No mine has 6P1-14 or somesuch (haven't actually got the amp yet, its in transit to me), so thanks for the pic. I called it a EL84PP clone because I wasn't sure of the actual tubes they use.
I also found an article from Audio Express on rebuilding this amp.
Apparently they are a bit variable in their construction quality (and safety
), so some basics will come before any mods.Gary
This may be close.
http://www.diyaudio.com/forums/tubes-valves/99165-aria-6p14-makeover.html
I just got one too, but haven't had time to work out the circuit yet.
I suspect they vary a bit anyway.
The build quality is as you might expect. On mine, only three of the four rubber feet actually touch the shelf, because there is a twist in the chassis. Not too bothered for the price, as i'll be re housing it anyway. There doesn't seem to be a chassis earth so take care.
However, it sounds much nicer than i expected, even with the Chinese tubes.
Took an hour or so to settle in.
Mine arrived with 6n1 tubes instead of 6n2, which was handy as i had some Russian 6n1p-ev tubes in stock. Got some more Russian 6n14p on the way.
I have to wonder if its worth the bother of building amps any more.
http://www.diyaudio.com/forums/tubes-valves/99165-aria-6p14-makeover.html
I just got one too, but haven't had time to work out the circuit yet.
I suspect they vary a bit anyway.
The build quality is as you might expect. On mine, only three of the four rubber feet actually touch the shelf, because there is a twist in the chassis. Not too bothered for the price, as i'll be re housing it anyway. There doesn't seem to be a chassis earth so take care.
However, it sounds much nicer than i expected, even with the Chinese tubes.
Took an hour or so to settle in.
Mine arrived with 6n1 tubes instead of 6n2, which was handy as i had some Russian 6n1p-ev tubes in stock. Got some more Russian 6n14p on the way.
I have to wonder if its worth the bother of building amps any more.
I guess not if the only thing you really want to do is rehash the same old tired work of others..
Personally I think one of these might be fun to play with, (they're rather like the stuff I played with 30yrs ago) but I'd rather build and debug one of my own designs..
Where is the challenge here?
Where is the challenge here?
What I wanted was a reasonably nice sounding amp that is aesthetically and financially acceptable to the rest of the household.
My budget stretches to the cost of a chassis punch (which is what this amp cost me), and if the result after mods is still below what I want, I have some chance of selling it on. Given my abilities to produce something that looks nice enough to take to market are zero, I think this is a good option.
I like a challenge too, but unfortunately, I am not in a financial position to afford to build the equipment of my dreams, and therein lies the challenge.
Gary
All good reasons not hinted at in your previous post, however with some very judicious scrounging at electronic surplus dealers, radio shows, and amateur radio flea markets you would be surprised at what you can put together for short money. I didn't always have money to burn on this hobby and still managed to scratch build a lot of pretty good things from recycled parts.
Making things look good is a matter of practice, patience, a few tools, and a plan - perhaps the most important item of all. I'm quite challenged in both the mechanical skill (other than cars??) department and am also not the most patient person. A lot of my stuff looks amateurish compared to what I see here and elsewhere...
That amplifier is a good place to start though under the circumstances I think, and you can have some fun tweaking it.
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Kevin,
In the USA you can build an amp pretty cheap even with new iron e.g. Edcor or Hammond. But iron is heavy and it costs a lot for freight if you want to buy the same iron from another country. A fully built amp from China may cost say $220-$280 shipped (talking 6P1 or EL84). We can barely build a small amp here in Australia from scratch for twice that. Ah thems the breaks
Ian.
In the USA you can build an amp pretty cheap even with new iron e.g. Edcor or Hammond. But iron is heavy and it costs a lot for freight if you want to buy the same iron from another country. A fully built amp from China may cost say $220-$280 shipped (talking 6P1 or EL84). We can barely build a small amp here in Australia from scratch for twice that. Ah thems the breaks
Ian.
Yep, it's the cost of the iron that stops me from being a prolific builder.
My newly aquired Chinese amp cost less than a decent mains TX, and performs annoyingly well.
Meanwhile my pride and joy homebrew SE amp has been relegated to the spare room.
The schematic i posted earlier turns out to quite different to my amp.
My newly aquired Chinese amp cost less than a decent mains TX, and performs annoyingly well.
Meanwhile my pride and joy homebrew SE amp has been relegated to the spare room.
The schematic i posted earlier turns out to quite different to my amp.
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I got inspired by the Suppo Audio circuit and applied it to a Mengyue Mini 6P1 amp. The result was spectacular, very good indeed, especially after replacing the 6N2 with 6N1P-EV Russian tubes. The difference was like night and day.
To do the conversion, I removed all the resistors except B+ and output tube cathode resistors from underneath the PCB. Then refitted the PCB into the amp and soldered all the new parts onto the copper side of the PCB, no traces needed cutting but 2 caps are lifted at one end with a jumper wire to attach them to the correct part of the circuit. This approach is a solution to the difficulty of tweaking these amps, now almost everything is accessed with just the bottom cover removed. My amp was the schematic in the 2nd post of this thread.
