Mullard 1960 era 12AX7s are nice. I believe these are the short plates. The Mullard 10M series long plates are even better. GE 5751 black plate are also a 12AX7 sub reported to sound very good.
Hi Interious,
The filament voltage should be within 5% of the rated voltage, 10% might be a bit wide.
The filament of the 12xx7 family are center tapped. You can tie the outsides together and apply 6.3 V to that junction and the center tap. An excellent tube to try is the 6EU7. It's a special low noise 12AX7A.
-Chris
The filament voltage should be within 5% of the rated voltage, 10% might be a bit wide.
The filament of the 12xx7 family are center tapped. You can tie the outsides together and apply 6.3 V to that junction and the center tap. An excellent tube to try is the 6EU7. It's a special low noise 12AX7A.
-Chris
anatech said:
Chris--
Will half voltage operation damage the tube or cause premature failure?
I will have to read up on this. It's been 30 years since I've seriously messed with tubes--ham radio days.
These amps are subject to return and are still under warrantee. I can't do mods on them yet. For this experiementation I have to live with the circuitry in its stock form.
Dave
Hi Dave,
The tube will not work at 1/2 heater voltage. Any emission would be so low as to be useless in that application. Don't do it.
If the Monarchy is under warranty, then don't mess with it. You can try other tubes. As Amperex has pointed out, the 12AX7 is a good tube. I like them in my Fisher preamp, and my Eico pre as well.
The only way for you to tell which one to buy is to listen to each available model. That way you can see how the designer handled each tube type. It's not really about the tube type, but the designer's skill. Your own tastes come into play as well.
-Chris
The tube will not work at 1/2 heater voltage. Any emission would be so low as to be useless in that application. Don't do it.
If the Monarchy is under warranty, then don't mess with it. You can try other tubes. As Amperex has pointed out, the 12AX7 is a good tube. I like them in my Fisher preamp, and my Eico pre as well.
The only way for you to tell which one to buy is to listen to each available model. That way you can see how the designer handled each tube type. It's not really about the tube type, but the designer's skill. Your own tastes come into play as well.
-Chris
Chris--
The mystery is that the 12v tubes do indeed work in this 6v amp. Less gain, but it works and sounds great with Mullard 12xx7 types so far.
I thought emissions would be too low as well. The filament isn't even visible and the tube runs barely luke-warm.
Is there danger to tube or amp running like this? I realize that the question may be impossile to answer without a schematic.
I know all of this sounds a bit nutty.
Dave
The mystery is that the 12v tubes do indeed work in this 6v amp. Less gain, but it works and sounds great with Mullard 12xx7 types so far.
I thought emissions would be too low as well. The filament isn't even visible and the tube runs barely luke-warm.
Is there danger to tube or amp running like this? I realize that the question may be impossile to answer without a schematic.
I know all of this sounds a bit nutty.
Dave
Hi Dave,
Yes, the gain will be very low. You may damage the tubes, I can't say for sure. But since the tubes are not working as they should, I would not continue.
The sound will change when the tubes are running properly. Better highs and lower distortion would be my guess. Right now, they are starved for current. I'm thinking it's hard on the cathodes.
-Chris
Yes, the gain will be very low. You may damage the tubes, I can't say for sure. But since the tubes are not working as they should, I would not continue.
The sound will change when the tubes are running properly. Better highs and lower distortion would be my guess. Right now, they are starved for current. I'm thinking it's hard on the cathodes.
-Chris
You think right. Running at low heater voltages will shorten cathode life considerably, not to mention reduce gain and transconductance, and increase distortion.
Ok guys. .....
I talked to Andy at Vintage Tube Services and he said the same thing regarding the cathode---bad. I'm not sure I understand the mechanism, but I believe you all!
I knew something had to be wrong about the idea.
Dave
I talked to Andy at Vintage Tube Services and he said the same thing regarding the cathode---bad. I'm not sure I understand the mechanism, but I believe you all!
I knew something had to be wrong about the idea.
Dave
Can lesser 6DJ8s sound obviously inferior?
I thought the JAN/Phillips sounded pretty good, but have papery, rough, hissy highs compared to the much smoother Mullard 12au7a and 12ax7, even with these tubes running at half filament voltage.
Note that I've yet to hear any of the better 6DJ8s. Mullards, Amperex, etc.
Dave
I thought the JAN/Phillips sounded pretty good, but have papery, rough, hissy highs compared to the much smoother Mullard 12au7a and 12ax7, even with these tubes running at half filament voltage.
Note that I've yet to hear any of the better 6DJ8s. Mullards, Amperex, etc.
