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Preamp with gain vs Power Amp with more power

karlsushi

karlsushi

pfm Member
I have been wedded to relatively low powered amps lately (SE, Class A, valves - that kind of thing). They work a treat in my smaller near-field system and really rather well in the larger living room one too. But I get the sense that there is still a bit of strain when playing at higher volumes in that bigger room. Or at least, that there could be a bit more 'ease' and 'control' to the sound.

One thing to note is that I do not use a separate pre currently. Either a Chord DAVE or Bricasti M3 DAC direct to amp. The two amps I'm currently using are either Icon Audio MB30SE monos or a Pass Labs Aleph 3. Hardly flea watts by any stretch at 30W each, but still. The Aleph 3 in particular is pretty low gain, so it feels like I'm really pushing it hard to get the volumes I'm sometimes after.

Appreciate one answer is higher sensitivity speakers, but I love my EJ Jordan Greenwich speakers (86dB, 16 ohms) so they're not going anywhere.

I'm thinking about a big beefy SE valve amp to provide a few more watts (845 or 805 valves), but they seem to be very big and very expensive.

So my question is, would a preamp with a bit of gain help to take some of the pressure off the amp and give me that better sense of ease and control at higher volumes? Or would you just be looking at an amp with more power?

The thing putting me off a pre is that I don't really want to sacrifice on the detail and transparency that I currently get using no preamp. But then I've never really owned a high-end pre.

Any ideas on the better route folks?
 
I think they bring different things to the party. The amp can only push out its rated output, so feeding it a louder signal doesn't mean you'll get a louder output if you're already pushing the amp a bit. Sounding 'strained' is, I think and as you suspect, a sign that the amp is getting outside its comfort zone. So more power is the only real way round that if you're keeping the speakers.

The addition of a preamp with gain does a different thing, IME. It adds 'drive' and 'energy' to the music, rather than loudness. It is possible, of course, that what you require is 'energy' rather than 'loudness' so a pre might, ironically enough, allow you to get a musically satisfying result while also backing off the power amp a bit.
 
Yes, fully agree with the above, good advice. You could also consider adding a sub or two. This would fill out the sound and careful positioning would bring lots to the party, by this I mean a heard improvement across the spectrum with more detail.

Even better would be to high pass the signal to the little metal coned drivers. If you crossed over to them at about 80 to 100Hz the speakers would have an easier time and could be played louder and with reduced distortion. Also removing the heavy lifting of the bottom 2 octaves from the amp especially the valve amp would also allow you to drive your amp harder and cleaner without saturating the output transformers.

If you go this route, a high-pass condition can be simply achieved by soldering in a small cap and resistor into the interconnect cables or better into the line stage or power amp. The values depend on the input impedance of the amp. Doing this obviously would require a sub/subs to provide the 2 bottom octaves which is what they are specifically designed to do. If you don't have a sub perhaps borrow one from a mate or outlet just to get an idea of what's possible. I can recommend the inexpensive small SVS SB1000 PRO. I have mine in a 5 x 7m room. A sealed box with the ability to be dialed in from your listening position via SVS App on your phone, great fun.

https://sound-au.com/articles/pllxo.htm Many articles on PLLXOs on the net.

I first tried this on a Rogers Cadet III with about 8W output. The amp sounded like it was a lot more powerful and with its tiny little OPTs gained clarity and detail.

For anyone interested in trying this but owns an integrated amp, it can be inserted in to the tape loop if it has one. Preferable for most as installing inside the amp would void the warranty.
 
Sue Pertwee-Tyr said:
I think they bring different things to the party. The amp can only push out its rated output, so feeding it a louder signal doesn't mean you'll get a louder output if you're already pushing the amp a bit. Sounding 'strained' is, I think and as you suspect, a sign that the amp is getting outside its comfort zone. So more power is the only real way round that if you're keeping the speakers.

