DIY Pre-amp with MP3 Player (and FM Tuner)

[Reid Malenfant]

24 0 24 200VA transformer

This below should be the best deal buy a long chalk

225VA 24 0 24 transformer.

Please remember that the last one needs VAT adding & it also needs shipping adding. But that would be the one I went for

[activexp]

Here's the 25V one:

http://cpc.farnell.com/multicomp/mct...25v/dp/FF01586

Power Rating: 225VA
Secondary Current Nom: 4.5A
Secondary Voltages: 2 x 25V
Transformer Mounting: Chassis
AC Power: 225VA
Approval Bodies: UL Recognised
Bolt Length: 60mm
Bolt Size Max: 6
Current Rating: 4.5A
External Diameter: 110mm
External Length / Height: 51mm
Mounting Type: Chassis
Output Voltage: 25V
Primary Voltages: 115V / 230V
Regulation: 7%
Secondary Power: 112.5VA
Temperature Rise: 56��C
Transformer Type: Toroidal
Weight: 2.2kg
Weight: 2.2kg

Looking at the data sheet for the 2022 it appears that some resistor values need to be calculated depending on the chosen supply voltage and refers to the under and over voltage protection. The formulas are all a bit over my head Looks like ljm decided to play safe with a max of 24V.

I'm all for keeping things simple so rather than attempting to swap components for 30V operation (the resistor values look a bit odd like 242K 1%) I reckon my best bet is 18V. That said I'm very interested in the transformer you have available!

What are the specs and diameter (i.e. will it fit my case)

Cheers,
Steve

[Reid Malenfant]

I'll give it a measure tomorrow Steve, it's a low profile toroidal on a PCB that has been wired in series. You may as well have the lot if taking it as there is an IEC mains chassis socket that you may be able to use on this project.

[activexp]

Hi Mark, that Airlink one looks the business and even with VAT and delivery the price is OK Your Google must be better than mine. Thanks for the link!

I'm still at the planning stage, sourcing all the bits so I haven't ordered anything yet. Hopefully the amp will fit in the same case as the pre-amp for a matching pair. Still undecided about a heat sink for the 2022 as I can't find any specifically for Tripath chips. The alternative is to use the back panel of the case, a cost effective solution

Cheers,
Steve

[Reid Malenfant]

I might be able to help you out with a heatsink, I have them coming out of my ears

Yes I'd go for the Airlink transformer, even over my 18V jobby!

I'll get back to you tomorrow anyway Steve as I'm just about to fire up the PJ & have a film

All the best

[activexp]

Board ordered from Zoe_Tsang, with any luck I'll get it before Christmas and give me something to do over the holiday

For the transformer I'm going for the 300VA one as it's not much more.

Any joy with the heatsink Mark?

Cheers,
Steve

[Reid Malenfant]

For the transformer I'm going for the 300VA one as it's not much more.

Any joy with the heatsink Mark?

Cheers,
Steve

Good choice on the trafo

Glad you reminded me about the heatsink

If I don't get back to you by next weekend send me a PM or put another reply on here I'm just trying to think what I have got that'd be suitable, in reality it doesn't need to be very big, but bigger = cooler & greater efficiency as well as the thing will last longer

You'll need to insulate the chip from the heatsink if it's attached to the chassis, I have stuff that'll cover that to so need to find it

[activexp]

Thanks Mark. The heat sink doesn't have to be particularly large. I've seen this one on eBay:



Should do the job If you've got anything similar PM me.

It won't be attached to the chassis so insulation isn't needed

Cheers,
Steve

[Reid Malenfant]

Hi Steve, you just reminded me & I think I have just the thing I'll have a dig in the shed tomorrow for a dead NAD CD player that has a similar heatsink on the back panel. Better still I'm sure it's anodised black

[Reid Malenfant]

Steve, please send me a PM & let me know your address

I have a nice black anodised heatsink for you that will be perfect for the job in hand