AmpsandSound Amplifiers and Speakers builder

Thanks @perogie, you’ve been a huge help to me with your advice on tube rolling. And thanks for not telling me the name of your expensive 5u4g - I’d rather not know, LOL.

3 Likes

You’re welcome!

That sounds like the appropriate game plan, and I have the same goal.

I defer to @perogie on rectifier matters as he is a rectifier whisperer.

3 Likes

Hi all. Hoping to get some input from our residents experts here.

I found a great combination of tubes for my Mogwai SE. Sound is clean, dynamic and full of details and textures; not fatiguing and not too rounded for my ears
Russian 5U4 (stock) + Tung-Sol 6SL7GT (stock) + JJ KT88

There is a tad of hum that seems to go away as the tube fully warms but i sense that it’s not completely black. Would a 12au7 w/ adapter play well here? Would it help with the noise floor?

3 Likes

Nice and thanks for sharing.

Yes, a 12AU7 with adapter should help, and is what I use with high sensitivity headphones. Switching to less powerful 6L6GC power tubes can help also, but less so.

2 Likes

Great. Thank you. I will try a 12au7 and see if that helps.

Prior to switching to the KT88s I was running Tung-Sol 6L6GC (stock) but found it to be a tad bright on some tracks. Still very dynamic but KT88 seems to be a slight more refined.

3 Likes

Welcome to the 12au7 collectors club. There seem to be a few of us (the majority with ampsandsound amps, as far as I can remember), hopefully not competing over the same tubes and driving the prices up. :grinning:

5 Likes

:slight_smile: I think I’ll stick to the less rare tubes for a while longer. Trying to find a combination of form factors that suites my taste then changing up brands/versions later. It’s soo hard to be slow and meticulous when it comes to trying tubes but I’M TRYING! :face_with_head_bandage:

3 Likes

Tell me about it. I’m trying to get less rare tubes too, just to get a feel what works for me, and I’m also trying to be slow and meticulous, and not overwhelm myself by ordering 10 tubes at a time. I’m finding that US tubes are a lot cheaper than European, even the rare ones.

I’m guessing you’re more knowledgeable about tubes than me, but we still face the same problems. It’s so hard to get recommendations from others because “it sounds great” has no meaning without context. We may have different amps, probably have different power and/or rectifier tubes in combination with the 12au7, and we may prefer different sounds. So I do a lot of triangulation, describing their sound compared to another tube, e.g. using a Baldwin/Ratheon 12au7 as my baseline, I can say that a Mullard 12au7 has more bass and less highs, a Mazda 12au7 has more highs, a Baldwin/Sylvania 12au7 is a little solid-statey and has more highs, but less than a Mazda, and an RCA cleartop has less mids.

The tube gurus like @perogie , @Wes_S and @bpcarb have been very helpful in giving me advice.

3 Likes

Not at all… I’m just trying things out based on what I’m reading here. And yes, the folks mentioned are certainly very knowledgeable and their posts have helped me out a LOT.

2 Likes

Ha. 6SN7 should also work as an input tube with lower gain, but hasn’t for me. If someone could please explore/verify, our collective 12AU7 supply should increase.

3 Likes

The 12AU7 is a killer tube, and the cool thing about it, is that there is a wide range of available sound signatures. Each maker does have a house sound, however as the years went by with slight variations in construction, some do sound better than others. A good rule of thumb is the earlier the better. There was some magic put into those tubes from the 50’s, that their latter versions just seem to lack. This magic I am speaking of, is having good inner detail, with a delicate touch, while sounding natural and organic. Once you hear this from a good NOS tube, it is impossible to go back to the lesser tubes. The latter versions of these tubes tend to be brighter/artificial and less organic sounding overall. Of course it depends on how good the gear is in the rest of the chain, whether or not you will hear the differences.

Here is an amazing resource for descriptions of lots 12AU7’s, that I agree with most everything said.

Happy hunting!

5 Likes

thanks for the link!

