drdna wrote:

I also use the 6SN7-2A3 DHT for my system (except subwoofer). Did you use the Electrocubes for the coupling capacitors? Was the internal wiring regular copper? The coupling capacitor is critical, of course. Also, I will say that silver wire, which many people hate: the fact is that it is a better conductor. My opinion is that the silver wire reveals a problem that is creating harshness and brightness from the OTHER parts of the system, perhaps from bad electricity as well. In my amplifier, careful choice of the coupling capacitor and using silver wire in the signal path corrected the problem of the sound being syrupy like in a dream where you are running is low motion.

I did not do anything with San-Audio SV-2A3 amp. I juts built to it original state. The parts in there are crap, including the coupling capacitor, I did not change anything, I need to order the parts to do the change but am not convinced that I will stay with 6SN7. Are you driving your 2A3 right from 6SN7 or you use the second part of 6SN7 as a direct-coupled second gain stage? I would like topologically to stay with 2 channels only as I do not need a lot of gain, quite opposite but  I might keep the 6SN7 – it is a good tube. I might even drop the cap from cathode bias in 2A3 – it shell kill all gain but it is what I might need. I do not know yet.

Can you post or explain the topology of your 6SN7-2A3?

I kind of disagree with Adrian. The wire, the coupling caps, the cathode resistors and many other things are superbly important but it is after the strategic topology is settled. In my view caps, resistor, wire and other things are responsible for the sounds, the minor things, the tactics. The big picture of the sound, the strategy is made by the macro topology. I properly, or I would say sonically-pretentiously, designed amp would sound strategically -properly with any, even with very poor parts and even with not the best assembling methods.

At this point I am not convinced that I will keep the topology of my experimental DH SET, there is a lot of thing that I do not like it.  This amp is Sun Audio SV-2A3. It is very straight forward and simple design.

It is up and running with all default parts, which are very bad I have to say. All tubes are Sovtek, I just took a liberty to put there 3A2 from WWII. I have no good rectifiers and no good 6SN7 and I have order a pair. Still I do not wont to invest a lot of efforts to make this amps to sound better and I most like will go two stage. I have no need for 40 time gain in driver stage. I might get rid of the second stage, make some other changes, or most likely will go with my 6E5P in a driver stge.

For a time being I would like to live with this amp as is for a few days. I drive with it my Tannoy Red full range. In addition I have the channel #3 from my Super Mils is the Injection channel, or a fill range Melquiades amp. So, I might run back and forth two full range amps: 6SN7-2A3/6A3 vs. the 6E5P-1/26C33C into the same speaker. I actually did it today, it was interesting. In a few days the better tubes will came and I might try to change the DHT amp for more sane operation.

So, far the only advantage that I see in my DHT is it boutique quality…

Romy the Cat wrote:

Can you post or explain the topology of your 6SN7-2A3?

Romy the Cat wrote:

The wire, the coupling caps, the cathode resistors and many other things are superbly important but it is after the strategic topology is settled. In my view caps, resistor, wire and other things are responsible for the sounds, the minor things, the tactics. The big picture of the sound, the strategy is made by the macro topology.

Romy the Cat wrote:

The 2A3 it feels like heavy-sunk time of tube and it constantly run a fully submerged. It has seriousness but it does not look at this point that it has lightness.

drdna wrote:

If you were using, for example, the Kron KR 2A3, you would not be commenting on the sluggish liquid sounds, and it would be very much more competitive with the Melquiades I am sure of it. Adrian

I always was kind of afraid of it. Any single zillion years tube I see is “NOS in box”, “measured as new” or “never work”. So, I wonder where those uses up old tubes are gone? Do people trash them or juts sell them “as new”. As many old tubes I ever bought with quoted transconductance figures never were the same after I received the tubes I am not even talking about “match tubes” what is always is a pure BS, they never matched at the necessary for me operational parameter, or gain.

It looks like that with DHT tube it is even worth. I measured the 2A3 and 6A3 that I have and they are so much off the specks what that it is not even funny. When I buy Russian 6C33C then they measure whatever they want then it is fine as they cost nothing. Those DHT tune are expensive but the same crap quality wise – very said. Looking at this I might understand Lamm who sell 6C33C for $100 per tube, assuring it compliance with specs.

