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SE807 Triode Dick Amplifier Questions
SE807 Triode Dick Amplifier Questions
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Old 9th April 2017, 10:38 PM   #1
lilstripe is offline lilstripe  United States
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Question SE807 Triode Dick Amplifier Questions

Long time lurker, first time poster...

I have some questions about the Triode Dick Single Ended 807 Amplifier design.
It would be helpful if someone could help answer my questions and if they have the time, describe how they derived the answers. I'm trying to learn.
I've built a lot of SS electronics gear but new to building tube amps. I get the basics of electronics but am no expert per say.

Questions as circled in the attached picture:
1. Is the purpose of this switch to allow the filaments to light up and then turn this switch on to apply the B+?
2. What current rating and/or DCR should I seek for the 10H chokes?
3. Power rating and/or PA rating of the OPT if 5K secondary is selected?
4. Any recommendations for an easy to obtain transformer that meet these specs for someone in the USA? Could always add separate filament transformers under the chassis if needed.

Thanks in advance for your time and responses,
Lilstripe
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Old 9th April 2017, 11:39 PM   #2
Mickeystan is offline Mickeystan  United States
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Lilstripe,

The purpose of the switch in the rectifier filters is to provide a hv standby function. Notice the switch is paralleled with a 180K 2w resistor. This resistor is to provide a leakage path for the electron cloud when the tube is heated ( and the switch in standby) as otherwise there would be no place for it to go and as I understand, such condition is not good for direct heated cathode of the rectifier tube. The two chokes should be rated for at least 150ma each. I would prefer them to be 200ma each but 150s will do. The output transformer should be rated for at least 15 watts so it has some head room against saturation on bass notes. This amplifier will likely make about 9-10 watts output. Output transformers can be purchased for Hammond, Edcor or many others here in the USA. Hope this helps.

Mickeystan

Last edited by Mickeystan; 9th April 2017 at 11:42 PM.
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Old 9th April 2017, 11:48 PM   #3
lilstripe is offline lilstripe  United States
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Curious,
How did you work the math to come up with 150-200ma for the chokes?
Thanks
Lilstripe
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Old 9th April 2017, 11:49 PM   #4
pieter t is offline pieter t  Netherlands
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Feedback in this schematic is indicated to be optional.
When not applied the large amount of voltage gain may be unpractical.

Last edited by pieter t; 9th April 2017 at 11:52 PM.
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Old 10th April 2017, 12:16 AM   #5
Wavebourn is offline Wavebourn  United States
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SE807 Triode Dick Amplifier Questions
Quote:
Originally Posted by lilstripe View Post
1. Is the purpose of this switch to allow the filaments to light up and then turn this switch on to apply the B+?
Yes. To let filaments to warm up, then KICK DAMNED SPARKS OUT OF THAT POOR TUBES!

Even manufactured as production amps have this STUPID FEATURE, sometimes even controlled by microprocessors!
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Old 10th April 2017, 01:20 AM   #6
Mickeystan is offline Mickeystan  United States
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One other point to consider is the 1st filter cap of 33uf is too large for a 5R4 rectifier. The 5R4 is recommended to only have a 4uf reservoir capacitor. The 5U4 is much better suited as it spec'd at 32uf to 40uf depending upon which data sheet you look at. The CV378 is a tube I do not know anything about so I will not comment on it.
Sorry I missed your 4th question in my original post. Assuming you can do with a 120v primary and do not need a 230v primary, Edcor makes a power transformer that will work for you by simply feeding all heaters except the rectifier tube from one 6.3v winding. You will still want to bias up the filaments with the resistor divider shown connected to the srpp filament winding one the schematic but don't worry it will not cause any problems. The transformer that Edcor makes currently that I am talking about is their XPWR-198. With these specs; 120V, 60Hz. line to 750V (375-0-105-375) at 300mA center tapped with a bias tap at 105V at 25mA, 6.3V at 6A center tapped and 5V at 6A. This transformer is listed with a price of $93.84. The 375-0375 secondary output versus 380-0380v is insignificant.

As for the size of the chokes, I simply swagged them as each should handle 150 ma (half the capability of the power transformer. Further, each channel of this amplifier will likely draw about 50 millamps or a little more at idle and maybe as much as 100ma or so on peaks while playing louder music.

Mickeystan
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Old 10th April 2017, 01:57 AM   #7
Wavebourn is offline Wavebourn  United States
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SE807 Triode Dick Amplifier Questions
Quote:
Originally Posted by Mickeystan View Post
Further, each channel of this amplifier will likely draw about 50 millamps or a little more at idle and maybe as much as 100ma or so on peaks while playing louder music.
It is SE amp.
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Old 10th April 2017, 03:05 AM   #8
Mickeystan is offline Mickeystan  United States
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Quote:
Further, each channel of this amplifier will likely draw about 50 millamps or a little more at idle and maybe as much as 100ma or so on peaks while playing louder music.
Waveborn, I must have had a senior moment when I made the above statement. Yes it is a single ended amplifier and I should have said it will draw about 50 milliamps class A in each channel. Thanks for the catch
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Old 10th April 2017, 01:16 PM   #9
Ketje is offline Ketje  Belgium
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Quote:
Originally Posted by Wavebourn View Post
Yes. To let filaments to warm up, then KICK DAMNED SPARKS OUT OF THAT POOR TUBES!

Even manufactured as production amps have this STUPID FEATURE, sometimes even controlled by microprocessors!
In this case it isn't so bad
The voltage allready goes up with the 18k series resistor and with those chockes no sudden high voltage shock with cathode decoupling C at zero.
Mona
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Old 11th April 2017, 12:30 AM   #10
lilstripe is offline lilstripe  United States
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Thanks for the info. Could you go into more detail on how to use this transformer with this schematic. For example, the 5v winding on this transformer doesn't have a center tap but the one in the schematic does. Likewise, how would one use the 6v tap to cover all the filaments and the SRPP setup?
Thanks
Pic attached


Quote:
Originally Posted by Mickeystan View Post
One other point to consider is the 1st filter cap of 33uf is too large for a 5R4 rectifier. The 5R4 is recommended to only have a 4uf reservoir capacitor. The 5U4 is much better suited as it spec'd at 32uf to 40uf depending upon which data sheet you look at. The CV378 is a tube I do not know anything about so I will not comment on it.
Sorry I missed your 4th question in my original post. Assuming you can do with a 120v primary and do not need a 230v primary, Edcor makes a power transformer that will work for you by simply feeding all heaters except the rectifier tube from one 6.3v winding. You will still want to bias up the filaments with the resistor divider shown connected to the srpp filament winding one the schematic but don't worry it will not cause any problems. The transformer that Edcor makes currently that I am talking about is their XPWR-198. With these specs; 120V, 60Hz. line to 750V (375-0-105-375) at 300mA center tapped with a bias tap at 105V at 25mA, 6.3V at 6A center tapped and 5V at 6A. This transformer is listed with a price of $93.84. The 375-0375 secondary output versus 380-0380v is insignificant.

As for the size of the chokes, I simply swagged them as each should handle 150 ma (half the capability of the power transformer. Further, each channel of this amplifier will likely draw about 50 millamps or a little more at idle and maybe as much as 100ma or so on peaks while playing louder music.

Mickeystan
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