Dave
Yes indeed. There were a lot of relabelled 6ES8s being passed off as 6DJ8, and they sounded absolutely awful in any circuit I tried them in. Some of the Eastern European ECC88 do not resemble the specification very well. I've got some Russian 6922 that show 40% differences in gm between sections. And so on and so on.
I've recently tested about 50 specimens of various 6DJ8 variants, including Amperex 6922, Phlips and Siemens E88CC, Mullard 6DJ8, and tons of PCC88 (althouh series heated, the filament characteristic makes it completely usable at 6.3V in 99% of all cases).
Here is what I found:
Many Eastern European NOS are utter rubbish, with gm at half what it should be, and sections unbalanced, as SY mentioned, by 40%. I have actually had Ei, Tungsram, Valvo and Telefunken tubes that have spent 20 years in a TV tuner show perfectly usable gm and very good matching, far better than aforementioned NOS. I did have a Mullard 6DJ8 with a bad filament 🙁 and best results by far were from the E88CC variants. Amperex 6922 was rather dissapointing. Ei PCC88 NOS show great gm matching and consistency although gm is not the highest of the bunch.
But, back to the topic:
It is VERY hard to compare something like a 6DJ8 and a 12AX7 without knowing how they are used - as far as characteristics go, you can hardly find two more different double triodes given the same envelope size. However, given we are talking about ahybrid amp, low Rp, high gm and relatively high plate current seems in order, given the capacitances that will be driven. To me, this immediately associates with one of the folowing:
6DJ8/6922/ECC88/E88CC and other variants thereof,
6FQ7/6CG7/ECC99
Possibly 12AT7 if you need higher mu
12AU7 if you must (it really is not very linear)
Here is what I found:
Many Eastern European NOS are utter rubbish, with gm at half what it should be, and sections unbalanced, as SY mentioned, by 40%. I have actually had Ei, Tungsram, Valvo and Telefunken tubes that have spent 20 years in a TV tuner show perfectly usable gm and very good matching, far better than aforementioned NOS. I did have a Mullard 6DJ8 with a bad filament 🙁 and best results by far were from the E88CC variants. Amperex 6922 was rather dissapointing. Ei PCC88 NOS show great gm matching and consistency although gm is not the highest of the bunch.
But, back to the topic:
It is VERY hard to compare something like a 6DJ8 and a 12AX7 without knowing how they are used - as far as characteristics go, you can hardly find two more different double triodes given the same envelope size. However, given we are talking about ahybrid amp, low Rp, high gm and relatively high plate current seems in order, given the capacitances that will be driven. To me, this immediately associates with one of the folowing:
6DJ8/6922/ECC88/E88CC and other variants thereof,
6FQ7/6CG7/ECC99
Possibly 12AT7 if you need higher mu
12AU7 if you must (it really is not very linear)
I totally agree with ilimzn and SY on their points. I'd like to add that whatever tube is used, you need a buffer stage before you can properly drive the mosfets.
The 6DJ8 / 6922 types suffer from high microphonics as well in some cases. Interesting for a frame grid tube, but that's what many years of experience has shown me. There are some good ones. Beware of some subs that draw higher heater current.
Basically, the 6DJ8 is a low voltage, higher current tube (to get good high frequency response, it is designed as a tuner tube for TV). 12AX7 is a higher impedance tube (low current, higher voltage) tube designed for audio. Both of these tubes can sound great in circuits properly designed for their characteristics. That's why I said the performance of these two is up the the designer, not so much the tube.
-Chris
The 6DJ8 / 6922 types suffer from high microphonics as well in some cases. Interesting for a frame grid tube, but that's what many years of experience has shown me. There are some good ones. Beware of some subs that draw higher heater current.
Basically, the 6DJ8 is a low voltage, higher current tube (to get good high frequency response, it is designed as a tuner tube for TV). 12AX7 is a higher impedance tube (low current, higher voltage) tube designed for audio. Both of these tubes can sound great in circuits properly designed for their characteristics. That's why I said the performance of these two is up the the designer, not so much the tube.
-Chris
I'm not an experienced expert on DIY, coming here to improve my skills, so please salt the following accordingly:
All tube types, I've found have a 'flavour' or family sonic signiature that underlies the sonic variations between brands.
For me, I don't mind the 12AX7. Ulike the 6DJ8, it was expressly designed for audio. It's worst trait is a mild 'haze' that you'll only ever notice if compaired to a better type (the 6SN7 - 6CG7 family comes to mind here. But I'm living with this quite comfortably in my own system right now, so don't make too much of this.)
