I am starting to move forward on my SCA 35 project and wanted to changed the output transformers in order to go from 8 and 16 ohm to 4 and 8 ohm. My question is this: Is the feedback resistor and capacitor which was optimized for the 16 ohm output level and impedance of the original transformer OK for the new transformer? I had sent a request to Dynakitparts.com a few weeks back, but have not got a response.
3 posters
SCA 35 Output Transformer
jwb474- Posts : 74
Join date : 2014-07-13
Age : 71
Location : Wolfforth, Tx
peterh- Posts : 1833
Join date : 2012-12-25
Location : gothenburg, sweden
You refer to R37 ( 82k ) ? Try 47k. The cap C21 you need a scope and make it as big asjwb474 wrote:I am starting to move forward on my SCA 35 project and wanted to changed the output transformers in order to go from 8 and 16 ohm to 4 and 8 ohm. My question is this: Is the feedback resistor and capacitor which was optimized for the 16 ohm output level and impedance of the original transformer OK for the new transformer? I had sent a request to Dynakitparts.com a few weeks back, but have not got a response.
preventing overshoot when feeded with squarevawes. 12 pF could be a good starting point.
jwb474- Posts : 74
Join date : 2014-07-13
Age : 71
Location : Wolfforth, Tx
You refer to R37 ( 82k ) ? Try 47k. The cap C21 you need a scope and make it as big as
preventing overshoot when feeded with squarevawes. 12 pF could be a good starting point.[/quote]
Yes. 47K does make sense since the max voltage is 1/2 of what it was. I do have the equipment to test the amp. On a related note, has anyone here used Virtins Technology's multi-instrument software? I am trying it out and it appears to be great for a hobbyist.
preventing overshoot when feeded with squarevawes. 12 pF could be a good starting point.[/quote]
Yes. 47K does make sense since the max voltage is 1/2 of what it was. I do have the equipment to test the amp. On a related note, has anyone here used Virtins Technology's multi-instrument software? I am trying it out and it appears to be great for a hobbyist.
jwb474- Posts : 74
Join date : 2014-07-13
Age : 71
Location : Wolfforth, Tx
jwb474 wrote:You refer to R37 ( 82k ) ? Try 47k. The cap C21 you need a scope and make it as big as
preventing overshoot when feeded with squarevawes. 12 pF could be a good starting point.
Yes. 47K does make sense since the max voltage is 1/2 of what it was. I do have the equipment to test the amp. On a related note, has anyone here used Virtins Technology's multi-instrument software? I am trying it out and it appears to be great for a hobbyist.[/quote]
peterh- Posts : 1833
Join date : 2012-12-25
Location : gothenburg, sweden
[/quote]jwb474 wrote:jwb474 wrote:You refer to R37 ( 82k ) ? Try 47k. The cap C21 you need a scope and make it as big as
preventing overshoot when feeded with squarevawes. 12 pF could be a good starting point.
Yes. 47K does make sense since the max voltage is 1/2 of what it was. I do have the equipment to test the amp. On a related note, has anyone here used Virtins Technology's multi-instrument software? I am trying it out and it appears to be great for a hobbyist.
It's more 1/sqrt(2) Thus 47 - 56 k is what you need as R37
rmyauck- Posts : 9
Join date : 2012-02-18
If it were me I would keep the vintage OPT's due to their well regarded sonics and try them with your speakers on the different taps with no regard to worrying about them not being matched. I think you will be pleasantly surprised!