We are fairly similar it seems in both the time we spent away from soldering and any electronics before taking up this hobby.I hope my comments don't delay your project for any meaningful length of time. As you'll soon see - a lot of the thread can simply be skimmed.
As an example... from Mark's guide for the boards on the first page.
"ii. All resistors Rnn except 3W parts R13 and R14. If you use a resistor lead
forming tool (like the Sparkfun TOL‐13114), you will quickly discover that the
small resistors need their leads bent to 0.50 inch pitch (12.5 mm)."
5% is fine. 1% usually does not cost much more, and I usually go that route.
As with many, I'm happy to share any information that might make your build go smoothly and relieve some stress. One recommendation that was given to me, was to buy the Dale resistors. They seem to be very well-regarded. In addition (and more important to me); in the need of any troubleshooting, if you orient the values to the top, others can help much more quickly if there are any in the wrong places etc.
Toroidy in Poland has excellent transformers. Get 300VA 2x 18V or 2x 20v for stereo. Bigger (More VA) doesn’t actually help much.
Resistors - 1/4W, 1% metal film resistors are what you need except where a 3W resistor is specified, then try to get metal film if possible.
In my opinion, fancy and expensive boutique parts succeed mainly in making your wallet lighter. They do little, if anything, for the quality of the sound.
Specific to M2x, do yourself a favor and choose only 2 or 3 of the input stages to begin. (It does not matter which, that all sound very nice and work beautifully) This will give you a choice of stages to listen to but limit the amount of things you need to find, source, and build in the beginning.
M2x is a little harder to build than some of the other Firstwatt amplifiers, but it’s sound is incredible and absolutely worth the effort. Go slowly and deliberately, take your time and take plenty of notes. You will enjoy the process!
Post your questions (and solutions) here as you go along, I’m sure others will have similar questions in the future, so it will be helpful to see what you do to solve the puzzle.
Resistors - 1/4W, 1% metal film resistors are what you need except where a 3W resistor is specified, then try to get metal film if possible.
In my opinion, fancy and expensive boutique parts succeed mainly in making your wallet lighter. They do little, if anything, for the quality of the sound.
Specific to M2x, do yourself a favor and choose only 2 or 3 of the input stages to begin. (It does not matter which, that all sound very nice and work beautifully) This will give you a choice of stages to listen to but limit the amount of things you need to find, source, and build in the beginning.
M2x is a little harder to build than some of the other Firstwatt amplifiers, but it’s sound is incredible and absolutely worth the effort. Go slowly and deliberately, take your time and take plenty of notes. You will enjoy the process!
Post your questions (and solutions) here as you go along, I’m sure others will have similar questions in the future, so it will be helpful to see what you do to solve the puzzle.
Thank you for the referrence to Toroidy in Poland, @6L6! Their transformers look very nice indead. Though shipping is still a bit expensive at EUR 20 (though they are in the neighboring country). Their "audio grade" one of 300VA is about EUR 78,- for me and the one from Triad Magnetics of "medical" grade (though 250VA) would be EUR 86,- (free delivery). So I will need to do my research yet.
What is the risk of going with 250VA? BTW, it has an integrated thermal switch, perhaps that helps if overloaded?
Overall, I consider my strategy being to go without the extra mu-metal insulation on Edcors (I am not picky, so perhaps I will not hear the hum?), but to succeed with that I would like to get a "quiet" power transformer (for a reasonable price). Does that make sence?
What is the risk of going with 250VA? BTW, it has an integrated thermal switch, perhaps that helps if overloaded?
Overall, I consider my strategy being to go without the extra mu-metal insulation on Edcors (I am not picky, so perhaps I will not hear the hum?), but to succeed with that I would like to get a "quiet" power transformer (for a reasonable price). Does that make sence?
Re: resistors and transformer
Hi avitkauskas,
regarding resistors, I recommend metal film, 600mW, 1%. I really like the Yageo resistors that you can get at Reichelt.de, for example. 0.05 EUR each if you by them in quantities of 10 or more, which I normally do - 10 or 20 of each value I order. The variation with temperature is 50 ppm / K, which is really good, and they have non-magnetic leads. I use them in almost all my builds (except for the 2W or 3W resistors ...)