The addition of a preamp with gain does a different thing, IME. It adds 'drive' and 'energy' to the music, rather than loudness. It is possible, of course, that what you require is 'energy' rather than 'loudness' so a pre might, ironically enough, allow you to get a musically satisfying result while also backing off the power amp a bit.
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This 100%
 
Of course it's not impossible that it's the speakers themselves that are becoming strained rather than the electronics.

I'm not familiar with what you have so I've no idea what their maximum SPL would be. Speakers tend to start to strain quite a bit before their max SPL though so that would only be a rough "guide".

How loud are you listening?
 
I can well imagine why you want to keep the Jordans.
As they are around 16ohms though I don't think the Aleph 3 will be supplying 30 watts.
Likewise a more powerful valve amp, with dedicated 16ohm taps? may be worth trying.

I've a pair of DIY double driver TL Jordans and they do take a bit of travel on the volume pot, especially with lower powered class A.
PP El34 work pretty well, surprisingly, though I generally don't listen that loud.
 
The Icon Audio amps don't have a 16 ohm speaker output. On the 8 ohm output you are effectively raising the input impedance of the output transformers. This may give you rather cleaner sound but it will be quieter, so you're not getting the stated output.

As stated above, don't confuse power with gain. If your volume control is near to maximum that's a good thing and nothing to worry about, as long as all kinds of sources and music are loud enough. Looks like there's a sensitivity switch on the Icons - you can play with that and the volume control and see what sounds better.
 
Loudspeakers are Voltage driven therefore the amp has to supply sufficient Voltage to handle the transient peaks of the music. Different speakers draw different amounts of current when they have a Voltage signal across them and this will define the power required.

A 16 Ohm speaker will draw half the power of an 8 Ohm speaker connected to the same amp. Thus your 30W amp can only deliver 15W max into 16 Ohms. You also risk driving the amp into clipping by turning up the wick and this may lead eventually to tweeter failure. So either a valve amp with a 16 Ohm output xformer tap or a beefier solid state amp is required.

DV
 
Speaking as a fellow Aleph 3 owner, they are not easy to find the right preamp for. I have reverted to a passive (Allegri+), but am actively considering commissioning a custom build. The Allegri works well with line sources, where 12 o'clock on the dial is a decent listening volume. In fact, I find that a totally hypnotic combination but predictably lacking some drive and sparkle.

Having corresponded with Pass Labs on this, I'm told Aleph 3s do like gain - ideally adjustable - and don't like high ohmage speakers. The original matching Pass Labs preamp (unobtanium btw) is a strange looking beast - a pot for left and right gain, and a "master" volume, almost like a guitar amp.
 
Tim Jones said:
Speaking as a fellow Aleph 3 owner, they are not easy to find the right preamp for. I have reverted to a passive (Allegri+), but am actively considering commissioning a custom build. The Allegri works well with line sources, where 12 o'clock on the dial is a decent listening volume. In fact, I find that a totally hypnotic combination but predictably lacking some drive and sparkle.

Having corresponded with Pass Labs on this, I'm told Aleph 3s do like gain - ideally adjustable - and don't like high ohmage speakers. The original matching Pass Labs preamp (unobtanium btw) is a strange looking beast - a pot for left and right gain, and a "master" volume, almost like a guitar amp.
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This is all very interesting. As others have suggested and this seems to confirm, the Aleph 3 might not be the best suit for my 16 ohm rated speakers.

There is no doubt that the Icon valve amps I have are a better audible match.

Based on the very helpful responses above, I'm thinking my best option is going to be saving up for a beefy new valve amp with 16 ohm speaker taps.

I may even speak to David Shaw at Icon in the meantime to see how easy it might be to add a 16 ohm tap to my existing monos.

The Aleph 3 sounds perfectly excellent in my second system with my little near-field speakers, so not looking to move it on just yet.

Thanks all.
 
Just a quick update following the very helpful answers to this thread a little while back.

