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Little Dot Tube Amps: Vacuum Tube Rolling Guide - Page 244

post #3646 of 10502
Quote:
Originally Posted by gibosi View Post
 

 

Just an update. With all these wires flying around, this arrangement is rather susceptible to picking up RF noise. Fortunately, moving it a few inches often helps, and after all, since this is a prototype, it is very acceptable until I can build a proper adapter box.

 

Also, I am happy to report that I was able to straighten the bent pins on one of my Bugleboys and it works fine.... Life is good. :)

Ordered some  Bugleboys now just waiting to see the hum issue resolved so the end product is 100% ,also dont really want to cut or bend pins on those i rather use¨THE BOX¨ if safe.

post #3647 of 10502
Quote:
Originally Posted by gibosi View Post
 

Just an update. With all these wires flying around, this arrangement is rather susceptible to picking up RF noise.

 

Perhaps it should be noted that the ECC88/6DJ8 is prone to parasitic oscillation. You might want to read up on that.

post #3648 of 10502
Quote:
Originally Posted by Oskari View Post
 

 

Perhaps it should be noted that the ECC88/6DJ8 is prone to parasitic oscillation. You might want to read up on that.

 

Searching Google does indeed confirm this . However, I did not have this problem when I was cramming two 6DJ8s into 7-pin sockets. So I have to believe that what I am hearing is due to having all these wires out in the open, picking up ambient RF.

 

The only possible indication of parasitic oscillation I experience is when I turn the volume to zero, there is a ground hum. Therefore, I don't turn the volume lower than 1, and all is fine.

post #3649 of 10502
Quote:
Originally Posted by MIKELAP View Post
 

Ordered some  Bugleboys now just waiting to see the hum issue resolved so the end product is 100% ,also dont really want to cut or bend pins on those i rather use¨THE BOX¨ if safe.

 

If pin-9 is tied to pin-8, the ground hum problem is absolutely resolved. :)

post #3650 of 10502
Quote:
Originally Posted by Audiofanboy View Post
 

I wouldn't worry too much about heater current on our amps with double triodes. I used pairs of 0.3A+ tubes for months without issues (actually 0.3A heaters the minimum I would consider using for pentodes and single triodes, I often used 0.4 and 0.45A tubes, so a total of 0.9A), so 0.6 to 0.9A total driver heater current. The tubes we're looking at now have pretty petty heaters compared to what we've been using lol!

 

Interestingly, and despite the high gain of the 12AX7 tube I'm using, I find that the amp runs pretty cool compared to my previous standards. And that can't be a bad thing!

 

So, I guess we've reached a temporary conclusion on what to do with the shield on 6DJ8 tubes huh? Great, now I can get started on my soldering work.

 

Btw, I've just added a large amount of tubes of all types to my selling thread; just putting it out here in case someone's interested (there's a pretty large array of choices there lol).

 

http://www.head-fi.org/t/671097/little-dot-driver-tubes-ef95-ef92-ef91-more

 

There's also a thread below that one in the classifieds with my last DR supertubes; if anyone wants a "glory package" along with nice driver tubes... I might also have a MK IV SE unit for sale in a few weeks, if someone is looking for an even more glorious package lol. It's not mine, but my father's, who hasn't used it much apart from the preamp section and doesn't see the point of keeping it (so, it doesn't have loose driver sockets like mine does lol).

 

Hi AFB and anyone else listening...

 

Re filament/heater current draw, all was OK using 1 triode per channel, but if we want to use both per channel (ECC88 mode) are we going to be in trouble? If it CAN be done safely, as I am

so ignorant in electronic circuitry, I would be most grateful for advice re pin wiring...

 

Cheers!

post #3651 of 10502

I received a small package today and now I am in heaven.

 

6922 / E88CC made by Amperex in the US.

 

After spending a few hours with this tube, it has jumped to the top of the pile (of some 400 tubes!). :)  But even though I think I am in heaven, I still think I should try some 12AX7. So this morning I purchased a Tung-Sol JTL 5751. The 5751 is a premium version of the 12AX7. However, the mu (gain) was lowered to 70 and the current was raised to .350 amps, compared to a mu of 100 and .300 amps for the 12AX7. Supposedly this was done to extend the lifetime and reduce microphonics and noise.

 

But for now, it's time for me to turn the volume up and go back to heaven.... :)

 

post #3652 of 10502

5751 is really a little different from the ECC83 though there are certainly many / some simularities. I have an amp that uses 5751 that doesn't use ecc83. It also uses separate E182CC and 5687 that many often consider similar also. 5751 are cetainly a good tubes (try RCA commands, Syvania Gold Brand and GE 5* also) to look at further when correctly used / biased.

