tardishead
Well-known member
I have had a pair of these with PSU for a couple of years now and I have struggled for a long time to get them properly working. I decided to fully learn what was going on with the circuit so took a couple of hours to investigate. There is absolutely no information on the web so I thought I would post my findings maybe to help others.
They are a very simple design triode strapped 6AU5a (SORRY THIS IS A MISTAKE - THE TUBE IS 6AU6A ) cathode follower output like Altec Coke Bottle. They have no output transformer - I will install a couple of 1:1 600r:600r transformers to provide balanced outs.
The cables needed resoldering and a couple of connections in the mics themselves were bad.
The power supply is very neat and has really good filtering for HT and DC heaters. Very good quality components. It says PREAMPLIFIER but it is a power supply.
I traced out the basic audio circuit.
The output connections are very strange - has anyone seen this before?? The output is totally unbalanced. I presume the only way to balance it is to get rid of the 30k and 1m resistors and add a transformer.
They are a very simple design triode strapped 6AU5a (SORRY THIS IS A MISTAKE - THE TUBE IS 6AU6A ) cathode follower output like Altec Coke Bottle. They have no output transformer - I will install a couple of 1:1 600r:600r transformers to provide balanced outs.
The cables needed resoldering and a couple of connections in the mics themselves were bad.
The power supply is very neat and has really good filtering for HT and DC heaters. Very good quality components. It says PREAMPLIFIER but it is a power supply.
I traced out the basic audio circuit.
The output connections are very strange - has anyone seen this before?? The output is totally unbalanced. I presume the only way to balance it is to get rid of the 30k and 1m resistors and add a transformer.