Trebla, I bought my amp a couple of years ago, does your new amp use a similar topology or did they change it for some other type?
Ian.
To do the conversion, I removed all the resistors except B+ and output tube cathode resistors from underneath the PCB. Then refitted the PCB into the amp and soldered all the new parts onto the copper side of the PCB, no traces needed cutting but 2 caps are lifted at one end with a jumper wire to attach them to the correct part of the circuit. This approach is a solution to the difficulty of tweaking these amps, now almost everything is accessed with just the bottom cover removed. My amp was the schematic in the 2nd post of this thread.
Trebla, I bought my amp a couple of years ago, does your new amp use a similar topology or did they change it for some other type?
Ian.
Playing with my Meng 6P1.
Not exactly what I call shielded transformers:
From the bottom. Craftsmanship is not as bad as some say.
Not exactly what I call shielded transformers:
An externally hosted image should be here but it was not working when we last tested it.
From the bottom. Craftsmanship is not as bad as some say.
An externally hosted image should be here but it was not working when we last tested it.
Nope. I think it caused hum problems. Soon I will know. It DOES HAVE A FUSE. It is built into the cord socket. At least they left off so much that in playing with it, I can learn about both tube circuits and execution. A lot can be gleaned from the old VTL handbook, or otherwise known as David's 100 page sales brosure you pay for. As I can't afford his amps, I did buy his book.
I am starting to think one of my first steps is a larger chassis. I need room for power supply mods, a second input, shielding the transformers etc.
I am starting to think one of my first steps is a larger chassis. I need room for power supply mods, a second input, shielding the transformers etc.
Thanks for posting the Suppo circuit. I want to hardwire at some stage but without the actual circuit diagram it would have difficult.
Mine is the dual input version, so a slightly bigger chassis. I haven't attempted to trace the circuit, but no diagram i've seen so far looks exactly the same.
I'll try and take a photo in the morning.
I've got to admit that it sounded pretty good, even with the Chinese tubes, once it had settled in for a few hours. Only problem for me is that i'm driving it with a tube output DAC, and i've got a bit too much gain.
Note that there are several differences between the 6P1 amp and schematic.
So far, the 10K grid isolation resistors are not there.
Symmetry adjustment is 20K, not 50K as shown.
Does not show the headphones connection.
The silkscreen has different resistor values than installed.
Seems dangerous not to have caps on the input, as you never know what is driving it. A small change in input offset would make a large imbalance from what I understand.
So far, the 10K grid isolation resistors are not there.
Symmetry adjustment is 20K, not 50K as shown.
Does not show the headphones connection.
The silkscreen has different resistor values than installed.
Seems dangerous not to have caps on the input, as you never know what is driving it. A small change in input offset would make a large imbalance from what I understand.
You might find the grid stoppers under the PCB (the non-copper side).
If I could suggest any worthwhile modification for this cct, it would be to swap the paraphase inverter/splitter for a concertina/cathodyne or a long-tailed pair. If you remove most of the components from the non-copper side of the PCB, you can reconstruct a new cct on the copper side, maybe a little bit messy, but works fine for experimenting, and very quick to make changes. I have done a LOT of resoldering on my PCB and have seen no signs whatsoever of any traces or pads even giving a hint of lifting, it seems a very solid PCB.
Re caps on the input, it seems the audio "convention" is for caps (or no DC) at the output of every source or line stage, but this is not written in stone so check your sources if in doubt.
Ian.
If I could suggest any worthwhile modification for this cct, it would be to swap the paraphase inverter/splitter for a concertina/cathodyne or a long-tailed pair. If you remove most of the components from the non-copper side of the PCB, you can reconstruct a new cct on the copper side, maybe a little bit messy, but works fine for experimenting, and very quick to make changes. I have done a LOT of resoldering on my PCB and have seen no signs whatsoever of any traces or pads even giving a hint of lifting, it seems a very solid PCB.
Re caps on the input, it seems the audio "convention" is for caps (or no DC) at the output of every source or line stage, but this is not written in stone so check your sources if in doubt.
Ian.
Just got mine - initial look
For the Americans reading this, substitute "tubes" for valves
Received my secondhand 6P1 Mini today and here are some observations I have made so far:
First, the 6P1's are shown as 6AQ5's on the top plate. Very odd, as the 6AQ5s I have see are all 7 pin valves, not 9 pin.
Previous owner had earthed the chassis so at least it's safe
I ran it up in place of my hacked ecl86 SE 3 Watt amp. The Mini has lots more power, but sounds poor in comparison. Quite tiring to listen for more than a few minutes. Mind you, I have been tweaking the ECL86 amp for months and it really sings now. Not bad for a 50 year old radiogram chassis still running the valves and factory transformers I got with it. And there are no "Audiophile" components in it either.
First thing I noticed is that the Mini immediately found the 60Hz resonance of the cheapo speakers I use on the SE.
