Group Buy
I would be interested in running the group buy. I also live near Mark. However I am moving right now so would only get the time mid December to start thinking about this. Would folks want just the boards or also little nice enclosures with knobs etc...
I've read the Haggerman paper and the Linear Audio article but still looking for that perfect solution which Mark provided.
Best Regards,
Theo
Happy Snubbing
I would be interested in running the group buy. I also live near Mark. However I am moving right now so would only get the time mid December to start thinking about this. Would folks want just the boards or also little nice enclosures with knobs etc...
I've read the Haggerman paper and the Linear Audio article but still looking for that perfect solution which Mark provided.
Best Regards,
Theo
Happy Snubbing
I've finished the lab work I was doing with Quasimodo V4, and I have a few extra PCBs and/or PCB + kit of all parts, which I am willing to sell to other DIYers and hobbyists, at my cost.
I don't want to sabotage Theo's "group buy" in any way, so I hereby grant Theo a 5-week option to buy some or all (16) of my remaining PCBs and/or kits of all parts, at my cost. If he wants to pick them up in person, I'll deduct the shipping cost: I am not trying to make a profit here. If Theo decides to buy these, he can add enclosures, connectors, switches, and whatever else he or his customers wish.
After five weeks (06 Jan 2014), I will begin to accept orders for any remaining Quasimodo V4s that Theo didn't buy. Including shipping, my price would be
PCB only: $8 {ship to USA}, $10 {CAN, MEX}, $14 {rest of world}
PCB + kit of all parts: $18 {USA}, $20 {CAN, MEX}, $26 {rest of world}
It surprised me how much more the components cost in thru-hole packages, than in surface mount. Distributors are exploiting an "inelasticity of demand" for thru-hole parts, and punishing the small group of people who still buy thru-hole. Also the PCB is twice as large (50 x 100mm instead of 50 x 50) in the thru-hole version.
As before, I will sell these to people who mail me a check. Either in your bank's home currency or in USD; I don't care, my bank doesn't care. Use the currency conversion rate from Google or from the Financial Times. Unlike last time, I won't accept Western Union any more. The headache for you the buyer is huge, the headache for me the seller is huge, and WU's fee structure is set up to discourage small transactions. No Bitcoin and no PayPal and no credit cards either. This may be a reason to buy from Theo instead of buying from me: Theo may offer a larger variety of payment methods.
So . . . . I won't be selling any QuasimodoV4s until at least January 06, 2014. Between now and then, Theo might arrange a group buy. I hope he does and wish him great success.
Meanwhile, for those who simply cannot wait, let me suggest you look at post #18 of this thread. One morning I threw together a Quasimodo test jig, on my solderless protoboard using non-exotic parts, and it worked acceptably. You can do it too. Vero board, Strip board, and dead bug over groundplane would also work.
I don't want to sabotage Theo's "group buy" in any way, so I hereby grant Theo a 5-week option to buy some or all (16) of my remaining PCBs and/or kits of all parts, at my cost. If he wants to pick them up in person, I'll deduct the shipping cost: I am not trying to make a profit here. If Theo decides to buy these, he can add enclosures, connectors, switches, and whatever else he or his customers wish.
After five weeks (06 Jan 2014), I will begin to accept orders for any remaining Quasimodo V4s that Theo didn't buy. Including shipping, my price would be
PCB only: $8 {ship to USA}, $10 {CAN, MEX}, $14 {rest of world}
PCB + kit of all parts: $18 {USA}, $20 {CAN, MEX}, $26 {rest of world}
It surprised me how much more the components cost in thru-hole packages, than in surface mount. Distributors are exploiting an "inelasticity of demand" for thru-hole parts, and punishing the small group of people who still buy thru-hole. Also the PCB is twice as large (50 x 100mm instead of 50 x 50) in the thru-hole version.
As before, I will sell these to people who mail me a check. Either in your bank's home currency or in USD; I don't care, my bank doesn't care. Use the currency conversion rate from Google or from the Financial Times. Unlike last time, I won't accept Western Union any more. The headache for you the buyer is huge, the headache for me the seller is huge, and WU's fee structure is set up to discourage small transactions. No Bitcoin and no PayPal and no credit cards either. This may be a reason to buy from Theo instead of buying from me: Theo may offer a larger variety of payment methods.
So . . . . I won't be selling any QuasimodoV4s until at least January 06, 2014. Between now and then, Theo might arrange a group buy. I hope he does and wish him great success.
