I have been building a G9 mic pre and in the process of sourcing the parts decided to try the Vigortronix versions of the OEP part. I completed the build and started testing, I lent the unit to a friend who was doing some tracking for an evaluation. My friend brought it back with the comment that the D.I input was great for bass but she found the mic input somewhat dark. I lent it to another friend who found the same and in fact found it dull. I must admit when I built it I only tested for general function before I lent it. Well I put it on the bench and swept it, I found something like a 9db per octave slope from about 8k. Thinking maybe I had done something wrong I removed the input transformer and terminated it and tested it. It was the transformer! Vigortronix part#VTX-101-003.
(with a claimed 30hz to 25khz) I replaced it with a generic transformer I had on hand which fixed the problem. However I still have in the unit the Vigortronix output transformer part#VTX-101-002 which appears to be functioning but I have a noise, something like a burbling 100hz which sits at about -55db this gets quieter when you switch the power off but only goes when you remove the power lead. The noise is independent of the output level setting. (I have the screening cans on)The power switch is a double pole switch so the power transformer is completely de-energised when off. However if I remove the output lead from the header the noise goes. I have played around using another transformer free of the board and connecting it to the output connector I get a similar noise however if I rotate the transformer the noise disappears. It seems to me it may be the construction of the Vigortronix transformer could be causing the fault. My experience with transformers is limited and its the last thing I expected from them. These Vigortronix transformers are supposedly an identical part to OEP as they are from a new start-up by the original guy from Oxford(Obviously not!)Has anyone else had experience with these?My guess is the noise is going to be from the output transformers. I bought these from Element 14
(with a claimed 30hz to 25khz) I replaced it with a generic transformer I had on hand which fixed the problem. However I still have in the unit the Vigortronix output transformer part#VTX-101-002 which appears to be functioning but I have a noise, something like a burbling 100hz which sits at about -55db this gets quieter when you switch the power off but only goes when you remove the power lead. The noise is independent of the output level setting. (I have the screening cans on)The power switch is a double pole switch so the power transformer is completely de-energised when off. However if I remove the output lead from the header the noise goes. I have played around using another transformer free of the board and connecting it to the output connector I get a similar noise however if I rotate the transformer the noise disappears. It seems to me it may be the construction of the Vigortronix transformer could be causing the fault. My experience with transformers is limited and its the last thing I expected from them. These Vigortronix transformers are supposedly an identical part to OEP as they are from a new start-up by the original guy from Oxford(Obviously not!)Has anyone else had experience with these?My guess is the noise is going to be from the output transformers. I bought these from Element 14