 

The Amperex US E88CC (6922) are certainly excellent tubes. Do look at the European 6922 however which I feel are better again, as are CCa, CV2493, E88CC-01s. However even the basic Mullard / Amperex EC88 / 6DJ8 from europe are excellent and often over looked. It is funny we started off with the cheapest Russian 6J5Ps and have made our way to Amperex 6922s! Don't you just love the LDs.

post #3653 of 10502
Quote:
Originally Posted by Nic Rhodes View Post
 

5751 is really a little different from the ECC83 though there are certainly many / some simularities. I have an amp that uses 5751 that doesn't use ecc83. It also uses separate E182CC and 5687 that many often consider similar also. 5751 are cetainly a good tubes (try RCA commands, Syvania Gold Brand and GE 5* also) to look at further when correctly used / biased.

 

The Amperex US E88CC (6922) are certainly excellent tubes. Do look at the European 6922 however which I feel are better again, as are CCa, CV2493, E88CC-01s. However even the basic Mullard / Amperex EC88 / 6DJ8 from europe are excellent and often over looked. It is funny we started off with the cheapest Russian 6J5Ps and have made our way to Amperex 6922s! Don't you just love the LDs.

 

Thanks for your comments. I do in fact have my eye on a GE 5751. And while I would really like to get a Sylvania Gold Brand, the prices I am seeing are way too steep for me.

 

And I agree completely regarding basic ECC88 / 6DJ8. As a "bottom feeder", I managed to obtain Mullard, Amperex (BugleBoy, A-frame Orange Globe and red-label), Siemens (both ECC88 and PCC88), Reflector 6N23p, Tesla PCC88, and GE 6DJ8. Even though for the most part, these were all "well used" tubes, and cheap, I figured that they still have at least 100 hours life left in them, which would be enough for me to get a handle on their sound. And for sure, all of these are excellent tubes. However, in the end, the Amperex BugleBoy is the one I kept in my amp.

 

So it seemed logical to assume that I should probably seek out an Amperex 6922, either Holland or US made. Ultimately, my final decision was dictated by price. I was able to get these Amperex US tubes at a great price, and I grabbed them.

 

And of course, I will keep an eye out for great buys on other European 6922, CCa, CV2493, E88CC-01s. With patience, I am really hoping that I can find a great buy on a German-made premium Telefunken, Siemens or Valvo. But these tend to be very pricey, so I am prepared for a long wait.....

post #3654 of 10502

Patience always delivers, I have bought 4 Siemens NOS boxed CCa recently for £50 each ($80US), Although not 'cheap' it is a fraction of what many CCa can  go for. Even better bargains to be had on CV2492 / CV2493 and E88CC-01s to be had which are often mislabeled or not recognised for what they really are. If you don't mind used tubes, then the saving escalate on these tubes which can have some really long lifetimes (10,000+ hrs on th some european ones are common enough). Also look at the 7 range (7DG8) with a slightly different heater. They warm up slower but should work fine here and are much cheaper! [7v as opposed to 6.3v]. There are also another class of tubes which are interesting which are the wire ended double triodes. These are easily soldered to 2 vector 7pin socket saver making conversions easier.

 

CV4069 premium 13D3

CV4033 premium 12AT7 / ECC81 [CV4024 with wire leads as opposed to pins]

CV4034 premium 12AU7 / ECC82 [CV4003 ditto]

CV4035 premium 12AX7 / ECC83 [CV4004 ditto]

CV4109 premium 7308 (6DJ8 / ECC88 like if you don't know it but up a level)...

 

these used to go for peanuts but certainly the latter now are more sought after.


Edited by Nic Rhodes - 10/23/13 at 10:11pm
post #3655 of 10502

Got my Telefunken 12AX7/ECC83 with ribbed plates in the mail this morning.

 

Expensive but a pretty good pick, considering. Pretty much full logo and silk writing (infamous for wiping off real easily) and even the small date codes (uc: 11-1959).

 

As they were supposed to, these are used but obviously super strong tubes. They give about the most gain I've ever had in my amp (lowest necessary volume levels, actually).

 

Critically speaking, I can't say, both from the first listen and after two hours of listening, that these are perfect tubes. I'm starting to understand what people mean by 6DJ8 tubes being "superior" to 12Ax7 types all things considered. These Tele tubes are awesome but not god tier, despite being pretty close to the best you can find in the 12Ax7 families.

