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A Super-Simple 6DJ8 Headphone Amp - Page 13

post #181 of 471
3/18/09 at 1:24am
Thread Starter 
Quote:
Originally Posted by kansei View Post
I've decided to sell my first "super simple" to finance building a Bijou. It's on eBay if anyone is interested.
Finally happened to look at the auction, and - good lord! - you drove speakers with this thing? Dang, skippy.

OT, but I'm kind of surprised you didn't try selling it on Head-Fi first; I'd think someone here looking for a headamp would snap it up in an instant.
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post #182 of 471
3/18/09 at 5:20am
I used the power supply from 8Audio and also my own 24v power supply. No difference.
My cans are AKG K300, but also tried a pair of Philips inear plugs (SHE- something). The AKG's are familiar for producing a bit too much bass, but with this amp nothing much below 100 Hz.
For tubes I used the supplied tube from 8audio, but also some NOS Philips gold pins that I use in my KT88 push pull integrated amp.
For a source I use a DDDAC with 24 parallel TDA1543 chips and my Philips DVD 963 SA player.
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post #183 of 471
3/18/09 at 7:21am
Quote:
Originally Posted by Nemo de Monet View Post
Finally happened to look at the auction, and - good lord! - you drove speakers with this thing? Dang, skippy.
They're tiny speakers. I use two of the surround speakers in my "lab" and drive them with my Millett or the "super simple". HSU Ventriloquist VT-12

Quote:
Originally Posted by Nemo de Monet View Post
OT, but I'm kind of surprised you didn't try selling it on Head-Fi first; I'd think someone here looking for a headamp would snap it up in an instant.
I had mixed feelings about posting it here at first because of board rules - I didn't want it to look like I am running a business (which I'm not, just trying to scrape up project $). Also, I stink at negotiating and selling on eBay usually works out well for me.
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post #184 of 471
3/18/09 at 4:31pm
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Quote:
Originally Posted by biarritz View Post
I used the power supply from 8Audio and also my own 24v power supply. No difference.
My cans are AKG K300, but also tried a pair of Philips inear plugs (SHE- something). The AKG's are familiar for producing a bit too much bass, but with this amp nothing much below 100 Hz.
For tubes I used the supplied tube from 8audio, but also some NOS Philips gold pins that I use in my KT88 push pull integrated amp.
For a source I use a DDDAC with 24 parallel TDA1543 chips and my Philips DVD 963 SA player.
What value PIO did you replace C101/C201 with? Also, have you checked and made sure that R101/R201 are actually 1Mohm?

The only other thing I can think of is to try adjusting R110/R210 (the trimpots) and see if they make a difference; otherwise I can honestly say I'm stumped.
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post #185 of 471
3/18/09 at 7:05pm
Quick question: did you use insulating pads on the heatsinks? I don't think they are necessary, but I'm probably wrong.

Also, I almost finished soldering the parts and I just noticed my trimpots have an horizontal screw instead of a vertical one, and are not accessible. Meaning I'll have to order two vertical ones and delay completing the amp yet again, lol.
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post #186 of 471
3/18/09 at 7:38pm
I didn't use them. Actually, I realized yesterday that I didn't even apply thermal grease(oops) so I've got to come up with a way to get the right 310 unscrewed without having to desolder and remove the 317 in front of it.
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post #187 of 471
3/20/09 at 3:49pm
Thanks for all your feedback regarding my bass problem. Today I finally had the time to purchase some new parts.
I added the attenuated input with two 470k ohm resistor running to ground.
I changed the input cap from 0.1uF to 0.47uF
And changed the output caps to 470uF.
The first change with the resisters was the best so far. Bass slightly improved as well. Changing the caps did not improve things noticable to me.
I adjusted the trimpot to see what this improved. They were originally set to about 16 volts. Above 18 volt the soun starts to fade. I decreased to about 12v. But no hugh changes in the bass regions.
It sounds not that bad now, but still I would like some more bass to it.
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post #188 of 471
3/20/09 at 8:07pm

It lives!