A lot of folks here like Vishay/Dale RN55. They are available from Mouser, for example, but I don't know how much you have to order to get free shipping to Lithuania.
Regarding transformers, I am very happy with the transformers from Toroidy. I have bought numerous transformers from them now, and have been satisfied with every one of them. Get a 2x18V or 2x20V, 300VA or 400VA transformer in Audio Grade (the middle quality - no need to spend the significant extra charge for the Supreme Audio, unless you want to show it off on the deck of the amp). The Audio Grades have been quiet for me. For the M2 / M2X you might have to experiment a bit with orientation and rotation of the power transformer and shielding of the signal transformers, regardless of the brand of power transformer. I got my M2 quiet with my 100 dB/W backloaded widebanders
Best regards,
Claas
Hi avitkauskas,
regarding resistors, I recommend metal film, 600mW, 1%. I really like the Yageo resistors that you can get at Reichelt.de, for example. 0.05 EUR each if you by them in quantities of 10 or more, which I normally do - 10 or 20 of each value I order. The variation with temperature is 50 ppm / K, which is really good, and they have non-magnetic leads. I use them in almost all my builds (except for the 2W or 3W resistors ...)
A lot of folks here like Vishay/Dale RN55. They are available from Mouser, for example, but I don't know how much you have to order to get free shipping to Lithuania.
Regarding transformers, I am very happy with the transformers from Toroidy. I have bought numerous transformers from them now, and have been satisfied with every one of them. Get a 2x18V or 2x20V, 300VA or 400VA transformer in Audio Grade (the middle quality - no need to spend the significant extra charge for the Supreme Audio, unless you want to show it off on the deck of the amp). The Audio Grades have been quiet for me. For the M2 / M2X you might have to experiment a bit with orientation and rotation of the power transformer and shielding of the signal transformers, regardless of the brand of power transformer. I got my M2 quiet with my 100 dB/W backloaded widebanders
Best regards,
Claas
I have two 400VA Toroidy's waiting to be installed in my M2X mono blocks. The standard toriods was starting to make some slight mechanical hum from time to time which was very annoying. So I took the decision to use the "big hammer" and get two of "these". I was promised that they are "dead silent".
I noticed that they have the yellow/green PG wire. Probably connected to the steel cap.....but I don't know yet.
I noticed that they have the yellow/green PG wire. Probably connected to the steel cap.....but I don't know yet.
Attachments
I’m using Plitron 225VA (115V + 2x18v) in my monoblocks currently very successfully, with DIYAudioStore PSU boards.
Building a pair of Mark Johnson designed switch/soft start boards.
PCB: low voltage On-Off switch drives AC mains relay \ includes soft start .. H9KPXG
Next up will be XRK971’s SLB PSU boards
The SLB (Smooth Like Butter) Active Rect/CRC/Cap Mx Class A Power Supply GB
Looking into 20v transformers myself. I’ve emailed Primrose, and a custom R-Core maker. Not heard back yet. Antek AS series always an option.
Lastly, cosmetically, I’m going to order Black front panels drilled for momentary anti-vandal switches, from HiFi2000, at some point. (Can’t order till I finalize the switches)
Love the sound from these amps! Worth making pretty.
Awesome with my new Daedalus speakers.
Thanks again Mark Johnson, 6L6, DIYAudioStore, and of course Mr. Pass.
Building a pair of Mark Johnson designed switch/soft start boards.
PCB: low voltage On-Off switch drives AC mains relay \ includes soft start .. H9KPXG
Next up will be XRK971’s SLB PSU boards
The SLB (Smooth Like Butter) Active Rect/CRC/Cap Mx Class A Power Supply GB
Looking into 20v transformers myself. I’ve emailed Primrose, and a custom R-Core maker. Not heard back yet. Antek AS series always an option.
Lastly, cosmetically, I’m going to order Black front panels drilled for momentary anti-vandal switches, from HiFi2000, at some point. (Can’t order till I finalize the switches)
Love the sound from these amps! Worth making pretty.
Awesome with my new Daedalus speakers.
Thanks again Mark Johnson, 6L6, DIYAudioStore, and of course Mr. Pass.
Those look great, and prices very competitive after you find the currency conversion.