The useful points from @Darth Vader and @les24preludes in particular, highlighting a potential mismatch with my current amplifier/s and my 16 Ohm rated speakers, led me to take the plunge on a pair of Ming Da Dynasty Cavatina valve monos.

During a bit of amp research, I contacted Mark at Malvern Audio Research (who is the UK importer for Ming Da) and as chance would have it, he had an ex-demo pair of the Cavatinas and a spare set of 16 Ohm output transformers sat in storage and awaiting a project in need of them.

The Cavatinas are SET amps using 805 output valves (uses 300bs for drivers) and a healthy 40W rated output.

Really pleased I took the plunge as they sound ruddy bloody excellent. My very moderately-sized EJ Jordan Greenwich (stand-mount) speakers seem to have turned into massive floor-standers overnight.

So in conclusion, I can answer my own OP: the answer is "Power Amp with more power" 🙂

Just wanted to update and offer my thanks for the helpful advice. Very happy đź‘Ť

Also, Mark at Malvern Audio Research deserves a big shout out. A great guy with incredible skill and knowledge and a top notch service to boot. The industry needs more like him!
 
And a couple of photos for anyone interested in some valve amp porn:

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53657061397_27d08b8989_w.jpg
 
Glad it's sorted. 16 ohm speakers are unusual, so you solved that issue. There's a lot of debate always about output transformers. They are basically just converters between input and output, and you have to assess what's happening with the tube > OPT > speaker interface to fully work out what's going on. As you found and fixed. All is not always what it seems.
 
les24preludes said:
Glad it's sorted. 16 ohm speakers are unusual, so you solved that issue. There's a lot of debate always about output transformers. They are basically just converters between input and output, and you have to assess what's happening with the tube > OPT > speaker interface to fully work out what's going on. As you found and fixed. All is not always what it seems.
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I'd just like to clarify the above statement.

Its essential to use the correct tap on the output transformer otherwise the output valve(s) will see the wrong anode load and may operate on the non-linear part of its characteristic curve thus leading to excessive distortion amongst other things.

DV
 
Jordan Greenwich is two fullrange drivers wired in series. Would wired in parallel which will give better sensitivity 89dB and 3-4 ohm impedance be better for modern valve amps with 8, 6, 4 ohm taps?
 
Darth Vader said:
I'd just like to clarify the above statement. Its essential to use the correct tap on the output transformer otherwise the output valve(s) will see the wrong anode load and may operate on the non-linear part of its characteristic curve thus leading to excessive distortion amongst other things.
DV
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That's what I was saying - you need to consider the whole tube > transformer > speaker interface. This will determine what tap on the output transformer is most suitable. The anode load as you say is related to the output tap because the transformer has different ratios of step-down depending on the tap used. For example, given a nominal 8 ohm speaker, a 3K transformer into 8 ohms would be 3K. With the same speaker it would be 6K on the 4 ohm tap and 1.5K on the 16 ohm tap. The 1.5K input impedance would be louder but unsuitable for the output valve. The 6K input impedance would be quieter but otherwise might sound as good or even better. Tubes like to see a load of at least 3x their output impedance, so a 300b at 800 ohm output impedance likes to see a 3K transformer. More than 3x can sound cleaner, so a 300b into a 5K transformer is liked by many. It's all about ratios with transformers.
 
karlsushi said:
Appreciate one answer is higher sensitivity speakers, but I love my EJ Jordan Greenwich speakers (86dB, 16 ohms) so they're not going anywhere.
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May I ask, did you listened their Marlow EV also when choose Greenwich? If yes, what was impressions on them?
 
gints said:
May I ask, did you listened their Marlow EV also when choose Greenwich? If yes, what was impressions on them?
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No sorry, can't help there. I am using the Greenwich in a fairly large room so the Marlows were never on the cards really.

I have wondered about them for my smaller near-field system though.

EJ Jordan do a 30 day returns policy, so just go for it. If you're thinking about them in a smallish room I doubt you'd be disappointed. Those Jordan full range drivers are rather special.
 
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