a...Rotel design

[sakis]

This is the basic schematic of the rotel 1080B nice straight forward simple topology operates from 73+73 volts claims 200W @8R and 300@4 ...how about a bit more power with some 10 volt more higher rails may be the same 5 sets of outpouts but 1943-5200 and may be the adition of a vi limmiter

any opinions ????

kind regards sakis

[bobodioulasso]

You'll have to find pre and drivers that fit too. These ones are 140v.

[sakis]

will check that ...thanks for your advice ... still 73+73 was the original stated voltage

regards sakis

[sajti]

For predrivers I recommend 2SC4793/2SA1837, for driver, use NJW0281/NJW0302.

Sajti

[bobodioulasso]

Or 2sc3263/2sa1294 as drivers

[Ian Finch]

Thanks for posting the circuit Sakis, I was curiouis too. It seems from the spec. that the original PSU is weak, like a lot of Hi-fi designs that only rate for 8 ohm power and bragging rights.

Maybe just a larger transformer and minor adjustments for current plus improving a few PCB track, resistor and driver issues are all that's needed to get closer to 400 W output - assuming that is enough for your needs.

You are the man for PA stuff and your avatar says it all for going up in voltage and overall power like Bobo says. FWIW, to me, the design looks 100% Hi-fi and would need safety features as you say and even a redesign for CCSs and LTPs to be optimum, stable and reliable when the amp. works hard into low impedance.

[sakis]

Ian .... methods like that has been used by many manufacturer so trafo is calculated to be on the edge just enough to meet the specs on a resistive load and then rail voltage to dive down under hard rive or demanding load

this is actually working also as an active limmiter but of course will increase distortions and create other problems if driven hard ...

concept is very simple ....this is supposed to be a quality HIFI amp so its expected to play loud but not pushed the same way as PA amplifier ....


yet again biger models like that 1090 which can provide almost double the power working with rails 96+96 is by far more complicated to clone and also equiped with all te needed goodies such is current sinks and sources and of course sophisticated VI limmiters

regards sakis

[wahab]

Rotel amplifiers where generally fine products , and this one
doesn t make exception.
Dual differential amps are more stable than classic
mono differential ones when supply voltages are
increased.
The compensation networks (560p + 220R) should
work with any BJTs , providing they are as fast as the
original ones.
One slight modification that can increase stability
is to add resistors in the emitters of the differentials
Bjts....47 to 100R should do it, but at the expense
of the THD ratio that would slightly increase...

[sakis]

good to see you WAHAB .... ( did you make any new music ??? ) thanks for advices i will keep them in mind ... will see this is a feature product ....will make a clone and see how it goes

kind regards sakis

[wahab]

Originally Posted by sakis

good to see you WAHAB .... ( did you make any new music ??? ) thanks for advices i will keep them in mind ... will see this is a feature product ....will make a clone and see how it goes

kind regards sakis

Hi, Sakis,

Well, no music these times, i was in my native country
for two months , in mountaineous areas , among olive trees..
Must look a lot like your country as well..

About this amplifier, i must aknowledge that this
is the kind of topology i prefer , and i always had
very good results with it.
No doubt that you ll experience the same satisfactory
functionning with this one.

cheers,

Wahab