How was shipping to US?
They even have a 2x21v option!
I’m a bit concerned with the 22v transformer option in my monoblocks, with only one amp board for loading.
Have you tried all the daughter cards with the 27v PSU? I would not mind a little more oomph from mine. I listen at -5db to -25db, depending on mood. I’m not sure if just going up to a bigger VA number, by itself, would help that, or if I should increase voltage a bit. My main board is a bit overbuilt, in resistors and capacitors, but I’m not sure about the opto, and transistors. My daughter cards are fairly pedestrian, with typical components. The cards are pretty small to get fancy with.
Thanks for the advice, I hadn’t really paid attention to Toroidy before, despite great reviews, due to lack of US shipping on their site. The other 2 that I mentioned previously have not responded for a few weeks now.
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Re: Toroidy voltages / shipping
Hi Bones13,
Toroidy do in fact any voltage you want, for a small surcharge. Just send them a mail and ask them. I have used this several times now, for example to get a 2x8.5V transformer to have the right voltage for regulated tube filaments.
Regarding shipping, several forum members have reported low shipping charges to the U.S. when ordering Toroidy transformers through TME:
Toroidal Transformers: Manufacturer
Of course, in that case you don't have the option of custom voltages
Regards,
Claas
Hi Bones13,
Toroidy do in fact any voltage you want, for a small surcharge
. Just send them a mail and ask them. I have used this several times now, for example to get a 2x8.5V transformer to have the right voltage for regulated tube filaments.Regarding shipping, several forum members have reported low shipping charges to the U.S. when ordering Toroidy transformers through TME:
Toroidal Transformers: Manufacturer
Of course, in that case you don't have the option of custom voltages
Regards,
Claas
Hi Bones13,
Toroidy do in fact any voltage you want, for a small surcharge
Regarding shipping, several forum members have reported low shipping charges to the U.S. when ordering Toroidy transformers through TME:
Toroidal Transformers: Manufacturer
Of course, in that case you don't have the option of custom voltages
Regards,
Claas
Thanks for that reference, I will have a look.
Very pleased with JFET pairs, obtained by simple & cheap procedure
I'm fooling around with a design which uses Fairchild J113 thru-hole JFETs, in a differential pair. These are the little brothers of the Fairchild J112s that were originally fabbed in Mountain View, CA. That's how the M2x input stage daughter card called "Mountain View" got its name.
Anyway, I decided to spend a modest amount of money, attempting to get several pairs of decently matched JFETs for my differential amps. And by "decently matched" I mean, "much better than picking two JFETs at random out of a bag".
So I placed a Mouser order, see Figure 1 below. I bought qty=100 pieces of the J113 and spent thirteen USD.
I slapped together a little test jig on my solderless breadboard (which I got very cheaply at Amazon (link)), see Figure 2 below. The circuit schematic is shown in Figure 3 below.
Each of the two J113s in the differential pair operates with 3.0 milliamps of DC bias current, so the test jig sets the JFET current to 3 mA. {how? By dialling the 25 turn trimmer until an ammeter says 3.000mA}. I set my adjustable DC power supply to 20 volts for these tests, which gives the JFET about the same VDS in testing, that it will see in actual operation. Then VGS is measured with a 4.5 digit voltmeter.
VGS sloooowly converges and I didn't feel like waiting forever, so I decided to record the measured value exactly 15 seconds after powering up the D.U.T. This may or may not be unwise, but it felt good at the time and I'm still glad I did it this way. My results are shown in Figure 4 below. It's a fairly high-res image and if you zoom in you can read my handwriting.
There are four "pages" of devices, 20 devices per page. So I "only" measured 80 parts, of the 100 I bought. $2.50 wasted, I suppose.
I knew I wanted to get a sorted list of measured VGS, and then look for adjacent measurements that were very very similar (or identical!). No doubt there are dozens of ways that can achieve this, some of them easier than others. I decided to use a spreadsheet, Microsoft Excel, because sorting numerical values is especially easy in a spreadsheet. Then I told Excel to subtract adjacent values, giving the delta-VGS for each pair of JFETs.