I already ordered BRIMAR CV4034 - 1970 Military Long Plate Prem from tubemonger but your comments are getting me jazzed. :grin:

And yes, i did splurge a bit after I said i wouldn’t do this… sigh. My first time on Tubemonger …

2 Likes

Nice man! That Brimar is an amazing tube, and I look forward to hearing your thoughts on them. I have nothing but great things to say about Tubemonger and their customer service is outstanding.

1 Like

Can the Kenzie Ovation and tube experts here confirm my understanding on 12S tubes and correct me if I’m mistaken:

I have the following tube types and I think I am ranking them in order of relative gain:

Raytheon 2C50 < 12SN7 < 12SL7 or 12SL7GT < Raytheon 2C52

My listening impressions and research thus far seem to confirm this ranking from least to most gain. I would also like to confirm if there are concerns with these tube substitutions. As far as I can tell, these tubes have similar heater voltages and the Kenzie performs well with any of them.

Thank you

4 Likes

Hi @Cryptowolf . I can confirm that above ranking except for 2C50 with which I have no experience, and all of my 12SL7 are GT so cannot confirm if there is a difference between those labelled otherwise. Makes me curious to try 2C50. My Ovation performs well with all the others but with higher or lower noise floor, which can be countered with a lower impedance jack. I sort of stopped rolling these days and just replace them when they go noisy…

4 Likes

FYI, here’s one suggestion against using 2C50.

The Raytheon 2C50 is a low-mu (9.5) dual power triode intended for aircraft control systems.
It has identical basing (8BD) as the 12SN7 but different electrical characteristics and I would not recommend using it as a substitute for a 12SN7.
The data’s can be found here:

http://www.wps.com/archives/tube-datasheets/Datasheets/Raytheon-DL-Q-7101-11-56-40M/12.JPG

6 Likes

I don’t have much to add beyond MokhaMark’s comments, other than you can read about the suffixes here, which should also apply to 12S_7.

http://www.audiotubes.com/6sn7.htm

6SN7GT / G:
This is the original version of this tube. It may be found in all three sizes of glass envelope. The Sylvania Tall Boy types have two triangular shaped plates facing each other mounted high in the tube, with either a top or bottom getter. Later GT versions were in a medium glass envelope with a green label and blackplates with bottom getter, sometimes called the “Bad Boy” 6SN7, and are sought after for their excellent sonics. The Bad Boy tubes are virtually identical to the military VT-231 from the early 1950s and are currently a less expensive alternative, but this could change as the Bad Boy fad catches on! A side note about Bad Boys, there were versions with 2 rivet holes in each plate, and versions with 3 holes. Both types sound identical. Don’t fall for the bogus story that only the 3 rivet hole types are the true “Bad Boys”! You will miss out on some great sound from the 2 hole type, since the 3 hole versions are more difficult to find, more expensive elsewhere, and don’t sound any different! I suspect the “3-hole only” story got started by my competition to justify charging a higher price for these tubes!
The early Sylvania GTA and GTB types had a top getter and silver flashed the entire top of the tube, sometimes called “chrome tops” or “chrome domes”. Many brands used this design, but the high mounted triangular plates means it most likely was made by Sylvania. An unusual twist on this design is the “Mouse Ear” Tung Sol 6SN7GT. This medium glass envelope tube has the high mounted triangular plates like the Sylvania, but also includes two large round clear mica supports at the top edge of each plate, parallel to the glass sides, looking a bit like Mickey Mouse Ears. These Mouse Ear Tung Sol tubes sound very nice and are worth seeking out. The early RCA “GT” types were usually in either a medium or short envelope and have a grey RF shield sprayed on inside the glass. The GE and KenRad types were similar, but the inner glass coating is deep black. These tubes usually have flat black plates, like large 12AX7 blackplates. The military versions of these are the VT-231 and are in very high demand today. Two rare early types worth grabbing at any price are the nickel base Sylvania 1940s vintage, and the early Tung Sol 1940s types with the black oval shaped plates, often found in blackglass. Both are very scarce and in high demand, which has depleted new old stocks. These have excellent sonics are are worth the extra price, if you find one. Tung Sol also made the SAME oval plate blackglass type for many other brands. Don’t hesitate to grab these, they are the same incredible tubes!