Funny, funny but those 2 47uf capacitors are the only eminent the worth to keep in this kit – they looks like very good polypropylene caps. I also a person who go uselessly go for chokes with high DCR not lover. Anyhow, I am not changing any magnetics in there. This kit is an opportunity for me to discover the necessary for me topology and I less concerned with parts at this point. Probably better tubes, better cap in cathode bias and better coupling cap is something that I might change as it will stay anyhow. The driver stage in the San-Audio is really makes me hectic – it has a gain of phonostage. Adrian was right when he got rig one stage in his kit. I would like to do the same but I did not desied if I will keep the 6SN7 of to put in there 6E5P.

I was considering to get the adaptor and to run my 6E5P

http://www.guitarcenter.com/Groove-Tube-Stubti-Tube-1-6SL7-to-12AX7-Octal-to-9-Pin-Adapter-212240-i1389751.gc

but the original tube sockets in the Sun Audio kit just horrible (the worse I even see!) and need to be replaced. If I do so them I might as well pit the 9-pin socket and close the book on 6SN7. Still, sine I have no gain the drive might be DHT as well… I do not know year and frankly I have no a lot of sense of identity how this amp sound as is.

Dealing more with Sun Audio SV-2A3 kit it amassed me how bad the kit was. The guys made very cheap, in fact I hardly believe that this company has anything to do with Japan – it looks more like K-Mart level of amplifier. I heard a number of very positive comments about Sun Audio kits, well but who heard from me that the people in audio are mostly Morons…

Anyhow, I trashed everything that comes from Sun Audio besides the chassis, transformers and power resistors. I also got rid one gain stage on 6SN7. I have no idea what they make gain without power but it is another subject. To build the Sun Audio kit took 3 hours. To rebuild if in my way with my parts took 30 min. I was listing it and I did not really like what I heard. It is not that the parts were bad or wires were not “silver enough”. It was all together juts some kind of “Ordinary Sound”.

I was not pleased and I decided to go for what I know/ I got rid of the 6SN7 and put my 6E5P with cathode bias in the driver stage. I did not like the sound as well, in fact I like it even less then with 6SN7. Then I grounded the 6E5P and put it in more Milq-like configuration. I end up with 360V on B+, 15K plate load, grounded cathode, 160V on plate and -3.5V on grid via a series battery. It was slightly better but still I did not like sound.

I recognize that I say “I do not like sound” but I can’t say anything more spastic. All of the sound that I get from it is not right. So, I figured that it is most likely I have no speaker to use with this amp. The Tannoy Red are syrupy crap and I hear nothing with them. I need just another more or less full range speaker to evaluate the way how I might be used the DHT tube to drive my MF channel. I did not drive with the new 6E5P-2A3 Milq-Sun-Audio my MF channel as I would like to make the amps its good and then to apply the presumed success of my Sun-Audio amp to my MF channel with DSET-type transformers. (Most likely it will be inner-stage transformer)

So, with absent of the right speaker I will put the Milq-Sun-Audio journey on hold. This week my mashie pals me to fins the Mini-Me speaker and it might be good for get “clean sound” out of the Milq-Sun-Audio. So, will see how the Mini-Me will turn out.

Now about the contemporary production of 2A3 . Adrian, you proposed the KR tubes as good contemporary tubes:

http://www.kraudioproducts.com/Kr/ProductDetail.aspx?CatID=13&ProductID=114

There are also the Emission Labs:

http://www.emissionlabs.com/datasheets/EML2A3-mesh.htm

and Sofia Electric

http://www.sophiaelectric.com/pages/se/2a3.htm

Did anyone have any experience with them?

Romy the Cat wrote:

I was listing it and I did not really like what I heard. It was all together juts some kind of “Ordinary Sound”. I recognize that I say “I do not like sound” but I can’t say anything more spastic. All of the sound that I get from it is not right.

Romy the Cat wrote:

Now about the contemporary production of 2A3 . Adrian, you proposed the KR tubes as good contemporary tubes. There are also the Emission Labs and Sofia Electric. Did anyone have any experience with them?

be wrote:

Could you tell a bit about how does this: "I end up with 360V on B+, 15K plate load, grounded cathode, 160V on plate and -3.5V on grid via a series battery." sound as compared to the normal Milq bias?

I did the following.

