I've had a K4040 for about 2 years now. I was not happy with the way it sounded stock. The Sovtek EL34's it came with made it harsh sounding. I put better tubes in and that improved the sound a lot but still not as good as I hoped. I ended up converting it to use KT88's and did some other mods.
Some of the mods I found at this site:
Vellemam Mod site
Now it sounds pretty decent and has plenty of power and is much more reliable than it was stock and I use it as a backup amp.
Dave
Some of the mods I found at this site:
Vellemam Mod site
Now it sounds pretty decent and has plenty of power and is much more reliable than it was stock and I use it as a backup amp.
Dave
George,
Why buy a kit and pay all that shipping and taxes on it, when you have to modify it and replace the tubes anyway?
Chassis and power transformers are cheap in India so at worst you'll have to import the output trans and some passives. Tubes can probably be found locally.
Build it from scratch.
Why buy a kit and pay all that shipping and taxes on it, when you have to modify it and replace the tubes anyway?
Chassis and power transformers are cheap in India so at worst you'll have to import the output trans and some passives. Tubes can probably be found locally.
Build it from scratch.
I agree, unless you can get the kit really cheap you will be better off building an established well designed DIY amplifier. I wouldn't have bought the Velleman except for the fact I got it for $400. And even with the mods I don't think it sounds nice enough to use as my main amplifier thought its not that bad....
Dave
Dave
Hi,
Years ago I had quite a few customers coming in asking for me to improve the Velleman kits.
While they're easy enough to improve, they're so limited by their topology that it's impossible to make them sound great.
Even major surgery isn't money well spent with these amps.
There are a few kits out there that are definetely beter sounding, even without tweaks.
Cheers,
Years ago I had quite a few customers coming in asking for me to improve the Velleman kits.
While they're easy enough to improve, they're so limited by their topology that it's impossible to make them sound great.
Even major surgery isn't money well spent with these amps.
There are a few kits out there that are definetely beter sounding, even without tweaks.
Cheers,
Thanks for all the input.
I prefer to get a kit because getting hold of all the components here is a fairly time consuming exercise. I recently did the AKSA amp which was quite easy because all I needed to get were the transformer and the chassis.
Bringing the kit across on one of my trips to the US isnt a problem ( no taxes or duties!) Could you suggest any decent kits priced below $800? I already have three amps at home and getting approval from the "Home Ministry" for another one wont be easy!
Speakers-one of my systems is a 95db AriaR, and MTM system using Focal mids and Raven R1 tweeters. Another system uses Scanspeak mids and tweeters. I use 12 inch powered subs.
Thanks for any input.
George
I prefer to get a kit because getting hold of all the components here is a fairly time consuming exercise. I recently did the AKSA amp which was quite easy because all I needed to get were the transformer and the chassis.
Bringing the kit across on one of my trips to the US isnt a problem ( no taxes or duties!) Could you suggest any decent kits priced below $800? I already have three amps at home and getting approval from the "Home Ministry" for another one wont be easy!
Speakers-one of my systems is a 95db AriaR, and MTM system using Focal mids and Raven R1 tweeters. Another system uses Scanspeak mids and tweeters. I use 12 inch powered subs.
Thanks for any input.
George
gjo said:
Hi
I don't like it soundwise
The first stage distorts way too much, the second may be OK and the phase splitter should be a differential pair, rather than the kathodyne, as this one is short of breath in the originnal design
Furthermore the bias of the kathodyne is bad, they changed that later on.
PP amps should never be fixed bias, as this is decreasing the balance in the output stage.
Not my favourite amp, not even after all my mods I once did for a customer
regards
I think this is a nice kit Jukebox Revival winkel altough i dont know anyone who build it, or how you will get it to india
Velleman K4040
Hi Tubies
I built the Velleman K4040 kit a few weeks back. It is my first valve project since my 15w mono p-p (2 x EL84s) back in 1972.
Evidently the kit quality has improved a bit since some of the previous posts and it now has WIMA MKP10 coupling caps, slightly better resistors, and good quality gold plated input and speaker connectors. All the valves were Elektro Harmonix except the two ECC83s, which were Sovtek.
The board is easy to assemble and the mechanicals are good quality and stunning appearance, but the unit is a cow to fit together into the chassis because it's very crowded at the rear. Also, some of the screw holes didn't align perfectly. Once mounted on the chassis, quite a few parts are difficult - but not impossible - to access. (My maxim is that if you can't access something easily, it will fail, just to spite you.). I'd recommend it only for very neat and patient constructors, but then we should all try to be such.
The assembly instructions are adequate but printed in an A5 booklet which means everything - eg the circuit - is difficult to read. I downloaded the .pdf of the booklet from the Velleman site, scanned the pcb overlay and schematics, and printed them out full size on A3 paper. If you're over 50 you should do this before you begin.
I had a hum issue at first on the R channel, which I traced to the Elektro Harmonix ECC82 preamp tube. Even brand new, it made hum. Replacing this with an old NEC 12AU7 of unknown provenance I found in my junkbox solved that. There was also distortion on the right channel which I think was due to a poor connection to the output transformer. The hum went away when I swapped the trafos and remained good when I swapped them back. Also, the instruction booklet suggests reducing the feedback by increasing the feedback resistor value, and I found this was necessary. The pcb should be scrupulously cleaned in IPA after assembly; with 450V HT around you cannot have a PCB smeared with flux residue and grime. I contacted Velleman Support over these issues and I'm pleased to say their response was prompt and well directed.
