vmps said:
just in case that you didn't spotted that- later Mark tried reg with gas toobz (even if he was very reserved regarding that
) and like it betterZen ch...ch...choky Mod is correct.
Mark is using OD3 regulator tubes instead...for that nice, purple glow!
It is too beautiful out here in the western Rockies today. Got to turn off the insane American football, turn off the Technics Jukebox in full random mode...turn on my Rockbox modded Sansa mp3 player, get on the bicycle and do some late afternoon riding..
Life is good!
Ciao, Choky!😀
Mark is using OD3 regulator tubes instead...for that nice, purple glow!
It is too beautiful out here in the western Rockies today. Got to turn off the insane American football, turn off the Technics Jukebox in full random mode...turn on my Rockbox modded Sansa mp3 player, get on the bicycle and do some late afternoon riding..
Life is good!
Ciao, Choky!😀
Mark A. Gulbrandsen said:
So Mark, which version of the gas-regulated power supply did you end up using on this version of the linestage?
TIA,
-- josé k.
I'm jumping on board!
I needed a new project to keep me sane. I'm thinking I'll build a 12b4 pre and then maybe a Baby-Huey or el-cheapo after that... I'm using a schematic I found elsewhere, I was suprised it wasn't posted here, that I could find. Here is a picture and a parts list. Other notes, it was suggested in another thread to change the first choke to a 20H and the following resistor to a 20k resistor, other than that no changes. I'm using the Bottlehead CCS because it was the easiest to find prepackaged. I was also thinking that maybe a Hammond 262F12 might get the power and filament done in one shot... Any advice would be appreciated!
I needed a new project to keep me sane. I'm thinking I'll build a 12b4 pre and then maybe a Baby-Huey or el-cheapo after that... I'm using a schematic I found elsewhere, I was suprised it wasn't posted here, that I could find. Here is a picture and a parts list. Other notes, it was suggested in another thread to change the first choke to a 20H and the following resistor to a 20k resistor, other than that no changes. I'm using the Bottlehead CCS because it was the easiest to find prepackaged. I was also thinking that maybe a Hammond 262F12 might get the power and filament done in one shot... Any advice would be appreciated!
Attachments
You might prefer the sound without the cathode bypass cap. Rig up a switch and try both.
Output impedance increases by (mu + 1) * 500 = approx 3500R.
Depending on input impedance of the amp you are driving, this may or may not be significant.
Output impedance increases by (mu + 1) * 500 = approx 3500R.
Depending on input impedance of the amp you are driving, this may or may not be significant.
Doh !
On closer inspection, there is no cathode bypass cap: it runs from the filament CT to ground...
On closer inspection, there is no cathode bypass cap: it runs from the filament CT to ground...
Thanks for looking anyway 🙂 I didn't get to fancy with the parts, my original list had all the audiophile stuff like 6 dollar resistors but was over 500 bucks, too much. The resistors are carbon composition and carbon film, the PSU resistors are metal oxide. The pot is just a dual gang audio taper from Alpha. The caps arn't all that special either, orange drops and sprague atoms, and a Sonicap. I can't get the resistors for the CCS until I get the manual, that is unless anybody has a copy they could look at so I can get it all at once 😀
CCS plate loaded 12B4 linestage
Hi,
have a look a few posts up, you will find my ugly handdrawing ;-)).
This is exactly the circuit that I am using.
To load the plate with a CCS, has a lot of advantages over a current sink at the cathode, the most important is the better PS-rejection.
I do not use a cathode resistor bypass cap because for my feeling it sounds much better without and the amplification factor is not affected much anyway.
I used standard good quality parts, no esoteric stuff, the preamp sounds very good and is very quite...you might have to select the tubes for low microphony.
have fun
pieroh
Hi,
have a look a few posts up, you will find my ugly handdrawing ;-)).
This is exactly the circuit that I am using.
To load the plate with a CCS, has a lot of advantages over a current sink at the cathode, the most important is the better PS-rejection.
I do not use a cathode resistor bypass cap because for my feeling it sounds much better without and the amplification factor is not affected much anyway.