Great instances of the 12AX7 minimise this above negative trait, and turn in a quite nice performance, with an engaging mind-range. Best so far for me and my system have been Mullard's. But there are also many US ones that I've liked too. (An old Sylvania comes to mind here).
There are wide variations in sonic quality between brands (and even within brands -- eg Mullard's own CV4004) which can be both good and bad: It makes tube-rolling/system-tuning fun, but when you finally find a type you like, you realise there aren't stacks of them around! On the other hand, it's a type that's likely to always be in current production and sonic quality has improved gradually over the years and hopefuly will continue doing so. (Last time I checked, the Sovtek 12AX7LPS was sounding quite nice to my surprise)
The 6DJ8 was designed for instrumentation, however has been an audio staple since the 60's.
The worst feature of this family is an overly-etched or hard 'steely' quality in the upper registers. I understand this is likely due to a high 3rd harmonic component. My expereince with the not-so good in this family, kind nearly turned me off this tube type. However...
Finding some good examples -- as with the 12AX7's -- minimised this negative quality to the point where I actually quite like what this tube can do. Barely harsh/hard at all, capable of airy -- even feathery -- upper-octave presentation. Reversing my previous assessment; this type is capable of great things in the right circuit. The bad: good instances can be expensive, and thus a target for fakers.
Again, currently in production. The JJ's aren't bad at all. I have a pair in my rig right now. The Sovteks (from about 3 years ago) weren't so good (flat lifeless, lacking in harmonic richness. But in the positive: they didn't sound bright or glarey!) If they improve their 6DJ8 sound as they have with their 12AX7 family, we'll all be set. I expect given demand for Audiophile 6DJ8's that they'll at least be trying.
I hope the forgoing was of partial use to someone!
All tube types, I've found have a 'flavour' or family sonic signiature that underlies the sonic variations between brands.
For me, I don't mind the 12AX7. Ulike the 6DJ8, it was expressly designed for audio. It's worst trait is a mild 'haze' that you'll only ever notice if compaired to a better type (the 6SN7 - 6CG7 family comes to mind here. But I'm living with this quite comfortably in my own system right now, so don't make too much of this.)
Great instances of the 12AX7 minimise this above negative trait, and turn in a quite nice performance, with an engaging mind-range. Best so far for me and my system have been Mullard's. But there are also many US ones that I've liked too. (An old Sylvania comes to mind here).
There are wide variations in sonic quality between brands (and even within brands -- eg Mullard's own CV4004) which can be both good and bad: It makes tube-rolling/system-tuning fun, but when you finally find a type you like, you realise there aren't stacks of them around! On the other hand, it's a type that's likely to always be in current production and sonic quality has improved gradually over the years and hopefuly will continue doing so. (Last time I checked, the Sovtek 12AX7LPS was sounding quite nice to my surprise)
The 6DJ8 was designed for instrumentation, however has been an audio staple since the 60's.
The worst feature of this family is an overly-etched or hard 'steely' quality in the upper registers. I understand this is likely due to a high 3rd harmonic component. My expereince with the not-so good in this family, kind nearly turned me off this tube type. However...
Finding some good examples -- as with the 12AX7's -- minimised this negative quality to the point where I actually quite like what this tube can do. Barely harsh/hard at all, capable of airy -- even feathery -- upper-octave presentation. Reversing my previous assessment; this type is capable of great things in the right circuit. The bad: good instances can be expensive, and thus a target for fakers.
Again, currently in production. The JJ's aren't bad at all. I have a pair in my rig right now. The Sovteks (from about 3 years ago) weren't so good (flat lifeless, lacking in harmonic richness. But in the positive: they didn't sound bright or glarey!) If they improve their 6DJ8 sound as they have with their 12AX7 family, we'll all be set. I expect given demand for Audiophile 6DJ8's that they'll at least be trying.
I hope the forgoing was of partial use to someone!
Hi Majestic,
Check out the 6922EH. At least they don't ring like so many others can. The 12AX7EH is quiet as well.
-Chris
Check out the 6922EH. At least they don't ring like so many others can. The 12AX7EH is quiet as well.
-Chris
Majestic--Very helpful indeed. The advice from everyone here has been incredibly helpful.
------------------------------------------
All,
I was examining the PCB of the 6dj8 version SE-160 which I currently have. There are several small package transistor or fet devices on the board. I wonder if these are used as buffers? (I don't know if I can get this info out of Monarchy's Mr Poon) If this is the case, the SRPP tube stage must simply be the input and gain stage. If this is the case, what is the point of having a tube in the circuit at all?
