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 Post subject: Re: 807 Williamson amp
PostPosted: Jun Sun 03, 2018 3:37 am 
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john8750 wrote:
Well, my wife said size does matter and big is better
I tend to agree with George Carlin that the old cigarette commercial jingle "it's not how long you make it. It's how you make it long" has merit.

https://www.youtube.com/watch?v=Y6FSJmEsSUA


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 Post subject: Re: 807 Williamson amp
PostPosted: Jun Sun 03, 2018 3:39 am 
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john8750 wrote:
Flipperhome wrote:
john8750 wrote:
Just wondering, is everything the same as anything?
Nope. Everything is "all" the things. Anything is a thing of any kind.

Anything may be a subset of everything but they're not the '"same" thing.

You can do "anything" you set your mind to. (cliché)
But it's quite impossible to do "everything." (Even if you knew what "everything" encompassed you'd run out of time.)

OK Mr Spock. I agree with your philosophy, I guess. Are we still talking about the amp chassis sides?
I doubt it. :lol:


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 Post subject: Re: 807 Williamson amp
PostPosted: Jun Thu 07, 2018 5:08 am 
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OK I will get over to the metal shop and cut the bottom panels around the 16th. The vent holes will be drilled here in my home shop. I think we should match the location and pattern, minus the actual socket of course, of the top chassis.
Any thoughts? Are you thinking about a final tube socket spacing plan? Still have time and no biggie yet.

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 Post subject: Re: 807 Williamson amp
PostPosted: Jun Thu 07, 2018 5:49 am 
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john8750 wrote:
OK I will get over to the metal shop and cut the bottom panels around the 16th. The vent holes will be drilled here in my home shop. I think we should match the location and pattern, minus the actual socket of course, of the top chassis.
Any thoughts? Are you thinking about a final tube socket spacing plan? Still have time and no biggie yet.
Actually, not matching the top panel is probably better because, depending on where you put them, they can cause a cross airflow rather than just straight up.

I think the socket spacing is fine as is (that's why I said you can use the center lines). It's just all the minor details that may not be right.


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 Post subject: Re: 807 Williamson amp
PostPosted: Jun Thu 07, 2018 6:19 am 
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Flipperhome wrote:
john8750 wrote:
OK I will get over to the metal shop and cut the bottom panels around the 16th. The vent holes will be drilled here in my home shop. I think we should match the location and pattern, minus the actual socket of course, of the top chassis.
Any thoughts? Are you thinking about a final tube socket spacing plan? Still have time and no biggie yet.
Actually, not matching the top panel is probably better because, depending on where you put them, they can cause a cross airflow rather than just straight up.

I think the socket spacing is fine as is (that's why I said you can use the center lines). It's just all the minor details that may not be right.



That's a good thought. How about a roll both front and back with the same number and size holes with the top? Evenly spaced.

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 Post subject: Re: 807 Williamson amp
PostPosted: Jun Thu 07, 2018 7:15 am 
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john8750 wrote:
Flipperhome wrote:
john8750 wrote:
OK I will get over to the metal shop and cut the bottom panels around the 16th. The vent holes will be drilled here in my home shop. I think we should match the location and pattern, minus the actual socket of course, of the top chassis.
Any thoughts? Are you thinking about a final tube socket spacing plan? Still have time and no biggie yet.
Actually, not matching the top panel is probably better because, depending on where you put them, they can cause a cross airflow rather than just straight up.

I think the socket spacing is fine as is (that's why I said you can use the center lines). It's just all the minor details that may not be right.



That's a good thought. How about a roll both front and back with the same number and size holes with the top? Evenly spaced.
Sounds good to me.


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 Post subject: Re: 807 Williamson amp
PostPosted: Jun Wed 13, 2018 1:34 am 
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Just thinking ahead, I would like to have a headphone circuit. So far on my small low power amps, I put the speakers on a dummy load and connected the headphone jack. But what about for an amp of this size? Like 25watt.

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 Post subject: Re: 807 Williamson amp
PostPosted: Jun Wed 13, 2018 3:24 am 
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john8750 wrote:
Just thinking ahead, I would like to have a headphone circuit. So far on my small low power amps, I put the speakers on a dummy load and connected the headphone jack. But what about for an amp of this size? Like 25watt.
I don't know that there's an 'official' way (I don't know of any 'hi power' tubes amps that had headphone outputs) but one way would be to do a voltage divider dummy load, to get the power down to the 'normal' level, and then do the headphone output as usual (tapping it off at the lower power point).


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 Post subject: Re: 807 Williamson amp
PostPosted: Jun Wed 13, 2018 3:42 am 
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john8750 wrote:
Just thinking ahead, I would like to have a headphone circuit. So far on my small low power amps, I put the speakers on a dummy load and connected the headphone jack. But what about for an amp of this size? Like 25watt.

Watch this video:
https://www.youtube.com/watch?v=hzD1dVmvqkw

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 Post subject: Re: 807 Williamson amp
PostPosted: Jun Wed 13, 2018 5:14 am 
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I guess the only problem is what to do with the speakers. How to silence them and still keep a load on the OT's.
Good idea Peter about the whole separate amp.
Good thought Flip. Just don't have the headphone circuit.
I don't really need it. Just something else to build.
Thank you Men, as always.

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 Post subject: Re: 807 Williamson amp
PostPosted: Jun Wed 13, 2018 6:11 am 
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john8750 wrote:
I guess the only problem is what to do with the speakers. How to silence them and still keep a load on the OT's....
You switch them out at the same time you switch in a dummy load.


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 Post subject: Re: 807 Williamson amp
PostPosted: Jun Wed 13, 2018 7:05 am 
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Flipperhome wrote:
john8750 wrote:
I guess the only problem is what to do with the speakers. How to silence them and still keep a load on the OT's....
You switch them out at the same time you switch in a dummy load.



