Yes that threw me as well and why I was unsure if my IC were correctly installed. I either missed that comment or forgot it. I'm also ready to power up after a couple of resistors I forgot to order come.
I have a few questions about connecting the power leads to the board, which I'll post later.
George has a lot of information about potentual output transformers here.
Component Testing | Tubelab
Elsewhere he has information about PTs as well, and these will vary depending on what you want to build tube wise. .
Not me.There are too many other current production options available. A quick search for 300B on the Antique Electronics Supply website will show several.
Perfect fit. They are the same ones used on the SSE board. I actually ordered mine from Handmade Electronics, since I was getting other stuff from there already and they fit perfectly too.
A question on grounding.
In a day or two, after the extra components have arrived, I'll be ready to connect everything up and test. In the original TSE I schematic, the HT centre tap connected to the ground, as it does in the TSE II, but in the SE I there is also the earth from the mains connecting to somewhere near the pad 4 that decides the heater voltage. I can't see anything to connect the mains earth in the SE II, but I remember George talking about this somewhere but can't now find it.
Q: Does the mains earth get connected to the board? and if so, where? I see that the chassis fixing holes are isolated, so it can't be through these.
Also, can the trim pots be mounter on the top tube side with out any problems (I think yes but want to double check) as it would be easier for me to adjust them on the top without turning the board over.
In a day or two, after the extra components have arrived, I'll be ready to connect everything up and test. In the original TSE I schematic, the HT centre tap connected to the ground, as it does in the TSE II, but in the SE I there is also the earth from the mains connecting to somewhere near the pad 4 that decides the heater voltage. I can't see anything to connect the mains earth in the SE II, but I remember George talking about this somewhere but can't now find it.
Q: Does the mains earth get connected to the board? and if so, where? I see that the chassis fixing holes are isolated, so it can't be through these.
Also, can the trim pots be mounter on the top tube side with out any problems (I think yes but want to double check) as it would be easier for me to adjust them on the top without turning the board over.
Hey George,
I've been reading and asking about triode loading and think I finally understand the compromises here, but would like to get your input on this.
Based on what you write here, on the 8ohm secondary, a 32ohm will present 20K and a 300ohm will present 187K.
If power were sufficient in this case, is there any point in putting a load resistor?
Based on a few computations, power output with or without a load resistor is more or less the same. Although with the load resistor, it seems like the distortion will be higher...
If that is true, why is it considered the "ideal" load?
You can mount the trim pots on either side -- see posts 113-116 in this thread for some different strategies for safely adjusting bias with the board installed in the chassis.
I made a reasonably clean version of the Eagle schematic and it is posted here, and it will also be posted in the first post of this thread. This the schematic of the BOARD ONLY, since it is what I made for PCB layout purposes. It does not include the transformers or other off board parts.
It also has a collection of Xs in the lower right corner. These are the mounting holes for the board itself, the heat sinks and the holes added for airflow. These must be in the schematic since they are actually placed on the board as SMD parts.
The left side of the schematic are the two amplifier channels.
The right center is the high voltage supply, both positive and negative.
The upper right is the DC heater supply and filament regulator circuit.
It also has a collection of Xs in the lower right corner. These are the mounting holes for the board itself, the heat sinks and the holes added for airflow. These must be in the schematic since they are actually placed on the board as SMD parts.
The left side of the schematic are the two amplifier channels.
The right center is the high voltage supply, both positive and negative.
The upper right is the DC heater supply and filament regulator circuit.
I have finished my amp now and it worked first time! And it sounds very, very good.
The B+ is a little too high and I want it to be 400v absolute max (I'm using 5k OPTs). Can we still decrease the voltage by increasing the C4 value, even though this is 10x the value of the TSE I C4. I see from the specs that the max capacitance is 60uF, so I guess it should be OK. Or would there be a better way to lower the B+ voltage.
The B+ is a little too high and I want it to be 400v absolute max (I'm using 5k OPTs). Can we still decrease the voltage by increasing the C4 value, even though this is 10x the value of the TSE I C4. I see from the specs that the max capacitance is 60uF, so I guess it should be OK. Or would there be a better way to lower the B+ voltage.
Attachments
You would decrease C4 to decrease B+.
Can use PSUD to simulate, or by trial and error.
What's C4 value, and B+?
Randy