Squeaky

Re: Helios 2128 + 22113 build attempt
« Reply #40 on: March 31, 2019, 09:22:55 PM »
With a bit of renewed interest in this thread I thought I might as well update with a couple of pictures.

The first picture is of a line module with only the HPF retained (no other eq). Unbalanced insert is added (I'll eventually work out the most appropriate place with a bit of trial and error). In hindsight I could have dispensed with the 1 transistor HPF buffer and just used the 22113 which would have ended up with that amplifier probably running at a happier operating point. Since I will build a few of these purpose built line modules I was thinking of building a couple of 2128-2128 modules to compare with the 2128-22113 modules.

This module could easily become a pre if the input transformer were changed and a gain switch were added (swap out the 0-20-40 pad that is currently in place). Module is unbalanced out but you could probably squeeze an output transformer in there if you cramped thing up a bit. I'll look to use this for something like an effects returns.

The second and third pictures are of a prototype router module. I think I almost know how I will proceed with this to the second (and hopefully the last) prototype. For the sake of headroom, and driving auxiliaries, it would have been better to use the 22113. The 0V layout was wrong, a bit overkill in places and a bit too much floating going on. Resistor and pot values, auxiliary loading also largely wrong.  Was a good learning experience.



Squeaky

Re: Helios 2128 + 22113 build attempt
« Reply #41 on: March 31, 2019, 09:25:41 PM »
First router shot

Squeaky

Re: Helios 2128 + 22113 build attempt
« Reply #42 on: March 31, 2019, 09:26:22 PM »
Second router shot

Whoops

Re: Helios 2128 + 22113 build attempt
« Reply #43 on: April 01, 2019, 08:50:53 AM »
Very nice work.

The 2128 pcb and 22113 pcb look great.

the cases look really good also,
from were are you getting those cases?

thanks

Squeaky

Re: Helios 2128 + 22113 build attempt
« Reply #44 on: April 02, 2019, 12:24:19 AM »
Thanks Whoops. Everything always seems to be a work in progress.

The cases are just Hammond 1441 series. Probably not narrow enough for most but I find them convenient given I am not too concerned with making everything as small as possible (which is probably a significant commercial driver).

Rocinante

Re: Helios 2128 + 22113 build attempt
« Reply #45 on: April 03, 2019, 12:46:29 AM »
Okay I wanted to be pretty certain I had the right schematics.  Its been awhile and a lot of similar schematics since I had done it.
On my first round of boards the Q7 base was wrong (I think) but I had fixed it by the time I did the next order. So that said just doing a double check on the Q4/Q7 area would be wise, albeit the later date of the file also corresponds with this being the later schematic/pcb order and makes me feel pretty certain this is correct.


If there's a harder way to do this, I haven't found it yet.