As a battery I use 3.5V Lithium single cell from computer supply. I did not build the Milq-type bias on the 2A3 amp and I can’t compare Milq vs. Battery bias on this amp. In a past, when I made the first Milq I did experiments with Milq vs. Battery. I do not remember the details already but obviously the Milq bias won. With this 6E5P-2A3 amp it looks like the Battery bias is more interesting then cathode bias. However what made me pissed is that the magnitude of details behind that “more interesting” has completely escaped me as my speakers do not handle any “fine moments”. The batteries are a tricky thing. Theoretically battery is an always charged capacitor, so in my case the signal flows via this capacitor. It would makes to compare the battery with fixed bias of non-Milq style, and perhaps a different type of batteries but I really can’t do it with my current full-range speakers.

drdna wrote:

I think this 2A3 must have a specific set-up to sound its best. You have not found it yet. To begin with and familiarize yourself with the sound of it, I suggest sticking with the topology that has been tested by amplifier designers, since they have tried many configurations before releasing their design. Let them do the work for you. Get to know it before a lot of experimenting. It is like swimming in the ocean at night.

The only change that I made (and I do not know at this point if it was a good change) was the change of the driver tube from 6SN7 to 6E5P. Objectively the 6E5P is way better driver then driver. In fact of you insist that I need to “sticking with the topology that has been tested by amplifier designers, since they have tried many configurations before releasing their design” then the 6E5P way more used tube then 6SN7 as a driver. The 6SN7 is used since 1940 and there were tones of amps built with it where the 6SN7 was a driver, mostly in 3 stages design. When 6E5P was “discovered” for audio use in 1999 than it would be very educational to look what Russians designer and DIYer use as driver. (I say Russians become 6E5P is very popular in there and conceded the king of the drivers). Since 1999-2000 no one use 6SN7 type tube anymore as everyone switched to 6E5P. The 6E5P is objectively ultimate 2 stage driver. It has 10 times more gain then 6SN7 (30 vs. 20 on 6SN7) it can push much more current (3.5W of max single plate dissipation on 6SN7 vs. 8.5W), has much lover plate impedance (7kOhm for 6SN7 vs. 1kOhm), and has higher bias that is very important for sources that swing a lot of voltage foe 2-stage amps. I mean objectively the 6SN7 is not even a competition for 6E5P as they are different level of drivers. Interesting that they were used for the very same purpose – vertical-deflection for TVs and oscilloscopes – it was exactly where Dima discovered it. Anyhow, I think if the 6E5P-class tube was able since WWII as 6SN7 then you would never see the 6SN7 to drive 2A3.

Saying all above I have to aphesis that I DO NOT MAKE ANY CLAIMS about sonic characteristics of 6SN7 vs. 6E5P. I know the 6E5P/6E6P very well but I never played with 6SN7. In fact it shell be a good tube and I heard a lot of good sounding devises with it. Still, as an universal driver and using the only objective data the 6SN7 is different class of driver that not even rivalry with 6E5P/6E6P. It would be interesting is somebody do sonic comparing of the 6E5P/6E6P vs… anything else indirect-heated out there.

Romy the Cat wrote:

I do not know what you mean by “specific set-up” and what San Audio did is very orthodox use of 2A3 and I did not change it. The only change that I made (and I do not know at this point if it was a good change) was the change of the driver tube from 6SN7 to 6E5P. Objectively the 6E5P is way better driver then driver.

Romy the Cat wrote:

I was not pleased and I decided to go for what I know/ I got rid of the 6SN7 and put my 6E5P with cathode bias in the driver stage. I did not like the sound as well, in fact I like it even less then with 6SN7.

I am taking about coupling capacitor between driver tube and the DHT. There are zillion way to do it and no one said that they need to be used. No one proved yet that a very good quality of caps shell be worse than other methods. In my case since the amp will be ultimately only HF it might use any coupling with equal success.

Since I might keep with 2A3 a very high grid resistor then I might use a very little cap. Furthermore if I want I might use the coupling cap as the high-path filter for my MF channel (it is 3200Hz electrical and 1000Hz acoustical). If so then the cap would be in nF level and it might be some kind of crazy expensive cupper in Teflon for instance… or even air. With 250K on 2A3 grid we arrive to 0.00018uf... what is 180pF – very much the capacitance that air cap can handle if they will be able to care the couponing voltage. I am a bit suspicion with this approach as in the past what I was wring the DSET curve with coupling capacitor in Mild I was not able to get my MF to sound right. I do not know what the reason was.

