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Re: DIY thoughts of the day

Posted: Sat Aug 31, 2019 2:01 pm
by karatestu
I am done with spending money with this diy lark. Spent far too much over the years. From now on i am just using the parts i already have, which is quite a lot :dance: . The surplus i will try and sell.

Phono stage is a Phono1. That is getting pulled apart with amp board and regs in a metal enclosure either in the TT or as close behind as i can. Very short arm lead if i do it that way. Think Naim prefix but better :grin: . PSU for that will be remote and consist of four 100VA EI transformers, MBR20200CT rectifier diodes and some kendeil 6,800uf caps. The last smoothing cap will be just before the regulators.

Speaking of regulators, there is only one positive and one negative reg in a Phono1. I need another three pairs which i will have to fabricate myself out of parts i already have knocking about. Doc's reg is extremely simple and i have the necessary parts already.

There will be six power amps using NVA boards (unless i blow one up) and i am giving all of them 2 psu's each like the A80 and A100 designs. So twelve psu's in all for the power amps (bloody hell) :o . In order to use up what i already have i will have to use four transformers with secondary voltages that are too high so some regulators are needed to drop the voltage a bit. They will be used on the front ends of the bass and mid frequency amps.

The tweeter amps will get two very nice 100VA EI frame transformers with twin centre tapped secondary windings. No regulators on these as the voltages are low enough to be used as is. All power amp psu's are going to be remote as well.

As for speakers, well i change my mind every day. As i dont intend buying owt else then my plan for BBCube style speakers with three isobaric 12 inchers, three 5" mids and three tweeters is not going to happen. I am going to have to make do :violin: with two isobaric 12 inchers, one 5" mid and one tweeter. Two bass drivers either down firing or one down firing and outer one front firing, one up firing mid and the tweeter front firing as usual.

Re: DIY thoughts of the day

Posted: Sat Aug 31, 2019 3:00 pm
by montechristo358
2 PSUs for each Amp, how does that connect up then?

Any benefit over using 1 PSU twice the size or just using up stuff thats available

Re: DIY thoughts of the day

Posted: Sat Aug 31, 2019 3:16 pm
by karatestu
It sounds better (IMO). The psu on front end duties is not subject to the voltage sag and ripple caused by the heavy load on the output stage.

As for connecting them up - the front end is isolated from the output stage on the amp board pcb. The two psu's have to have their 0V connected at some point. The hard part is finding out where the best place to do that is.

Re: DIY thoughts of the day

Posted: Sun Sep 01, 2019 6:57 am
by karatestu
A thread on another forum reminded me of the experiments i did with moving my speaker crossovers (B&W P4 that are in retirement) from the speaker cabinet to directly behind the amplifier. I had about 6 inches of wire from amplifier board to the filters. I could not believe the improvement it brought. Nobody on the forum could come up with a technical reason why it should make any difference at all but it did and several very well respected members reported the same.

Of course the idea was poo pooed but i wasn't the last member there to try it and imagine the improvements :grin: . Anybody who is curious about it then give it a go. You need another set of speaker cables though or the biwire option for nva amps to keep capacitance low. Just don't get any inductors too close to any transformers or you will get some hummmmmm. Better still - get some speakers with no crossover to start with :dance: . I never tried moving the padding resistor and 3.3uf cap on my nva style speakers back to the amp or even inside it. There are no inductors involved to pick up transformer emi so it could go right on the end of the amp board. :think:

That got me thinking about doing the high pass filter at line level in the power amp's input stage and ditching the 3.3uf cap. But i dont know what effect that would have and if it would play nicely with a passive resistive volume control. Also no cap before the tweeter equals good bye tweeter if the amp goes dc at any time.

Re: DIY thoughts of the day

Posted: Thu Oct 10, 2019 8:04 pm
by karatestu
Listening to my system now waiting for my band members to show up for rehearsal. Got a pub gig on Saturday.

I wish it sounded this good through the day as well. It's magical now unlike earlier when it gave me a headache. Bloody farmers polluting the mains supply round here :roll:

Re: DIY thoughts of the day

Posted: Tue Oct 29, 2019 5:25 pm
by karatestu
Copied this from another site

"This is the musicians dillemma and why they are typically not good evaluators of sound reproduction. They only hear the performance. If the performance is good then the reproduction is good and vice-versa. Until you can learn to seperate those two very distinct things - the performance and the reproduction - you will never understand what I am talking about. One can be good and the other bad, they are distinctly seperate things."

i am not sure what to make of this . I am leaning to the view that it is mostly :Bllocks:

Re: DIY thoughts of the day

Posted: Tue Oct 29, 2019 6:15 pm
by slinger
karatestu wrote: Tue Oct 29, 2019 5:25 pm Copied this from another site

"This is the musicians dillemma and why they are typically not good evaluators of sound reproduction. They only hear the performance. If the performance is good then the reproduction is good and vice-versa. Until you can learn to seperate those two very distinct things - the performance and the reproduction - you will never understand what I am talking about. One can be good and the other bad, they are distinctly seperate things."

i am not sure what to make of this . I am leaning to the view that it is mostly :Bllocks:
I'd go so far as to say self-important pseudo-psychological :hbs:

Re: DIY thoughts of the day

Posted: Tue Oct 29, 2019 6:24 pm
by Daniel Quinn
It isn't. It's fairly simple and starightforward language. It may be genius or shite, what it ain't is self important psudo psychological.

Re: DIY thoughts of the day

Posted: Tue Oct 29, 2019 6:42 pm
by joe
I'd have thought it was a statement of the bleedin obvious, meself.

Re: DIY thoughts of the day

Posted: Tue Oct 29, 2019 7:03 pm
by CN211276
joe wrote: Tue Oct 29, 2019 6:42 pm I'd have thought it was a statement of the bleedin obvious, meself.
and me.