ZV8 Capacitors & Questions

[Michael Rothacher]

I'm working on a ZV8 build and a have a few questions:

1. Would a 2,200 uF cap work in C1?
2. Would a 16V cap work in C2?
3. The schematic (of ZV8) in the ZV9 article is slightly different than the one in the ZV8 article. (R6, R5, and 100R in parallel w/output. Is one more optimized than the other?
4. Would the cascode modulation, mentioned in ZV9, work in ZV8 (C2 to Ground)?
5. Should same technique used to select R1 (in ZV9 article) be used for ZV8?

Thanks for your help

Mike

[Michael Rothacher]

I ask questions 1 and 2 because I want to use my Black Gates

[Michael Rothacher]

More dumb questions I always wanted to know but was afraid to ask:

1. What components are technically in the signal path? In other works, if wanted to use the best resistors, etc., which ones are critical? How do you identify the "signal path"?

2. DC blocking capacitors in amps are high pass filters right? What determines Fc? Is R the source impedance? In the output coupling cap situation is R the output impedance of the amp or the speaker impedance?

3. How do you measure the impedance of a power supply? Does this matter if the amp draws constant current?

4. Is there some sort of "summer camp" available at Firstwatt?

[Nelson Pass]

Originally posted by mrothacher
1. Would a 2,200 uF cap work in C1?
2. Would a 16V cap work in C2?
3. The schematic (of ZV8) in the ZV9 article is slightly different than the one in the ZV8 article. (R6, R5, and 100R in parallel w/output. Is one more optimized than the other?
4. Would the cascode modulation, mentioned in ZV9, work in ZV8 (C2 to Ground)?
5. Should same technique used to select R1 (in ZV9 article) be used for ZV8?

Originally posted by mrothacher
6. What components are technically in the signal path? In other works, if wanted to use the best resistors, etc., which ones are critical? How do you identify the "signal path"?

7. DC blocking capacitors in amps are high pass filters right? What determines Fc? Is R the source impedance? In the output coupling cap situation is R the output impedance of the amp or the speaker impedance?

8. How do you measure the impedance of a power supply? Does this matter if the amp draws constant current?

9. Is there some sort of "summer camp" available at Firstwatt?

You ask a lot of questions.

1. Yes, but the bandwidth would be less.

2. Yes, definitely

3. For the most part these are just conveniences for thumps and
such.

4. Yes.

5. No, you need to experimentally find the new "sweet value"
for the different circuit. The Zv9 value would be a good start.

6. Usually signal path is the route from input to output, but I
think you would be safer to think of all the parts as being in the
signal path, no?

7. Fc of blocking caps is Fc = 1/(6.3 * R * C) where R is Ohms
and C is Farads. Your example of 2200 uF with an 8 ohm load is
9 Hz @ -3 dB

8. The impedance of the supply is the voltage variation divided
by the current variation. Yes, it matters if the circuit has constant
draw.

9. How much is in your checking account?

[Michael Rothacher]

Nelson:

You're great for answering all those personally.

Thanks very much. That's very helpful.



Question 9:

Where there's a will there's a way! When camp Firstwatt opens count me in.

[Michael Rothacher]

Just in case its of any use to a fellow builder:

If Fc is 9 Hz with an 8 Ohm load and a 2,200 uF cap then:

BdB = 20*LOG(1/(SQRT(1+(Fc/F)^2))

So were -0.8 db at 20 Hz

On par with many tube amps.

[Nelson Pass]

Originally posted by mrothacher
Just in case its of any use to a fellow builder:

If Fc is 9 Hz with an 8 Ohm load and a 2,200 uF cap then:

BdB = 20*LOG(1/(SQRT(1+(Fc/F)^2))

So were -0.8 db at 20 Hz

On par with many tube amps.

Not really good enough

[Michael Rothacher]

Tube amps, or the frequency response?




I could do 2 in parallel for 4400 uF, but there goes my checkbook.

[Nelson Pass]

Frequency response. Try some Black Gates paralleled, along with
maybe some Elma silks in parallel and then some fine film caps
(polypropylene preferred). Get the value up to 10,000 uF or so.