The Dreadnought front end card, available today in the diyAudio Store, followed a similar evolutionary path as Wayne's 2018 linestage. When it was released in 2021, Dreadnought's output stage called for the super fast Fairchild pair KSC2690AY / KSA1220AY as the first choice on the Parts List. Same as WLS2018. Dreadnought's Parts List specified TTC004BQ / TTA004BQ as the second choice for output transistors. Now that Fairchild has put the KSC/KSA pair on End-Of-Life, people are building their Dreadnoughts using the TTC and TTA.
Dreadnought runs from a boosted, single ended power supply: (+60V , GND ). If you wanted to, you could reengineer it to use bipolar supplies instead. And if 60 volt rails are way more than you need, you could reduce the supplies too.
It might be a potential starting point for a "discrete opamp using TTC004 + TTA004 as the output stage".
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[sigh] yes I'm a kindly, tired old man with a poor memory.
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Anything between 50-100ohm will work beautifully. It's not particularly critical, and something is better than nothing.
100 Ohm works.
The PSU Group Buy kit ships with a 68R snubber. We tested several transformers. 50-100R works, and 68R was a good value in the range.
The PSU Group Buy kit ships with a 68R snubber. We tested several transformers. 50-100R works, and 68R was a good value in the range.
I got a text yesterday at 4:30pm (EST) saying the kit was back in stock. I went to buy an hour later and they were all gone...Yikes! Any idea when they will be available again?
I am similarly afflicted, but I prefer to describe myself as "having a youth deficit". 😉
One channel ready for testing:
In short: it works, music comes out. Bit of hum with the ear to the speaker, but that is to be expected as it is completely unshielded.
I've soldered in some resistors provisionally, those that might have to be changed for a different value. R27 is 777R here, to get 4mA bias. Q1-4 are 2SK170BL with Idss around 9.3mA. And just as they did in a previous build of the Pearl 2, they cause a bit of trouble here. I get 3.6 mA across each of the source resistors, 13.5mA across R8. As a result the voltages around Q5 are not what they are supposed to be. Vc = 3.439, Vb = 4.058, Ve = 3.432. Other voltages are close to what has been posted before, so they seem allright.
What would be the best solution for this? Change the value of R4-7 to 15R, 18R or 20R? Does R8 have to be the same value as R4-7? Would there be a penalty in gain/noise if I do this?
I prefer to use my matched quads of 2SK170BL, but getting 2SK209 would be an alternative. How closely matched are they? How much of them would I have to buy to get a 2 closely matched quartets (or 1 octet)?
In short: it works, music comes out. Bit of hum with the ear to the speaker, but that is to be expected as it is completely unshielded.
I've soldered in some resistors provisionally, those that might have to be changed for a different value. R27 is 777R here, to get 4mA bias. Q1-4 are 2SK170BL with Idss around 9.3mA. And just as they did in a previous build of the Pearl 2, they cause a bit of trouble here. I get 3.6 mA across each of the source resistors, 13.5mA across R8. As a result the voltages around Q5 are not what they are supposed to be. Vc = 3.439, Vb = 4.058, Ve = 3.432. Other voltages are close to what has been posted before, so they seem allright.
What would be the best solution for this? Change the value of R4-7 to 15R, 18R or 20R? Does R8 have to be the same value as R4-7? Would there be a penalty in gain/noise if I do this?
I prefer to use my matched quads of 2SK170BL, but getting 2SK209 would be an alternative. How closely matched are they? How much of them would I have to buy to get a 2 closely matched quartets (or 1 octet)?
You will not implement the onboard regulators?
I see this as one of many "nice" features in P3 design.
Your external regulator board you could implement -+18V regulators and use it as "pre-regulator" for P3?
I see this as one of many "nice" features in P3 design.
Your external regulator board you could implement -+18V regulators and use it as "pre-regulator" for P3?