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In Reply to: RE: Need help with corner frequency calculations. posted by Cougar on January 22, 2015 at 16:42:20
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nt.
To properly calc. the corner freq., you'll need to include the output LOAD ? of the preamp with the input z of the amp(13K).
Both resistance values would be in parallel. Depending on the output topology (Cath. Foll. or Grounded Cath.) that could be a few Kohms. (1K to 1Meg)
1
1/R1 + 1/R2
When a tube pre (BAT VK-30) is used to drive a SS amp, you can remove the input coupling cap. from the SS amp as the tube pre already has one. Some have OPTs after the tube stage. Redundant coupling caps do not work well at all.
I suggest posting your query of impedance matching and topology on Amp/Pre.
Mention the BAT # in the subject and Victor will fill in the blanks. :-)
Hope this helps.
Cheers,
W
1uF output coupling caps. one each for - and + in balanced mode. One cap for single end mode.
Then you can replace the amp's 3.3uf input caps with a pair jumper wires.
The rest of the fine tuning will/might be done to the output stage of the BAT. Again, depending upon the topology. Victor can help you with this.
It may be possible or necessary to increase the amp's 13K input Z.
Do NOT throw caution to the wind here!
Cheers,
W
my amp has a 3.3uf cap and 13k input impedance? My amp has 330uf input coupling cap and 33kohm input impedance.
BAT has output caps on the VK-30 preamp and on the input of their amps. They are usually 100kohm preamp out and input to amp.
Assuming Amp 33K Zin and 100K pre load out.
159154
1/(1/33,000 + 1/100,000) 331uf = 0.0194Hz -3db
159154
1/(1/33,000 + 1/100,000) 1uf = 6.41Hz -3db
Going lower than 0Hz for a -3db never works IMHE!
Swap those 330uf lytics 4 jumpers and enjoy until you follow up w/Victor, if so desired.
Good question...my mistake.
Still, the scenario is the same.
Then you can replace the amp's 330uf input caps with a pair of jumper wires.
The rest of the fine tuning will/might be done to the output stage of the BAT. Again, depending upon the topology. Victor can help you with this.
It may be possible or necessary to increase both the amp's input Z and the BAT's output load if you want a high quality low uf(below 1.0uf) coupling cap in the preamp.
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