Feedback Summary & Wait List GB Green Light
So we had some builds shown in the main phono thread by now. The Folded Simplistic Phono board proved working fine, no surprises when following the PDF guide carefully. No particular problems of hum or buzz troubled the builders when practicing the normal packaging and grounding routine as described in the guide.
A couple of subjective evaluations by experienced simplistic builders suggested that this implementation enhances the resolution over their previous hardwired attempts even on the current circuitry architecture. All in all, a good start for this project.
What we also gathered is that not all nominally same AC secondary transformers would produce the same raw DC level depending on manufacturer, regional wall power level, size etc.
Expected there would be Tx variations, nobody had a real problem in the end, most used nothing extra to adjust the raw DC down since up to 50V is workable, few used drop resistors.
Some rules of thumb:
1. 32-36VAC secondary transformers can be used as long as the resultant raw DC does not fall below 10V drop between it and the phono's B+. Such a voltage difference keeps Q1x less capacitive and the CCS robust.
2. Raw DC is not to exceed 50V when loaded with the phono reg CCS consumption (about 100mA per channel including PSU bleeder resistors current). That is not to stress Q1x and Q2x for dissipation and VDS max.
3. Transformers may be bigger than 30VA per channel as some builders used equal or more than 2X50VA toroid, R-Core, or 100VA single toroid with double secondaries plus electrostatic and magnetic shields with success.
Opinions on productivity of this practice vary, most favored to oversize for ease of mind that there will be no bit of performance left unexploited when discussing it in the thread.
Its down to practical considerations also like box sizes and ability to keep the PSU and main boxes adequately apart. Non shielded big transformers would throw stronger magnetic field and lose less voltage when loaded of course. So a 36VAC 30VA model maybe ends up with equal AC secondary level to a 34VAC 80VA model etc.
4. Primary fuse must be T (slow blow) and matching the suggested fusing times two found on the transformers label or spec sheet. Or just that figure if a single core double secondaries model is chosen.
As some builders used the guide's simple raw DC PSU with no problems, also its safe loop breaking from protective earth grounding scheme, I thought to prepare a board suggestion for that just for aesthetic continuity and ease of build to those it may interest. Its a 80x95x2mm double layer design that includes RDrop provision between bridges and filter capacitors for adjusting the raw DC level in case of out of the ballpark secondaries. 2W or 5W resistors space is given for that. It can be just a wire link if the Tx voltage is OK, 2W 0.47R to 1R just for smoothing the rectification cycle lessening its EMI depending on caps & diodes quality/subjectives, or 5W droppers for few Volts. Axial 1A or TO-220 favorite diodes like MUR120/820 etc. can be used. No sinking is needed. The filter capacitors need be snap in type only.
If enough people will require that board maybe Tea can investigate its practicalities and include it in the supplementary wait list GB launch or not, I am just presenting it. Click on the pictures if appearing squat.
So from my side there is no further delay for builds feedback gathering to issue, I am content.
People you can organize your new GB at will now, good luck, merry Xmas and happy holidays soon.
So we had some builds shown in the main phono thread by now. The Folded Simplistic Phono board proved working fine, no surprises when following the PDF guide carefully. No particular problems of hum or buzz troubled the builders when practicing the normal packaging and grounding routine as described in the guide.
A couple of subjective evaluations by experienced simplistic builders suggested that this implementation enhances the resolution over their previous hardwired attempts even on the current circuitry architecture. All in all, a good start for this project.
What we also gathered is that not all nominally same AC secondary transformers would produce the same raw DC level depending on manufacturer, regional wall power level, size etc.
Expected there would be Tx variations, nobody had a real problem in the end, most used nothing extra to adjust the raw DC down since up to 50V is workable, few used drop resistors.
Some rules of thumb:
1. 32-36VAC secondary transformers can be used as long as the resultant raw DC does not fall below 10V drop between it and the phono's B+. Such a voltage difference keeps Q1x less capacitive and the CCS robust.
