Upgrading from a LB T10 (maybe to an EAR834 kit)?

[m00dawg]

I know I know there's a lot of content about all these. I know StepheK has a lot of good info on building an EAR834 (https://audiokarma.org/forums/index.php?threads/diy-ear834-clone-phono-stage-build-series.972728/). I've been watching Stephe's videos on that plus learning about what 300B's are even for (that's all new to me) plus some of the Littlebear stuff.

I have a Littlebear T10 (torodial transformer version) now which I just recently upgraded to Electro-Harominx 12AX7's (up from Russian milspec tubes). Those EH's tricked me at first as they sounded really poor at first but have since warmed up and it's been a great jump up. They now sound excellent. I held off for a while because of the whole Russian invading Ukraine thing (EH tubes come from Russia - so that's a problem).

I run a Technics SL-1200MK3 with a Denon DL-301. That goes into a step-up transformer I purchased from someone off VinylEngine. That goes into the LB. The LB then just goes to a small mixer I use for my powered monitors in my studio. There's other things in this chain I can upgrade but want to focus on the phono stage for the moment.

Even before Stephe's video series, I was aware the T10 has some weak points. The RIAA curve. Having to put tin on the bottom of the acrylic case, possible wrong loading resistor (for MM carts - not sure how much this hits me given my MC/SUT setup).

So I've been looking at the various EAR834 solutions. I was fond of the two chassis solution I found and almost just bought that as a starting point to upgrade, when I noticed they have a male connector that's exposing the 200V voltages right off the pins. Why they didn't go with a female socket there made me nervous. I could swap that around, but figured I might consider more kit solutions or fixing the T10 (though it could stand to have a new case). Something that lets me move the SUTs internal would be nice too (though not 100% sure if I'll keep that setup when it's time to swap cartridges - open to suggestions there though the DL-301 has been great).

This was a long roll-up to being curious about if there is anyone that offers kits that might include a pre-cut chassis and PCB sourced from a known good supplier? Looking basically to improve upon the T10. It's been a good phono amp for sure (it obliterates my CA 640P) but thought I'd see what's out there. Improving the RIAA curve in particular.

 

[tabarddn51]

Hi, You will find just as many problems with the kit & made up EAR kits from China. I Have done 3, 2 worked well after some tweaking, one never worked. Remember you are dealing with very high voltages here, lethal if you get thing wrong!!
However an interesting thing I found out (to late for me, however) is the EAR has enough gain to drive a 103, so it will also drive a 301. The trick is to change the loading resistor from 47k to the size suitable for your MC.

Cheers

 

[m00dawg]

Yeah I'm aware of the high voltages. I had some initial issues with swapping to the 12AX7's which had me sweating due to that. I'm used to working with mains voltages and building low voltage linear PSUs, though tubes certainly require more respect since you're got high voltage in the circuit. The inconsistency with Chinese built EAR clones is one reason I was wanting to consider a kit. Essentially just the PCB, maybe the tube sockets, and chassis and that's about it. Stephe's method involves grabbing an unpopulated PCB (from China, though surprised no one has made these more directly or there isn't a KiCAD project for it or some such) and fabbing the case. I could fab a wooden case or arcylic case as I have a laser cutter, but don't really have the tools to work with metal.

I think to improve the T10, it's just swapping some resistors and caps in places. I need to re-watch Stephe's videos on that but I have seen other recommendations over on VE before too. It has a healthy amount of gain so I wonder if I can try a loading resistor swap. I've connected my turntable directly to the LB with my DL-301 before. I doesn't sound _bad_ but does need a lot more gain on my mixer and that raises the noise floor (hum) to an audible volume.

 

[mcgjohn]

a few years ago there was a very long thread on the EAR clones. Quite a few AK'ers have them. A person can also buy one of the clones as plug and play. As for step ups, so many options there as well.

 

[m00dawg]

Yep I've read through that thread, along with others. As I recall the main one is huge. I didn't find any kit chassis there. The chassis thing I guess I take for granted in other spaces (I laser cut Eurorack cases and make panels from FR4 - same material as PCBs). I just don't have any tooling to cut a case well. Probably an extruded case I could look at and perhaps replace the sides/top with something 3D printed or laser cut as a compromise. I don't think it's worth investing in metal tooling just for this thing.

Means I may just save up, perhaps do some minor upgrades to the T10 in the meantime, until I can get one of Stephe's.