Hello boywonder. I've managed to get some basic specs for the amplifier:
Velleman K4040 Power Amplifier
Specifications:
· 2 x 90Wrms in 4 or 8W.
· Up to 2 x 15Wrms full class A.
· Bandwidth: 8Hz to 80Hz (-3db/1W).
· Harmonic distortion: 0.1% @ 1W/1KHz.
· Signal to noise ratio: >105dB (A weighted).
· Input sensitivity: 1Vrms.
· 115VAC or 230VAC / 500VA max.
There isn't much more information than that except that the original EL34 valves have been replaced by 6SN7 x4 & KT88 x4 and that other upgrades were carried out (no info as yet on these). The work was done by a chap who worked for GEC as a radio engineer so I guess they will have been carried out to a hight standard.
Les
Velleman K4040 Power Amplifier
Specifications:
· 2 x 90Wrms in 4 or 8W.
· Up to 2 x 15Wrms full class A.
· Bandwidth: 8Hz to 80Hz (-3db/1W).
· Harmonic distortion: 0.1% @ 1W/1KHz.
· Signal to noise ratio: >105dB (A weighted).
· Input sensitivity: 1Vrms.
· 115VAC or 230VAC / 500VA max.
There isn't much more information than that except that the original EL34 valves have been replaced by 6SN7 x4 & KT88 x4 and that other upgrades were carried out (no info as yet on these). The work was done by a chap who worked for GEC as a radio engineer so I guess they will have been carried out to a hight standard.
Les
89dB speakers and 1W of average output power will sound quite loud in the domestic environment.
Difficult to hold a conversation, while only 8' from the speakers.
Peak output of ~108dB +3dB for peakref sinewave +3dB for a pair, -8dB for 2.5m listening distance gives a very adequate 106dBpk with 90W maximum, if the speakers can manage 106dBpk
But check the impedance of the speakers.
Are they 8ohm, or 4 to 8ohm, or 6ohm, or 4ohm.
Valve output stage likes to drive a load fairly close to the impedance selected at the transformer.
Many speakers have an impedance range that does not match well to valve amplifiers.
Difficult to hold a conversation, while only 8' from the speakers.
Peak output of ~108dB +3dB for peakref sinewave +3dB for a pair, -8dB for 2.5m listening distance gives a very adequate 106dBpk with 90W maximum, if the speakers can manage 106dBpk
But check the impedance of the speakers.
Are they 8ohm, or 4 to 8ohm, or 6ohm, or 4ohm.
Valve output stage likes to drive a load fairly close to the impedance selected at the transformer.
Many speakers have an impedance range that does not match well to valve amplifiers.
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hey-Hey!!!,
Class A is not only defined as both tubes conducting. It is also to include both tubes conducting at full power. Hence the term AB. At less than full power both are conducting, but at some point it will be only one. AB can be biased fairly close to A or B, but part of the whole Class A operation says that the idle point is conducting enough to avoid cut off at full pwer too.
This whole X watts at full power and some fraction of that in class A is a marketing ploy. An operating point( combination of load, B+ and idle current ) capable of avoiding cut off at full power is more linear than the AB one and IME sounds better. It takes large tubes to make large power and since too many consumers went in for the power race....
cheers,
Douglas
Class A is not only defined as both tubes conducting. It is also to include both tubes conducting at full power. Hence the term AB. At less than full power both are conducting, but at some point it will be only one. AB can be biased fairly close to A or B, but part of the whole Class A operation says that the idle point is conducting enough to avoid cut off at full pwer too.
This whole X watts at full power and some fraction of that in class A is a marketing ploy. An operating point( combination of load, B+ and idle current ) capable of avoiding cut off at full power is more linear than the AB one and IME sounds better. It takes large tubes to make large power and since too many consumers went in for the power race....
cheers,
Douglas
Hello AndrewT. The Kef UniQ 80's are 8ohms impedence and I have them hooked up in series to a pair of Mordaunt Short 25Ti's also rated at 8ohms to help boost the midrange and treble. I think that should give me 4ohms altogether, but I'd like to check to make sure. Can you advise me how to do this - can I take a reading from the end of the speaker leads if I disconnect them to give me a combined impedence, or do I need to measure each speaker at the posts to check their individual accuracy?
I'm hoping that the Velleman K4040 will give me a fuller/richer sound which might mean I don't need to run 2 speaker pairs. The K4040 is rated at 'Output power: 2 x 90Wrms music power for loads of 4 or 8 ohm' so I'm assuming that the speaker setup I will will run quite happily with this. Do you think this is correct logic? I'd be glad of any advice you may have.
