Would this circuit lend itself to point-to-point construction? I can't see where it wouldn't, but wondered if there was a significant advantage to using the circuit board 🙂
The build doc is 135 pages of absolute awesomeness.
The build doc is 135 pages of absolute awesomeness.
@rockies914 well, the advantage of the PCB is NOT having to do point-to-point lol but you certainly could, I don't think there is any benefit however. And thanks!
No thank you! This project is awesome. I have a pair of KT8c that I want to try (poor person's KT66-ish, with a 300v screen voltage restriction), and want to use the UK B5 socket instead of an adapter. Plus I can use some fancy-shmancy silver wire, etc, haha!
One quick question on the output transformer specs: neither the Earhard transformer specifcation pdf, nor the Lundahl site shows the gap current, and Don Audio's page says it's a 30ma gap. Does the LL2765 get ordered with a 60ma gap, or are they all 60ma and the DA page isn't 100% accurate?
Gotcha. Just keep in mind the chassis wasn't laid out for point-to-point, you'll probably need to add some holes for terminal strips and whatnot. You could just use an adapter for the KT8c, but it's your project!
You can order almost any transformer or choke from Lundahl with whatever gap current you require. Check the BOM, the gap currents are included there. You simply need to communicate to the Lundahl distributor what gap current variation you are ordering. In this case, the LL2765 is gapped for 60mA.
I may use a different chassis 🙂 I have an external power supply for B+ that may work well, and I think I have an angled case with interior room for the 6SL7s & power/driver tubes.
I'm thinking Hiwatt-style and quality layout. I'll probably get it working quickly, then rebuild it to that level of quality using the initial experience.
I'm thinking Hiwatt-style and quality layout. I'll probably get it working quickly, then rebuild it to that level of quality using the initial experience.
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I didn't know that and thanks. I'm not new to tube amp/circuit repair, but brand new to ordering DIY tube transformers and chokes.
One other question: did you experiment with running gain tubes other than the 6SL7 family? I was specifically thinking of octal pentodes, wired as triodes. If not, that's something I can play with more easily in a PTP build 🙂
No I didn't. Keep in mind you are entirely dependent on the input tube for voltage gain in this circuit, so you need an input tube with a medium to high gain to reach any considerable amount of power. 6SL7 was chosen as it is high gain, widely available, and very linear. But you can definitely experiment with others, just make sure you use the appropriately spec'd anode choke. You could also use a CCS load, but the B+ needs to cover the bias voltage plus the peak AC voltage swing plus the dropout voltage of the CCS in that case.
As an aside, since I was very happy with the sound of this amplifier, I am going to be building myself a one off transformer coupled variation. It will use triode strapped E810F or D3a inputs, Dave Slagle 1:1 ISTs, and a triode strapped HY69 directly heated pentode output stage with Dave Slagle output transformers. Probably will be my last headphone amp, assuming it turns out well.
As an aside, since I was very happy with the sound of this amplifier, I am going to be building myself a one off transformer coupled variation. It will use triode strapped E810F or D3a inputs, Dave Slagle 1:1 ISTs, and a triode strapped HY69 directly heated pentode output stage with Dave Slagle output transformers. Probably will be my last headphone amp, assuming it turns out well.
I did! Thanks gents. Got the xformers on order too. I really like Landfall Systems but I'm thinking I may do my own chassis this time around. I've nearly forgotten what a PITA it is to cut out an IEC sized hole out of thick gauge steel so it's time to remind my lazy ***.
The Lundahl covers are very unique looking so I'm ordering those and will probably powder coat them. Could be robin's egg blue, brick red, white metallic... we'll see what the powdercoater has languishing on the shelf.
Thanks again L0rdGwyn, it's been a while since my last project.
No problem, if you do your own chassis and want to use the PCB, just make sure everything lines up correctly, the tolerances are pretty tight to get the PCB to drop right onto the tube pins like they do in the instructions.
Excellent instructions. Am tempted to make this just because of the confidence instilled there.
Nice start, the build instructions are so complete I will end up putting this in front of other amp projects due to ease of build ( having case predrilled and fitted is big time saver).
Bill
Bill
@metaldog99 do you still have PCBs? If so, I'm interested but I cant PM you as I'm a new member here. Please PM me.