1st-Timer starts Amp7 build

[AmpNoob]

Hi,

1st I just want to say that the Amp7 isn't the ideal 1st build before someone else comes along and says the same thing

But I like the challange, and after receiving the components from 41hz I don't think it looks that intimidating to
soleder together though (Might feel different after starting the build).

I just sat down and winded the toroids (24 turns like it says in the pdf)

Will be used as HIFI PowerAmp

Just wondering if someone could give me some examples of a good toroid transformer choise for this amp (nothing exotic) ?
(and maybe also something for V10)

Also if someone would be so kind as to share if they hare a good gain/resistor selection that matches this application ?

Sorry for being souch a newbie !

O-boy I have a lot of reading to do

[V-bro]

Hi, I admire your courage! I wasn't that brave a few years ago before the whole thing started!

The transformer choice, well at RS components they sell nice encapsulated ones that should have far less mechanical hum. This has been a problem with some amps I've built, not a big problem, but nicer to have something in the room that doesn't hum at all from the casing... The only down side to them is you can't add more windings, so for V10 and VN10 you need two extra AC supplies. These can also be created from a dual output small aux. transformer, like those small blue block transformers. You need at least 4VA per rail, so an 8VA at minimum.

I can advise you to read Audiophools Truepath documents too, this amp is much the same as the AMP7. His site is http://www.maedos.com

Perhaps also not a bad idea to show us what tools you intend to use so we can perhaps give some advise on them too, or perhaps even prevent catastrophy....

Please do ask before ruining anything! We are here to help!

[AmpNoob]

Hi V-Bro

Thx a lot for answering my questions

I'll try to take babysteps when moving forward with this.

I'm going to read through "maedos.com" a couple of times. (really a goldmine)

RS seems to have a great selection and good prices, but have to be a company in order to place an order.

This is what I have on my shopping list so far.

Tools
-------
- new solding iron with temparature control (old one is crappy)
- 60,40 solder (have the eco friendly stuff at home but find it hard to work with)
- Somekind of magnifying glas with a lamp in it
- ISO alcohol

500VA TOROIDAL 2X 40v

8 x MUR820
Snubber capacitors
12 x 10000uf Capacitors
Bleader resistor/s

12 VA 12 VAC (2x) or 12 VA 9 VAC (2x) Block transformer ?
Rectifiers for the Block transformer
Snubber capacitors

fuseholders & fuses

Speaker terminals
Input terminals

Socket for the TA3020 chip

Seems like digikey sells to end-customers. Are they any good ?

I still have some PCB making stuff somewhere (tank,pump,heater)

Probably forgot lots of stuff. Will start with getting the right tools and then
try to start with the AMP7 kit itself.

Do I need a softstart to keep the fuses from blowing in my home ?
Is there any drawback to using a block transformer instead of a toroid ?
Should I go for a PS2-P+P ?

[V-bro]

Hi, you forgot some regulators, I would recommend a 7810L for the VN10 (1A version) and this supply needs no snubbers, then for the 5V (V10) I would take an LM317T, snubbers the whole thing. As a matter of fact it's not a bad idea to take a PSU1-VR kit for the both, these have rectifiers, regulators, snubbers etc. etc..... and one kit is two circuits...

Then the transformers, if you are in the US it's not much use for me to offer to order from RS for you. Maybe someone else here can help here? Digikey have good stuff, but I don't like their sales policies much, in any case towards foreign parties....(I got all sorts of surveys to fill in before I could even order, asking what I needed the parts for, maybe some anti terrorism thingy....)

Softstart definitely necessary! The PSU1-SS is great, it also has a mains filter on the board. A simple softstart is also a good option, I always place two NTC resistors of 5R in the mains lines, then bypass them with an AC voltage relay on a secondary winding of the transformer. I have posted a schematic here a few times, can look it up...

The PS2-P+P is not really holding up with this amp, I've tried and it got bloody hot on the VN10 supply...

A 12VA block transformer with dual 12V outputs is a good option, make sure the two secondaries are 100% separate and isolated though!!

[AmpNoob]

Hi,

Oh, then I'll stay away from PS2-P+P !
(good that you adviced me since I would have bought that one for sure unless you hadn't)

I'll most likely follow your advice and go for the PSU1-VR.

I'm living in Sweden.

Will try to find your softstart schematic in the forum.

Tomorrow I'll go looking for a soldering iron/station so that I can get started.

Once again thx for all the help. Feels like I've already avoided a few pitfalls

[V-bro]

http://nl.farnell.com/finder/55-32-8...vac/dp/1169234
http://nl.farnell.com/epcos/b57238s5...471?Ntt=ntc+5R
http://nl.farnell.com/block/fl10-12/...12v/dp/1131489

[AmpNoob]

Thx,

I started soldering a few components on.

had to change the size of the tip of the soldering iron and adjust the heat until it really went smothly!

Went pretty well with nice little peaks of tin except for the very 1st one.

However I can't find where C26 is supposed to go on the PCB. Listed in the BOM in bag 1.

Have I missed something ?

[V-bro]

C26?! Can't find it anywhere, what value is it supposed to be? And what details are listed?

[AmpNoob]

In the BOM it says

Spec: 3.3 uf 1 hmt Cap 50V Cer 0.1uF X7R 10% RM2.5 Qty 3 C19,C21, C26

Comment: Decoupling

[AmpNoob]

Hi,

As I understand it some of the resistors needs to be calculated to match
the size of the transformer and the input source.

Or are everything pre-selected in BOM optimized ?

Would be great if someone could supply some standard values that I could use.

I haven't gotten the PSU parts yet so I am a little bit flexible. The usage for the
AMP is as a HIFI pre-amp.

I know it's a bit lazy but I don't want to misscalculate and end up with smoldering ashes
where the rest of my hifi equipment used to sit.