This might help…
An externally hosted image should be here but it was not working when we last tested it.
Cs was added to the layout as an auxiliary cap in case it was needed. I would have to look to see if it was used as I don't recall if I needed it or not.
Resistors R1 & R2 along with R4 lift the filament supply so that it is closer to the +525 VDC HT voltage to avoid exceeding the maximum heater-cathode voltage rating of the valve. This is done simply by adding a DC voltage bias to the heater supply.
Please note that the relays needed to be mounted on the bottom side of the board because it turns out the relay energizing coils have a polarity and I did not know that when I laid them out. The fix was to mount them on the bottom of the board.
An externally hosted image should be here but it was not working when we last tested it.
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Behold!
An externally hosted image should be here but it was not working when we last tested it.
I give you Version 1.1
However, I was too cheap to actually throw away the Version 1.0 board after populating it and finding the issue and re-spinning the design and paying another $90 for a prototype board with a one week delay.
If there is enough interest in these boards I will be using the Version 1.1 design.
Hi to all, my name is Nicola.
First of all congraturations for this amp!!!
Few days ago I've finished to build my own SIY speaker (http://goo.gl/mThHlu)
Now I'm looking for an amplifier to build and this is the project is so interesting.
I have only one question... which is the output power of this amp at 8ohm speaker???
I don't need the exact power but only an approximative value.
tks so much
Nicola
First of all congraturations for this amp!!!
Few days ago I've finished to build my own SIY speaker (http://goo.gl/mThHlu)
Now I'm looking for an amplifier to build and this is the project is so interesting.
I have only one question... which is the output power of this amp at 8ohm speaker???
I don't need the exact power but only an approximative value.
tks so much
Nicola
Hi to all, my name is Nicola.
First of all congraturations for this amp!!!
Few days ago I've finished to build my own SIY speaker (http://goo.gl/mThHlu)
Now I'm looking for an amplifier to build and this is the project is so interesting.
I have only one question... which is the output power of this amp at 8ohm speaker???
I don't need the exact power but only an approximative value.
tks so much
Nicola
50 Watt per channel.
Thanks so much!!!
May be that in few weeks I will start to build it.
If will I need some information may I write you in PM?
Tks a lot
Nicola
Thanks so much!!!
May be that in few weeks I will start to build it.
If will I need some information may I write you in PM?
Tks a lot
Nicola
Absolutely!
Hi Loren42,
I'm late getting to this thread, but want to add my thanks for posting your design. I do have one question on the schematic. It looks like you don't have any frequency compensation in the circuit, not even the typical lead compensation capacitor across feedback resistor R22. Have you seen any tendency to oscillate at high frequencies? Not questioning the design; just curious about how you made it stable.
Thanks.
I'm late getting to this thread, but want to add my thanks for posting your design. I do have one question on the schematic. It looks like you don't have any frequency compensation in the circuit, not even the typical lead compensation capacitor across feedback resistor R22. Have you seen any tendency to oscillate at high frequencies? Not questioning the design; just curious about how you made it stable.
Thanks.
Good to know. I just designed a Williamson-like amp and added the lead compensation capacitor as a precaution. When I simulated the design in LTspice using a transformer model from Robert McLean (see link below), the simulation showed that the phase margin wouldn't be adequate without the lead compensation. Maybe I should try the amp without it...
http://www.diyaudio.com/forums/tubes-valves/181578-spice-transformer-model-spreadsheet.html
Good advice I received
Could I suggest that you look at the thread 'Parallel push pull KT88', the last few pages. The amp designed there is a different topology, but much was learnt and the performance considerably improved by cautiously exploring the behaviour of the design as GNFB was increased.
Could I suggest that you look at the thread 'Parallel push pull KT88', the last few pages. The amp designed there is a different topology, but much was learnt and the performance considerably improved by cautiously exploring the behaviour of the design as GNFB was increased.
Pete Millett also gives a nice description of the high frequency stability and compensation issue in his discussion of his universal push-pull driver board.
Push-pull driver board
About half-way down the page is a section titled "Stability and global NFB." It's a good read.
Hi Loren42,
Great project and good to see that so many people are interested in building an amp from your design.
Only came across this thread today. In case you are looking to get cheap PCBs made, this is the Chinese fabricators I use for cheap prototype PCBs.
PCB prototyping
Quality of the PCB blanks is very good for that price (I design electronic professionally). Not sure what files they can handle for the layout - I send Gerber files as it is the industry standard.
Hope that helps and happy assembly!
Great project and good to see that so many people are interested in building an amp from your design.
Only came across this thread today. In case you are looking to get cheap PCBs made, this is the Chinese fabricators I use for cheap prototype PCBs.
PCB prototyping
Quality of the PCB blanks is very good for that price (I design electronic professionally). Not sure what files they can handle for the layout - I send Gerber files as it is the industry standard.
Hope that helps and happy assembly!
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