[DKJones96]

There is always some sort of margin for error built into those voltage ratings so staying 1 volt above is just fine. I have a 35v I think 3300uF cap in there because they don't make very many 25v caps with a 10mm lead spacing until you get to stupidly high capacitance ratings.

 

[AnA1995]

This afternoon, I went to the usual electronic component selling mall and found one shop selling a cap rated 80v of 1000uf which has 10mm spacing between the leads. So, once my amp arrive, I will do a measurement of the supplied power supply if it stay at 24v. If not, I may change it to higher rated voltage cap just to be on the safe side. Higher rating prolong the life span of the cap I think. Thanks..

 

[Stevesebastianb]

Here are some photos of the very same 6DJ8 amp that I am building which is almost near completion, should be finished this coming weekend!

 

[DKJones96]

You do plan on using larger heatsinks than the ones you used on the 317s for the 310s right? You'll roast those 310s in no time if you use those.

You cheated! You did the casework first, I think the first 100 hours of mine's life was spent on a table top lol. Nice work so far, what input caps did you go with?

 

[Zigis]

Just read this tread. Very interesting amp, however many unnecessary parts.
R107, if you not use LED, R106, C105 too, don't now about C104.

And most important, I wonder no one notice this before - input cap C101 - absolutely unnecessary, even harmful for sound quality.
Amp owners, try to bypath input cap and tell us, what you hear.

I am thinking, maybe I can try to build something similar, but with Aikido output stage with 2 x LM317, instead of 2sk310

 

[DKJones96]

Are you sure it's unnecessary? The grid has a DC offset which some direct coupled players may not like.

I agree that R106 isn't necessary if you don't use the LED, however, if you want the LED to power up slower you can use a larger value for C105. The larger the value the slower it lights and dims when powering on. You could even get it to match the heater speed if you play with it enough.

 

[Zigis]

Yes, I am sure it's unnecessary in 99,9% cases, however I am not sure for what case reminding 0.1% are

You can see any todays tube amp schematics, headphones, preamp or integrated poweramp, you hardly find one with input cap before grid.

Just minute ago I made a check. I measure DC offset on input of my MJ 6n1p hedamp with pot on max volume. Wen I turn amp on, there was 1 mV on 1 sec, then, wen amp is working there isn't any DC ( jumping between 0.1mV and 0)

If LED is only for decorative purpose, not part of CCS or heater regulation, anyone is free to use or not to use it. I see folks reported amp work similar with and without LED.

I see at this amp only as at schematic, not planing to order board. Especially I like simple and clever heater powering, no need special regulator or large hot power resistor.
This is like in SS, only with widely available tube.

Are 2sk310 and LM317 as hot as SS mosfets?

 

[DKJones96]

The 310s run SS hot, easy. The 317s run pretty cool when you are using a 6922/6DJ8 but I tried with a 6N1 (not enough gain at these low voltages) and it had 450mA vs 300mA heater current at 6.3 volts and the 317s ran pretty hot in that configuration.

I tried everything with that 6n1. 48v it sounded much better but the 317s got too hot for comfort and were running past their 40v in-out difference spec.

Now that you mention it. I want to build a P2P version of this amp.

 

[AnA1995]

My biggest worry is the heat from those 2sk310. If it is as hot as Mosfet, I think I have to get a spacious chassis to house it with room for bigger heatsinks. But, the 2sk310 is on the PCB and thus limit the size of the heatsink we could use. Come to whose, will get additional heatsink to "join" to the existing one to increase the efficiency of heat transfer.

Maybe de-solder the 2sk310 and clamp them on the chassis for better heat transfer if really needed. See how once I got my set...

 

[DKJones96]

I put my 310s on the aluminum chassis with isolators using wires from the pcb.

 

[AnA1995]

I got the amp yesterday. Tested and the sound is better than my CMoy amp.

However, I have encountered two concerns here.
1) The "pick-pop" sound during ON and OFF of the amp. Is it common for this type of output Transformerless amp?
2) The heatsink is pretty hot for the 2SK310 MOSFET.

Humm...see how...

 

[DKJones96]

It does have a pop on startup. Since the tube has to warm up anyways I usually just turn the amp on when I get home and put my headphones on whenever I'm going to listen to them so it isn't a problem. Sometimes I never do listen to it and my headphones just sit there amping sound from shows or whatever I happen to be doing on the computer.

 

[AnA1995]

Thanks DKJones96, yes, the "noise" even happen by switching ON or OFF the main wall power. The noise is so powerful that it will definitely damage the headphone and our hearing. I am pretty concern. Read somehere a thermistor was use for such application. I am not sure how it is done. Anyone could advise. Thanks.

 

[DKJones96]

I've been trying to figure out a way to soft start it but can't come up with anything as of yet. The pop you hear is the output stage rushing up to bias and anything you do to slow that will cause the amp to sound different. Well, anything I've come up with anyways.

 

[cfcubed]

Quote:

Originally Posted by DKJones96 /img/forum/go_quote.gif I've been trying to figure out a way to soft start it but can't come up with anything as of yet. The pop you hear is the output stage rushing up to bias and anything you do to slow that will cause the amp to sound different. Well, anything I've come up with anyways.

Guess you may be trying to come up with a solution short of something like amb ε12 ? Because it's much the go-to piece for this sort of thing. It's proven & transparent SQ-wise, except for those that believe they can hear the affect of relay contacts. But I guess incorporating such thing would not make this such a "super-simple" amp any longer.

Otherwise its the pull the headphones plug bit during pwr on & pwr off for most (all?) direct/DC coupled output or capacitor coupled output headamps I would think.