I swapped to my KEF TLs, and while tamer, the bass is definitely peaky. The high end sounds like it cuts off sharply too, but I haven't measured response yet.
On to the bench and popped the bottom off to do some voltage measurements.
First thing I noticed is that the power transformer is for 220v mains, and so the valve voltages are all way too high with our 235v mains. The HT is 283v, should be no more than 250v for these valves, and with the screens connected directly to HT the valves run really hot and would have a short life. Even the filaments are running at about 7v.
I'm going to put a resistor in the mains lead to the switch to drop the primary voltage to 220v. That should cool things a little.
Things are so hot that V1 seems to be going into runaway, as the cathode voltage heads up to nearly double the other 3 valves within a couple of minutes. It's the valve that's suffering as I've swapped V1 and V2 and the runaway followed the valve. I'll see what happens when I get the HT under control.
I'm sure the excess voltages can't be good for the sound quality either.
Gary
For the Americans reading this, substitute "tubes" for valves
Received my secondhand 6P1 Mini today and here are some observations I have made so far:
First, the 6P1's are shown as 6AQ5's on the top plate. Very odd, as the 6AQ5s I have see are all 7 pin valves, not 9 pin.
Previous owner had earthed the chassis so at least it's safe
I ran it up in place of my hacked ecl86 SE 3 Watt amp. The Mini has lots more power, but sounds poor in comparison. Quite tiring to listen for more than a few minutes. Mind you, I have been tweaking the ECL86 amp for months and it really sings now. Not bad for a 50 year old radiogram chassis still running the valves and factory transformers I got with it. And there are no "Audiophile" components in it either.
First thing I noticed is that the Mini immediately found the 60Hz resonance of the cheapo speakers I use on the SE.
I swapped to my KEF TLs, and while tamer, the bass is definitely peaky. The high end sounds like it cuts off sharply too, but I haven't measured response yet.
On to the bench and popped the bottom off to do some voltage measurements.
First thing I noticed is that the power transformer is for 220v mains, and so the valve voltages are all way too high with our 235v mains. The HT is 283v, should be no more than 250v for these valves, and with the screens connected directly to HT the valves run really hot and would have a short life. Even the filaments are running at about 7v.
I'm going to put a resistor in the mains lead to the switch to drop the primary voltage to 220v. That should cool things a little.
Things are so hot that V1 seems to be going into runaway, as the cathode voltage heads up to nearly double the other 3 valves within a couple of minutes. It's the valve that's suffering as I've swapped V1 and V2 and the runaway followed the valve. I'll see what happens when I get the HT under control.
I'm sure the excess voltages can't be good for the sound quality either.
Gary
Hi Gary,
I can recall seeing inconsistent voltages on the grids of the output valves in the early days when running it on 240V. Yep you are right the 220V tranny does make the internal voltages higher than what is comfortable with 240V input. I am using a 240V to 220V step-down convertor for the short term.
Regarding sound quality, if the trimpot in the paraphase inverter is not adjusted correctly it may not sound too good. Some popular designs on the net with a reputation for good sound quality use a long-tailed pair phase splitter with a CCS in the tail. Apparently the CCS enforces symmetry on the two outputs. Maybe I should have gone that way, but I'm very happy with the sound of the Suppo-based cct. It still needs a bit of work e.g. higher B+ required for the 6N1P, connecting feedback causes oscillation, minor issues really Maybe I should tweak it in the direction of Sy's Red Light District amp, it's already close to that schem. I also replaced the cathode resistors of each output valve with an LM317 which ensures correct bias current for each valve. No heatsinks required for the LM317's. The possibilities are endless.
I see we can now get these amps for $180 AUD shipped if one can wait 6 weeks for shipping.
tvr - All the Meng Yue 6P1 PCB's are the same, but the component contents differ? It's like each owner is given a little surprise
Ian.
I can recall seeing inconsistent voltages on the grids of the output valves in the early days when running it on 240V. Yep you are right the 220V tranny does make the internal voltages higher than what is comfortable with 240V input. I am using a 240V to 220V step-down convertor for the short term.
Regarding sound quality, if the trimpot in the paraphase inverter is not adjusted correctly it may not sound too good. Some popular designs on the net with a reputation for good sound quality use a long-tailed pair phase splitter with a CCS in the tail. Apparently the CCS enforces symmetry on the two outputs. Maybe I should have gone that way, but I'm very happy with the sound of the Suppo-based cct. It still needs a bit of work e.g. higher B+ required for the 6N1P, connecting feedback causes oscillation, minor issues really
Maybe I should tweak it in the direction of Sy's Red Light District amp, it's already close to that schem. I also replaced the cathode resistors of each output valve with an LM317 which ensures correct bias current for each valve. No heatsinks required for the LM317's. The possibilities are endless.I see we can now get these amps for $180 AUD shipped if one can wait 6 weeks for shipping.
tvr - All the Meng Yue 6P1 PCB's are the same, but the component contents differ? It's like each owner is given a little surprise
Ian.
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