1) please describe your "20-20k Hz sweep"
Where do you get it from?
How long does it take to sweep end to end?
2) you are using a *linear* frequency scale which is useless, you need a logarithmic sweep.
Where do you get it from?
How long does it take to sweep end to end?
2) you are using a *linear* frequency scale which is useless, you need a logarithmic sweep.
The curves you're familiar with seeing are log-log, and that's really a good idea for your current project.
All good fortune,
Chris
All good fortune,
Chris
Build a sound card interface (to avoid overloading the line input) and use something like RMAA.. properly set up, it can give very accurate results (even with onboard sound)
You can use a loopback cable (line out to line in) to get baseline measurements of how good your soundcard is too
RightMark Audio Analyzer. Products. Audio Rightmark
You can use a loopback cable (line out to line in) to get baseline measurements of how good your soundcard is too
RightMark Audio Analyzer. Products. Audio Rightmark
Output transformer matching at different Voltages?
By data the 6V6 in SE has output load impedance of 5k at 250V but 8.5k at 315V. If my amp runs at 280V the load would be roughly 7k than?
Or if I have 5k OT but the amp is running at say 300V is there a way to match them without needing to change the amp voltage?
Somehow I can't imagine having to use a different OT for Voltages that only differ in about 50V. How is that done?
By data the 6V6 in SE has output load impedance of 5k at 250V but 8.5k at 315V. If my amp runs at 280V the load would be roughly 7k than?
Or if I have 5k OT but the amp is running at say 300V is there a way to match them without needing to change the amp voltage?
Somehow I can't imagine having to use a different OT for Voltages that only differ in about 50V. How is that done?
You don't need an exact match. Two reasons for this: the quoted figure is a compromise between power and distortion so deviation either way is not too serious, valves and (traditionally) valve circuits are not that precise.
Use the 'wrong' OPT and you get a different compromise.
Use the 'wrong' OPT and you get a different compromise.
You would draw a new load line for it with 280v on one end and then the current point you figure from 280v and your OPT load as the other end. Then slide it up to your bias voltage and current you need on the new load line.
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Your load impedance is determined by the output transformer and the speaker connected to it. I wouldn't rely too much on the data sheet recommended specs. You can get much better information by drawing a new load line using the plate curves.
In this case, you really just want to first make sure the combination of your operating point and the loadline doesn't put the tube over the dissipation limits and second that is isn't stuck in a nonlinear part of the graph (where lines are all squished together).
In this case, you really just want to first make sure the combination of your operating point and the loadline doesn't put the tube over the dissipation limits and second that is isn't stuck in a nonlinear part of the graph (where lines are all squished together).
Right so it can be done but it's not that critical unless the Voltage is way out. Thanks.
I've never had problems when I use OTs designed for 6V6 but also tried few OTs designed for 6BM8 with 6V6 and never could get the output right. Mainly the distortion would set in too early as volume goes up. Those are 5.6k but at 200V (by data which is all I have to go on) so I thought at 300V they might go way off the 5.6k. These OTs look big enough to handle the extra 2 Watts of 6V6 so I'm not sure why they distort so early otherwise they sound decent.
I've never had problems when I use OTs designed for 6V6 but also tried few OTs designed for 6BM8 with 6V6 and never could get the output right. Mainly the distortion would set in too early as volume goes up. Those are 5.6k but at 200V (by data which is all I have to go on) so I thought at 300V they might go way off the 5.6k. These OTs look big enough to handle the extra 2 Watts of 6V6 so I'm not sure why they distort so early otherwise they sound decent.
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May start using my FFR (Fast Freq. Response) Test Bench what is much faster than a sweep. Requires a ADC/DAC using same master clock... 😀
Hp
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'Early' distortion means that the valve is running out of voltage (OPT Z too high) or current (OPT Z too low) or grid swing (biased too cold) or hitting grid current (biased too hot).
Ok so possible amp design problem. I've build this amp years ego, at the time I knew even less than now. I'll go over it and see what I did. One thing I'm remember is that the B+ is only around 250V, maybe falling 50V short of the 300V to get enough power for the 6V6 PP? As it is now it is louder than my other SE 6V6 at 280V but starts distorting at about the same loudness level.
16 ohm to to 8 ohm speaker for Hifi
Using 16 ohm OT to 8 ohm speaker often worked well for me in guitar amps but I think for Hifi it might be another thing since I want the sound to be reproduced accurately without any changes to it like scooping mids etc.
I have some 16 ohm OTs but not sure if I should even bother trying them for 8 ohm Hifi speakers. Anyone has some experiences with this?
Using 16 ohm OT to 8 ohm speaker often worked well for me in guitar amps but I think for Hifi it might be another thing since I want the sound to be reproduced accurately without any changes to it like scooping mids etc.
I have some 16 ohm OTs but not sure if I should even bother trying them for 8 ohm Hifi speakers. Anyone has some experiences with this?
10k/4ohm OT for 5k tube and 8ohm speaker?
I'm messing around with 6BM8 and have 10k/4 ohm OT that seems to sound impressively good and strong with this 5.6k output load tube.
Am I correct to assume that using 4 ohm secondary with 8 Ohm speaker halves the primary of the OT from 10k to 5k? That would be good match.
I'm messing around with 6BM8 and have 10k/4 ohm OT that seems to sound impressively good and strong with this 5.6k output load tube.
Am I correct to assume that using 4 ohm secondary with 8 Ohm speaker halves the primary of the OT from 10k to 5k? That would be good match.
Hmm I must have I misunderstand what I was reading yet again 🙂. I guess it would be bad for the plates with not enough load. Sounds very good for only 3W tho I must say.
Still pretty loud even if 1W. I was driving pair of big Advent speakers with one single tube in mono. Sound is good ( to a point) but has that old tube TV character to it even with different matching OT 🙂. Not sure if it's because it's a TV tube not really designed for quality audio but it was a good experiment anyway. I've also tried 6GW8, that has better sound, similar to EL84 (in my ears).
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