I'm about halfway through the Ironradio mods. If you buy this kit you MUST do these for both reliability and sonic improvement. Next step will be JJ tubes for all the ECC8x and eventually a conversion to 8 x KT88s. I'm not going to do the long-tailed pair phase splitter mod suggested elsewhere.
Initially it sounded muddy and unimpressive with the dodgy EH tube for V11, but at the present point in its modification it's not bad at all, sonically. It has virtually no hum at all, plenty of guts and has that distinctive mellow valve sound due to the even harmonics and their distribution. It reproduces a Hammond organ as only a valve amp can, in a way that will thrill you. Compared to my all-digital PowerDAC open loop switching amplifiers (see my other posts) it lacks the unreserved raw punch in the bass and it doesn't sound 'quite as accurate'. It may also be a tad bright in the mid, but I'm still running a Sovteks and EH tubes.
The K4040 is advertised as 90W per channel, but in practice it's already clipping and it only makes about 75W just before the onset of visible non linearity can be seen on a scope. The frequency response is as claimed, but I noticed that there's a bit of peaking slightly beyond the upper limit claimed by Velleman. I've not yet measured the THD+N. When I've fitted the JJ valves and done all the remaining Ironradio Phase 1 and 2 mods, I will bring home the Prism dScope III from work and put he K4040 thoroughly. I'll post the results on the forum.
In conclusion I will say that I'm well pleased with my K4040. The kit cost about 1k Euros and was delivered quickly from a German vendor on e-bay.
The K4040 is definitely only for experienced constructors who are prepared to do some relatively straightforward modifications and tweaks to get the best out of it. If that's you, I would recommend the K4040.
Hi Tubies
I built the Velleman K4040 kit a few weeks back. It is my first valve project since my 15w mono p-p (2 x EL84s) back in 1972.
Evidently the kit quality has improved a bit since some of the previous posts and it now has WIMA MKP10 coupling caps, slightly better resistors, and good quality gold plated input and speaker connectors. All the valves were Elektro Harmonix except the two ECC83s, which were Sovtek.
The board is easy to assemble and the mechanicals are good quality and stunning appearance, but the unit is a cow to fit together into the chassis because it's very crowded at the rear. Also, some of the screw holes didn't align perfectly. Once mounted on the chassis, quite a few parts are difficult - but not impossible - to access. (My maxim is that if you can't access something easily, it will fail, just to spite you.). I'd recommend it only for very neat and patient constructors, but then we should all try to be such.
The assembly instructions are adequate but printed in an A5 booklet which means everything - eg the circuit - is difficult to read. I downloaded the .pdf of the booklet from the Velleman site, scanned the pcb overlay and schematics, and printed them out full size on A3 paper. If you're over 50 you should do this before you begin.
I had a hum issue at first on the R channel, which I traced to the Elektro Harmonix ECC82 preamp tube. Even brand new, it made hum. Replacing this with an old NEC 12AU7 of unknown provenance I found in my junkbox solved that. There was also distortion on the right channel which I think was due to a poor connection to the output transformer. The hum went away when I swapped the trafos and remained good when I swapped them back. Also, the instruction booklet suggests reducing the feedback by increasing the feedback resistor value, and I found this was necessary. The pcb should be scrupulously cleaned in IPA after assembly; with 450V HT around you cannot have a PCB smeared with flux residue and grime. I contacted Velleman Support over these issues and I'm pleased to say their response was prompt and well directed.
I'm about halfway through the Ironradio mods. If you buy this kit you MUST do these for both reliability and sonic improvement. Next step will be JJ tubes for all the ECC8x and eventually a conversion to 8 x KT88s. I'm not going to do the long-tailed pair phase splitter mod suggested elsewhere.
Initially it sounded muddy and unimpressive with the dodgy EH tube for V11, but at the present point in its modification it's not bad at all, sonically. It has virtually no hum at all, plenty of guts and has that distinctive mellow valve sound due to the even harmonics and their distribution. It reproduces a Hammond organ as only a valve amp can, in a way that will thrill you. Compared to my all-digital PowerDAC open loop switching amplifiers (see my other posts) it lacks the unreserved raw punch in the bass and it doesn't sound 'quite as accurate'. It may also be a tad bright in the mid, but I'm still running a Sovteks and EH tubes.
The K4040 is advertised as 90W per channel, but in practice it's already clipping and it only makes about 75W just before the onset of visible non linearity can be seen on a scope. The frequency response is as claimed, but I noticed that there's a bit of peaking slightly beyond the upper limit claimed by Velleman. I've not yet measured the THD+N. When I've fitted the JJ valves and done all the remaining Ironradio Phase 1 and 2 mods, I will bring home the Prism dScope III from work and put he K4040 thoroughly. I'll post the results on the forum.
In conclusion I will say that I'm well pleased with my K4040. The kit cost about 1k Euros and was delivered quickly from a German vendor on e-bay.
The K4040 is definitely only for experienced constructors who are prepared to do some relatively straightforward modifications and tweaks to get the best out of it. If that's you, I would recommend the K4040.
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