Alternately, since my driver stage has a very good RL filter in it’s grid and all the rest MF amps will run no bass I might use galvanic coupling. The problem with transformers is also bandwidth and phase distortion but in my care it might not be the factor (the beauty of DSET topology). Since my MF amp will not care LF the intestate transformer might have no inductance and to have as few tune as it need to do the coupling. I have ordered a very fast 1H transformer with 80% nickel core, 50ma gap, that shell theoretically run TV signal. OK, I am kidding about TV but it will have no phase problems under 100K. The transformer is made by a quite knowledgeable person, so it might be very interesting.

Probably I shell give a try to one of the direct-coupling versions. If I have higher voltage in super Milq then 400V then I might try the Jack Elliano’s idea of reactance coupling.

http://www.electra-print.com/2a3drd.php

Still, my leading at this point are air cap or a small and very none-inductive transformer that at HF shell be as good as a straight wire.

This is the idea that I like. It looks like it is a Slovakian company and this amps is two stage with a reasonable driver and it looks like they make their own 2A3.

http://www.jj-electronic.com/index.php?option=com_content&task=view&id=2&Itemid=31

I have no idea how it sounds. I their des description the target this mps for WLM, Lowther, Fostex, Cabasse, Loth-X users, that pertly makes me to want vomit. I do not know also about 10W from a single 2A3. I do not feel good about DC voltage for heater supplies. There is something “white-flagish” in DC in out tube.  Still, I welcome the des that has no extra stages… I wonder how the JJ Electronic in the pantheon of new production of the 2A3 tubes?

Is something brewing in the former Czechoslovakia? The whole country is the size of a half of New Jersey but they have 3 manufactures that do “objectionable” tube today. Is it the same rebranded group of people behind of all of them?

Romy the Cat wrote:

Is something brewing in the former Czechoslovakia? The whole country is the size of a half of New Jersey but they have 3 manufactures that do “objectionable” tube today. Is it the same rebranded group of people behind of all of them?

Adrian,

Are any of those new tubes besides the Chinese tubes are single plated?  I have bought some very nice 2A3 and 6A3 double plated from 1942 and 1944 and it will give me an ability to see what is going on with vintage tubes.

I was not pleased with advertised vs. actual measurement of those tubes, even those the tubes I got were “new”. The most interest probably shell be belong the single plated tubes but they are very pricy, more expensive then the new production of the tubes. The good part is that with the new production it is possible to have assured and stable measurement of the tubes and the only concern would be this one:

http://www.goodsoundclub.com/Forums/ShowPost.aspx?postID=9301#9301

There is something else.  If you look at the Srajan Ebaen’s pictures:

http://6moons.com/audioreviews/jj2a3/40.html

then you will see something that really makes me conserved. Srajan shoots it for the same of sexy look and he does not understand it but is anything in there that make you nervous? Look at the second image from the bottom where the amp is shot in dark. The blue light radiated from the sake around the filaments is OK in DHT. If the covers around cathodes have some hole then the projection of the whole to the glass might also pick up some blue light – that is normal as well. However if the whole balloon on the perimeter of the glass turns bleu then it is a very high evidence that the tube is filled with crap gas and shell be conceded faulty.  If I paid money for the blue aura tube I would return it and would ask for refund.

BTW, what you will be commenting on your new tubes then can you for me to  pay less attention to their bass and more pay attention to  texture and tone in the upper region?

Romy the Cat wrote:

Are any of those new tubes besides the Chinese tubes are single plated?

Romy the Cat wrote:

I have bought some very nice 2A3 and 6A3 double plated from 1942 and 1944 and it will give me an ability to see what is going on with vintage tubes.

I assembled SUN 2A3 amp for my friend and found it to be quality kit  and very easy assemble. Kit was old .I think late 90's so maybe quality deteriorated since then. I have variety of 300b Czech tubes and (Eml 300b , KR 300BLX 842VHD ) bought them to build 300b Melquiades but compression drivers buing frenzy is draining all modest resources I have. Lstening to those tubes I have to agree with Adrian assesment . The thing which attracted me to them was AA tube guys opinion that they sound solid state . They expressed the same opinion about6C33C so I fthght that this DHT will fit in the schema of things.
Back to topic I found VT52 to be the best sounding tube, harmonically rich, dimmensional with full seductive midrange withouto little histerical qualities of tubes like 45, 6A3 . In Sun kit it sounded considerably better (to me ) with simple DC 6.3V filament than 6A3 and 45 amp .

