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Tuesday, December 24, 2013

300B Tube Amplifier

300B Tube Amplifier - a blast from the past!

We was cleaning up my hard drive and guess what I have found? A Zip file containing one of the 300B amplifiers we built >10 years ago. (Our new products won't be in this format, this design and also the parts used are now leagues ahead of what is used 10 years ago.)

This 300B tube amplifier was made in around 2002-2003. It is still working fine as far as I know and is still in good shape/service.

It's a simple design using RC coupled 3 stage topology. 5687-RC-5687-RC-300B. Customer wanted it to be as simple as it can be so that all the components can be used are of audiophile quality. It is tube rectified with 5U4G, having a choke input configuration for better sound and regulation.The chokes and output transformers are from Hammond. 3 chokes are employed for excellent filtering and Left / Right channel separation.

Power transformer are locally with flux band and copper shield on the cores for absolute quietness. Filament for 300B are DC for zero hum as it is used with high efficiency vintage speakers.



300B Tube Amplifier
 All transformers are 90 degC against each other for lower noise coupling in such a small chassis. Well, it is actually bigger than it seems, and heavy too. There are a total of 6 transformers on the amp!
All the transformers are caged for safety and shielding.
 Stay away, itchy hands / fingers!
Top view - 5687 - 5687 - 300b - 300b - 5U4G


It comes with separate filament + HT switches.


JJ 300B + Tung Sol 5687 + RCA 5U4GB


Input are just next to preamp tube for shortest signal path.


J&K Audio Design
25/12/2013

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* Finished amplifiers, DACs, audio gadgets, upgrades and repairs - this is not our core business and we do it out of passion. We do not have fixed models, fixed price and we customize for each individuals. The sky is limit of creativity.

* Our product lines are always improving and increasing. If you do not see what you want, contact us!

* Please email for volume discounts, distributor and OEM pricing.

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