i replaced the electrolytics in this amp. overall it sounds much better, but, it has acquired the "breaking surf" sound. could that be a tube or a resistor?
thanks in advance.
mikeB.
gibson ga8t amp (approximately 1965) (2-6bq5,2-6eu7, 1-6ca4)
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Prairie Dawg
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Re: gibson ga8t amp (approximately 1965) (2-6bq5,2-6eu7, 1-6ca4)
plate load resistors maybe?
If you believe in coincidence you're not looking close enough-Joe leaphorn
Re: gibson ga8t amp (approximately 1965) (2-6bq5,2-6eu7, 1-6ca4)
I'm not quite sure what you are hearing, though you are to be commended for the good metaphor! As Prarie Dawg says, plate load resistors are a possibility.
The schematic I have shows the old config: 12AX7, two 6BM8, 5Y3. The PI is a split load.
I'm wondering, from 1965, with two 6EU7 and two 6BQ5, if that one has the inter-stage transformer instead of a tube PI. (Black elephant hide?) If it has the tx, it would probably be located on the outside of the chassis between the 2nd 6EU7 and the 1st 6BQ5. I am wondering if you are hearing it burning out. Unfortunately, this is something with which I have personal experience, and that is why I said, I'm not sure what you are hearing.
Change the old plate load resistors and see if that cures it. If it doesn't, well, you are probably going to want to buy the expensive clone of that tx sold by Mercury Magnetics. You could try to find an appropriate replacement. The turns ratio is 1:2.4, not anything in current production.
I have an open one that's available if you know how to rewind. If I recall, the primary is open, so that means unwinding the whole thing.
The schematic I have shows the old config: 12AX7, two 6BM8, 5Y3. The PI is a split load.
I'm wondering, from 1965, with two 6EU7 and two 6BQ5, if that one has the inter-stage transformer instead of a tube PI. (Black elephant hide?) If it has the tx, it would probably be located on the outside of the chassis between the 2nd 6EU7 and the 1st 6BQ5. I am wondering if you are hearing it burning out. Unfortunately, this is something with which I have personal experience, and that is why I said, I'm not sure what you are hearing.
Change the old plate load resistors and see if that cures it. If it doesn't, well, you are probably going to want to buy the expensive clone of that tx sold by Mercury Magnetics. You could try to find an appropriate replacement. The turns ratio is 1:2.4, not anything in current production.
I have an open one that's available if you know how to rewind. If I recall, the primary is open, so that means unwinding the whole thing.
Re: gibson ga8t amp (approximately 1965) (2-6bq5,2-6eu7, 1-6ca4)
thanks to both of you. i'll check out the resistor. since i have to get back in it, i'll check my connections i soldered today also.