View Full Version : Leben CS300 models X, XS etc
Has anyone experience of the various CS300 models ? I know the base model has a few less watts 12 as opposed to 15, just wondering what else the upgrades bring, if any and if it's worth spending the extra.
Hi Steve,
I had the xs and thought it one of the better amps I've had. Quite gutsy for its rating, more dynamic than you'd think. Much preferred it to the CS600 I also had at the same time. But, I've always liked the EL84 amps I've heard, so I'm probably a bit biased :rolleyes: OTOH, I'm not sure it'd really be any different from similar stuff from Audio Innovations, WAD, AN, etc ...
I've had the basic 300 before Pete. Just wondering if it's worth stretching a bit more for one of the other versions.
I love my AI500 but ready for something newer and a bit more stylish now the family holiday is out of the way.
Went for the base 300 model. Forgot how great these sound.
southall-1998
30-10-2016, 16:09
How does the 300 stack up to the 600?
S.
I've never heard a 600, it's way out of any budget I've ever had.
Went for the base 300 model. Forgot how great these sound.
Excellent! Not sure what speakers you have this week, but remember to try the different speaker tappings (4,6,8 ohm switch thingy). I found the 6 ohm setting worked best with some (allegedly) 8 ohm speakers, so may be worth a bit of experimenting?
Still have my WLMs Pete. Had them around 6 months :ner:
Not sure what speakers you have this week,
:rofl::rofl::rofl::rofl::rofl:
pete, you are very naughty.
steve, nice one. Ive heard good things about these
I've recently purchased a cs300x, loving it so far. First time I've heard the holographic sound stage thing I've read so much about.
As far as I was able to work out, the cs300 came with sovtek pre and power valves, the cs300x NOS GE 51571 pre valves and Mullard NOS el84 and I think the cs300xs had the NOS GE 51571 pres combined with the Sovtek el84s.
I'm going to have a bit of fun tube rolling with mine, and also give the Mullards a rest until I get my main speakers sorted out. I've got a set of 1950's GE triple mica 5751s, which I'll probably try out and then save as above, and a set of JJ el84s on the way.
Be interested to hear of any other users experience with different valves in this amp.
I've recently purchased a cs300x, loving it so far. First time I've heard the holographic sound stage thing I've read so much about.
As far as I was able to work out, the cs300 came with sovtek pre and power valves, the cs300x NOS GE 51571 pre valves and Mullard NOS el84 and I think the cs300xs had the NOS GE 51571 pres combined with the Sovtek el84s.
I'm going to have a bit of fun tube rolling with mine, and also give the Mullards a rest until I get my main speakers sorted out. I've got a set of 1950's GE triple mica 5751s, which I'll probably try out and then save as above, and a set of JJ el84s on the way.
Be interested to hear of any other users experience with different valves in this amp.
I had the bigger brother of the CS300 in my system for a bit, the CS600. It's true that it did do that holographic "3-D" soundstage thing very well, and majored on finesse and detail, but at the same time, it had very little bass control, probably due to high output impedance, not something you'd expect (or want) from a PP at that price. Fabulous with strings/light orchestral though. That design, I imagine, would work best with very sensitive loudspeakers having low cone mass, or horn systems very well indeed. Not one for the head-bangers. Changing valves wont change much in the way of sound. It is biased fairly conservatively and runs well within its efficient operating envelope so one valve, for any given type and output, will pretty much give a sound like any other run at reasonable volumes. Changing valves can't alter how the circuit is designed. It may make a little difference when run hard, depending on how each valve distorts, but my own findings were that with the stock valves, they sounded fine. Personally, I'm a fan of Sovtek, Harma and JJ. Very reliable valves. Unless you have a valve tester, NOS can be a very hit and miss proposition unless you are assured of buying matched and tested. I find Watford Valves to be a more reliable proposition that E-bay for matched valve supply.
I agree about the CS600, Paul ... I found the same thing. However, I also had the CS300xs, which I think is probably better engineered. IME, it certainly did a much better job of controlling speakers (Harbeths, even 15 inch Tannoys) than the 600, despite its lower power rating.
southall-1998
02-11-2016, 15:00
What is the second hand selling price for the C300XS?
S.
That's good to know about the tubes not making that much of a difference in this amp, it will certainly save me a little cash!
The bass is perhaps not as well controlled as with a solid state amp, certainly into my low sensitivity speakers that are attached at the moment, but my aim is to find a pair of high sensitivity speakers to run it with eventually. I can see why people may be often disappointed when they go from SS to valves, but for me the positives in terms of texture and fluidity outweigh the slight reduction in impact.
