After some work.... (started with a bunch of small caps 10pF 33pF 40pF 47pF 56pF) for C2y, I finally got the rig singing... and I mean Really singing... I must congratulate Salas and Teabag for the splendid work on the design, component values choice, clear pdf and wonderful pcb.
As usual I started with C1, being very carefull to get a close match between channels.... I measured 20 pairs and settled for 47.4nF obbligato caps.
Please bear my simple math:
2187 / 0.0474 = 46139 So I needed to get R14 + R4 // R7 to be near 46139
I searched my stock and found:
R14 = 47200 // 2M02 = 46122
R4 = 2200 sharp so:
R4 + R14 = 46122 + 2200 = 48322
For R7 I got 0.991M ohms
So total resistance is 48322 // 0.991M = 46076ohms (quite near 46139) I rest my case
Now 750 / 46076 = 0.016277 ( 16.277nF) and that is what I needed for C2
Based on (several) previous folded builds, I estimated second stage Miller to be near 1.03nF
So I needed 16.277 - 1.03 = 15.24nF for C2
Found in my stock a really nicely matched pair of copper foils measuring 15.2nF and so I estimated the need for 40pF C2y.
After first listening sessions I found this PCB folded to sound really good but not magical (I was using only the stock 15.2nF for C2) and so started to experiment.... as you might have read in the beginning, I used caps ranging from 10pF to 56pF and guess what.... In the end the chosen value was the 40pF SM that I initially had calculated.
Now bass goes really deep but articulated, mids are sweet and highly detailed and highs are spot on.... now harshness at all, sounstaging is outstanding and the stereo image is projected in my room as an integrated whole.
I am really amazed with the difference some small picofarads can make in C2.
No need for wigh current shunts or over spec TX... just listen and fine-tune your values and you will reach full on bliss at some point.
As usual I started with C1, being very carefull to get a close match between channels.... I measured 20 pairs and settled for 47.4nF obbligato caps.
Please bear my simple math:
2187 / 0.0474 = 46139 So I needed to get R14 + R4 // R7 to be near 46139
I searched my stock and found:
R14 = 47200 // 2M02 = 46122
R4 = 2200 sharp so:
R4 + R14 = 46122 + 2200 = 48322
For R7 I got 0.991M ohms
So total resistance is 48322 // 0.991M = 46076ohms (quite near 46139) I rest my case
Now 750 / 46076 = 0.016277 ( 16.277nF) and that is what I needed for C2
Based on (several) previous folded builds, I estimated second stage Miller to be near 1.03nF
So I needed 16.277 - 1.03 = 15.24nF for C2
Found in my stock a really nicely matched pair of copper foils measuring 15.2nF and so I estimated the need for 40pF C2y.
After first listening sessions I found this PCB folded to sound really good but not magical (I was using only the stock 15.2nF for C2) and so started to experiment.... as you might have read in the beginning, I used caps ranging from 10pF to 56pF and guess what.... In the end the chosen value was the 40pF SM that I initially had calculated.
Now bass goes really deep but articulated, mids are sweet and highly detailed and highs are spot on.... now harshness at all, sounstaging is outstanding and the stereo image is projected in my room as an integrated whole.
I am really amazed with the difference some small picofarads can make in C2.
No need for wigh current shunts or over spec TX... just listen and fine-tune your values and you will reach full on bliss at some point.
The PSU board has power resistor positions from rectifier to main filter cap.
Either for mild value anti-EMI purposes rC or higher ripple reducing RC or to simply compensate for an overachieving secondary and get some filtering too.
Wow... writing so fast I almost forgot about R5 R6
Let us imagine R5 // R6 = R5*
R5* x C1 = 318uS
2187uS / 318uS = 6.87735
As I have R14 (total) = 46076 ..... then:
R5* = 46076 / 6.87735 = 6700
For R5 I have a nice pair of 6750ohm kiwames
For R6 I have a pair of 1M125 Allen bradleys
So R5* = 6750 // 1M125 = 6710 ohms (really near 6700... so I rest my case again)
Quite simple but it takes a lot of work to be able to find the right combinations using the "limited" stock values in my bin.
Let us imagine R5 // R6 = R5*
R5* x C1 = 318uS
2187uS / 318uS = 6.87735
As I have R14 (total) = 46076 ..... then:
R5* = 46076 / 6.87735 = 6700
For R5 I have a nice pair of 6750ohm kiwames
For R6 I have a pair of 1M125 Allen bradleys
So R5* = 6750 // 1M125 = 6710 ohms (really near 6700... so I rest my case again)
Quite simple but it takes a lot of work to be able to find the right combinations using the "limited" stock values in my bin.
Only your TT's cable will suffice. (The 369's Input+Miller will be more but its degenerated and cascoded also).
The mini grabbers and cables aren't influential with their inductance when you trim values so closely? Or picking hum?
There is less gain than my old set up. It seems to be a bit lacking in the bass output as well, what could be the cause of that?
Have you got extra line gain? What is the system's gain structure? You could be missing the pre pre + MM total gain you had before or some grunge from the flicker noise previously. Could partially also be due to the Hovlands but not there to say for sure. But you should at least feel more information even if not tonally right yet. What C2Y you got? Trim it up if the tonality is light.
This case I salvaged from an old High End CDP from Denon, It is 1cm high and I placed a new front (10mm thick alu from Modu)
It is covered in thick copper in the inside. Quite heavy.
If done as per the pdf it should sport 62dB at 1khz.
If you lack bass, you can try increase C2y a bit. Also try lowering your cart VTA... also try a higher cart loading resistor.
If you measured your caps and resistors (in the riaa filter) you can post the values here so we can have a better look. Sometimes it R5//R6 end up with a slightly higher value then indicated in the pdf, you could notice a bump in the mid frequencies (around 1k) and that might give you the impression of lacking bass.
Attachments
Last edited: