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Old 14th November 2005, 12:00 PM   #1
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Default 6DJ8 or 12xx7 for hybrid amp (Monarchy)

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.

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Old 14th November 2005, 12:02 PM   #2
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A schematic could be helpful....

Cheers

Andrea
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Old 15th November 2005, 12:47 AM   #3
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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.
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Old 15th November 2005, 01:04 AM   #4
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Quote:
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.
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Old 15th November 2005, 01:24 AM   #5
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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.
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Old 15th November 2005, 02:43 AM   #6
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Quote:
Originally posted by 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.
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.
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Old 15th November 2005, 02:46 AM   #7
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Quote:
Originally posted by SY


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.
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Old 15th November 2005, 03:30 AM   #8
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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.
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Old 15th November 2005, 05:18 AM   #9
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Quote:
Originally posted by 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.
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.
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Old 15th November 2005, 06:14 AM   #10
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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.
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