That's good to know about the tubes not making that much of a difference in this amp, it will certainly save me a little cash!
The bass is perhaps not as well controlled as with a solid state amp, certainly into my low sensitivity speakers that are attached at the moment, but my aim is to find a pair of high sensitivity speakers to run it with eventually. I can see why people may be often disappointed when they go from SS to valves, but for me the positives in terms of texture and fluidity outweigh the slight reduction in impact.
It's not to much the loudspeaker sensitivity that determines bass control as the damping factor and whether the amp can maintain a constant voltage with a varying current demand (the current demand being a factor of impedance with frequency). Some valve amps can't, even though they may be designed to maintain a constant voltage.
A lot depends upon the amplifier's output impedance and power supply. Generalising, a good valve amp ought really to use a choked supply and have an output impedance of under an Ohm. Most don't, even expensive ones. A few do (Radfords being one example). If your speakers can be driven loud and the crossover losses are low, then the amount of bass generated depends on whether the amp can deliver sufficient voltage/current at low frequencies. If crossover losses are high (relatively speaking) and speaker minimum impedance is quite low, you're on a hiding to nothing if using an amp with high output impedance irrespective of sensitivity. That just determines how loud the speakers will go, but without adequate damping factor, frequency response tends to follow the impedance profile of the loudspeaker being driven.
You can have exactly the same issue with sensitive loudspeakers which exhibit low impedance (typically in the bass region) and relatively high crossover losses.
Arkless Electronics
02-11-2016, 18:24
It's not to much the loudspeaker sensitivity that determines bass control as the damping factor and whether the amp can maintain a constant voltage with a varying current demand (the current demand being a factor of impedance with frequency). Some valve amps can't, even though they may be designed to maintain a constant voltage.
A lot depends upon the amplifier's output impedance and power supply. Generalising, a good valve amp ought really to use a choked supply and have an output impedance of under an Ohm. Most don't, even expensive ones. A few do (Radfords being one example). If your speakers can be driven loud and the crossover losses are low, then the amount of bass generated depends on whether the amp can deliver sufficient voltage/current at low frequencies. If crossover losses are high (relatively speaking) and speaker minimum impedance is quite low, you're on a hiding to nothing if using an amp with high output impedance irrespective of sensitivity. That just determines how loud the speakers will go, but without adequate damping factor, frequency response tends to follow the impedance profile of the loudspeaker being driven.
You can have exactly the same issue with sensitive loudspeakers which exhibit low impedance (typically in the bass region) and relatively high crossover losses.
A psu with a choke is largely an irrelevance in this day and age... "back in the day" when smoothing capacitors were thought of as large if they were 32uF, they were much more important in getting a hum free supply of reasonably low impedance, but today, when we have 470uF etc smoothing caps readily available at a reasonable price, a cheaper RC supply will suffice.
The output transformer is of course very important to bass quality in a valve amp. It is quite common for a big valve amp capable of 100WPC @ 1KHz for 0.2% THD to only be capable of 20WPC... and at 5% THD... by the time the frequency drops to 20Hz;)
A psu with a choke is largely an irrelevance in this day and age... "back in the day" when smoothing capacitors were thought of as large if they were 32uF, they were much more important in getting a hum free supply of reasonably low impedance, but today, when we have 470uF etc smoothing caps readily available at a reasonable price, a cheaper RC supply will suffice.
The output transformer is of course very important to bass quality in a valve amp. It is quite common for a big valve amp capable of 100WPC @ 1KHz for 0.2% THD to only be capable of 20WPC... and at 5% THD... by the time the frequency drops to 20Hz;)
That's as maybe Jez, but I'd take a proper choked supply over the use of caps every time ;) One way may suffice, but many top notch valve amps use choked supplies for good reason. It's easier on the rectifiers and with caps only, saw tooth ripple wave forms are produced rather than largely sinusoidal with a choke. Chokes also mean very small ripple voltages, so I'll stick my neck out and say of the two, a good choked supply is the better way and produces a cleaner supply.
Of course output transformers are very important. Balancing low distortion with high bandwidth yet maintaining relatively low output impedance (never truly achievable without feedback and some time compensation within the feedback circuit) is very difficult to achieve and good output transformers don't come that cheaply.
For the record, I have several valve amps here that deliver under 2%THD at full output and way less than 1% at half output. Another is on its way which measures far less than that, in fact not far off a competent SS amp. Quality of design and parts are everything ;). By comparison, I know of some SS amps which measure appallingly wrt THD at low demand yet are good at higher outputs...go figure. There's good and bad examples in both genres.
