No, d1x's voltage is a very small part of such a high rail. Q3x has to produce adequate current to run the Vref series drop voltages lot which are 0.6Vbe+LedVf+R3xdrop+Vr2xdrop. That's to have enough max as well as a proper adjust range to hit good tp1-tp2 readings. When its hard to find specific q3x idss as in the bom and you are short of enough rail kick up R3x's value to compensate the loss of Vr2x's max reach. Try 1k extra in series to R3x for starters so to check what's needed.
From what TT & cart its driven? Any build/system pics?
Hmmm... well...
two tables: one Rek-O-Kut idler drive in a stacked plinth, 12” Jelco and Nakaoga MP200; and a belt drive based on a Rek-O-Kut platter and bearing (and Pyramid’s SG4 motor controller and bldc motor) with SME 312s and Lyra Delos.
The rest is a hodge-podge in constant flux. But currently, a simple diy monitor-controller (preamp) based on a pair of Jensen 990c op amps, feeding some Pioneer RM07s.
Knda weird combo, I know, but it sounds good to my ears.
two tables: one Rek-O-Kut idler drive in a stacked plinth, 12” Jelco and Nakaoga MP200; and a belt drive based on a Rek-O-Kut platter and bearing (and Pyramid’s SG4 motor controller and bldc motor) with SME 312s and Lyra Delos.
The rest is a hodge-podge in constant flux. But currently, a simple diy monitor-controller (preamp) based on a pair of Jensen 990c op amps, feeding some Pioneer RM07s.
Knda weird combo, I know, but it sounds good to my ears.
I forgot to mention: the Delos is feeding a pair of Sowter 1480 SUTs, (or Cinemag 3440)
I know that with these combos, 43db of gain is a bit high, but every time I’ve built an IC phono pre (some of them pretty good) I have prefered them with gain bumped up a bit.
Though, I am aware that I am loosing some headroom.
Thanks, again, to Salas for sharing this project, and Teabag for making up the PCBs and minikits!
I know that with these combos, 43db of gain is a bit high, but every time I’ve built an IC phono pre (some of them pretty good) I have prefered them with gain bumped up a bit.
Though, I am aware that I am loosing some headroom.
Thanks, again, to Salas for sharing this project, and Teabag for making up the PCBs and minikits!
Step up transformers tend to tilt up their response towards HF a bit I have found in bench tests when the source resistance (cart) is above their recommended source spec or they tilt a bit down when it's lower than that spec. Many don't mention or they mention a range. Is your tonal balance ok with both carts in combination with the phono's curve? If bit bright you can go up to 400pF C2Y (15.4nF total). If bit dim you can trim down C2Y value.
I have a few different cap values on hand to try out for C2Y, but it sounds pleasingly neutral as is—just following the original schematic.
Sowter worked pretty hard on the 1480 to keep it from “ringing” and to get an even tonal balance. It is meant to be used without a zobel. Tonal balance between the Nakaoga and Lyra/Sowter is very similar, so I think Sowter achieved their goal.
The Cinemags, though quite clear and concise and fun, need a zobel in my setup and I haven’t gotten around to figuring that one out yet. (Sometimes the ringy-zingy-ness is fun, sometimes not so)
Sowter worked pretty hard on the 1480 to keep it from “ringing” and to get an even tonal balance. It is meant to be used without a zobel. Tonal balance between the Nakaoga and Lyra/Sowter is very similar, so I think Sowter achieved their goal.
The Cinemags, though quite clear and concise and fun, need a zobel in my setup and I haven’t gotten around to figuring that one out yet. (Sometimes the ringy-zingy-ness is fun, sometimes not so)
Howdy fellers, I just plugged up for the first time and I can’t seem to get my amp boards to act remotely right. First, thanks for the design, the gathering of materials and organization of a group build. I can’t wait to tweak this out and give a listen.
Now for some measurements. My DCV+ to ground on both boards is 24.99v. Deadly accurate. All LEDs accounted for and acting right, . My Rail+ to Grnd on both boards is 24.5V dead on the nose. VR2X does nothing on either board, and there is no heat going on at Q6X or Q1X. K’, what gives? As you might imagine, TP1 to TP2 is way high at 7.44V on both boards, dead nuts. Looking forward to some advisements.
Now for some measurements. My DCV+ to ground on both boards is 24.99v. Deadly accurate. All LEDs accounted for and acting right, . My Rail+ to Grnd on both boards is 24.5V dead on the nose. VR2X does nothing on either board, and there is no heat going on at Q6X or Q1X. K’, what gives? As you might imagine, TP1 to TP2 is way high at 7.44V on both boards, dead nuts. Looking forward to some advisements.
So. It seems that I had C2X where the + lead of the electrolytic would have gone if I were to have taken that route. Not sure what that route accomplished but I’m feeling like I might have fried some components. I popped that cap out and put in a provisional 2.2uf cap correctly installed and m, well, still the same. Not getting anything on C2X, E5X, etc. .
Thanks for getting back so quickly. Here are my findings
Volltage+ at both boards is 25.25
Q6X 3.1/0
Q2X 19.5/19.45
Q3X .631/.293
Q4X 21.17/24.07
Q5X 3.25/0
So I'm trying to learn a thing or two as I go so any explanation, what ever you have time for, of what happened as well as what can be done about it would be helpful. Thanks again.
Both Q1x seem operating. Measure voltage drops between legs of each R1x
Second Q6x seems not operating
The drain to ground voltage at both Q2x could indicate low raw DC. Measure DC input
Q3x maybe both working but reflect differently due to possible second Q6x problem
Q4x same as above
Q5x Same as above
Second Q6x seems not operating
The drain to ground voltage at both Q2x could indicate low raw DC. Measure DC input
Q3x maybe both working but reflect differently due to possible second Q6x problem
Q4x same as above
Q5x Same as above
Alrighty, wasn't sure if I was doing this right, so what I did was read source to ground and source to V+ on FETS...
source to ground
Q3X 0/0
Q4X 0/0
Q5X 22.5/24
source to V+
Q3X 25.2/25
Q4X 25/25
Q5X 3/.6
and the IR drop at R1X was .57/.51
If I did that wrong, please advise regarding a better way
source to ground
Q3X 0/0
Q4X 0/0
Q5X 22.5/24
source to V+
Q3X 25.2/25
Q4X 25/25
Q5X 3/.6
and the IR drop at R1X was .57/.51
If I did that wrong, please advise regarding a better way
Drain to ground measurements are more useful at the JFETs. You did not report the DC level at the power connectors coming from the bridges and big caps raw PSU to the phono boards shunt regulators though.
But the R1x drops gave a valuable clue. The pulled current is low, about as much as the phono circuits would draw alone. Healthy indication would be 1.35V-1.5V on each 15 Ohm R1. So the build's shunt regs don'r even function for useful current setting right now.
I would start by replacing Q1x Q6x and Q4x. Also restore C2x to its right value. Work on one channel's reg first until solution is reached. So not to do tedious double rework while experimenting and gathering clues. Good luck and keep reporting/asking.
But the R1x drops gave a valuable clue. The pulled current is low, about as much as the phono circuits would draw alone. Healthy indication would be 1.35V-1.5V on each 15 Ohm R1. So the build's shunt regs don'r even function for useful current setting right now.
I would start by replacing Q1x Q6x and Q4x. Also restore C2x to its right value. Work on one channel's reg first until solution is reached. So not to do tedious double rework while experimenting and gathering clues. Good luck and keep reporting/asking.