I wonder if I would be better off building or buying something like an Aleph, and if I've got to have tubes somewhere, use tubes in the front-end. DAC/Pre-amp, etc. I do love the tube sound, it's like coming home--so relaxed and natural.
Also:
* It sounds like the 6CG7/6FQ7 is worth a try since it is a supposed to be a miniature package version of the highly regarded(?) 6SN7.
* After all of this talk and exploration, I'm almost tempted to return these amps and design my own hybrid, which would require a lot of study. But by the time I do that, why not use an all tube power amp?
One reason is because I'm going to build ER Audio's "Acorn" ESL and was looking for an amp that will drive this load (2 ohms at 10khz). ER recommends a "doubling" amp and these Monarchy hybrids will do this. So I thought the hybrid would be a good solution: drive capabilities of mosfets along with some tubiness. I do know that there are tube amps that will drive ESLs, but then you are dealing with even more tubes and the sourcing frustrations are thus multiplied.
So the hybrid seemed like an ideal compromise.
------------------------------------------
All,
I was examining the PCB of the 6dj8 version SE-160 which I currently have. There are several small package transistor or fet devices on the board. I wonder if these are used as buffers? (I don't know if I can get this info out of Monarchy's Mr Poon) If this is the case, the SRPP tube stage must simply be the input and gain stage. If this is the case, what is the point of having a tube in the circuit at all?
I wonder if I would be better off building or buying something like an Aleph, and if I've got to have tubes somewhere, use tubes in the front-end. DAC/Pre-amp, etc. I do love the tube sound, it's like coming home--so relaxed and natural.
Also:
* It sounds like the 6CG7/6FQ7 is worth a try since it is a supposed to be a miniature package version of the highly regarded(?) 6SN7.
* After all of this talk and exploration, I'm almost tempted to return these amps and design my own hybrid, which would require a lot of study. But by the time I do that, why not use an all tube power amp?
One reason is because I'm going to build ER Audio's "Acorn" ESL and was looking for an amp that will drive this load (2 ohms at 10khz). ER recommends a "doubling" amp and these Monarchy hybrids will do this. So I thought the hybrid would be a good solution: drive capabilities of mosfets along with some tubiness. I do know that there are tube amps that will drive ESLs, but then you are dealing with even more tubes and the sourcing frustrations are thus multiplied.
So the hybrid seemed like an ideal compromise.
Hi Interious,
An all tube amp would easily drive this with a 2 ohm tap.
Each amplifier sounds the way it does due to design. There are great solid state amps using mosfets or bipolars. There are hybrids and tube. I judge each one on it's own merits. I am working on redesigning the Counterpoint SA-100 (it's come a long way so far). It's a hybrid design, with problems. My favorite amps so far, one tube and one SS.
The reason for the tube in yours is to provide voltage gain with a specific sound. The other parts could be buffers and / or current sources. Buffers are needed to drive the gate charge in the mosfets.
A hybrid is one way to do this, there are others that you may happen across. Try your amp with the speakers and make sure you like the sound. That's what this all boils down to.
-Chris
An all tube amp would easily drive this with a 2 ohm tap.
Each amplifier sounds the way it does due to design. There are great solid state amps using mosfets or bipolars. There are hybrids and tube. I judge each one on it's own merits. I am working on redesigning the Counterpoint SA-100 (it's come a long way so far). It's a hybrid design, with problems. My favorite amps so far, one tube and one SS.
The reason for the tube in yours is to provide voltage gain with a specific sound. The other parts could be buffers and / or current sources. Buffers are needed to drive the gate charge in the mosfets.
A hybrid is one way to do this, there are others that you may happen across. Try your amp with the speakers and make sure you like the sound. That's what this all boils down to.
-Chris
yes, any silicon in the circuit could be to provide a current sink/source for the tube. An excellent use for them if you can get past the "use a transistor - go to jail" tube-design school 😉
(I'm kinda there myself, truth be told; but with the right design they can actually be quite a helpful 'evil' 😛 )
However, they do still influence the final sound quality of the unit. That's the trick many of us are here for though -- when to use what, and how much, to get the right 'sound' we seek?
Re: 6CG7/6FQ7's. I've not met one of these that I haven't liked (give me time 😀 ). Too many of them in a circuit would be a 'bad' thing, though. Interestingly, their sonic qualities don't seem to vary as much from brand to brand as with the 12AX7 and 6DJ8 families. But this is not to say that there isn't a difference! As a bonus, there are seemingly plenty of them around too and at reasonable prices.
If you end up using one of these, try an RCA 'clear-top' as your benchmark (simply for a reference point) and roll other brands to compare. (Make sure you get try some with black-plates 😉 )
I know what you mean about the hybrid power-amp thing too. My ideal loudspeakers would be a pair of Apogee's, which, if I were to ever aquire, would pretty well necessitate (to my own way of thinking anyway), a silicon-based output stage. That or try for an 833 based tube amp which I'm worried would be too risky for a newbie like myself to attempt at this stage
(I'm kinda there myself, truth be told; but with the right design they can actually be quite a helpful 'evil' 😛 )
However, they do still influence the final sound quality of the unit. That's the trick many of us are here for though -- when to use what, and how much, to get the right 'sound' we seek?
Re: 6CG7/6FQ7's. I've not met one of these that I haven't liked (give me time 😀 ). Too many of them in a circuit would be a 'bad' thing, though. Interestingly, their sonic qualities don't seem to vary as much from brand to brand as with the 12AX7 and 6DJ8 families. But this is not to say that there isn't a difference! As a bonus, there are seemingly plenty of them around too and at reasonable prices.
If you end up using one of these, try an RCA 'clear-top' as your benchmark (simply for a reference point) and roll other brands to compare. (Make sure you get try some with black-plates 😉 )
I know what you mean about the hybrid power-amp thing too. My ideal loudspeakers would be a pair of Apogee's, which, if I were to ever aquire, would pretty well necessitate (to my own way of thinking anyway), a silicon-based output stage. That or try for an 833 based tube amp which I'm worried would be too risky for a newbie like myself to attempt at this stage
Only found one 6CG7 I did like- Raytheon black plate with center shield in the older red & blue box with white lettering. Careful, later Raytheons in the red & white box were made in Japan.
I am soaking up everything you guys are telling me.
I made a tube Tesla coil using 4 paralleled 833As. Spectacular, but I probably ruined all 4 tubes. What a waste.
I've been doing more listening and it is apparent that none of the 6 volt tubes I have on hand are acceptable in contrast to the Mullard 12xx7 types. Even my Panasonic XR10s are superior.
What to do?? The perennial audio question, made worse if you're a DIYer.
I just acquired a single Heathkit W-5M with 16309 Peerless output transformer. I wonder if it would be worthwhile to get another one and rebuild both? The sensitivity of the "Acorn" ESL is 89 db. The W-5M may be sufficient since I listen at around 65-70 db.
In the mean time, I really should try a 6CG7 in this SE-160. Vintage tube Service mentioned the 7AU7, but I assume the SE-160 is optimised for 6DJ8 types. The srpp circuit used must be very forgiving because it seems to work with anything. But "working" doesn't equate to optimized.
Do you guys have a favorite tube source? Many show up on a search.
VTS?
Anybody here tried an Aleph? I've read through the Pass group many times.
I made a tube Tesla coil using 4 paralleled 833As. Spectacular, but I probably ruined all 4 tubes. What a waste.
I've been doing more listening and it is apparent that none of the 6 volt tubes I have on hand are acceptable in contrast to the Mullard 12xx7 types. Even my Panasonic XR10s are superior.
What to do?? The perennial audio question, made worse if you're a DIYer.
I just acquired a single Heathkit W-5M with 16309 Peerless output transformer. I wonder if it would be worthwhile to get another one and rebuild both? The sensitivity of the "Acorn" ESL is 89 db. The W-5M may be sufficient since I listen at around 65-70 db.
In the mean time, I really should try a 6CG7 in this SE-160. Vintage tube Service mentioned the 7AU7, but I assume the SE-160 is optimised for 6DJ8 types. The srpp circuit used must be very forgiving because it seems to work with anything. But "working" doesn't equate to optimized.
Do you guys have a favorite tube source? Many show up on a search.
VTS?
Anybody here tried an Aleph? I've read through the Pass group many times.
Hi Interious,
I would rebuild the Heathkits to original spec. Possibly replacing the caps with modern parts. They will sound good.
Since you are a DIY guy, experimenting will lay the groundwork for what to do next. Build your own circuits up.
I buy from New Sensor these days, Electroharmonix where I can. Sometimes 7581A's from the Jan / Mil stock.
-Chris
I would rebuild the Heathkits to original spec. Possibly replacing the caps with modern parts. They will sound good.
Since you are a DIY guy, experimenting will lay the groundwork for what to do next. Build your own circuits up.
I buy from New Sensor these days, Electroharmonix where I can. Sometimes 7581A's from the Jan / Mil stock.
-Chris
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