I'm going to make a PCB set for SY at my cost, to thanks him for sharing his design and helping me with this project.
can the circuit be used without the cinemag? thats for changing unbalanced to balanced signal so what happens if the unbalanced signal is injected without the cinemag?
It will work fine, but the transformer really is effective in getting rid of all sorts of noise you didn't even know was there.
Nice work on the PCB!
I was thinking of using a TVC instead of the input-trafo, to kill 2 birds with one stone...and maybe have an improved volume-control...
These seem ok, (and cheap!):
http://cgi.ebay.com/HIGH-QUALITY-24...Z3284QQcmdZViewItemQQ_trksidZp1742.m153.l1262
Arne K
I was thinking of using a TVC instead of the input-trafo, to kill 2 birds with one stone...and maybe have an improved volume-control...
These seem ok, (and cheap!):
http://cgi.ebay.com/HIGH-QUALITY-24...Z3284QQcmdZViewItemQQ_trksidZp1742.m153.l1262
Arne K
Take note that these PCB's were designed to allow for a lot of options, choice of caps casing, use of transformer surge reducer TH1, HV relays or not, etc...
So make sure to read the Parts List and look at the schematics before assembling the PCB's. You may need to install jumpers at some places, if you don't use some optional parts.
I'll try to write a small document listing all the options but it is not done yet.
GROUNDING CONNECTIONS:
This preamp use a very specific Grounding scheme. There is a lot a separate GND (HV, HTR, Signal, Power, etc...) that need to be correctly connected for optimum performance. You need to correct all the PCB correctly. I'll put together a schematic for the connection but it is not done yet either...
So make sure to read the Parts List and look at the schematics before assembling the PCB's. You may need to install jumpers at some places, if you don't use some optional parts.
I'll try to write a small document listing all the options but it is not done yet.
GROUNDING CONNECTIONS:
This preamp use a very specific Grounding scheme. There is a lot a separate GND (HV, HTR, Signal, Power, etc...) that need to be correctly connected for optimum performance. You need to correct all the PCB correctly. I'll put together a schematic for the connection but it is not done yet either...
And the Regulators PCB completed as well. Just a few parts are missing until I select the correct leds resistors and timing capacitors.
I'll start testing them in a few days.
The big film caps are held in place using silicone to reduce microphony effect.
I also found the cap's leg connected to the outer film layer and connected this leg to ground for best noise immunity.
I'll start testing them in a few days.
The big film caps are held in place using silicone to reduce microphony effect.
I also found the cap's leg connected to the outer film layer and connected this leg to ground for best noise immunity.
Attachments
Rectifier PCB HV and LV sections all tested Ok. I'll post schematics with voltages once I'm done.
Regulator PCB, HV Regulators are both working perfectly.
Didn't test the LV Regulators section yet.
Regulator PCB, HV Regulators are both working perfectly.
Didn't test the LV Regulators section yet.
Regulator PCB, LV section tested Ok too. Now, I just have to complete the preamp PCB and test it.
Looking good 😀
Looking good 😀
I should have tested all the boards by next week. Then I'll do a relay input PCB and a small pcb to mount the Cinemag transformers.
If I get some time over the next week or so, I'll be putting together a BOM from mouser. If anyone has part number etc etc to contribute, they would be greatly appreciated.
Algar-emi: when I get this done, I'll forward you the info and you can add it to your BOM sheet.
Fran
Algar-emi: when I get this done, I'll forward you the info and you can add it to your BOM sheet.
Fran
I never got a chance to do theBOM yet, but hope to in the next few days.
Did you get any further with the build?
Fran
Did you get any further with the build?
Fran
One question for you SY. I always wondered why you didn't go balanced with this line stage. You have the transformer right there, that I believe can be wired for phase splitting and I believe you are a PP kinda guy. Why SE?
Still working on assembling the power supply. Here the umbilical cable. It is made of two cables (4 wires each + shield, Belden 83396 silicone rubber cable), each separately shielded. HV and control wire in one, LV in the other. With some nice expandable Sleeving.
Attachments
Josh, my soon-to-be-published preamp article (I think it's in the June AX) is indeed balanced output. But at the time I built the Heretical, I would have had to rework my electronic crossover (which the preamp drives).
In all honesty, I've never found much of a difference between balanced and unbalanced in using short-ish (<3m) interconnects at line level, despite the theoretical superiority. There are some interesting reasons, which I'm sure have already occurred to you, to use a balanced drive at high level, like 20V, to the power amp. One of the nearly-finished projects I have is an EL84-based unity gain balanced-in power amp, sort of a tube analog to the First Watt F4. But the only place I think that balanced has a REAL advantage in home audio is between cartridge and RIAA amp.
In all honesty, I've never found much of a difference between balanced and unbalanced in using short-ish (<3m) interconnects at line level, despite the theoretical superiority. There are some interesting reasons, which I'm sure have already occurred to you, to use a balanced drive at high level, like 20V, to the power amp. One of the nearly-finished projects I have is an EL84-based unity gain balanced-in power amp, sort of a tube analog to the First Watt F4. But the only place I think that balanced has a REAL advantage in home audio is between cartridge and RIAA amp.
SY said:
but you must admit that some pre-WWII era VT4C booster amp is completely sane solution for any living room .........
(and we both know that these are certainly made before F4 .........
)- Status
- Not open for further replies.