2. Raw DC is not to exceed 50V when loaded with the phono reg CCS consumption (about 100mA per channel including PSU bleeder resistors current). That is not to stress Q1x and Q2x for dissipation and VDS max.
3. Transformers may be bigger than 30VA per channel as some builders used equal or more than 2X50VA toroid, R-Core, or 100VA single toroid with double secondaries plus electrostatic and magnetic shields with success.
Opinions on productivity of this practice vary, most favored to oversize for ease of mind that there will be no bit of performance left unexploited when discussing it in the thread.
Its down to practical considerations also like box sizes and ability to keep the PSU and main boxes adequately apart. Non shielded big transformers would throw stronger magnetic field and lose less voltage when loaded of course. So a 36VAC 30VA model maybe ends up with equal AC secondary level to a 34VAC 80VA model etc.
4. Primary fuse must be T (slow blow) and matching the suggested fusing times two found on the transformers label or spec sheet. Or just that figure if a single core double secondaries model is chosen.
As some builders used the guide's simple raw DC PSU with no problems, also its safe loop breaking from protective earth grounding scheme, I thought to prepare a board suggestion for that just for aesthetic continuity and ease of build to those it may interest. Its a 80x95x2mm double layer design that includes RDrop provision between bridges and filter capacitors for adjusting the raw DC level in case of out of the ballpark secondaries. 2W or 5W resistors space is given for that. It can be just a wire link if the Tx voltage is OK, 2W 0.47R to 1R just for smoothing the rectification cycle lessening its EMI depending on caps & diodes quality/subjectives, or 5W droppers for few Volts. Axial 1A or TO-220 favorite diodes like MUR120/820 etc. can be used. No sinking is needed. The filter capacitors need be snap in type only.
If enough people will require that board maybe Tea can investigate its practicalities and include it in the supplementary wait list GB launch or not, I am just presenting it. Click on the pictures if appearing squat.
So from my side there is no further delay for builds feedback gathering to issue, I am content.
People you can organize your new GB at will now, good luck, merry Xmas and happy holidays soon.
I was thinking for a GB for the resistors but it seems that most of the people have ordered theirs
R2 and R3 resistors are kind of hard to find (3-11 ohm). Looking around I found these options
PRP9372 100ppm 1% from Hifi Collective
Welwyn MFR4 50ppm 1% from Farnell UK
For the rest of the resistors I've found no source with spot on values like
Farnell which stocks Welwyn RC55 0.1% 15ppm but for example
R8 51.1 (47 needed)
R4 1.81K - 2,21 (1.8K - 2,2K needed)
R14 47,5K (47K needed, I don't think one should alter this one)
Should I go on with the buy or any other European source is available ?
R2 and R3 resistors are kind of hard to find (3-11 ohm). Looking around I found these options
PRP9372 100ppm 1% from Hifi Collective
Welwyn MFR4 50ppm 1% from Farnell UK
For the rest of the resistors I've found no source with spot on values like
Farnell which stocks Welwyn RC55 0.1% 15ppm but for example
R8 51.1 (47 needed)
R4 1.81K - 2,21 (1.8K - 2,2K needed)
R14 47,5K (47K needed, I don't think one should alter this one)
Should I go on with the buy or any other European source is available ?
For some reason 47,5 k seems to be da standard amongst high precision bulk foil resistors in that range.
Here is possibly another:
http://www.elfa.se/elfa3~se_sv/elfa/init.do?init=2&shop=ELFA_SE-SV&item=10-521-93
Regards
http://www.elfa.se/elfa3~se_sv/elfa/init.do?init=2&shop=ELFA_SE-SV&item=10-521-93
Regards
Not that I know the real difference but those two I beleave go under "metal film" and not "bulk foil"
Good ones, I have used such enough times. Not as incisive as VAR but clean and naturally soft.
No, its about different construction techniques. One is a helix the other is etched foil.
Ok, film and foil seemed the same for me 🙂
I better read my datasheets better ;-)
Regards