Les
I'm hoping that the Velleman K4040 will give me a fuller/richer sound which might mean I don't need to run 2 speaker pairs. The K4040 is rated at 'Output power: 2 x 90Wrms music power for loads of 4 or 8 ohm' so I'm assuming that the speaker setup I will will run quite happily with this. Do you think this is correct logic? I'd be glad of any advice you may have.
Les
Forget about multiple speakers if you want improved sound.
Augmentation, when properly implemented, can improve the sound, but that is not simple to achieve.
As to the impedance of your speakers.
You will need to measure the resistance of each voice coil. An 8ohm driver will usually have a resistance of ~80% of it's rated impedance.
If any one and/or both drivers measure outside the range 5r5 to 9r0 then you don't have 8ohm speakers.
One advantage of many valve amplifiers is an output impedance in the bass range that is higher than most Solid State amplifiers.
This higher output impedance interacts with the Speaker Q and changes the bass response relative to the remainder of the audio spectrum. This may suit your listening room or may not.
Augmentation, when properly implemented, can improve the sound, but that is not simple to achieve.
As to the impedance of your speakers.
You will need to measure the resistance of each voice coil. An 8ohm driver will usually have a resistance of ~80% of it's rated impedance.
If any one and/or both drivers measure outside the range 5r5 to 9r0 then you don't have 8ohm speakers.
One advantage of many valve amplifiers is an output impedance in the bass range that is higher than most Solid State amplifiers.
This higher output impedance interacts with the Speaker Q and changes the bass response relative to the remainder of the audio spectrum. This may suit your listening room or may not.
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I realize that an amp should not be powered up in open circuit. What I was wondering was whether it was possible to test the overall impedence someway, using a meter, but measuring from the amplfier end - rather than measuring each speaker serperarely and calcilating it from that ie. measure it in operation?
Les
Les
Sorry about the confusion over series/parallel wiring. I think you are right AndrewT. I have bought the Velleman amp and will run it with just the main Kef speakers. I think that the valve amp will help provide a better bass and hopefully be better all round than my current ss Marantz.
Thanks for the advice.
Les
Thanks for the advice.
Les
Hello again.
I've taken delivery of the Velleman amp and have hooked the Marantz cd player straight to it with no pre-amp. I've also taken your advice and ditched the second set of speakers, so it now goes to the Kef Q80s and you are right - the sound is very pure.
I have noticed a difference between the valves and solid state in terms of warmth and clarity. The only thing I need is a way of controlling volume - at present the cd player defaults to maximum volume when it is powered up, so everytime I switch on I have to reset the volume before playing the cd, or else the speakers would be overworked.
What do you think would be the easiest way to incorporate a volume control without having an adverse effect on the sound reproduction?
Les G
I've taken delivery of the Velleman amp and have hooked the Marantz cd player straight to it with no pre-amp. I've also taken your advice and ditched the second set of speakers, so it now goes to the Kef Q80s and you are right - the sound is very pure.
I have noticed a difference between the valves and solid state in terms of warmth and clarity. The only thing I need is a way of controlling volume - at present the cd player defaults to maximum volume when it is powered up, so everytime I switch on I have to reset the volume before playing the cd, or else the speakers would be overworked.
What do you think would be the easiest way to incorporate a volume control without having an adverse effect on the sound reproduction?
Les G
Thanks. Would it have much effect on the quality if I went for a simple kit like this Velleman Velleman Volume and Tone Preamp (70-4023)
It might be useful to have a basic tone control as well?
Les G
It might be useful to have a basic tone control as well?
Les G
Whether or not to have tone controls is a personal choice. If you decide to have them then an active baxandall circuit (like the vellemann you linked to) is a good way to do it.
For volume contol you simply need a volume control. You can, if you wish, incorporate a balance control too but many people manage without one.
For volume contol you simply need a volume control. You can, if you wish, incorporate a balance control too but many people manage without one.
Ok, thanks DF96. I suppose the most direct route is to just have a volume control, which should give the purest playback ie. as close to the way the music was originally recorded.
Since it is being re-interpreted electronically anyway it must be coloured by the amplifier in use at any one time - the Velleman valves sound different to the Marantz ss anyway so what you say about it being personal choice/taste makes sense.
Since it is being re-interpreted electronically anyway it must be coloured by the amplifier in use at any one time - the Velleman valves sound different to the Marantz ss anyway so what you say about it being personal choice/taste makes sense.
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