Meanwhile, for those who simply cannot wait, let me suggest you look at post #18 of this thread. One morning I threw together a Quasimodo test jig, on my solderless protoboard using non-exotic parts, and it worked acceptably. You can do it too. Vero board, Strip board, and dead bug over groundplane would also work.
Since that date, I assembled five more V4 boards and all have performed satisfactorily, in 3 different countries.
Group Buy Expectation
Thanks for the offer Mark.
I will certainly take one however don't want to keep these hot little items out of others eager hands. I'm in the middle of a move so everything is a bit uprooted for me until next month.
let's get this batch out there, if there are others interested after that we can proceed with a group buy and order up some boards with some nice to have features or enhancements if requested. So I'm listening, though I will let Mark's feedback on a particular request guide me.
Best Regards,
TAJ
Thanks for the offer Mark.
I will certainly take one however don't want to keep these hot little items out of others eager hands. I'm in the middle of a move so everything is a bit uprooted for me until next month.
let's get this batch out there, if there are others interested after that we can proceed with a group buy and order up some boards with some nice to have features or enhancements if requested. So I'm listening, though I will let Mark's feedback on a particular request guide me.
Best Regards,
TAJ
Selling my last Quasimodo V4 (thru hole) PCBs+kits
I don't plan to organize a Group Buy myself, I am glad to let tjencks do that. Please create a thread in the Group Buys forum of this website, to discuss features, prices, and payment options for tjencks's Group Buy. This ain't it.
I do have 16 extra PCBoards + full sets of components of Quasimodo V4 thru-hole, which I am willing to sell at my cost. Starting today.
I'm only selling the V4 PCBoard and/or PCB+kit of all parts. I'm not selling enclosures, connectors, binding posts, switches, jacks, plugs, screen printed front panels, or power supplies. If you want those, don't buy from me. Instead, post a message in Tjencks's Group Buy thread, telling him what you want, and why everybody else should want that too.
The .zip archive attached to post #58 of this thread contains a photograph of a fully assembled V4 board, its circuit schematic diagram, the Bill Of Materials, and Gerber plots for two fab houses: seeed and OSH Park. Everything you need to assemble a board, everything you need to buy components for a blank board, everything you need to order a batch of boards from a PCB fab, and/or everything you need to organize and run a group buy if that's your pleasure.
After these 16 V4 boards gone, I doubt I'll purchase-and-sell more of them; I'm not particularly interested in being a kit maker or kit seller. If tjencks or somebody else wants to do this, they have my blessings.
My prices (including shipping but not package-tracking) are:
It surprises me how much more the components cost in thru-hole packages, than in surface mount. Distributors are exploiting an "inelasticity of demand" for thru-hole parts, and punishing the small group of people who still buy thru-hole. Also the PCB is twice as large (50 x 100mm instead of 50 x 50) in the thru-hole version.
As before, I will sell these to people who mail me a check. Either in your bank's home currency or in USD; I don't care, my bank doesn't care. Use the currency conversion rate from Google or from the Financial Times. Unlike last time (QM V3), I won't accept Western Union any longer. The headache for you the buyer is huge, the headache for me the seller is huge, and WU's fee structure strongly discourages small transactions. No Bitcoin, no PayPal, and no credit cards either. Will I change my mind if you ask me another 500 times? No. This may be a reason to buy from tjencks instead of buying from me: tjencks may offer a larger variety of payment methods.
If you can't mail me a check, perhaps your bank will sell you an international money order. Perhaps you can persuade a friend of yours to mail me a check from their checking account. Perhaps you can persuade a fellow member of diyAudio to mail me a check, and then reimburse that member via PayPal. You might start a thread saying "Somebody help me! I have no checking account! Please!!!"
How to order
December is a busy month for me; several days may pass between receiving your check and shipping out your Quasimodo(s).
I don't plan to organize a Group Buy myself, I am glad to let tjencks do that. Please create a thread in the Group Buys forum of this website, to discuss features, prices, and payment options for tjencks's Group Buy. This ain't it.
I do have 16 extra PCBoards + full sets of components of Quasimodo V4 thru-hole, which I am willing to sell at my cost. Starting today.
I'm only selling the V4 PCBoard and/or PCB+kit of all parts. I'm not selling enclosures, connectors, binding posts, switches, jacks, plugs, screen printed front panels, or power supplies. If you want those, don't buy from me. Instead, post a message in Tjencks's Group Buy thread, telling him what you want, and why everybody else should want that too.