6SN7GTA / GTB:
This is the later improved version, and the improvements were primarily geared toward the TV chassis designers who demanded more max. plate wattage and voltage, where vertical circuits can put up to 1500 volt pulses at 7 watts on the plates. For hi-fi audio use, these improvements are meaningless. These are fine tubes, nonetheless. Most are found in the short glass envelope, but some brands like Raytheon used the Tall Boy style. Sylvania made tubes have the triangular plates mounted lower, and set at angles to each other, although some of the very earliest examples of the GTA types still used the dull blackplates facing each other. RCA used the flat black plates “sideways” to each other, and GE used the grey plates parallel to each other. The Sylvania types in demand have a large top getter patch. The earliest Sylvania GTA types have a green label and heavy top getter flashing extending down the sides of the tube. Watch for the very rare “Tall Boy” Sylvania 6SN7GTA, one of the few tall glass tubes made by Sylvania for this tube type, said to rival the military types in sound quality. The early GTB types are similar, but most have a yellow or red label, with some rare first production run tubes still out there with the 1940s green label. Watch for these tubes, made by Sylvania for other brands like Zenith, Philco, and Motorola. They are currently bargain priced and are the same fine tube as those with the Sylvania label! The versions from the 1960s have the getter just covering the top of the tube. All of these have the same black triangular plates and are excellent tubes. The GE types have a side getter and large parallel grey plates, and the RCA used both bottom or side getter. Some side and bottom getter types have 2 getter patches on top, right above the plates. This often happened during the factory gettering process with 6SN7 types that did not have top getters. It is not a sign of use, as the spots are usually bright silver and visible on tubes still sealed in the box. Most other vintage USA brands you find will have been made by these three vendors, and will be one of the above variations, regardless of brand on the label. A few were made with brown micanol bases, the RCA types being very dark brown, the GE types being a lighter, marbled brown. The brown micanol bases are most often found in military tubes, as they resist heat, moisture, and fungus/mildew growth. It was not uncommon, however, for manufacturers to repackage unsold military surplus tubes in “civilian” boxes and sell them to the general public. Many audiophiles prefer either the Sylvania chrome tops, the RCA, or the GE side getter over any others, even over the military or redbase types. These are all a great bargain now, and are sure to be rare and expensive tomorrow.
6SN7W / WGT / WGTA:
This type indicates a military spec tube that was not made for consumer use. These usually have extra support posts on the plate structure, heavy mica spacers, and brown micanol bases. These also have the famous triangular shaped black plates. They have been ruggedized to withstand shock, the brown low loss micanol base resists mold, mildew, and fungus growth, and they can withstand heat even if used upside down. The early Sylvania 6SN7W types from the 1940s had a metal collar around the base, then later a black base. These look internally alot like the early Sylvania GTA types listed above. Sylvania made these for other brands as well, including RCA. Easy to spot as they have the triangular blackplates facing each other in a short bottle, with a very heavy chrome top flashing extending down the sides of the tube. These are RARE and worth seeking out! The WGT and WGTA types all had brown bases. Only the WGTA types made in the late 70s and 80s reverted back to black bases then coin or wafer bases. These are all wonderful tubes, are long lived, and sound fantastic. No wonder they are fast disappearing from the vintage market.

4 Likes

Thank you for the info. I haven’t put many hours on the 2C50 tube. The person who sold it to me said it was a substitute for the 12SN7.

Adding a link to a spec sheet:

2C50

1 Like

I see the 2C50 being useful as an output tube versus an input tube. Very low amplification (10).

Same case using 12SL7 (70) versus 12SN7 (20). 12SL7 is more of an input tube (as is 2C52 {100}).

12SL7 can be subbed with 12AT7 (mid-60), 12AX7 (high-100) and 12 AU7 (low amplification - 20). Adapters required. You can interchange them but they have vastly different gains.

I’ve never used or seen a 2C50.

@MokhaMark

4 Likes

There’s an Encore listed on Ebay right now with a pretty nice array of tubes and a Jupiter capacitor upgrade. Pretty sweet deal
Encore on Ebay

3 Likes