audio-talk

MoFo type scenarios require a preamp with a bit of voltage gain; I'm already working on a valve preamp using 2P29L valves that'll give around 20dB of gain but as I also have a pair of Sony 2SK60 V-FETs I thought it would be interesting to use them in a preamp circuit from over on DIY Audio. The 2SK60 FETs are choke loaded (Hammond 157G).

As I had a bit of time over the weekend I started by assembling a volume control module using a Seiden switch and a couple of Dave Slagle's Autoformers.

A bit more progress with the volume control build this morning. The Slagle autoformers are fully connected and I've added a 'backplane' board with the input/output sockets. The backplane also holds a pair of my BUF-03 output buffer modules so 'll have unity/gain options for the preamp. I'm waiting on delivery of some trimmer pots for the buffer stages before I can connect it up to test.

Hi Ray,

Nice design and very nice work!

I have been researching using my Sony's for a Luminaria following your recommendation and it looks very interesting!

ciao

James

Cheers James. I also had some PCBs for the 'New Luminaria' section fabricated - the aim is to stack them in front of the autoformer board so I end up with quite a neat, compact preamp unit.

I got the required stand-offs yesterday so here's a preview of the whole assembly. Still waiting on the trimmer pots for the buffer stage before I can wire it up and give it a try, looks like they'll be another fortnight or so before they're back in stock.

Lovely work Ray. Your stuff looks like finished commercial stuff rather than DIYery.

Cheers. I guess we all have our stengths and weaknesses - I'm not so hot on the eletronics theory stuff so I tend to follow where others have gone before in that respect but I do seem to be able to visualise ideas and I get a lot of pleasure from this hobby from creating something that looks shoddy as well as sounds good.

I received the trim pots for the buffer stage and installed them this afternoon so I'll be able to test the volume control with buffer now - I've got the week off so I'll get onto it ina day or two.

I've also assembled one o Nicks (Jack's) Statistical Regulator kits to power the gain stage. Schematic calls for 120VDC, which is 21 zener diodes. I ignored the instructon sheet and installed them in groups of 10 in the outer rows and then linked the rows with zener #21 under the board. I need to put a rectifier pre-filter board together next.

Quality work .

Daniel Quinn wrote: ↑Sun Aug 07, 2022 5:42 pm Quality work .

Cheers, I do try.