Building a DIY amp with NVA amplifier boards

[karatestu]

When i used diy Avondale based amps and B&W P4 (still got them all )i moved the crossover filters actually inside my amplifiers This is how Les W runs his set up (a separate crossover box right behind his amps) and a few others. I tried it and was totally amazed at how much clearer everything was - the window had been cleaned some what.

You have to have a dedicated amp for tweeters though, or biwire from amp to speakers) And don't get any inductors too close to a transformer or huuuuummmmmmm will be the result. After i reported my purely subjective findings a few others tried it and agreed with me. However, there were several who could not think of an electrical reason why anything could be different (it was on pfm after all ).

Anybody who has a dedicated tweeter amp really should give it a go. Nothing ventured nothing gained, it's easy to revert back. In diy NVA land it is even easier. Only the capacitor in series with the tweeter needs to be moved to the amp. I will of course be trying it again when i have lived with the six pack of amplifiers for a while

[karatestu]

I have no spare TIS cables (well i have one that was made as a digital cable) so for these last two amps i have had to solder some solid single core silver wire from the amps on the next level up on my rustic rack. Just soldered the signal and 0V to the back of the phono sockets inside the said amps. Must remember to get the channels the right way around

Ultimately all these six nva amp boards are going on one sheet of 6mm aluminum with the volume controls central. I will be making a sort of six channel integrated amp with off board PSU. All the transformers and rectifiers are going as far away from the rest as possible. The capacitors will be mainly at the psu end with the final capacitors in the parallel chain being near the respective amplifier boards.

That is a way off yet though. I need to get these six channels going and here what effect it has with giving every driver size it's own dedicated amp. The only fly in the ointment is the naca 5 i am having to use initially. I hope it doesn't effect the outcome to much otherwise i may have to put it on the bass amps.

[karatestu]

It is done And it works

I have listened to three albums since adding the last two amps to the tweeters, i can't drag myself away. I had reservations whether this would bring about any change or improvement. The following is my purely subjective opinion (as is my way) and could be tinged with expectation bias and a host of other psychological effects that i don't know about.

Is putting a six pack on a three way Doc inspired speaker beneficial ?................Hell yes I am at risk of every change being a jaw dropping improvement. I don't seem to be able to put a foot wrong (touch wood) and i think i have the Doc to thank for that and putting us all on the the track to audio fulfilment

So the four tweeters wired in series per channel now have their very own amplifiers. This is just about the pinnacle of my amplifier journey apart from putting the tweeter filter caps on the end of the amplifier boards in the amplifiers themselves. There could be a possibility to add another psu to each amp like the statement range but quite frankly i don't think i can do with the hassle and expense of doing it to six amplifiers. Not to mention the added room needed to house more psu's

So, in a nutshell i am extremely happy with the result and if there is no more scope for improvement with amplifiers then i am not at all bothered. I will get my kicks elsewhere (speakers ? ) Even with Naim Naca 5 on the tweeters there is certainly enough improvement to warrant shelling out for another set of LS6.

So, get to the point and stop wittering on I initially thought that this step would if anything, only affect the treble. Wrong, and i should not fall in to this trap anymore as it happens time and time again. The higher frequencies and instruments such as cymbals have matured in to something wonderful. There is more composure but at the same time no drop in dynamic ability, it still sounds like music just more so. There is more detail now uncovered. Female vocals on Air Moon Safari that i am listening to now are just so more natural and convincing that i now know this woman intimately Little things are so important and the extra detail has brought a better understanding of how she sang it.

I listened to Dinosaur Wonder Trail before this. I have listened to this album over and over again over the last few days. Nothing else has been played . There was a strange noise one of the tracks and did not know what instument was doing it or if it was just a sound effect random noise. Turns out it is the trumpet with a recording effect applied. I would never have known that before adding the amps. There is lots of other low level harmonic information that just rounds off an instrument or voice as it were. Before the instrument was square (or maybe with slightly rounded corners). Now they are perfectly round and whole, more juicy and inviting. It's like trading up your girlfriend for one with a rounder ass. Yummy.

But these changes have brought added composure in the middle frequencies and bass as well. The performance of the band as a whole has matured and now sounds like the singer has had singing lessons since you last saw them live. Either that or they were feeling a bit off last time. You have got to look at the whole picture rather than just concentrating on particular frequency bands. The keyboard player just got a new keyboard with much better samples on board. This not only makes them sound better but the whole band benefits and they play better as a result. The audience is moved more and they have a better time. Its what its all about.

Enough spouting of bollox.