I'm very pleased to report that: For the 100 JFETs that I happened to buy, and the subset of 80 that I happened to test, and the test jig and test protocol I used,
For the money spent, and the amount of my own time invested, I'm delighted with the results. Absolutely delighted.
_
I'm fooling around with a design which uses Fairchild J113 thru-hole JFETs, in a differential pair. These are the little brothers of the Fairchild J112s that were originally fabbed in Mountain View, CA. That's how the M2x input stage daughter card called "Mountain View" got its name.
Anyway, I decided to spend a modest amount of money, attempting to get several pairs of decently matched JFETs for my differential amps. And by "decently matched" I mean, "much better than picking two JFETs at random out of a bag".
So I placed a Mouser order, see Figure 1 below. I bought qty=100 pieces of the J113 and spent thirteen USD.
I slapped together a little test jig on my solderless breadboard (which I got very cheaply at Amazon (link)), see Figure 2 below. The circuit schematic is shown in Figure 3 below.
Each of the two J113s in the differential pair operates with 3.0 milliamps of DC bias current, so the test jig sets the JFET current to 3 mA. {how? By dialling the 25 turn trimmer until an ammeter says 3.000mA}. I set my adjustable DC power supply to 20 volts for these tests, which gives the JFET about the same VDS in testing, that it will see in actual operation. Then VGS is measured with a 4.5 digit voltmeter.
VGS sloooowly converges and I didn't feel like waiting forever, so I decided to record the measured value exactly 15 seconds after powering up the D.U.T. This may or may not be unwise, but it felt good at the time and I'm still glad I did it this way. My results are shown in Figure 4 below. It's a fairly high-res image and if you zoom in you can read my handwriting.
There are four "pages" of devices, 20 devices per page. So I "only" measured 80 parts, of the 100 I bought. $2.50 wasted, I suppose.
I knew I wanted to get a sorted list of measured VGS, and then look for adjacent measurements that were very very similar (or identical!). No doubt there are dozens of ways that can achieve this, some of them easier than others. I decided to use a spreadsheet, Microsoft Excel, because sorting numerical values is especially easy in a spreadsheet. Then I told Excel to subtract adjacent values, giving the delta-VGS for each pair of JFETs.
I'm very pleased to report that: For the 100 JFETs that I happened to buy, and the subset of 80 that I happened to test, and the test jig and test protocol I used,
- I was able to find ten pairs of devices whose VGS @ 3.0mA were within 5 millivolts. The absolute value of (VGS_A - VGS_B) was below 0.005 volts, for ten different (A,B) pairs.
For the money spent, and the amount of my own time invested, I'm delighted with the results. Absolutely delighted.
_
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And I'm delighted that you've shared your intent, methodology, and detailed results. Absolutely delighted. I have everything except Q1 in my spares and a need to learn how to do this properly.
Thank you as always for your contributions to the group.
@JeffreyJuice... check it out. You may already know how to do this in your sleep, but I certainly did not. This could come in very handy if I grasp this correctly... which should never be assumed.
I have everything except Q1 in my spares and a need to learn how to do this properly.Thank you as always for your contributions to the group.
@JeffreyJuice... check it out. You may already know how to do this in your sleep, but I certainly did not. This could come in very handy if I grasp this correctly... which should never be assumed.
In the past, i struggled a bit trying to eliminate hums induced from the trafo, so this M2x project was delayed till now. With a bit of time now, i decided to try out twin voltage rails smps.
To my surprise, it works well for me!
No hums and buzz now, i can crank up the Yarra Preamp with Melbourne DB inside M2x.
One mistake i made was to select too high a voltage for my smps, +/- 29Vdc. My bad!
Thru the CRC ...12600uF - 0.33R - 12600uF, i managed to get it down to the low +/- 28'ish Vdc. This smps from Cresnet power up fine with no hick-up at all, it's been running in this config for 3 weeks.
Due to the supply voltage, i can only use Melbourne DB safely. My first power up killed both my Tuson DB, then i ran without DB(bypass-direct) and Melbourne DB in Yarra then.
Since Melb works so well with M2x, i now uses WBA18 inside Yarra Preamp.
Totally happy with these setup so far, clean sweet musical M2x!
Thanks N.Pass, M.Johnson, 6L6, Xrk,Sami and all others for sharing their knowledge generously here.