel, so you get more voltage or more current, depending on your needs, out of each one.
Or else bridge the channels in each, either in series or parallel, so you get more voltage or more current, depending on your needs, out of each one.
That would work, but I'd just short one input and leave the rest of the circuit as-is.
You may want to sell them some day.
You may want to sell them some day.
Sorry, I missed the ESL-57 part, in which case you must definitely not series-bridge them, as the ESL-57s have an absolute 17V limit that you must not exceed.
I still don't see the point.
I still don't see the point.
D
Deleted member 537430
I had mentioned that I was not going to strap them, so I’m not sure why you’re warning me not to.
Walker specifically designed that amp to match the ESL requirements, so I'd only use one channel per ESL.
D
Deleted member 537430
So we’re back to where we started. I may try the one channel thing and see if there’s any perceived difference compared to using just one stereo version.
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I suspect that you'll hear a difference. Give the amps a chance to burn in, if they haven't been used for a while.
The Quad 303 is a single ended amp, with the voltage regulator on the negative part of the power supply.
If you short the earth leads between two Quad 303 at minimum and get a lot of hum on both channels, and probably blow the R115 of resistor.
If your preamp isolates left and right channels earths you will be fine. I used Isolating transformers to solve this after numerous mess ups.
If you short the earth leads between two Quad 303 at minimum and get a lot of hum on both channels, and probably blow the R115 of resistor.
If your preamp isolates left and right channels earths you will be fine. I used Isolating transformers to solve this after numerous mess ups.
I'm curious if you will hear a difference. Are your 303s exactly the same (components, bias etc.)?
The Quad 303 is a push-pull amplifier, AC coupled, with a single supply rail and ground. It isn't 'single-ended'.
I don't know which 'earth leads' you mean, as there are two per channel, or three overall.
I would fairly confidently expect not to hear a difference, given the regulator and the very substantial headroom it has to operate in.
These are the instructions to parallel the 405 but should work with the 303, I think the main advantage is that you can site each amplifier next to the speaker with very short speaker leads
https://www.dadaelectronics.eu/uplo...Documents/Quad-405-Monoblock-Instructions.pdf
https://www.dadaelectronics.eu/uplo...Documents/Quad-405-Monoblock-Instructions.pdf
The factory Quad 303 bridging instructions can be found here: http://dadaelectronics.com.au/doc/Audio/Quad/Quad 303/Q 303 bridge.pdf.
I don't see any advantage of short speaker leads vs long line level leads as opposed to the other way around. Rather the contrary I would have thought.
I don't see any advantage of short speaker leads vs long line level leads as opposed to the other way around. Rather the contrary I would have thought.
ejp wrote "Parallel monoblocks can't hurt. Series monoblocks can indeed hurt, for the reason I mentioned." ejp needs to go back to the books!
Please expalin how you can parallel the channels when:
The gain structure of each channel is not exact and once channel with the higher output will try to deliver current into the output stage of the other channel.
Marantz "offered" this insane suggestion in the 1960's with their model 15. They said a 0.3 ohm 50w resistor must be in series with each "hot" output and then the other ends of these resistors must be tied together. Then a ground strap should be installed so the two power supplies could talk to each other.
This was a disaster with many Model 15s blown up.
This can be done with opamps and low level discrete opamps as their current is so low and simple 4.7-10 ohm resistors work well. We do this for noise issues where we parallel up to 6 discrete opamps of our design.
ESL-57 wants to use one channel of each 303. Why? These have regulated supplies and only driving one or both channels makes ZERO difference. There is no headroom in these amps due to the regulation.
ejp really needs to hit the books as he wrote "The Quad 303 is a push-pull amplifier, AC coupled, with a single supply rail and ground. It isn't 'single-ended'."
It is 100% single ended as the output has one leg connected to the ground system within the amplifier and this is classified as SINGLE ENDED as compared to a bridged amplifier where the outputs are driven by each half of the balanced bridge.
Please expalin how you can parallel the channels when:
The gain structure of each channel is not exact and once channel with the higher output will try to deliver current into the output stage of the other channel.
Marantz "offered" this insane suggestion in the 1960's with their model 15. They said a 0.3 ohm 50w resistor must be in series with each "hot" output and then the other ends of these resistors must be tied together. Then a ground strap should be installed so the two power supplies could talk to each other.
This was a disaster with many Model 15s blown up.
This can be done with opamps and low level discrete opamps as their current is so low and simple 4.7-10 ohm resistors work well. We do this for noise issues where we parallel up to 6 discrete opamps of our design.
ESL-57 wants to use one channel of each 303. Why? These have regulated supplies and only driving one or both channels makes ZERO difference. There is no headroom in these amps due to the regulation.
ejp really needs to hit the books as he wrote "The Quad 303 is a push-pull amplifier, AC coupled, with a single supply rail and ground. It isn't 'single-ended'."
It is 100% single ended as the output has one leg connected to the ground system within the amplifier and this is classified as SINGLE ENDED as compared to a bridged amplifier where the outputs are driven by each half of the balanced bridge.
Mistake after mistake here. The Quad document I cited above shows how to connect the channels in parallel, and you are once again confusing single-ended with single rail. The opposite of single-ended is push-pull, not bridged, by which you appear to mean 'dual-rail' rather than the two-channel bridging we are talking about in this thread.
My books: Radio Designer's Handbook, Morgan Jones, Douglas Self, et al.
My books: Radio Designer's Handbook, Morgan Jones, Douglas Self, et al.
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I concur with Moer that a capacitively coupled, or directly coupled for that matter, amplifier with a single output lead is single-ended. Most of the above circuits are also single ended push-pull. ejp, I think you may be confusing single ended with single transistors (like a class A stage perhaps). Amplifers which are not single ended are differential, or bridged with balanced outputs. These require two outputs, so obviously not single.