[karatestu]

Now listening to Mahavishnu Orchestra The Lost Trident Sessions. This is one of my go to test albums. It is so lively, energetic, dynamic and the best recorded of the three first albums. It never fails to blow me away.

I now have the greatest understanding of John Mclaughlin's guitar playing that i ever had. Hidden doubled up parts have emerged, the tone of his guitar and amp are crystal clear, echo and the recording venue are much more apparent. His playing has seemed to become faster, the notes and phrases stop and start more cleanly.

The sound is floating around in the room. Guitar's panned from one side to another and back again, i am amongst the musicians. I feel like my speakers are Leslie cabs

[karatestu]

I know.................. pictures or it didn't happen

[Alfi]

FANTASTICO Stu.

The culmination of much thought and dedication to the cause of a sound presentation that suits you perfectly; well almost as I guess there will no doubt be more from the rustic workshop and sound laboratory that is Chez Stu!



Alfi.

[karatestu]

Thanks John.

Other diyers usually get compliments about how nice their latest creation looks. I don't get any of them (obviously ) but one day i would like to. I put together stuff in a way that recycles materials and i always have a thought for accommodating future changes as i go along . All the untidiness is a means to an end. There is an end goal and one by one things are slowly coming together. Hopefully i will then be able to focus my thoughts on cosmetics and building attractive looking pieces of furniture. Well, that's what they are (or should be) as me, my family and visitors will eventually have to look at it day in day out and live around it.

I am feeling rather proud of myself today. Doc sold me all these boards quite a while ago and finally i have them all up and running. I hope he would have enjoyed watching my antics. The music is simply mesmerising today. I am sat dribbling with an open mouth.

[karatestu]

A picture of my lovely new amplifiers This is the bottom level of my rustic rack made out of fence posts and odds and ends of wood. The levels are 32 cm apart because kit put in close spaced racks are the work of the devil.



I had to use two 200VA toroids out of some old Naim NAP140's and some lovely Avondale Audio EI transformers. I had to replicate the Avondale CAP6 rectifier and capacitor boards as i didn't have any left for the last two output stages. No regulators on the front ends like the other amps as i don't have any volts to spare for dropout. The heat sink is only 20 cm sq of 2 mm aluminum. And it is hardly even warm Its only temporary but serviceable. The mid bass and bass amp heat sinks are very large sheets of 6 mm aluminum and they are much warmer (but only tepid).

A bit of scrap hardboard was used for the make shift back panel which is only there to hold the speaker outlet sockets (cheap as chips from Rapid). As i knew i was going to be using naca5 for these amps i had to get the socket spacing right or the plugs would not go in the sockets And they are right angle plugs so i had to put the sockets up high and put some wood under the shelf to make sure the naca5 could exit properly. Pain in the ass.

Here are the three levels NVA of amplification - two mid bass amps on top shelf, two bass amps below that and the new tweeter amps at the bottom. Highly attractive i think you will agree. These stands will be made available to order - price TBC

[Alfi]

Awesome work Stu..

Looks like a mix of Avondale EI transformers, Canturbury Windings Toroids and even Nuvotem Talema toroids(ex Naim?) by the looks of it, with Avondale Minicap 6 Power supplies and Hackercaps perhaps too?

I'd just clothe it in 6mm Perspex Stu and leave it as it is for folk to wonder at what's going on in there. I also like the arty cut along the top of lower speaker connection board - bloody awesome m8!

Alfi.

[karatestu]

Hey John,

Yes you are right. The big white toroids are canterbury windings audio grade transformers (superb by the way - as you know ) which inter winding electrostatic screen and outer guass band shielding round the whole thing. Apparently toroids are best the taller you can wind them so i got Terry to make the tallest ones he could wind them (90mm). They are beasts.

The Avondale EI transformers are also lovely things. They sound so good on the front ends of the tweeter amps. I think they filter more carp out of the mains than toroids because of less capacitance between the primary and secondary windings but have a bigger stray field. I love em

The nuvotem 200VA from NAP140's are the black ones. They do hum a bit but not as loudly as my BMU when my farmer mate across the road is using his welder.

The rectifier and cap banks are a mix of Avondale cap6 on the output stages and minicap on the input stages. No hackercap boards. The last two i had to make myself out of tufnol boards, kendeil caps, MBR20200CT schottky rectifiers and some 2 mm solid tinned copper wire. All point to point
Yes you spotted my arty hardboard. I ended up breaking that bit off across my knee

Perspex around the whole lot would cost a bomb i reckon as there are another two shelves above the ones in the picture for the sources and phono amp.