Aries Cerat Tech Blog

Building a 250W class A amplifier

 

Everybody wants more power.SE amplifiers are unmatched in sonic quality,however,not everyone owns a high performance highly sensitive speaker.

Design parameters for our task is sticking to Class A,and the need for a simple tube design delivering 250W per channel.Difficult task indeed.

Lets start with the output tube.I never liked the KT-XX family and the EL-XX close relatives.I always prefer DHT for our SE amplifiers and preamplifiers.However,i wanted to keep the step down transformer as low ratio as possible.Can we use a 2~4:1 ratio transformer and keep parasitic capacitance and inductance as low as possible?

Well,you need very high current/low resistance tubes to keep it in True Classs A mode with such a low ratio step down tranny .My favorite non DHT tube is the Sveltava 6C19p , a very high current ,very low resistance tube.It's internal resistance is about 9 times lower than a 845 tube.

Push pull designs...are not my favorite.So how can we get 250W in SE Class A topology.We use two parafeed SE OTL(!!) amplifiers per channel in balanced mode.This is not push pull as one might say,but two separate SE OTL amplifers ,one of which is inverted.

Each SE OTL parafeed bank is biased at 2.5~3Amperes,so 5~6Amperes in total!!

Driver stage uses my all time favorite E280F,high tranconductance tube,in my opinion the best mid-signal tube out there.We use a proprietary topology,which uses a combination of direct coupling and inductive coupling,for uncompromised performance.Driver stage can swing more than 100Vrms with bandwidth of DC~250Khz!

So,two SE OTL parafeed amplifiers in balanced mode driving an ac coupled 4:1 transformer can deliver 250W in Class A?You bet.

The reflected output resistance is 0.35 Ohms without the use of global or local reedback,and the max current swing is a record breaking 24 Amps!

The 120kg monoblocks will be launched soon.Stay tuned.

 

250w

New exciting stuff coming soon

 

New mono-blocks based on proprietary hybrid technology coming up. 120W true Class A ,zero feedback, 12A biased amplifiers, very soon to be presented.

New ultra wide bandwidth tube topology

 

Many insist that no new tube circuits excist,and if any,are just copies

of old textbook circuit variations....

Well,prepare to be suprized.

A new way of using triodes is born,in fact you can say it is a whole new active component .

How's 5Hz to 500Khz sound for a tube circuit,with 7ohm output impedance ,without local or global feeback anywhere in the circuit.

This trully novice technology is getting ready to take form inside our newest preamplifier yet,ready to lauch later this year...

Stay tuned....

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