thomasdf
Well-known member
Hello
A long time ago I was given a set of spare parts, transformers and such among which was a pair of Lundahl LL1538 and LL1539.
Knowing a famous console brand used the 1538 as mic input in a legendary preamp / channel design I thought I'd give this design a shot, in 51x format.
I pretty much went 1:1 on the schematic but this experience is a lot of first times for me : Kicad (used to be a Eagle user... but it's way too expensive) and 500/51x format.
Here is where I am so far :
I have some questions regarding the design :
- what's the deal with R113 / R114 and the trimmer there ? On some schematics the value is "L5240" ?
- what are the most appropriate values for the 5534 capacitors ?
- output transformer : orig transformer is the infamous "pumpkin" is 1:2+1 so am I right to think my option B wiring is better ? LL1539 is 2:1+1 so option B here is reversing the transformer and using it 1:2 and using 2nd tap of primary as 1:1 output for feedback.
I am curious to try to swap U1 for a TDA1034, if I can source some. Maybe I'll add a parallel footprint.
I am open to any input, advice etc. I plan to share the PCB design / gerber when I am done.
Cheers !
Thomas
A long time ago I was given a set of spare parts, transformers and such among which was a pair of Lundahl LL1538 and LL1539.
Knowing a famous console brand used the 1538 as mic input in a legendary preamp / channel design I thought I'd give this design a shot, in 51x format.
I pretty much went 1:1 on the schematic but this experience is a lot of first times for me : Kicad (used to be a Eagle user... but it's way too expensive) and 500/51x format.
Here is where I am so far :
![RougeUn_Aug2_V1.png RougeUn_Aug2_V1.png](https://cdn.imagearchive.com/groupdiy/data/attachments/85/85618-934de6df6bb56737ee96e1a1ad734e0f.jpg)
- what's the deal with R113 / R114 and the trimmer there ? On some schematics the value is "L5240" ?
- what are the most appropriate values for the 5534 capacitors ?
- output transformer : orig transformer is the infamous "pumpkin" is 1:2+1 so am I right to think my option B wiring is better ? LL1539 is 2:1+1 so option B here is reversing the transformer and using it 1:2 and using 2nd tap of primary as 1:1 output for feedback.
I am curious to try to swap U1 for a TDA1034, if I can source some. Maybe I'll add a parallel footprint.
I am open to any input, advice etc. I plan to share the PCB design / gerber when I am done.
Cheers !
Thomas