Wojtek wrote:

I assembled SUN 2A3 amp for my friend and found it to be quality kit  and very easy assemble. Kit was old .I think late 90's so maybe quality deteriorated since then. I have variety of 300b Czech tubes and (Eml 300b , KR 300BLX 842VHD ) bought them to build 300b Melquiades but compression drivers buing frenzy is draining all modest resources I have. Lstening to those tubes I have to agree with Adrian assesment . The thing which attracted me to them was AA tube guys opinion that they sound solid state . They expressed the same opinion about6C33C so I fthght that this DHT will fit in the schema of things. Back to topic I found VT52 to be the best sounding tube, harmonically rich, dimmensional with full seductive midrange withouto little histerical qualities of tubes like 45, 6A3 . In Sun kit it sounded considerably better (to me ) with simple DC 6.3V filament than 6A3 and 45 amp .

About the out tubes I have a strong bias to 6.3 as Milq has already a very good a 14A supply for ½ 6C33S and to hook up one more amp for something like 6A3 will be very easy and comfortable. To be persevered I have order a transformer with 6.3 primaries and multiple secondarys:  2.5V, 5V, 7.5V. Still I would like do not have any AC transformers in the Milq chassis. People usually do not like 6A3 and any high voltage DHT time as they are too loud with AC supplies. However, in my case the amp will be DSET, high-passed at 3.2kHz, and I do not think that it will be a problem with noise at all. I did not feel that any modulation would be a problem as well. I might stay with 2.5V if the 2A3 turn out to be better than 6A3, I do not know at this point.

There are 3 basic groups of those tubes as I see them. First one has plate of sub 1000R: 2A3/6A3, AD1 and many others. The second has plate between 1500R and 2000R: 45, VT52 and many others. And the third one has plate above 5K: 10, VT25 and many others. Each groups need own transformer, I have a few for the first gas and none for the last groups. I personally would like to use something like 10Y and with my DSET setting it would not be a problem to wide a high-ratio transformer.  So, if I go for none-2A3 solution then it would be most likely not the second group but the third one. It is possible that the first group will be enough for me, of even that my single-stage high-mu IDHT will do just fine in the end. I will see how the Sun Audio kit will behave with MiniMe and will go from there. The MiniMe shell have a very upper range and if it was the case then it will decide the thing…

In the thread GM70 vs. 6C33C two year back I have written that the only tube that I would like to trey in Milq besides 6C33C would be YO-186.

I am not sure that it might be a right direction or even interesting direction but I picked yesterday a party of YO-186 tubes. The YO-186 is incredibly rare Russian tube and has a mysterious reputation in there. It is so uncommon that it has a unicorn status and trios few who use pray to YO-186 as it is something out of this world. I do not know if there is any rational in it. Russians might be right and the YO-186 might be a unique sounding tube, it might be in a pair with western equivalents or it might be worst then western alternatives. I took the YO-186 just to address its unicorn status and to see if any merit exists behind the YO-186 cult sonic reputation. I have very limited expectation as it looks Russians made YO-186 as an alternative to Western tubes. Generally those alternative tubes were not as good as Western tubes. The Russians own tubes development was much more interesting where they did not try to imitate any and created own things from scratch… talking about the 6E5P, 6C33C, 1P24B…

Anyhow, the YO-186 was a Russian made hybrid between AD1, AD101 and 45 tubes. The YO-186 is like AD1 has 4V and 1A filament. Cares 250V on plate, can do higher of necessary. Default plate current 60mA, bios of minus 40V, 15W anode dissipation. It has lover gain then AD1 – 4 vs. 6 and has slightly higher plate impedance - 1200R,  that brings it in the camp of 45 tubes. The YO-186 started production in mid of 30s and were made to the beginning of 60s. The primary use of them was reportedly in movie theater amplifiers even though I have no idea what the purpose was to have 1.5W tube in there.

If anyone heard any amp with this tube then let me know. I know that there is a South Korean company that makes rare amps with YO-186 but I do not know anyone who has it.