I used standard good quality parts, no esoteric stuff, the preamp sounds very good and is very quite...you might have to select the tubes for low microphony.
have fun
pieroh
Re: Parts list
I had a look at the parts list.
You could save some money, if you use motor run (paper in oil) caps or some nice PIO caps from Russia (ebay!) as coupling caps and only use one choke in the power supply.
Although I love to use chokes in audio circuits, even a simple CRC filter will also do the job because of the high PS-rejection of the current source.
pieroh
Hi,athos56 said:
I had a look at the parts list.
You could save some money, if you use motor run (paper in oil) caps or some nice PIO caps from Russia (ebay!) as coupling caps and only use one choke in the power supply.
Although I love to use chokes in audio circuits, even a simple CRC filter will also do the job because of the high PS-rejection of the current source.
pieroh
To Pieroh
Hello !
would it be possible in your schematic with an anode CCS, to substitute the cathode resistor by a string of leds, to obtain the same grid/cathode voltage?
Thanks
R.C.
Hello !
would it be possible in your schematic with an anode CCS, to substitute the cathode resistor by a string of leds, to obtain the same grid/cathode voltage?
Thanks
R.C.
Re: To Pieroh
I'm not pieroh , but - yes
you must use adequate number of LEDs for needed voltage , and adequate No of paraleled strings ; you don't need more than 5mA through one string
SY will advise you regarding exact current through led string
Ciu said:
I'm not pieroh , but - yes
you must use adequate number of LEDs for needed voltage , and adequate No of paraleled strings ; you don't need more than 5mA through one string
SY will advise you regarding exact current through led string
About CCS and leds
Hello !
No matter either if you are'nt Pieroh, appreciated answer !
I send to Pieroh, he has done the first part, CCS on plate, he could test the two different topologies, and give us any comparative comment.
I have in mind the simplistic schema SY posted here, a compound line preamp, first stage was grounded cathode , CCS on plate, a led on cathode ; second stage, a cathode follower with just a CCS on cathode !!! That's all !!!
I've seen different B+ with 12B4, in this case, with CCS and Leds (20mA, -13v ?), wich value would be optimum (the lower voltage, the simpliest to find caps for PSU )
Thanks
R.C.
Hello !
No matter either if you are'nt Pieroh, appreciated answer !
I send to Pieroh, he has done the first part, CCS on plate, he could test the two different topologies, and give us any comparative comment.
I have in mind the simplistic schema SY posted here, a compound line preamp, first stage was grounded cathode , CCS on plate, a led on cathode ; second stage, a cathode follower with just a CCS on cathode !!! That's all !!!
I've seen different B+ with 12B4, in this case, with CCS and Leds (20mA, -13v ?), wich value would be optimum (the lower voltage, the simpliest to find caps for PSU )
Thanks
R.C.
Re: Re: About CCS and leds
Hi Pieroh,
Your CCS seems easy enough to implement with low parts count. I have been a happy 12B4 user for some time now, currently using plate chokes and LED at cathode. I'm going to try your CCS at the plate next and see what I get. DO the transistors get very hot (only the MJE350?)? Is it better I just attached them (it) to the chassis? Have you tried other CCS?
p.s. any difference between TMJE350 and MJE350?
cheers!
Hi Pieroh,
Your CCS seems easy enough to implement with low parts count. I have been a happy 12B4 user for some time now, currently using plate chokes and LED at cathode. I'm going to try your CCS at the plate next and see what I get. DO the transistors get very hot (only the MJE350?)? Is it better I just attached them (it) to the chassis? Have you tried other CCS?
p.s. any difference between TMJE350 and MJE350?
cheers!
pieroh said:
The TMJE350 appears to be similar to the MJE350. Different manufacturer with their own part number.
There should be no problem in this application.
There should be no problem in this application.
Thanks Ashok.
Pardon my ignorance. Can someone also explain what is the bottom BJT and LED doing? I guess the top one sets the constant current... Also the current through the LEDs seems a bit low?
Pardon my ignorance. Can someone also explain what is the bottom BJT and LED doing? I guess the top one sets the constant current... Also the current through the LEDs seems a bit low?