Arkless Electronics
02-11-2016, 20:09
That's as maybe Jez, but I'd take a proper choked supply over the use of caps every time ;) One way may suffice, but many top notch valve amps use choked supplies for good reason. It's easier on the rectifiers and with caps only, saw tooth ripple wave forms are produced rather than largely sinusoidal with a choke. Chokes also mean very small ripple voltages, so I'll stick my neck out and say of the two, a good choked supply is the better way and produces a cleaner supply.
Of course output transformers are very important. Balancing low distortion with high bandwidth yet maintaining relatively low output impedance (never truly achievable without feedback and some time compensation within the feedback circuit) is very difficult to achieve and good output transformers don't come that cheaply.
For the record, I have several valve amps here that deliver under 2%THD at full output and way less than 1% at half output. Another is on its way which measures far less than that, in fact not far off a competent SS amp. Quality of design and parts are everything ;). By comparison, I know of some SS amps which measure appallingly wrt THD at low demand yet are good at higher outputs...go figure. There's good and bad examples in both genres.
Most of that I agree with but in the case of the choke you obviously mean a choke input PSU... Very expensive due to the size of the choke required and, as I said, now that we have big smoothing caps readily and cheaply available, largely redundant. The possibly £100+ cost of a suitable high quality choke could be spent elsewhere in the amp to considerably greater effect;)
SS amps which measure badly at low power are of course non class A... and probably mainly class B! Valve amps designed for highest power output from a given set of valves rather than low distortion will demonstrate the exact same effect.
It's not to much the loudspeaker sensitivity that determines bass control as the damping factor and whether the amp can maintain a constant voltage with a varying current demand (the current demand being a factor of impedance with frequency). Some valve amps can't, even though they may be designed to maintain a constant voltage.
A lot depends upon the amplifier's output impedance and power supply. Generalising, a good valve amp ought really to use a choked supply and have an output impedance of under an Ohm. Most don't, even expensive ones. A few do (Radfords being one example). If your speakers can be driven loud and the crossover losses are low, then the amount of bass generated depends on whether the amp can deliver sufficient voltage/current at low frequencies. If crossover losses are high (relatively speaking) and speaker minimum impedance is quite low, you're on a hiding to nothing if using an amp with high output impedance irrespective of sensitivity. That just determines how loud the speakers will go, but without adequate damping factor, frequency response tends to follow the impedance profile of the loudspeaker being driven.
You can have exactly the same issue with sensitive loudspeakers which exhibit low impedance (typically in the bass region) and relatively high crossover losses.
Interesting, how does one go about finding out the damping factor and output impedance of an amp? Would they be listed in a manual or is if something that needs to be measured yourself?
I believe I was chatting to you Paul on pinkfish re my Tannoy Eatons (cross overs will be going to you at some point), are they a good match for the Leben, they certainly sound like it when working correctly.
Radford Revival
03-11-2016, 10:54
Interesting, how does one go about finding out the damping factor and output impedance of an amp? Would they be listed in a manual or is if something that needs to be measured yourself?
It may be in the manual, however, this is often erroneously referred to, even by many manufactures in their own specifications and manual, as the nominal impedance match (ie 4Ω or 8Ω). Simply put this is the impedance the amplifier is optimized to drive and is why many valve amps have taps for 4Ω, 8Ω and sometimes 16Ω. Due to this mislabelling however sometimes the only way to know is indeed measuring it yourself, or finding someone who has.
The output impedance, is essentially a figure put on what's equivalent to an impedance between a perfect voltage source and the speaker. On an amplifier with moderate feedback, this may look like 1Ω on the 4Ω tap, and perhaps 2Ω on the 8Ω tap. To the speaker, this is ROUGHLY, but NOT equivalent to a 1Ω or 2Ω resistance in series with itself. This will therefore have implications for speaker damping.
In reality it's not a pure resistance, its magnitude and phase varies with frequency. On amplifiers with feedback it tends to rise a little bit with frequency as the loop gain falls off (among other reasons). Some valve amplifiers also exhibit a rise at the bottom end too, and some may even exhibit a peak in impedance (typically in the low single digit Hz) due to poorly selected coupling capacitors interacting with the inductive rolloff of the output transformer. For all transformer coupled amps, as the frequency approaches DC you approach the DC resistance of the winding(s) that drive the load.
To confuse things further, on amplifiers with very little damping, the output impedance can indeed approach the matching impedance, so the output impedance on the 4Ω tap can really be around 4Ω. In extreme examples it can even exceed it and such amplifiers are probably best avoided unless you know for a fact that they will work correctly with your particular speakers.
The only thing to add to Will's post above, is that to compicate matters further, it's not just the actual output impedance of the amp that you need to consider when looking at the load it has to drive.