The .zip archive attached to post #58 of this thread contains a photograph of a fully assembled V4 board, its circuit schematic diagram, the Bill Of Materials, and Gerber plots for two fab houses: seeed and OSH Park. Everything you need to assemble a board, everything you need to buy components for a blank board, everything you need to order a batch of boards from a PCB fab, and/or everything you need to organize and run a group buy if that's your pleasure.
After these 16 V4 boards gone, I doubt I'll purchase-and-sell more of them; I'm not particularly interested in being a kit maker or kit seller. If tjencks or somebody else wants to do this, they have my blessings.
My prices (including shipping but not package-tracking) are:
PCB only: $8 {ship to USA}, $10 {CAN, MEX}, $14 {rest of world}
PCB + kit of all parts: $18 {USA}, $20 {CAN, MEX}, $26 {rest of world}
PCB + kit of all parts: $18 {USA}, $20 {CAN, MEX}, $26 {rest of world}
It surprises me how much more the components cost in thru-hole packages, than in surface mount. Distributors are exploiting an "inelasticity of demand" for thru-hole parts, and punishing the small group of people who still buy thru-hole. Also the PCB is twice as large (50 x 100mm instead of 50 x 50) in the thru-hole version.
As before, I will sell these to people who mail me a check. Either in your bank's home currency or in USD; I don't care, my bank doesn't care. Use the currency conversion rate from Google or from the Financial Times. Unlike last time (QM V3), I won't accept Western Union any longer. The headache for you the buyer is huge, the headache for me the seller is huge, and WU's fee structure strongly discourages small transactions. No Bitcoin, no PayPal, and no credit cards either. Will I change my mind if you ask me another 500 times? No. This may be a reason to buy from tjencks instead of buying from me: tjencks may offer a larger variety of payment methods.
If you can't mail me a check, perhaps your bank will sell you an international money order. Perhaps you can persuade a friend of yours to mail me a check from their checking account. Perhaps you can persuade a fellow member of diyAudio to mail me a check, and then reimburse that member via PayPal. You might start a thread saying "Somebody help me! I have no checking account! Please!!!"
How to order
- Send me a PM containing your shipping address, and the number of PCBoards/full_kits you want to buy
- I will send you a PM reply containing my mailing address in USA
- Mail your check to me at my address
- VERY IMPORTANT: after you mail the check, send me a PM saying "I mailed the check"
- When I receive your check, I will mail you the quantity of V4's you ordered & send you a PM
December is a busy month for me; several days may pass between receiving your check and shipping out your Quasimodo(s).
I'm surprised the more knowledgeable guys here haven't responded to this one...
Spare through hole PCBs
I downloaded the artwork files and had Seeed make me a set of the through holes boards. I have 5 spare at present. I'll do the same as offered above for anyone who would like one. PM me for details and you will need to be able to pay via Paypal. I'm in New Zealand.
PCB only: US$14 to all locations.
I downloaded the artwork files and had Seeed make me a set of the through holes boards. I have 5 spare at present. I'll do the same as offered above for anyone who would like one. PM me for details and you will need to be able to pay via Paypal. I'm in New Zealand.
PCB only: US$14 to all locations.
Has anyone checked the sensitivity of the identified snubber value when the primary winding is not shorted, but rather is part of loop with series impedance? This may need a few different core/winding construction examples to cover their possible influence.
Similarly, for a HV valve secondary with centre-tap full-bridge rectifier - where the recommended setup is to short the 'non-conducting' half winding, although in operation that winding would not be shorted per se at the time of interest.
Similarly, for a HV valve secondary with centre-tap full-bridge rectifier - where the recommended setup is to short the 'non-conducting' half winding, although in operation that winding would not be shorted per se at the time of interest.
Short-circuiting zeroes the effect of that particular winding in the ringing behaviour, by not contributing to the inductance of the resonance. That is what I have understood.
Since ringing occurs at switch off of the diodes, then when diodes are on, you can't be afraid of ringing. So, in a centre tapped transformer, when half the winding will be supplying energy to the reservoir, it will not be liable to ring, but silmutaneously, the other half will have its diode switch off and could ring.
In short, I get that short circuiting a winding does not imply that it will be short circuited during real use, rather it shows us that it will not play any role in the resonance of the other, which will happen in real use.
Of course, I may be wrong. This is what I seem to recall as a conclusion I had made when read the application note.
Since ringing occurs at switch off of the diodes, then when diodes are on, you can't be afraid of ringing. So, in a centre tapped transformer, when half the winding will be supplying energy to the reservoir, it will not be liable to ring, but silmutaneously, the other half will have its diode switch off and could ring.
