Dansette amp

[george1960]

Just wondering a bit, has anyone ever removed the old valve amp from a Dansette and fitted a modern amp. If so how did you do it and what amp did you use?

[Michael Maurice]

I’ve never done it, but the biggest challenge would be having a very high input impedance to match the crystal or ceramic cartridge.

What’s wrong with keeping the original amp?

[Herald1360]

Just about any modern amp module that would fit will do. Power supplies might be an issue, though there's likely room to fit an off the shelf SMPSU or a homebrewed linear one.

High input resistance if required is easily done with an opamp unity gain buffer.

You won't need high power- 5W or so will be plenty.


Why though? Cheap fix for dead valve(s) or output TX?

[Tim]

No, but it wouldn't be that difficult to convert a single valve one one to say an ECL/UCL82.

I did replace the monitor amplifier in a Ferrograph series 6 tape recorder once, as the original(Germanium) transistor version took down the heater supply whenever it was connected!
I also remember sending away for the manual and circuit diagram, hoping I could fix the amplifier. I even contacted the seller and asked them if the diagram showed the transistor amp, before I parted with my postal order.
When it arrived there was just a square box drawn in labelled "transistor amplifier! The data had cost me £12( that was in the early 90's) I was livid!


ISTR I used something like an LM380 in the end, running from the DC heater supply in the machine and feeding the original speaker. The problem in that case was too much input, so I had to make a potential divider.

The fet op amps such as TL071/081 would be fine here, but they might actually have too high impedance. Perhaps a resistor of a few meg across the input might help.

[RojDW48]

I used one of these - TDA2030A Audio Power Amplifier Boards Module Mono15W-18W DC 12V-24V AMP Board - to replace a Dansette amp with a dead transformer. Cheap as chips and adequate, but loads of matching resistance needed for the input.

[G8UWM-MildMartin]

I did it to a Portadyne rather than a Dansette about 30 years ago, using a TDA2030A and (long obsolete) RS PCB and increasing the resistor shunting the input (pin 1) from the usual 22K to somewhere around 470K (I forget now.)
Currently on Ebay, there are available for 99p including postage:
"TDA2030A DIY Electronic Audio Power Amplifier Board Mono 18W DC 9-24V Kit"
The PCB is worth more than that and if the IC proves to be is a no-good fake, an LM1875 from a reputable source for a couple of pounds can be substituted.

[Station X]

George.

Are you proposing to fit a new amp to the player in this abandoned thread:-

https://www.vintage-radio.net/forum/...d.php?t=156956

If so I think you'd do better and learn more by fixing the existing amp.

[Edward Huggins]

Of course the character of the original Dansette will be change for ever if you change out the amplifier. There will then be the issues of crystal cartridge input impedence matching, the adding and location of the tone controls and the speaker matching as the Dansette will have a 3 ohms unit installed. There's more to this than just changing the amp!

[george1960]

Originally Posted by Station X

George.

Are you proposing to fit a new amp to the player in this abandoned thread:-

https://www.vintage-radio.net/forum/...d.php?t=156956

If so I think you'd do better and learn more by fixing the existing amp.

NO not at all I was just curious that's all, I was just wondering if anyone had ever done it.

[Al (astral highway)]

Lots of people do it, George.

I don’t. There’s no judgement if anyone wants to.

[Ed_Dinning]

Hi George, I think there have been some sub threads on the Dansette and other similar types.
Perfectly possible and quite easy to do but watch the cartridge or you may nedd a pre amp.

Ed