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AMP (Fanless) Suggestions for Auratones AND Reftones?

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Re: AMP (Fanless) Suggestions for Auratones AND Reftones?

Postby Arpangel » Wed May 20, 2020 7:57 pm

James Perrett wrote:
Arpangel wrote:
Hugh Robjohns wrote:Yes, and 303s. Amazing how often those old hi-fi Quad amps turned up in lo-fi studio applications!

Yes, I wish mine didn’t have the volume knobs though. I suppose it would be a simple job to bypass them, but he's drilled holes, shame.

Before you go taking the pots out remember that the standard 405 is much too sensitive for a typical mixer output so you may well need some kind of internal attenuator anyway. My 405 is fed via a home made attenuator adaptor.

Of course, if you really want to get into things you could change the circuit around the input op-amp to reduce the sensitivity but be aware that the 405 circuit is fairly cleverly designed and relies on various parts of the circuit having the right time constants for stability so any mods need to take this into account.

Thanks James, I’m running a 33 preamp with it right now, and everything is fed into that, all that’s going into the 405 is the output of the 33 via the appropriate lead.
I’m also running an Art Clean Box into the 33 from my interface, balanced to unbalanced, it all sounds fine. It’s just that the volume pots needn’t be there, so I may as well just get rid of them
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Re: AMP (Fanless) Suggestions for Auratones AND Reftones?

Postby James Perrett » Wed May 20, 2020 11:05 pm

Looks like removing the pots should be fine if you use them with the Quad the preamp.
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Re: AMP (Fanless) Suggestions for Auratones AND Reftones?

Postby iasomph » Sun May 24, 2020 1:46 am

Thanks to all for the replies! I've been quite busy in these latest days but I'm finally back. I resume the thread since I'm finally at the final choice :clap: I will chose one of these three amps (they seem more tailor-made to cube speakers, so it seems the easiest and safest way to go):

Auratone A2-30 https://www.thomann.de/gb/auratone_a2_30.htm

Drawmer CPA-50 https://proaudiosystems.co.uk/drawmer-c ... r-amp.html

Speaking about power, these two seem very similar with 30W / 25W RMS 8 ohm. The Drawmer seems to have some more bells and whistles, like the possibility to bridge the channels and arriving at 100W RMS 8 ohm this way. But other than this and small things, these two amps seem more or less equivalent.

Drawmer MPA-90 https://proaudiosystems.co.uk/drawmer-m ... r-amp.html This one is more powerful, 50W RMS 8 ohm with the possibility of a more powerful bridged channel as well.

Considering that the Vintage Auratone speakers 5PSC has these specs:
"Power handling: 35 watts nominal / 70 watts music power. Sensitivity 90db 1W/1M", and that the Reftones can handle more power if needed, would you suggest the less powerful A2-30 / CPA-50 or the more powerful MPA-90?

Non of these 3 amps has any kind input gain control, and for the moment I will connect the amp directly to the Babyface Pro XLR outs. Probably in the future I will add a monitor controller, but I'd prefer adding it later, when I'll change room in few months.

So I have a couple of questions:

- with the A2-30 / CPA-50 will I still need an attenuator like this: https://rothwellaudio.16.ekm.shop/balan ... rs-3-p.asp for a correct input gain staging or would be enough to lower a little the digital volume control on the Babyface Pro by some db?

- if I go with the MPA-90, which is more powerful (still, 50W RMS 8 ohms don't still seem a huge power to me after all), will I still be fine without attenuators, or with this amp amp I should need to buy them?

My main worry is to damage the speakers (especially the vintage Auratones, which handle less power than the Reftones and I suppose are also more delicate, being a design of 35 years ago) if the amp is too powerful for them.

Thanks again for your marvelous help! Can't wait to order one of these amps and finally try the speakers :)
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Re: AMP (Fanless) Suggestions for Auratones AND Reftones?

Postby Hugh Robjohns » Sun May 24, 2020 10:57 am

iasomph wrote:Drawmer CPA-50

Be aware that he CPA50 is an obsolete product no longer manufactured. Drawmer only offer the MPA90 now.

...would you suggest the less powerful A2-30 / CPA-50 or the more powerful MPA-90?

I'd always go for a slightly more powerful amp on the basis that if the amp isn't powerful enough the likelihood is that it will be turned up into overload, and amplifier clipping is what kills speakers. But taking that approach assumes that you can engineer an appropriate gain structure to minimise any risk of amplifier overload!

....and for the moment I will connect the amp directly to the Babyface Pro XLR outs.

