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Posted new design: "Jonokuchi" destop amp - Page 4

post #46 of 52

First Tube Amplifier build but after deciding on the "Jonokuchi" destop amp as a first build I haven't been able to find any recent updates form other builders, I have some questions to be answered and hopefully will find some help here - I'm looking forward to getting the PCB soon so I can get started. 

 

 

 

 

 

First question is about the #6-32 x 1/4" standoffs for supporting the PCB, Should the standoffs be metal (which I'm assuming would ground the PCB to the chassis) or Nylon to prevent grounding the PCB ?

 

 

Second - Would a pair of Sylvania GE 6EM7 tubes be a suitable replacement for the 13EM7 13v filament tubes ? I haven't been able to find many 13EM7 tubes and was wondering if there are any tubes that could be used as replacements ?

 

 

Any input on better quality replacements for C5 and C6 - 0.1uF 630V coupling capacitors ? I've been looking at the Obbligato Gold Premium Capacitors 

 

 

Last - I'm thinking about a minimalist chassis design with a cleaner look, Would it be possible to conceal the three transformers inside the chassis if kept away or shielded from the PCB ?

 

 

 

 

Also for anyone who may be building this project soon here's one update for now on the Jonokuchi BOM as this part is no longer available from Mouser -

 

 

D1 - Fairchild Bridge rectifier 2A 50V - 3N253  (Mouser Part # 512-3N253) is no longer available so I'm using the following in it's place 

 

Mouser Part #:
625-2KBP005M-E4
Manufacturer Part #:

2KBP005M-E4/45

Manufacturer:

Vishay Semiconductors

Description:

Bridge Rectifiers 2.0 Amp 50 Volt

 

 

 

 

 

 

 

 

 

 


 

 
 
post #47 of 52

First Tube Amplifier build but after deciding on the "Jonokuchi" destop amp as a first build I haven't been able to find any recent updates from other builders, I have some questions to be answered and hopefully will find some help here - I'm looking forward to getting the PCB soon so I can get started. 

 

 

 

 

 

First question is about the #6-32 x 1/4" standoffs for supporting the PCB, Should the standoffs be metal (which I'm assuming would ground the PCB to the chassis) or Nylon to prevent grounding the PCB ?

 

 

Second - Would a pair of Sylvania GE 6EM7 tubes be a suitable replacement for the 13EM7 13v filament tubes ? I haven't been able to find many 13EM7 tubes and was wondering if there are any tubes that could be used as replacements ?

 

 

Any input on better quality replacements for C5 and C6 - 0.1uF 630V coupling capacitors ? I've been looking at the Obbligato Gold Premium Capacitors 

 

 

Last - I'm thinking about a minimalist chassis design with a cleaner look, Would it be possible to conceal the three transformers inside the chassis if kept away or shielded from the PCB ?

 

 

 

 

Also for anyone who may be building this project soon here's two updates for now on the Jonokuchi BOM as these parts are no longer available from Mouser - 

 

 

C1,C2 - 1uF 100V film cap 5mm LS  Wima (Mouser Part# 505-MKS21/100/10) using the following in it's place 

 

VISHAY-RODERSTEIN

MKP-1837 Metalized Polypropylene

Film Capacitor

 

http://www.partsconnexion.com/capacitor_film_visrod.html#14846

 

 

D1 - Fairchild Bridge rectifier 2A 50V - 3N253  (Mouser Part # 512-3N253) using the following in it's place 

 

Mouser Part #:
625-2KBP005M-E4
Manufacturer Part #:

2KBP005M-E4/45

Manufacturer:

Vishay Semiconductors

Description:

Bridge Rectifiers 2.0 Amp 50 Volt

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


 

 
 

 

post #48 of 52

I've got the PCB for this kit almost fully populated, waiting on tube sockets (got a couple of different styles to try) before cutting the top plate.  I've also left off the switches and jacks on the front edge, thinking of doing a slightly larger case so I'll need to adjust the spacing of the front controls.

 

I didn't realize until I started this post that this is kind of a necro-thread; anyone built one of these kits lately?

post #49 of 52

This build was a fun one. And requires patience since ordering the transformers took about 6-7 weeks for delivery. Well worth it. Lots of power, and sounds great. Anyone thinking about building one, go for it. Tubes are still readily available if you know where to look. Check antique radio supply or vacuumtubes.net

:beerchug: 

post #50 of 52

So kool! Thanks for sharing yet another neat amp!

post #51 of 52

Hey Guys,

 

Thank you Mr. Millett for creating such wonderful projects for us do to. Just bought all the parts, and I guess the transformers will arrive in 6-8 weeks. So excited, this is my first DIY project. I have a Computer Engineering degree, but nowhere close to that of a EE, so just a bit nervous about the high voltage. If you guys don't mind, I have a few questions:

 

1. What gauge of wiring should be used for the speaker binding posts to the PCB, along with the RCAs?

 

2. I see that HighFlying9 added a power light to the project. If I wished to add an LED, perhaps with an inline resistor to ground, where should I connect LED in terms of power to? It's been a while since I did some EE, software engineering is a bit easier, hehe. Using this as a reference: http://electronics.stackexchange.com/questions/32965/add-on-off-indicator-led-to-circuit

 

Please let me know if there is an easier solution.

 

3. It looks like both the 1/4" and 1/8" jacks can be placed on the board. I have the Sennheiser HD 650 and a BeyerDynamic DT 990 250 ohm. That's a combined impedance of roughly 550 ohms. Would the amp be able to drive both sets of headphones at once, one placed on the 1/4" and another on the 1/8"? 

 

4. I also have a set of Behringer Audio Truth 3030A (active studio near field monitors), which I connect using a direct input box (input is RCA, output is balanced XLRs to the speakers). Will I have any issues if I use the output of the 1/4" or the 1/8" to RCA to send the signal to the direct input box? Just curious as to your take on it.

 

5. I've been doing a lot of reading at: http://www.diyaudio.com/forums/tubes-valves/182269-jonokuchi-new-desktop-amp-little-red-board.html

It seems that spacing the OPTs by 2 or more inches away from each other helps the hum. I am thinking of going with acrylic as an enclosure, instead of a metal one. Will I have issues with the POT humming with acrylic, or any other issues?

 

Sorry if I have really dumb questions, just trying to learn a bit. Thanks for the help. 


Edited by guppysb - 1/17/15 at 4:06am
post #52 of 52

Built one of these myself,

 

I have to say that on my beyer T70's this amp struggles a bit. I have to run at close to full tilt to get the volume these headphones need.

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