[AnA1995]

I have a feeling that I may have connected all the components in a not so "grounding friendly" way.. especially the 1000uF capacitors. Kindly help to see if could spot problem with the connections if any as below. Thanks.

 

[Lifthanger]

in this drawing 24V is shorted to ground, but I don't think you actually did that when building

.

why are both 1000uF caps between 24V and ground. One of them should be behing the mosfet. It seems more and more likely, that I'm just unable to read a handdrawn schematic.

 

[fran]

All circuit grounds should come together at one point. All PS grounds come together at another point - usually just at the main PS caps. Then using heavy gauge copper connect circuit ground point to PS ground point.

Now you ahve 2 "star" grounds connected together. Lastly make up a circuit breaker for connection to chassis (safety) ground:

Wire 2 regular diodes 69 style ie back to back. Solder in a 15R 5W resistor in parallel with the 2 diodes. Lastly solder in a 0.01uF cap also in parallel with diodes. Connect ground point at PS caps to chassis through this.

This is what it looks like (see the part at the top right of this pic:



Once you get that sorted out, then come back to us if you still have a problem


Good luck!!

Fran

 

[AnA1995]

Hi fran, thanks for your detailed advise. Appreciated. Will try and get back the result here.

Quote:

Originally Posted by fran /img/forum/go_quote.gif All circuit grounds should come together at one point. All PS grounds come together at another point - usually just at the main PS caps. Then using heavy gauge copper connect circuit ground point to PS ground point. Now you ahve 2 "star" grounds connected together. Lastly make up a circuit breaker for connection to chassis (safety) ground: Wire 2 regular diodes 69 style ie back to back. Solder in a 15R 5W resistor in parallel with the 2 diodes. Lastly solder in a 0.01uF cap also in parallel with diodes. Connect ground point at PS caps to chassis through this. Once you get that sorted out, then come back to us if you still have a problem Good luck!! Fran

 

[Seaside]

If you need to redo your work, take all great advices so far into consideration.
And allow me tell you something for you.

- I think regulated PS is a must. I just tried unregulated PS for the heck of it, and I got hum. The hum went away when I put regulated PS back in. So please add some regulation circuit.

- Your PS must able to put out at least 0.65A at 24V, over 1A recommended.

- If I redo mine, I will use quality multi turn trimmer. Cheap ceramic trimmer I had on mine makes crackling sound whenever I turn it, and its hard to adjust.

- Mine, built on purf board, not cased yet, sometimes picks up noise when I move it arround. This should be taken care of when cased properly.

- Blue LED is high intensity type, Red LED is standard type. Make sure you don't use high intensity type Red LED.

Good luck.
Anyway this thread makes me want build another MHHA p2p way just like you did.

 

[Seaside]

Heck, I just realized I never took any picture of my MHHA picture yet. So I just took one. If you still want to see click here

 

[AnA1995]

Thanks Seaside for your precious advise. I will use the regulated supply eventually.

Yes, mine is about 3A at 24v. So, should be enough.
Quote:

- Your PS must able to put out at least 0.65A at 24V, over 1A recommended.

May I know what is your trimmer for? Mine is for the cathode resistance and I use a simple preset for it. Wondering will it get hot? I had used a normal preset for the LM338 regulator circuit and it gets warm. Need those better and higher value wire wound trimmer I think.
Quote:

- If I redo mine, I will use quality multi turn trimmer. Cheap ceramic trimmer I had on mine makes crackling sound whenever I turn it, and its hard to adjust.

I am using all high intensity type for both LEDs.... please advise the reasons for the need to use standard type? Noise? Thanks.
Quote:

- Blue LED is high intensity type, Red LED is standard type. Make sure you don't use high intensity type Red LED.

 

[FallenAngel]

3A @ 24V?! Are you using a cheap switching supply? I definitely recommend going with a half-decent transformer in a box, not switching supply, they're about $10-$15 usually.

Seaside - damn, I love looking at your builds, always draws me back to building stuff on perfboard (I usually MUST build at least an LM317 supply for something on perfboard once a month

)

 

[AnA1995]

No, it is a toroidal transformer not the switch-mode type. I only use the switch-mode PS for testing. Thanks.

