L12-2 CFP OUTPUT AMP 120W*2 8R

[Ian Finch]

Mine came with Toshiba TTC5200 and TTA1943 even though the picture on ebay shows Sanken.

Hmm ...I thought the advertised LAPT Sankens were too good to be true. Well, that's HK Ebay stores.
I've had a look at old threads and tried to find data sheets for those TT prefix equivalents to 2SC5200/A1943.
'Can't see anything credible yet, other than that they are indeed Toshiba products - perhaps not made
to the same process as in the Thai plant.

They should be up to the task though, given the rating and larger case for better dissipation.

[Ian Finch]

Doing a small amount of digging, it seems from Toshiba's own website references, that TT prefix parts identify Chinese production.
Officially, there is no need for concern there.
There are a few suppliers of kits and built-up L12-2 modules. One of them, Zoe_Tsang, shows pics of original On-semi ss transistor
packaging and Sanken output transistors. I think they are trying to tell us something there.
This is the schematic they post on the web. You can see it is not screwed up like that above in #6 :

.

[r_merola]

Dear Ian Finch

I tottaly agred with you.
This schematic is very similar with Yamaha small amplifier and it have extra compenents like the transistor like diode in position Q17 and Q19(i suppose). When you see the PCB there is one TO92 TR missing.
Worth by the price offer.

regards

[Evenharmonics]

Originally Posted by Ian Finch

.

Which resistor controls bias?

[ATAUDIO]

Originally Posted by Ian Finch

Doing a small amount of digging, it seems from Toshiba's own website references,

Very interesting amp!

One of the few that I have seen around with double output CFP. Once I had published here a simple design (JAS - Just Another Sziklai) in such way (it is still under very slow development, ( I have recently modified the VAS but it come up one day...)
Some people here and elsewhere argue that such kind of output is almost impossible to stabilize, so the fact that it is around with a mixed choice of outputs is somehow reassuring.
From my few tests , it is not so.
Thermal stabilty is rock solid (never really had a problem in such sense with a CFP in general), high frequency stability can be an issue, but if the PCB routing is done well and you do not get too extreme compensation values, it is easily working. My impression on prototype listening is that those amps sound really "fast" , i.e. with cristal crear highs and well controlled bass. Ideal for soprano voices, let´s say.

[ATAUDIO]

Originally Posted by Evenharmonics

Which resistor controls bias?

Guess the ratio R10/R19 or do you mean you would like a pot?

[Evenharmonics]

Originally Posted by ATAUDIO

Guess the ratio R10/R19 or do you mean you would like a pot?

May be in the future if I have more free time to play around with it.

On mine, the voltage across R13 and R20 measure 12mV and 10mv. What do you think?

[ATAUDIO]

Originally Posted by Evenharmonics

May be in the future if I have more free time to play around with it.

On mine, the voltage across R13 and R20 measure 12mV and 10mv. What do you think?

That should be around 40-50 mA. That´s perfect for my taste, but you migh hear different opinions. I follow the current of thinking that CFP should be biased low, at the limit of the crossover distortion. People more skilled than me have given some physics about that, but I cannot reacall who, at the momement.

[Boscoe]

Originally Posted by Evenharmonics

May be in the future if I have more free time to play around with it.

On mine, the voltage across R13 and R20 measure 12mV and 10mv. What do you think?

Do you measure any DC offset?

[Evenharmonics]

Originally Posted by Boscoe

Do you measure any DC offset?

It's -24mV DC 5 minutes after powering up with no input and no load.