 

Still, I'm not trying to make it sound like they're bad, it's quite the opposite in fact; I'm just giving truthful impressions in all absolutes. Like I said, these are great! People say they're "thin and airy". While I get the airy part, these are definitely not thin; if anything they have a pretty thick and creamy (not warm) midrange and tight deeeeep controlled bass (the most infra I've ever heard on my amp, and that's saying a lot). Highs are definitely well extended (the Tele reputation), without a hint of sibilance or piercing pain like some people say. These tubes do "come on strong" depending on the types of music you're listening to though. Since they're very balanced and extended, the music can kind of spill all of its guts at you in ways you're not used to.

 

They have this odd sense of deep detail and control, but at the sense time they make you feel like you're not hearing the last word in resolution or focus. It's weird, you hear everything but it all sounds so breezy and soft that you don't think you're hearing the absolute maximum of details, but you actually are... You'd have to try it to get what I mean.

 

Compared to my EI 12AX7 with Tele smooth -later- plates, the genuine ribbed Tele have more energy and extention. The EI are warmer and more "harmonically rich" like the guitar crowd says, probably a bit less detailed, though like I said the details on the ribbed Tele don'tt sound like details, whereas details on the EI sound like you're getting pretty good resolution and focus. I know, I'm explaining this poorly...

 

Anyway, very nice tubes the ribbed Tele are, but I'm still quite fond of my smooth plate EI. I'll give my final comments when I get a chance to AB both directly. Unless I get my Orange Globes first, obviously lol.

post #3656 of 10502

I got today 3 different 6DJ8 tubes. Westinghouse made in USA -63, Amperex made in Holland -74 and Voskhod 6N23P -84 with rocket logo. All of these need pin 8-9 connection to get rid of hum. I found little praise to 6N23P from internet: http://app.audiogon.com/listings/tubes-nos-voskhod-rocket-logo-6n23p-6h23n-giant-killers-only-35-a-pair-2013-05-16-accessories-32828 I do not have CCa:s to compare and not going to get one, i have some different plans...


Edited by Artsi - 10/24/13 at 9:21am
post #3657 of 10502

I am getting ready to build adapter boxes for the double triodes. My thinking is to build two boxes, one for 6-volt tubes, and a second one for the 12-volt tubes. In this way I can keep it simple and eliminate the switch.

 

So.... I have a few questions for those of you who have more experience with projects such as these. First, I need to buy a 9-pin socket. It appears that there are two types, one for circuit board mounting and one for chassis mounting, so obviously, I need to buy the latter. But I do not know how to securely mount these sockets onto the box in such a way that they can sustain the considerable stress of inserting and removing tubes. Some have mounting flanges to allow the socket to be secured with screws, but I don't know I can use screws with a plastic box. Looking closely at Artsi's box, I don't see any screw heads, so I do not how know his socket is mounted.

 

Also, I notice that there are gold plated sockets. But I am wondering if it is harder to solder wires to gold-plated metal?

 

And what kind of connecting wire would be best? Solid core? Stranded? Gauge?

 

Thanks!


Edited by gibosi - 10/24/13 at 9:46am
post #3658 of 10502
Quote:
Originally Posted by Artsi View Post
 

...............I found little praise to 6N23P from internet: http://app.audiogon.com/listings/tubes-nos-voskhod-rocket-logo-6n23p-6h23n-giant-killers-only-35-a-pair-2013-05-16-accessories-32828 I do not have CCa:s to compare and not going to get one, i have some different plans...

 

According to this reviewer, Voskhod 6N23P manufactured from 1974 through 1980 are quite good:

 

http://www.head-fi.org/t/549508/schiit-lyr-the-tube-rolling-thread/8595#post_9625620

post #3659 of 10502

Plastic box is pretty hard. I glued socket with epoxy to it. Used about 20 gauge stranded wire. Don't know what is best. 

post #3660 of 10502
Quote:
Originally Posted by gibosi View Post

According to this reviewer, Voskhod 6N23P manufactured from 1974 through 1980 are quite good:

http://www.head-fi.org/t/549508/schiit-lyr-the-tube-rolling-thread/8595#post_9625620

I would second that, adding the older the better generally. Plus there are two styles in this era. I am sure I have some 1972s however.

Edit post says much the same outside 1972 bit!
Edited by Nic Rhodes - 10/24/13 at 11:58am
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