6DJ8 or 12xx7 for hybrid amp (Monarchy)

[Interious]

Monarchy makes the Fet-valve hybrid SE-250 in 12xx7 and 6DJ8 versions.
Owner Mr Poon is reluctant to recommend one over the other for some reason. I have the SE-160 which is excellent, especially with the JAN/Phillips 6DJ8.

I want to upgrade to the higher power 250 version and do not know which to get. I've done a lot of research. There are love hate relationships with both the 12xx7 types and 6DJ8 types (6922, 6N1P, etc.) Actually, the 6DJ8 version will also accept the 6CG7/6FQ7, which I believe is a 6SN7 type, which I've not tried.

The single tube SRPP stage in these amps is used to drive a mosfet output stage, like Van Alstine's Fet-valve or the old NYAL Moscode. Van Alstine does use the 12AT7.

Comments?

 

[Andypairo]

A schematic could be helpful....

Cheers

Andrea

 

[Interious]

Right--a schematic would be helpful. I didn't ask because I assume that information is proprietary.

I know this is one of those questions that is difficult to answer. I guess I'm trying to figure out which tube type is generally sonically superior. I have some experience with 6DJ8 types (Curcio "Daniel" preamp), but not with the 12xx7 types.

Some people say the 12AX7, for example, is a no brainer over the 6DJ8; while others think it should be limited to guitar amp duty. That's a radical variation.

Glass Audio had an article on the 6DJ8 which concluded that it's not suitable for high-end audio. OTOH, The noted Joe S at Audio Asylum seems to prefer the 6DJ8 (Joe's tube Lore).

I know that both types have been used in excellent high-end commercial preamps over the years.

I do know that the tube in the SE-160 and 250 is used in an SRPP configuration and drives the 12 mosfet output stage.

I hesitated posting this question because of the vagaries involved, but I thought I would give it a shot. Thanks for your response.

 

[SY]

Glass Audio had an article on the 6DJ8 which concluded that it's not suitable for high-end audio.

That was not a reliable article. The author evidently tested relabelled 6ES8 and at low current! When someone says something ridiculous like, "The 6DJ8 is unsuitable for audio," ask them if they think that a mint pair of Marantz 9s should be thrown away.

 

[Eli Duttman]

The combined gate capacitance of paralleled FETs is considerable and not easy to drive. AVA solves the problem by cascading FETs. I have no idea about Monarchy's methods. I'm dubious about a 12AX7 driving any sort of difficult load. With a "hot" operating point, I think the 6n1p would do better than the 6DJ8.

Since Monarchy can work with mu 20 6SN7s, perhaps they could cook up somthing that uses the mu 22 ECC99, which is a kick butt high current driver. The ECC99 draws 800 mA. of heater current. That could be a problem. Both the 6SN7 and 6n1p draw 600 mA. of heater current, while the 6DJ8 and 12AX7 draw but 300 mA.

 

[Interious]

The combined gate capacitance of paralleled FETs is considerable and not easy to drive. AVA solves the problem by cascading FETs. I have no idea about Monarchy's methods. I'm dubious about a 12AX7 driving any sort of difficult load. With a "hot" operating point, I think the 6n1p would do better than the 6DJ8.

Since Monarchy can work with mu 20 6SN7s, perhaps they could cook up somthing that uses the mu 22 ECC99, which is a kick butt high current driver. The ECC99 draws 800 mA. of heater current. That could be a problem. Both the 6SN7 and 6n1p draw 600 mA. of heater current, while the 6DJ8 and 12AX7 draw but 300 mA.

Eli,

I have the SE-160 version and have tried the Sovtek 6N1P and 6H30P.
Also Hungarian(???) Amperex, Jan/Phillips and Sylvania 6DJ8s.

With my Ellis 1801b, the Jan/Phillips 6DJ8 is the best match. The 6N1P has an odd sound that is difficult to describe. The 6H30P is soft, flabby, very smooth, rolled off, and noticeble less gain. (Monarchy claims the filament supply can handle the ~0.9 amps, but the tranny and regulator run very hot).

I'm building a set of ER Audio ESLs which will probably change everything. Frank Alles in Stereotimes does prefer the 6N1P for driving his Eros ESL panels with the SE-160.

Sylvania is too dry and flat while the "Hungarian" Amperex 6DJ8--supplied with the Audio Amateur Curcio Daniel kit in the 80s-- is by far the tubiest, excessively warm and syrupy.

The 6SN7 is an octal socket tube, so I assume you're referring to my mention of the 6CG7/6FQ7 above.

Monarchy is generous with their time but a bit quirky which makes things difficult. But the SE-160 is a very fine amplifier though.

 

[Interious]

That was not a reliable article. The author evidently tested relabelled 6ES8 and at low current! When someone says something ridiculous like, "The 6DJ8 is unsuitable for audio," ask them if they think that a mint pair of Marantz 9s should be thrown away.

Wow---Very interesting. Did not know that. It does fly in the face of a lot of successful applications.

 

[SY]

I've taken the trouble to actually measure several authentic varieties of 6DJ8 which is why I'm willing to make such a strong statement. Low distortion and benign harmonic distribution in common cathode and vanishingly low distortion as a cathode follower.

For the curious, the best-measuring version was CCa. I only had four sections to measure, but they were consistent.