Additive to that are reactive losses from loudspeaker cables and passive crossovers, specifically low frequency filter series losses (ie inductors).
To work out DF, you divide the minimum loudspeaker impedance load by the sum of the amplifier's output impedance at that frequency plus the crossover/speaker cable losses.
Most loudspeaker runs of sensible domestic lengths of up to say 5m per side should only exhibit reactive losses of say 0.1 to 0.2 Ohms maximum (loop resistance plus capacitative and inductive reactance). Many mainstream loudspeakers will use cored inductors of around 0.3 to 0.5 Ohm DCR, so adding the two you have say 0.7 Ohms to add to your amplifier's output impedance.
If we take a not untypical valve amp output of around 2 Ohms (PP with feedback), we have a 2.7 Ohm output impedance driving a load which for a typical 8Ohm nominal impedance loudspeaker may be closer to 6.5 Ohms minimum at bass frequencies, so you can see that DF is only around 2.4 which is simply inadequate to control most bass cones. Sealed boxes can be a little easier to control due to the lower "Qtc" but in general you ought to aim for a figure of around 7 to 8 bare minimum for adequate control and preferable double figures. Better valve amp designs like one of Will's Radford STA amplifiers have a circuit which (Will can correct me here if wrong) exhibit much lower output impedances, of under 0.2 Ohms, hence their suitability for driving large Tannoys in vented enclosures and maintaining vice like grip on them! I dare-say that Anthony's amplifiers are also very good in this respect.
Some SS amp manufacturers may proudly list their DF in spec sheets as, say, 500, but don't be fooled. With crossover losses etc, into the same 6.5 ohm load, they are still subject to that same laws of physics and the same 0.7 ohms needs to be added hence for the same example above, actual DF is more like 11. In actual fact, any DF figure stated much over 20 or 30 is pretty meaningless as far as amp specs go for this reason. Of concern as well as DF is also whether an amp can maintain required current into a fixed voltage at minimum loudspeaker impedance.
In general terms, you should look for an adequately rated power supply (preferably choked if for a valve amp) and as low an output impedance as possible. This is rarely possible with single ended valve amp designs which use no feedback as their actual output impedance tends towards their DCR of the windings of the output transformers, so 4 Ohms is not untypical, hence they are best suited to very high efficiency low mass designs such as horns, where they excel. The caveat is that if choosing high efficiency and high sensitivity loudspeakers, you have yet another factor to consider which is signal to noise ratio (S/N). The higher the system sensitivity, the higher the S/N performance needs to be to combat circuit noise. TRON are one example of a manufacturer who specialise in producing amplifiers of exceptionally high S/N performance for this reason.
Had a bit of time with this playing through my WLMs now and it's quite startling how much detail this amp picks up on compared with my AI500. Whilst it doesn't have the same body and warmth or all out meatiness, it has a crisp, very textured presentation. Dropped larger holed donuts in the the WLMs base mounted bass port and it's really coming together.
Bit of John Campbell - down in the hole - playing with real grip and drive, guitar hanging in the air... A lot of height to the image too. Very promising.
southall-1998
10-11-2016, 20:55
Someday, I'd like to try an AI500, but fitted with EL-34's.
S.
The AI500 is a great amp, no doubt about that. Certainly no worse than the Leben to my ears.
southall-1998
10-11-2016, 21:10
I use an old pair of AN J's in the garden room. The AI500 will certainly have no issues, driving them for sure!
Is the AI500 still serviceable?
S.
There seems to be enough knowledgable folk who know the amps really well to address any issue that may arise.
Difficult to separate the Leben and the mod'd AI500. Finding it pretty difficult to choose between the two to be honest and one has to go before my missus looks at the savings account :D If it's so close I should just choose the cheap un ....right?
Put both up and keep the one that doesnt sell..
I've got two buyers already waiting for each!
Ah then its tricky :scratch:
I've done a little bit of tube rolling with this amp and as someone said earlier, the differences between the tubes are not that great. Which is fantastic news! Mine came with a set of oldish Mullard el84's and some 2 mica GE 5751's from the late 1980's from what I can make out. I got some 3 mica black box plate GE 5751's from 1956 and also some brand new JJ el84's. There are some subtle differences between them all, but it really is very small, possibly imaginary level. I'm happily using the later 2 set of valves at the moment and it sounds fantastic. I'll keep the Mullards and use them when I get some more suitable speakers, but its good to know this amp sounds great running a set of valves costing £40, rather than £300 or so!
I'm still fairly confused about speaker matching and so it'd be great to hear from other users on what worked well for them.
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