Well, what wattage should the load resistors be?

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 Post subject: Re: 807 Williamson amp
PostPosted: Jun Wed 13, 2018 11:10 pm 
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john8750 wrote:
Flipperhome wrote:
john8750 wrote:
I guess the only problem is what to do with the speakers. How to silence them and still keep a load on the OT's....
You switch them out at the same time you switch in a dummy load.

Well, what wattage should the load resistors be?
I think 10 watt should be sufficient because you should never see 24 Watt continuous. The 25 Watt is for transient peaks and average power should be on the order of 1 or 2 Watt at full volume, say 4 Watt just to allow for extremes.

This is the wiring for a 4 or 5 Watt amp. The speakers were on a switched phone jack, which allowed for automatic switching of the speaker load.

Attachment:
Speaker-Headphone Wiring - simpler.jpg
Speaker-Headphone Wiring - simpler.jpg [ 68.25 KiB | Viewed 365 times ]


For a high power amp replace the single 8 Ohm for a divider that sums to 8 Ohm and take the headphones off the middle tap, set so it is 5 Watt when the amp is at 25 Watt.

This only works if you switch OUT the speakers because when the speakers are used the power is still 25 Watt. If you want to be able to use both at the same time (why?) you need to divide down the output with a resistor network that sums to 120 Ohm (in parallel with the speakers).


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 Post subject: Re: 807 Williamson amp
PostPosted: Jun Thu 14, 2018 12:53 am 
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That is just about the same circuit I use. I have a switch to cut off the speakers, and power up the head phones. It works fine. Will my circuit work as good for the Williams/Flip amp?
Attachment:
headphone schematic.jpg
headphone schematic.jpg [ 67.41 KiB | Viewed 361 times ]

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 Post subject: Re: 807 Williamson amp
PostPosted: Jun Thu 14, 2018 1:35 am 
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john8750 wrote:
That is just about the same circuit I use. I have a switch to cut off the speakers, and power up the head phones. It works fine. Will my circuit work as good for the Williams/Flip amp?
Attachment:
headphone schematic.jpg
Well, that's exactly what I described except the ratio of the two load resistors should be changed for 25 Watt while keeping the overall load at (or close to) 8 Ohm.


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 Post subject: Re: 807 Williamson amp
PostPosted: Jun Thu 14, 2018 2:07 am 
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Flipperhome wrote:
john8750 wrote:
That is just about the same circuit I use. I have a switch to cut off the speakers, and power up the head phones. It works fine. Will my circuit work as good for the Williams/Flip amp?
Attachment:
headphone schematic.jpg
Well, that's exactly what I described except the ratio of the two load resistors should be changed for 25 Watt while keeping the overall load at (or close to) 8 Ohm.



Okie Dokie. :wink:

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 Post subject: Re: 807 Williamson amp
PostPosted: Jun Thu 14, 2018 6:17 am 
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john8750 wrote:
Flipperhome wrote:
john8750 wrote:
That is just about the same circuit I use. I have a switch to cut off the speakers, and power up the head phones. It works fine. Will my circuit work as good for the Williams/Flip amp?
Attachment:
headphone schematic.jpg
Well, that's exactly what I described except the ratio of the two load resistors should be changed for 25 Watt while keeping the overall load at (or close to) 8 Ohm.
Okie Dokie. :wink:
Actually, I think two 4 ohm 10 Watt resistors, and then a 120 Ohm from the junction to the headphones, will work just fine.

It depends on the volume you expect but power is voltage squared so the voltage divider needs a roughly 1/2 divider for a 4X increase in power. So if 'direct' is good for 5 Watt then 1/2 is exact for 20 Watt and 25 Watt is so close to 20 Watt that you'd never notice the volume difference.

Now, you might say "but I used two 5 ohm for 10 Watt." Yes, well, 25 Watt is 2.5 times as much power but that's only 4 dB over 10 Watt. You may notice it's a 'bit' louder but not enough to matter.


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 Post subject: Re: 807 Williamson amp
PostPosted: Jun Thu 14, 2018 2:14 pm 
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There are several considerations when using phones. First is the phones impedance.

Second is to note that phones, like speakers, like to have a voltage source driving them.

Third is that you want to use as little amp power as necessary, to reduce distortion,
assuming a Class A amp ... if its class AB or B you need more power to
avoid crossover distortion.

Fourth you want to not hear background hum, so you can run really really low power out.

That said, 220 ohms in series with modern phones is very from being a voltage source,
you probably don't want more than 5 or 10 ohms. So you likely want to tap
farther down the power resistor divider string than half way.


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 Post subject: Re: 807 Williamson amp
PostPosted: Jun Thu 14, 2018 4:35 pm 
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dtvmcdonald wrote:
There are several considerations when using phones. First is the phones impedance.

Second is to note that phones, like speakers, like to have a voltage source driving them.

Third is that you want to use as little amp power as necessary, to reduce distortion,
assuming a Class A amp ... if its class AB or B you need more power to
avoid crossover distortion.

Fourth you want to not hear background hum, so you can run really really low power out.

That said, 220 ohms in series with modern phones is very from being a voltage source,
you probably don't want more than 5 or 10 ohms. So you likely want to tap
farther down the power resistor divider string than half way.






Thanks for that thought. I believe the 220ohm series resistor was calculated with that in mind. The circuit I posted is used on all my small powered amps. Seems to work very well. Most other circuits I look at use a 120ohm. Agree, depends on the headphones being used.

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 Post subject: Re: 807 Williamson amp
PostPosted: Jun Thu 14, 2018 10:02 pm 
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Edcors will be here Monday. So I need to finish the 6V6JV and get busy.

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