I refer you to my previous statement!
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Re: AMP (Fanless) Suggestions for Auratones AND Reftones?

Postby iasomph » Sun May 24, 2020 2:17 pm

Hi Hugh, thanks again for your effort in helping me taking the best decision!

Actually, also the MPA-90 seems to be discontinued. They have some pieces in stock, but it seems the product is no longer made and will be replaced by a new product later on (if you check, it's in stock in very few places). But, since it seems a nice sounding class D amp (I have read a review and both the CPA-50 and MPA-90 use nice Anaview class D module, so it should be a nice sounding amp!) and since I found a nice deal also on the MPA-90, why not going with it, even if it's going to be discontinued? You think it may be a risky decision?

If I go with the MPA-90, would be enough to lower the digital volume control on the Babyface Pro for obtaining a decent (not optimal, but decent) gain structure? I don't mind if I lose 2-3 bits working with the Auratones for the moment. How many db's you think I should lower digitally on the Babyface, for using a 30w speaker (like it is the Auratone) with a 50 w amp without blowing it?

If it's just 10-15 db to lower on the Babyface Pro, this shouldn't be dramatic for the moment. On the contrary, if I will not be able to make a decent gain structure in this way, I can consider adding a pair of attenuators ( you suggest 10 db, 15 db or 20 db attenuator in this case?).

I'm considering the Audient Nero (which I think I may add to my setup in few months) and it has +- 15 db trimming on each speaker output, so the attenuators may become a useless piece of equipment later on, if I will proceed with the Nero.

But, if I need the attenuators now to protect the speakers and obtain a decent gain structure for these remaining months, I will add them to the purchase. Better spending other 60£ than blowing the speakers :)
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Re: AMP (Fanless) Suggestions for Auratones AND Reftones?

Postby iasomph » Mon May 25, 2020 3:16 pm

iasomph wrote: If I go with the MPA-90, would be enough to lower the digital volume control on the Babyface Pro for obtaining a decent (not optimal, but decent) gain structure? I don't mind if I lose 2-3 bits working with the Auratones for the moment. How many db's you think I should lower digitally on the Babyface, for using a 30w speaker (like it is the Auratone) with a 50 w amp without blowing it?

If it's just 10-15 db to lower on the Babyface Pro, this shouldn't be dramatic for the moment. On the contrary, if I will not be able to make a decent gain structure in this way, I can consider adding a pair of attenuators ( you suggest 10 db, 15 db or 20 db attenuator in this case?).

.....if I need the attenuators now to protect the speakers and obtain a decent gain structure for these remaining months, I will add them to the purchase. Better spending other 60£ than blowing the speakers :)

Don't leave me now Hugh, I'm ready to pull the trigger on the MPA-90, as you suggested :D
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Re: AMP (Fanless) Suggestions for Auratones AND Reftones?

Postby Hugh Robjohns » Mon May 25, 2020 5:21 pm

iasomph wrote:If I go with the MPA-90, would be enough to lower the digital volume control on the Babyface Pro for obtaining a decent (not optimal, but decent) gain structure?

Obviously you can run with the Babyface digital volume control reduced, but I can't really hazard a guess about how much, or what effect that will have on the signal-noise ratio.

Unfortunately, while most RME interfaces have the option of selecting different output signal voltage ranges, I don't think the Babyface does (it would have been useful to select the lowest (-10dBV) option).

How many db's you think I should lower digitally on the Babyface, for using a 30w speaker (like it is the Auratone) with a 50 w amp without blowing it?

:shocked: Er... All The Way! And then raise it gradually to assess an appropriate operating level.

I can consider adding a pair of attenuators ( you suggest 10 db, 15 db or 20 db attenuator in this case?).

You'll need to work out what kind of attenuation you need. I can't anticipate as it depends on the speaker sensitivity, the amp power, the position of the speakers inthe room in relation to you, and your preferred listening levels...
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Re: AMP (Fanless) Suggestions for Auratones AND Reftones?

Postby iasomph » Mon May 25, 2020 5:53 pm

Thanks Hugh, you are amazing! I just ordered it!

I got a pretty good deal on it, so....I pulled the trigger. I hope it will sound good and also will be a reliable product, since I'm only getting one year warranty on this instead of the two standard years. But the brand seems a very good one, so....let's hope well :)

Unfortunately only the new Babyface Pro FS got the adjustable output, doh :headbang:

from https://www.rme-audio.de/babyface-pro-fs.html :

+19 / +4 dBu switch on the bottom adds a direct way to reduce the output level, thus improves SNR for sensitive active monitors, avoids distortion / overload, and helps to keep TotalMix FX faders near 0 dB instead of high attenuations.
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Re: AMP (Fanless) Suggestions for Auratones AND Reftones?