In short, I get that short circuiting a winding does not imply that it will be short circuited during real use, rather it shows us that it will not play any role in the resonance of the other, which will happen in real use.
Of course, I may be wrong. This is what I seem to recall as a conclusion I had made when read the application note.
The energy being managed by the snubber is distributed in the secondary winding that was just conducting current through a diode. At that time the secondaries are both unloaded, except for the snubbers, stray capacitive coupling (which is soaking up some of the energy), and inductive coupling to other windings (with their loadings).
Mark, you mention your preferred snubber capacitor is the EPCOS B32529 series. I'm wondering what would dictate the choice of voltage for these. Obviously they'd need to be rated for the AC voltage of the secondary but I'm wondering if there are benefits to voltage ratings that are much higher. (Newbie question.)
The exact passage is
What this means is
- In my opinion, a crucial factor in selecting Cx and Cs is tan δ
- Metallized film capacitors have excellent tan δ
- EPCOS makes a series of metallized film capacitors called B32529, which is one of my favorites for snubber applications
To appreciate the reasons for this preference, replace the idealized Cx in Appendix A, with a more realistic circuit model of Cx which includes its dissipation factor tan δ. { For now, continue to pretend that Cs is ideal, and continue to ignore its dissipation factor. You can include the tan δ of Cs in a later step. } Grind through the Laplace transforms, find the new transfer function H(s), and equate its denominator with the denominator of a canonical second order system. Solve for the natural frequency omega_n and for the damping factor zeta. How does a nonideal Cx with non-negligible dissipation factor tan δ, affect the damping? Does it make you want to say: YUCK, let's find a way to get rid of this messy complexity and its impediment to performance?
Or, if you don't feel like manipulating Laplace transforms at the moment, take it on faith that better tan δ makes better snubbers. If you're cautious, take it on faith that better tan δ does not make snubbers worse. Can't hurt, might help: why not?
Or, if you're too skeptical to take it on faith, but not energetic enough to perform the mathematical grunt-work yourself, I recommend you remember that the Quasimodo idea is a negative feedback control system, in which the human operator functions as the error amplifier. If the scope trace is underdamped, the operator twirls the variable resistor RV1 a little more clockwise. If the scope trace is overdamped, the operator twirls RV1 a little more anticlockwise. If the scope trace is critically damped, the operator asks her/his spouse for a celebratory mug of beer.
Optimization of the damping factor occurs without ever knowing the dissipation factor tan δ of the capacitor(s) in the snubber. If you can tame your transformer's secondary ringing to your satisfaction, using capacitors made of green cheese, who cares what the waveforms might have looked like if you'd used other capacitors (metallized film? C0G ceramic? silver mica? polystyrene?) instead.
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The DC voltage across the snubbing capacitor is equal to the DC voltage applied by the circuit.
For a transformer secondary the DC voltage is near enough zero Vdc.
The AC voltage across the snubbing resistor depends on the ratio of reactance to the snubbing resistor.
This ratio changes for every frequency coming to the snubber.
It is quite a complicated procedure to come up with a very approximate value for the total applied voltage.
The safest is to select a capacitor AC voltage rating that exceeds the secondary maximum AC voltage.
I suspect a much lower voltage rating could be used, but I have never tried that. Too risky for my philosophies.
For a transformer secondary the DC voltage is near enough zero Vdc.
The AC voltage across the snubbing resistor depends on the ratio of reactance to the snubbing resistor.
This ratio changes for every frequency coming to the snubber.
It is quite a complicated procedure to come up with a very approximate value for the total applied voltage.
The safest is to select a capacitor AC voltage rating that exceeds the secondary maximum AC voltage.
I suspect a much lower voltage rating could be used, but I have never tried that. Too risky for my philosophies.
Maybe tan δ gets better and better, as capacitor voltage rating goes higher and higher? I don't know, haven't studied the datasheets for that.
I'd just convert transformer secondary RMS voltage rating into a waveform-peak value, multiply by a number larger than 1.0 to obtain a margin-of-safety, and take that as the minimum DC voltage rating I'd be willing to use. Then I'd check to see whether there are other reasons (tan δ ? price ? availability ? form factor ?) to prefer one voltage rating more than another.
I'd just convert transformer secondary RMS voltage rating into a waveform-peak value, multiply by a number larger than 1.0 to obtain a margin-of-safety, and take that as the minimum DC voltage rating I'd be willing to use. Then I'd check to see whether there are other reasons (tan δ ? price ? availability ? form factor ?) to prefer one voltage rating more than another.