I just turned on my Super Simple a few minutes ago and it works great! It actually sounds pretty nice, plenty of details and very nice mids, even with brand new caps that still need to settle. It might be placebo, but I think it has the potential to sound better than my boutique Starving Student, which has a fatter but less precise sound.

I used a NOS Russian 7DJ8 tube (got plenty of those and NOS Philips/Amperex 7DJ8 too) so I tweaked the LM317 resistors to serve slightly less current (2x150ma). I used boutique parts: Silmic II electrolytics, Obbligato film caps, and an Alps Blue Velvet pot. There's zero hum or noise.

Now I will have to concoct a case tall enough to accommodate the huge 1000uF Silmics, probably from wood and aluminum.

Edit: forgot the pic.

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post #189 of 471
3/20/09 at 8:19pm
Congratulations, Ludoo.

I just tried the Philips JAN ECG 6922 tube and it's by far the best tube I've ever heard in this amp. It's very light and airy. The mids and highs are incredible.
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post #190 of 471
3/20/09 at 8:25pm
Quote:
Originally Posted by kansei View Post
Congratulations, Ludoo.

I just tried the Philips JAN ECG 6922 tube and it's by far the best tube I've ever heard in this amp. It's very light and airy. The mids and highs are incredible.
Well, I can't wait to try my 7DJ8 Philips on it. I'm listening to it now, and it sounds in a different league from my SS. I'm really glad I built it.
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post #191 of 471
3/20/09 at 9:03pm
I'm about to build my second one. Just need some heat sinks, trim pots, a potentiometer and misc input and output connectors. Still trying to get a good deal on heat sinks, looking at eBay seller wonderco_buy79 who has some reasonably priced goodies.
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post #192 of 471
3/23/09 at 1:06am
Where do you guys have your bias set to? I've had to turn mine to where the flat spot on the trimpot is facing the 317 on their sides to get even sound from my phones. (might be an arrow on yours, depends on what pot you are using)

Can the tube really be that imbalanced?
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post #193 of 471
3/23/09 at 4:26am
Quote:
Originally Posted by DKJones96 View Post
Where do you guys have your bias set to? I've had to turn mine to where the flat spot on the trimpot is facing the 317 on their sides to get even sound from my phones. (might be an arrow on yours, depends on what pot you are using)

Can the tube really be that imbalanced?
My trimpots are turned about the same on the two channels. I have multiturn trimpots so it's hard to say, but when I set them up with the multimeter there was quite a bit of play in both directions before I found the right spot.
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post #194 of 471
3/23/09 at 7:44am
Quote:
Originally Posted by DKJones96 View Post
Where do you guys have your bias set to? I've had to turn mine to where the flat spot on the trimpot is facing the 317 on their sides to get even sound from my phones. (might be an arrow on yours, depends on what pot you are using)

Can the tube really be that imbalanced?
I've had some tubes turn up on a single channel only until I adjusted the trim pots. You can measure DC on tube pin #1 and #6 (connect a multimeter between the pin and ground) and adjust for the same voltage. The middle ground for my amplifier is around 20V, although I am unable to adjust some of the tubes I tried below 25v.

However, it's tough (impossible?) to hear the difference unless you're too low on one of the channels and fading out.
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post #195 of 471
3/23/09 at 6:25pm
Thread Starter 
Quote:
Originally Posted by DKJones96 View Post
Can the tube really be that imbalanced?
Yep, even if it's supposedly "matched". From what I recall from the old SOHA Mk. I threads, low-voltage amps like this use the tubes outside their intended design specs, so even with tubes that have been "matched" at more normal operating voltages, "your mileage may vary".

I still haven't installed trimpots in mine yet (too busy listening to it, and trying to debug a retarded USB connector issue on another project), and am just using, I think, 470ohm resistors in each side. So far most of the tubes I've tried haven't had any audible inbalance, and the one that did - a "matched" 6DJ8, actually - was slight enough that it was correctable with a little tweak of the Windows balance slider. Maybe I'm just lucky, but all the tubes I've measured have been within 1V, section-to-section.
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