Author Topic: EAR834P Clone Build  (Read 817 times)

Offline MusicMan_ZA

Re: EAR834P Clone Build
« Reply #15 on: November 20, 2020, 05:51:18 PM »
I have the Douk Audio version of the EAR 834P. If you guys need me to take photos of it "topless", let me know. Perhaps it could be of some help in terms of ideas,  layout, components, etc. Please note that I bought it factory assembled.

Thanks Ajay-L, it can only help.
What do you think of yours?

If I am not mistaken, there are a few differences between the red JIMS Audio and the Douk Audio boards, e.g.
the Red JA board has the valve heaters connected in series, so they need to be fed with 12.6V (and I am going for DC).

Currently trying to find one (a single) suppliers (seems impossible) where I can get all my components from, this year, without buying 1000 of each item I need 2 of, and not costing a King's Ransom. :-(

But the planning of the build is a lot of fun!


I love music - analog and digital. Even listening to the Blues makes me happy. During the day I coach and counsel, after hours I indulge in my second passion - listening to vinyl and restoring turntables. Some I keep, some I sell...

Offline MusicMan_ZA

Re: EAR834P Clone Build
« Reply #16 on: November 21, 2020, 12:24:24 PM »
I already have two questions!

1. Looking at the schematic, which also shows the two power supplies, the 12.6VDC for the valve heaters
is rectified from the AC in "full wave" fashion (this is how I always do it). However, the 250VDC HT power is only "half wave" rectified. Is there a reason for this, and must it be done this way, or can I build a "full wave" rectifier circuit?

(or am I reading all that wrong?)

2. On the PCB I can see where the incoming 250VDC (+) connects (going to (+) of the first 2 33uF 400V capacitors), as well as the incoming 12.6VDC (+) (going to pin 4 of the first valve - then out at V1-5, in at V2-4, out at V2-5, in at V3-4 and V3-5 is connected to ground on the PCB). However, even though there are many ground connections on the board, they are all connected / common ground. Does this then mean that the 250VDC (-) and the 12.6VDC (-) leads from the two power supplies connect to the same common ground on the PCB?

Thanks in advance  :thumbs:

I love music - analog and digital. Even listening to the Blues makes me happy. During the day I coach and counsel, after hours I indulge in my second passion - listening to vinyl and restoring turntables. Some I keep, some I sell...

Offline fredeb

Re: EAR834P Clone Build
« Reply #17 on: November 21, 2020, 05:20:28 PM »



1. Looking at the schematic, which also shows the two power supplies, the 12.6VDC for the valve heaters
is rectified from the AC in "full wave" fashion (this is how I always do it). However, the 250VDC HT power is only "half wave" rectified. Is there a reason for this, and must it be done this way, or can I build a "full wave" rectifier circuit?

(or am I reading all that wrong?)

The HT supply is halve-wave voltage doubler , probably used because transformer required it , so yes , build full wave HT supply as per usual .



2. On the PCB I can see where the incoming 250VDC (+) connects (going to (+) of the first 2 33uF 400V capacitors), as well as the incoming 12.6VDC (+) (going to pin 4 of the first valve - then out at V1-5, in at V2-4, out at V2-5, in at V3-4 and V3-5 is connected to ground on the PCB). However, even though there are many ground connections on the board, they are all connected / common ground. Does this then mean that the 250VDC (-) and the 12.6VDC (-) leads from the two power supplies connect to the same common ground on the PCB?


Yes , common ground , you could also elevate heater ground to ~60-70V above HT ground , which in my experience makes the circuit quieter .

 

...evolution is the gradual development and stratification of progressive series of wholes, stretching from the inorganic beginnings to the highest level of spiritual creation.
Jan Smuts

Online handsome

Re: EAR834P Clone Build
« Reply #18 on: November 21, 2020, 06:53:14 PM »
Heaters are in series so 37.8V required.

Offline MusicMan_ZA

Re: EAR834P Clone Build
« Reply #19 on: November 21, 2020, 07:53:38 PM »
Heaters are in series so 37.8V required.

 :nfi: I based my thinking on this: "The ECC83 / 12AX7 has a '9A' pinout, which has three connections to the two heaters. This means they can either be run in series from a 12.6V supply or in parallel from a 6.3V supply. ".

Thanks for the info!  :thumbs:
I love music - analog and digital. Even listening to the Blues makes me happy. During the day I coach and counsel, after hours I indulge in my second passion - listening to vinyl and restoring turntables. Some I keep, some I sell...

Online handsome

Re: EAR834P Clone Build
« Reply #20 on: November 21, 2020, 08:15:18 PM »
You are correct but in that schematic you have 3 valves, with 12.6V heaters, in series

Offline Ajay-L

Re: EAR834P Clone Build
« Reply #21 on: November 22, 2020, 01:17:15 PM »
Thanks Ajay-L, it can only help.
What do you think of yours?

If I am not mistaken, there are a few differences between the red JIMS Audio and the Douk Audio boards, e.g.
the Red JA board has the valve heaters connected in series, so they need to be fed with 12.6V (and I am going for DC).

Currently trying to find one (a single) suppliers (seems impossible) where I can get all my components from, this year, without buying 1000 of each item I need 2 of, and not costing a King's Ransom. :-(

But the planning of the build is a lot of fun!


In terms of sound quality, I really do like it, there is however room for improvement. It does have some of that tube magic and has a well developed soundstage. Pay attention to component choices, especially those in the signal path and the RIAA network. On my one, the RIAA network has silver mica capacitors (can be seen between the valves on the right, on the second last pic), so that's something you should consider putting in on your build. Also, if your one has the volume control, use a good quality potentiomenter or consider not including it at all, unless it's going to be doing preamp duties. On my one, the potentiometer is not a good quality one and does affect performance. I currently have it wide open, but will consider disconnecting that in the future.

Pics as promised below.

Exterior





PSU







Signal Section








Offline MusicMan_ZA

Re: EAR834P Clone Build
« Reply #22 on: November 22, 2020, 02:47:25 PM »
Thanks for the pics, Ajay-L - it does look good!  :thumbs:
I love music - analog and digital. Even listening to the Blues makes me happy. During the day I coach and counsel, after hours I indulge in my second passion - listening to vinyl and restoring turntables. Some I keep, some I sell...

Offline MusicMan_ZA

Re: EAR834P Clone Build
« Reply #23 on: November 22, 2020, 03:44:21 PM »
You are correct but in that schematic you have 3 valves, with 12.6V heaters, in series

Thanks Handsome, info appreciated. :thumbs:
I love music - analog and digital. Even listening to the Blues makes me happy. During the day I coach and counsel, after hours I indulge in my second passion - listening to vinyl and restoring turntables. Some I keep, some I sell...