I got a batch of 5 for testing from jlcpcb. About 50 bucks. But over half of that was shipping. Shipping has gone up about 2x. I also economized by going for a 1 oz. board but the final one would be 2 oz. I would guess the price would be in the $15 range plus shipping.
Good question. I wanted it to fit the diyaudio chassis. I don’t want to run wires and so with this layout you can make the connections to input/output jacks, switch, and volume pot very close to the PCB. Hope is to make it look tidy. Now that we are not running tens of milliamps, heatsinks are not needed, so the actual circuit is small. I am also working on a really cool headphone buffer that I plan to add to the front (between volume pot and input switch).
Big boards can accept, more easily, big capacitors! No complaints from here!
I will wait patiently for the BIG order to arrive with the hopes that many will make their musical lives more enjoyable by building this line stage to go with their TDV amplifiers. And somewhat lesser amplifiers if that is the case ...
I will wait patiently for the BIG order to arrive with the hopes that many will make their musical lives more enjoyable by building this line stage to go with their TDV amplifiers. And somewhat lesser amplifiers if that is the case ...
Oh yes!
Go Rahul, go Rahul, go Rahul!
With provision for big swing and high slew rate. 🙂 This is going to be EPIC!
@ra7
Just got to my mind that I have some u440 ( https://www.farnell.com/datasheets/910106.pdf ) that are specifically designed and built for differential inputs on high demanding measuring instruments (excellent matching and bandwidth).
Have you ever tried them? Based on your experience, can they work well? They have some voltage limitation, but 25Vgs seems still acceptable for a 2Vrms signal, with its 20dB margin.
As a pmosfet, have you tried vp0106?
Thank you in advance,
Roberto
Just got to my mind that I have some u440 ( https://www.farnell.com/datasheets/910106.pdf ) that are specifically designed and built for differential inputs on high demanding measuring instruments (excellent matching and bandwidth).
Have you ever tried them? Based on your experience, can they work well? They have some voltage limitation, but 25Vgs seems still acceptable for a 2Vrms signal, with its 20dB margin.
As a pmosfet, have you tried vp0106?
Thank you in advance,
Roberto
Hi Roberto,
They would no doubt work well, but they might be better suited to a differential design. That is where the U440 would shine. Looks like a great part.
Yes, I did try the VP0106. In fact, it was in there for a long time, and it produces fine sound. But it sounded edgy compared to the J175. In fact, any mosfet I tried sounded edgy compared to J175. The one exception is LND150, but even that I would say is the best of the mosfets, not as good as a JFET operated in the right region.
During this process, I started looking at Vgs v Id curves for all devices. And I found that for devices where the natural operating point for this design coincides with a wide linear Vgs v Id area sound the best. Once the signal starts getting into the curved portion of the Vgs v Id curve, it starts generating higher order harmonics and then it doesn't sound as good.
Best,
Rahul
They would no doubt work well, but they might be better suited to a differential design. That is where the U440 would shine. Looks like a great part.
Yes, I did try the VP0106. In fact, it was in there for a long time, and it produces fine sound. But it sounded edgy compared to the J175. In fact, any mosfet I tried sounded edgy compared to J175. The one exception is LND150, but even that I would say is the best of the mosfets, not as good as a JFET operated in the right region.
During this process, I started looking at Vgs v Id curves for all devices. And I found that for devices where the natural operating point for this design coincides with a wide linear Vgs v Id area sound the best. Once the signal starts getting into the curved portion of the Vgs v Id curve, it starts generating higher order harmonics and then it doesn't sound as good.
Best,
Rahul
Thanks, I always used VP0106 in the tens of mA range, I will now try J175 to compare. I’m curious to hear the difference!
VP0106 and LND150 (buffered, in some cases) are what I used as test driver for SE tube amps (because of the capability to work at 450V). It swings whatever you need with small ratios of local feedback, clean output and high gain.
It is a matched part, which makes it more suitable for circuits that need matched n-channel parts, such as a differential input. See this one for example:
https://www.diyaudio.com/community/...t-input-exicon-output-10-watt-class-a.389498/
If you have LND150 in the gain position, then a J176 or J74 might be more appropriate as the input follower. Idss of j175 is too high for lnd150. I imagine the lnd150 operates at between 1-5 mA DC. So, you’d want a jfet that is linear in that region. Look at the Vgs v Id curves for various devices in that region.
ra7 and Rick, thank you for your answers. I have ordered a pair of THF-51 and they should soon be here. I will most probably try a choked loaded version first.
It seems you included the buffer in the new PCB (telling from the transistor count), would you mind posting the complete schematic? I would like to order parts and perhaps try the circuit on a breadboard.