I did this several times at this model but also various other models. In general it is an advantage to increase the series resistance to 47K, 56K or 68K and it is guaranteed that no occur of the mentioned unwanted effect - additional cable capacitance of long leads to the sub haven't influence to the main signal pad for sat speakers (also important if one use an pre-amplifier even with low output impedance).
But if connect this pad for midrange or high frequency amp, sound is muddy without shine and fine dynamic (but this fact doesn't matter at frequencies below 100 Hz).
Yes, it's too easy to install whatever you like in there. Now to adjust the current and drop the dissipation to sane levels. The existing LED has dropped significantly in efficiency since it was new anyway.
Nice one, I've got parts on order. I'll try to get the current nice and low 👍
Thanks for your comments, tiefbassuebertr. If I'm understanding correctly, you are suggesting it would be better to change the 10K series resistors in the A3i to higher value, but even if I do make this change, you suggest the design is not good as a full range pre-amp output anyway, in fact it acts a little like a low pass filter.
Ok, to look at other solutions, I was looking at the pre-out circuit in a Denon PMA-700AE that I have here and would like to hear what you guys think of it:
If I'm reading the circuit correctly, it seems to me not a real pre-amp output (yet marked as "Pre-Out" on the schematic), but could this pad be added to other amplifier outputs (such as A3i) to create a decent low level output? 🤔
Cheers,
Trev
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The levels are pre-amp like. If the amp is delivering 1 watt into 8 ohms (which is8 volts peak to peak) you will see around 300mv peak to peak at the pre output or approx 100mv rms.
That kind of thing can be added to any amp.
That kind of thing can be added to any amp.
Thanks for doing the calc's Karl, I'll consider knocking one up.
As an experiment, I'll temporarily replace the CA A3i with the Denon to see how the sub performs with the Denon's "Pre-Out" signal.
As an experiment, I'll temporarily replace the CA A3i with the Denon to see how the sub performs with the Denon's "Pre-Out" signal.
I connected the Denon PMA-700AE up to the system (in place of the CA A3i) and its line output levels matched well with the JBL sub inputs.
The test reminded me how awful that Denon amp sounds though (in my opinion, of course 🙂).
Anyway, to save me buying parts and building a similar attenuator, I forked out £6.50 and bought a device made by Pyle (PLVHL60) , which I think is primarily aimed at the in-car audio market. It works a treat but thought I'd show the circuit on here for opinions, in case you guys can see anything concerning. My thoughts are with the power rating of the 200 ohm resistors (1/2W) across the speaker outputs of the amp, should I consider uprating them? (BTW, I don't know the details of the transformers)
Cheers
Let's put some numbers in and play it safe. If the amp puts out 50 watt rms/8 ohm then that means it delivers 20 volts rms. We don't know the split across the resistors (because of the transformer and its secondary loading) so let us say the first 200 ohm might see most of that voltage.
The power rating would need to be 2 watt.
In practice and for normal program material you could well find the 0.25 watt parts fitted are absolutely fine. For full sustained sine testing they need to be closer to 2 watt. Also the first 200 ohm will not see the full voltage (if it did that means zero across the transformer) and so that fact also significantly reduces the requirements.
The power rating would need to be 2 watt.
In practice and for normal program material you could well find the 0.25 watt parts fitted are absolutely fine. For full sustained sine testing they need to be closer to 2 watt. Also the first 200 ohm will not see the full voltage (if it did that means zero across the transformer) and so that fact also significantly reduces the requirements.
I use the same device exactly (Amazon) to connect my monitor to the stereo system in my bedroom. Perfect!
Denon products sound different than the Cambridge for sure, but it shouldn't be a bad sounding unit. Now that I look at the schematic, I see something odd for a Denon. No driver stage for the outputs. That won't perform well.
Denon products sound different than the Cambridge for sure, but it shouldn't be a bad sounding unit. Now that I look at the schematic, I see something odd for a Denon. No driver stage for the outputs. That won't perform well.
Thanks, I'll keep an eye on it, and uprate the resistors necessary
Ah, that's good to hear, so it copes ok with the output of the Monitor. I can say it's the best I've heard the sub sound out of all the configurations I've tried driving it; punchy and tight.
Yes, it probably isn't a bad unit in a different system, to be fair. I always found it a bit hard, even harsh, so that the sound seems loud, even when it really isn't. Also I notice occasional low frequency boom at unfitting times, like it's found a frequency band it likes and makes sure you get it! Neither of these I can dial out using the tone controls. Maybe a combination of my speakers, the room and my old ears don't work with the Denon. Shame really as it has some features I like, such as remote control, switched mains power outputs and switchable A/B speaker outs. 👍
No, in the last part of my post I discovered what is unusual for Denon in that unit. It doesn't sound good. There are no driver transistors between the outputs and Vas. It isn't your imagination, that unit will not sound good. I've never seen Denon do that before.
I would sell it off. Another Denon (check the schematic first - or send it to me and I'll look) would make you very happy. That one - no! I wouldn't touch it with a 10 foot pole. Normally Denon products are well designed and sound better than average.
-Chris
I would sell it off. Another Denon (check the schematic first - or send it to me and I'll look) would make you very happy. That one - no! I wouldn't touch it with a 10 foot pole. Normally Denon products are well designed and sound better than average.
-Chris
Ok Chris, so it's a bit of an odd one then, this amp. I will unlikely ever use it, so I'll probably sell it as I don't like the sound anyway. I'll stick with the Cambridge Audio for now 👍