Quote:

Originally Posted by FallenAngel /img/forum/go_quote.gif 3A @ 24V?! Are you using a cheap switching supply? I definitely recommend going with a half-decent transformer in a box, not switching supply, they're about $10-$15 usually.

 

[Zigis]

AnA1995 and Seaside, can you please measure, have you any DC on grid? With nothing playing and turning volume up and down, do you hear any noise?

I bulid samething like simple 6dj , but with 24V Aikido output with 2 x LM317.
It works, sound nice, i listen amp right now, but with input caps, because 200-300 mV on grid.

I don't now, how to fix it, i don't like idea - 2 caps in signal line.

I use with 24V 1A switching PS from Ebay:
BRAND NEW 24V 1A AC / DC Power adapter Power supply - eBay (item 280325831406 end time Aug-20-09 02:58:19 PDT)

 

[Seaside]

AnA1995.
It's not a heat issue or anything. That single turn trimmer I used was a crap. I want to use quality trimmer if I had to make it again, and I think multi turn trimmer would make me easy to adjust more accurately.

Why not high intensity type for red LED position? Because sijosae said so.
Vf of standard type is about 1.8~2V, and that of high intensity type is about 3~3.2V. This Vf difference could affect the voltages across the parts used thereafter. He suggested 1.2K instead of 1.5K if someone want to use high intensity type at red led position.

FallenAngel, always thanks for your kind words.

 

[Seaside]

Zigis.
What do you mean by DC on grid?

A Super-Simple 6DJ8 Headphone Amp - Head-Fi: Covering Headphones, Earphones and Portable Audio

Is it the amp you're talking about?

That amp is kind of similiar to earlier version of MHHA. They all are DC based and so there's DC everywhere. That's why there's output cap right before the headphone output. Mine measures 9.5V DC before output cap, less than 1mA DC after it. You shouldn't see much DC after the cap. Your output cap maybe is defective? I don't see why input cap has anything to do with DC in those amps. I hear no noise when playing with pot even at the max volume.

If the above is the amp you're talking about, I suggest you use 470~1000uF /35 or 50V at C103. 25V cap at 24V input is big no no to me. Cap should be 35V or 50V type. This cap is to keep some charge so that the charge stored in it prevents the amp from making banging sound when the power is turned on and off. About C102, use descent cap you have, for it directly affect the quality of sound output. I think 470uF do the job there.

Regarding the PS you linked, it looks like linear PS which is good, but can't see anything about regulation.

 

[Zigis]

Hi Seaside ,
yes this is A Super-Simple 6DJ8 amp I build, partly. Tube input stage is the same, output stage changed - 2 x LM317 as in John Brosky 24V Aikido output stage, see post 70:
http://www.head-fi.org/forums/f6/sup...67/index5.html

Yes I am talking about DC on grid, in amp's input. Thats why in Super Simple they use input cap C101.
In my amp on grid is about 200-300mV, and if I connect pot directly, without input cap, like in MHHA, there is noise wen turning pot. There are no noise on any position itself, min or max, noise is in moment wen you rotate pot, like in bad, heavy used pot (however it is new Alps), this is alway signal - DC on pot. DC come from tube, not from source, I check it.

Try to measure DC on grid with pot on max and nothing connected to input.

PS I linked looks like linear, but it is switching, without transformer, in description they say it too.

Amp sound good, but I don't like 2 caps in signal path - input and output. It is too much, one output cap is enough.

 

[AnA1995]

I am using the IEC socket with power ON/OFF switch include "Neon" light. Will the Neon light introduce some noise too? Anyone use neon light before? I remembered I had read someone using it without noise problem. Anyway, please advise if possible. Thanks.

 

[AnA1995]

Last night, I connected external power supply to drive tha amp. At the same time, I connected another power cable to the toroidal transformer and power on. However, the power supplied from the toroidal was not connected to power the amp. Just to test if there was any interferance cause by the toroidal trans. The result.... YES; it cause interferance.

So, redo the cabling may or may not help in eliminating the hum issue here. As maybe the toroildal is really too near the circuit.