Postby iasomph » Mon May 25, 2020 9:14 pm

At this point I need the last advice: how to connect the MPA-90 to the vintage Auratones? Of course from sound card to MPA-90 I will go balanced (XLR), but then? Should I really need to cut a cable and connect it bare wire to the amp and to the speakers?

I see many people advice using banana plugs for this sort of connections, but it seems they are forbidden in Europe (even if Thomann seems to sell banana plugs anyway) .

Any pre-made cable for connecting the amp to the Auratones without having to go with bare wire? :headbang:
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Re: AMP (Fanless) Suggestions for Auratones AND Reftones?

Postby James Perrett » Mon May 25, 2020 9:56 pm

I'd just use banana plugs - they're fine provided you connect everything before powering up. Mind you, quite a few speakers here are connected with bare wires but they're very fiddly compared to banana plugs.
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Re: AMP (Fanless) Suggestions for Auratones AND Reftones?

Postby iasomph » Mon May 25, 2020 10:17 pm

Thanks James! Any advice about the diameter of the cable I should get? I saw many hi-fi discussions about high end cables, diameters, etc etc :lol: of course I think they are a little exaggerated most of the time.

Any reasonably priced good cable you may suggest?
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Re: AMP (Fanless) Suggestions for Auratones AND Reftones?

Postby Sam Spoons » Mon May 25, 2020 10:45 pm

basic two conductor mains cable is fine, even quite small stuff will work fine on a short run but I usually use 1.5mm2 twin, something like this :-

https://www.screwfix.com/p/nexans-3182y-white-2-core-1-5mm-flexible-cable-10m-coil/7968t

I'd use whatever connectors are most convenient, domestic amps usually have banana plugs or bare wire connectors (or both) and either will work fine.
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Re: AMP (Fanless) Suggestions for Auratones AND Reftones?

Postby Hugh Robjohns » Mon May 25, 2020 11:36 pm

iasomph wrote:Should I really need to cut a cable and connect it bare wire to the amp and to the speakers?

It's the normal solution -- if a bit agricultural...

I see many people advice using banana plugs for this sort of connections, but it seems they are forbidden in Europe (even if Thomann seems to sell banana plugs anyway).

It's because the dual-banana plug block that used to come on pre-made speaker cables can be encouraged to fit into a European mains socket. So the EU went all nanny-ish on us and decided to ban them rather than educate the public on how not to kill themselves!

If you are intelligent about it, banana plugs (and even dual-banana plugs) are perfectly safe and are still widely available from all the usual electronics suppliers.

However, if bare wires and banana plugs fill you with dread, 'Spade' terminals (crimp or solder types) are generally better anyway under the binding posts of the amplifier.

But whatever you do, make absolutely sure there are no stray wires (if using bare wires) that could cause a short, or that the spades terminals aren't touching and can't move to cause a short! It won't burn the house down or destroy your chosen amp if there is a short, but it's very annoying if it happens and you have to rummage at the back of the gear to sort it! :lol:

Any pre-made cable for connecting the amp to the Auratones without having to go with bare wire?

Shouldn't think so for a moment. I think the connectors on the back of a vintage Auratone are screws, so suitable size spade terminals or bare wires are probably needed. And they won't take very thick cables!

Image

For 'ickle Auratones I'd just go an buy some 6A (0.75mm^2) two-core mains cable, strip the ends, and use that!

You could go chunkier and use 10 amp (1mm^2) or 15 amp (1.5mm^2) cables if you want, or if the cable runs are long, but you might find it a challenge getting them into the Auratone terminals.
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Re: AMP (Fanless) Suggestions for Auratones AND Reftones?

Postby iasomph » Tue May 26, 2020 1:21 am

Thanks!

How to say if my Auratones can accept also banana plugs? My model is a little more "modern" than the 5C; it's the Primo 5PSC, made some years layer, maybe it's been updated in that regard. To me the inputs look like 5-way binding posts (so they should accept banana plugs), correct?

Image

Image
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Re: AMP (Fanless) Suggestions for Auratones AND Reftones?

Postby James Perrett » Tue May 26, 2020 1:37 am

Yes, those accept banana plugs as well as spade connectors (provided they aren't too big) and bare wires.
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