 

[Interious]

I've taken the trouble to actually measure several authentic varieties of 6DJ8 which is why I'm willing to make such a strong statement. Low distortion and benign harmonic distribution in common cathode and vanishingly low distortion as a cathode follower.

For the curious, the best-measuring version was CCa. I only had four sections to measure, but they were consistent.

Interesting.

Care to mention experiences with other 6DJ8s? Is it possible to get a superior tube for less than $100/pair? Somebody on Audiogon reports the current production Ei are good.

I posted these same questions at Audio Asylum and somebody claimed the 12AX7 version is a "no-brainer". I asked if he would elaborate but received no response. But based on your testimony here I'm inclined to go with the 6DJ8 version. You guys sound like you know tubes.

Obviously the application is critical. As noted, this is for driving a mosfet output stage, not for preamp duty.

 

[cominup]

Hi Interious,

In my opinion, 6DJ8 is better.

Why? Firstly, becuz of its anode voltage. To open 6DJ8, >30V is OK, maximum voltage is 100VDC. So, you can use single Power Transformer to use for voltage stage and power stage.

With 12xx7, you should use Xformer which has secondary out 200VAC at least. So, another Xformer could be use.

And, secondary is Zout. with 6DJ8 in parallel, Zout is enough for next stage. But 12xx7, linestage xformer could be needed.

Hybrid, I love to do becuz we can get musical of tube and power of transitor. But it is not easy to complete. Goodluck and looking for your result soon.

 

[SY]

Care to mention experiences with other 6DJ8s? Is it possible to get a superior tube for less than $100/pair? Somebody on Audiogon reports the current production Ei are good.

There are a lot of good 6DJ8s out there for far less than $100. It looks like Triode Electronics has NOS Philips E88CC for $9 each; they're excellent. I used an E88CC variant in the Heretical preamp.

No experience with Ei. I haven't tried the Tesla/JJ versions yet, but I've had such good experience with their other tubes, I'd probably give them a shot if I were out buying new.

The Siemens-branded tubes that came with the Curcio ST-70 mod kit were curious- reasonably linear, but the mu was consistently way out of spec (ranged from 20-23 in the eight sections tested).

edit: SND has NOS 6KN8, a higher mu version of the ECC88, for $20.

 

[Alastair E]

12xx7 versus options

The 6DJ8 and its variants like the E88CC etc, are an excellent tube in my opinion--BUT its just that--Some may prefer the 12xx7 types, but personally I dont really like that series. (some, Ive found have been a bit noisy and michrophonic for my liking, while others command silly money......)

My personal taste extends to the good old 6SL/SN7 series, even the cheap easy to get Russian versions are worth a try, but they are larger Octal types, so retrofitting involves re-socketing or making adaptors--sometimes far from ideal, but great just for experimenting.........

So much in tube lore, is due to personal taste--Dont let anyone tell you a tube isnt good in a particular application till youve tried it yourself--You may discover a very unlikely tube that suits your taste perfectly, and the operating point will make any tube sound bad if not optimal so its worth remembering to check/alter this when changing between types--There are SO many small double-triodes out there to try....................

 

[qwad]

yea 6dj8 have a rep for being microphonic, so a 6sl/sn , may be more preferable cheers TC

 

[anatech]

Hi SY,
Just curious. The Electroharmonix have at least been non-microphonic. They sound decent. Have you had a chance to play with them. The reason I ask is that they are reasonably priced and may be a good starting point.

-Chris

 

[Interious]

The 6CG7/6FQ7 is essentially a 6SN7 in a miniature 9-pin package, I believe. Should roughly the same performance be expected, with possible differences in microphonic behavior?

 

[SY]

Chris, I haven't used EH; all of my tests have been on NOS. Do you know who manufactures them?

 

[anatech]

Hello SY,
They come out of Russia. Reflector maybe? Our friends at New Sensor created them.

So far, everything I have tried is way better than average. I've had about two dud's. The 6922's solved issues in the Counterpoints and sound good. The 12AX7's tend not to be microphonic. The outputs are good and the 6SN7's I have tried I am happy with.

The best part is that they are not expensive. I have not actually sat down and characterized their performance. Subjectively they seem to be good.

Give Mike a call, maybe he will send you some.

-Chris

 

[amperex]

12AX7

I prefer the 12AX7 version as many more NOS tubes were manufactured & many do sound great.

As for my experience with 6DJ8, only tube I liked was Siemens 1960 year AO code with grey shield. Many other brands just did not perform to my liking.

 

[Brian Donaldson]

I just bought a pair of JJ ECC88, and they look sloppy and have different gain. I just got the headphone amp up and still need to look at the rest of the circuit, but it's so simple and I always measure each resistor with VOM before I install it, So I think it's likely the tubes.

 

[Interious]

Re: 12AX7

I prefer the 12AX7 version as many more NOS tubes were manufactured & many do sound great.

As for my experience with 6DJ8, only tube I liked was Siemens 1960 year AO code with grey shield. Many other brands just did not perform to my liking.

Thanks for that input Amperex.

To all--what is the predicted effect of running a tube at half filament voltage? I'm trying 12XX7 tubes in the SE-160, which is configured for 6.1 volts for 6DJ8 types.

Circa 1960 Mullard 12AX7s seem to sound better than any 6 volt tube I have on hand. Richer, more spacious, more palpable; but less neutral --tubier, which I like but not if it's excessive.

The sensitivity penalty is not subjectively as great as anticipated.