Looking good! Plywood makes it sound better.
Ha, yeah makes it easy to swap the switching telco ring supplies for a couple of transformers. Switchers just hooked up to rectifier/cap board to start.
This has been a lesson in impedance matching. Started with old Siliconix U401 dual JFETs in the input buffer, but their Zout was too high (about 150 ohm) to drive the reflected Zin of the auto-former MoFo combo (50k/36 = 1389 ohm). B1 with LSK170B was just low enough about 50 ohm. Last experiment will be the Curl buffer just like M2 input. Its Zout is in the single digit range, but alas, not single-ended.
BTW my avatar is my re-purposed Zen v4 chassis upgraded to M2 monoblock. Everyone should have an M2.
experiments continue with the Mofo.
Two components needed for Big-MoFo. Arrived at my home the Hammond 193V and smps MeanWell LRS-200-24. Changes to the cabinet to place under the power supply. I wait to have time to put a panel connector to supply the 230V AC and complete the wiring.
In the meantime I have exhumed my old tube pre with 6SN7 sylvania (this is the KISS of Ciro Marzio: simple common cathode with plate loaded by an autotransformer .... zero electrolytics on the circuit and on the power supply ... only caps in polypropylene CLC ... 5Y3 rectifier) and the quality of the Mofo came out explosively ..... I just forgot that I had only 12 Watt available .... only 12w .... but my pre can field 20db of gain .... and the MOFO sings ... really wonderfully. no constriction or hardening .... perfect.
The experiment with the pre of juma(with supply Salas shunt) of which I mentioned in a previous post I was not satisfied ..... only 10-11db of gain and lack of vitality '.... but it is probably only unsuitable to work with the Mofo dates its characteristics (no gain).
Now let's see what happens with Big-MoFo ... I suspect an increase in the dynamics and quality of the soundstage .... which is already high quality.
Now that I have found the good companion for the MoFo I would have a little question for Mister Rotacher but also for all those who want to give me an opinion.
I am convinced of the importance of a well conceived power supply for each device and every time I have taken care of this aspect I have had happy results.
I wonder: is it irrelevant in the case of Mofo to move from a SMPS to a linear power supply?
this is a crucial consideration .... a well done linear is more expensive and requires space .... but if it's worth it there are many valid solutions
Two components needed for Big-MoFo. Arrived at my home the Hammond 193V and smps MeanWell LRS-200-24. Changes to the cabinet to place under the power supply. I wait to have time to put a panel connector to supply the 230V AC and complete the wiring.
In the meantime I have exhumed my old tube pre with 6SN7 sylvania (this is the KISS of Ciro Marzio: simple common cathode with plate loaded by an autotransformer .... zero electrolytics on the circuit and on the power supply ... only caps in polypropylene CLC ... 5Y3 rectifier) and the quality of the Mofo came out explosively ..... I just forgot that I had only 12 Watt available .... only 12w .... but my pre can field 20db of gain .... and the MOFO sings ... really wonderfully. no constriction or hardening .... perfect.
The experiment with the pre of juma(with supply Salas shunt) of which I mentioned in a previous post I was not satisfied ..... only 10-11db of gain and lack of vitality '.... but it is probably only unsuitable to work with the Mofo dates its characteristics (no gain).
Now let's see what happens with Big-MoFo ... I suspect an increase in the dynamics and quality of the soundstage .... which is already high quality.
Now that I have found the good companion for the MoFo I would have a little question for Mister Rotacher but also for all those who want to give me an opinion.
I am convinced of the importance of a well conceived power supply for each device and every time I have taken care of this aspect I have had happy results.
I wonder: is it irrelevant in the case of Mofo to move from a SMPS to a linear power supply?
this is a crucial consideration .... a well done linear is more expensive and requires space .... but if it's worth it there are many valid solutions
Attachments
Nice work sonteroexperiments continue with the Mofo.
Two components needed for Big-MoFo. Arrived at my home the Hammond 193V and smps MeanWell LRS-200-24. Changes to the cabinet to place under the power supply. I wait to have time to put a panel connector to supply the 230V AC and complete the wiring.
In the meantime I have exhumed my old tube pre with 6SN7 sylvania (this is the KISS of Ciro Marzio: simple common cathode with plate loaded by an autotransformer .... zero electrolytics on the circuit and on the power supply ... only caps in polypropylene CLC ... 5Y3 rectifier) and the quality of the Mofo came out explosively ..... I just forgot that I had only 12 Watt available .... only 12w .... but my pre can field 20db of gain .... and the MOFO sings ... really wonderfully. no constriction or hardening .... perfect.
The experiment with the pre of juma(with supply Salas shunt) of which I mentioned in a previous post I was not satisfied ..... only 10-11db of gain and lack of vitality '.... but it is probably only unsuitable to work with the Mofo dates its characteristics (no gain).
Now let's see what happens with Big-MoFo ... I suspect an increase in the dynamics and quality of the soundstage .... which is already high quality.
Now that I have found the good companion for the MoFo I would have a little question for Mister Rotacher but also for all those who want to give me an opinion.
I am convinced of the importance of a well conceived power supply for each device and every time I have taken care of this aspect I have had happy results.
I wonder: is it irrelevant in the case of Mofo to move from a SMPS to a linear power supply?
this is a crucial consideration .... a well done linear is more expensive and requires space .... but if it's worth it there are many valid solutions
I have linear supply and i like sound very much. Sorry i can’t help you more.
Thanks El ReinoNice work sontero
i can’t help you more.
You are welcome !!
my question is for those who have made a comparison or think that in this amplifier a linear power supply is essential ... so I also welcome your experience
Hi everyone.
I need some help with the MoFo I'm building on a proto board - I can not bring the current down, it stays at around 4A.
The choke is a microwave transformer @200mH, 1.9 ohm (measured with my cheap LCR meter).
FET is IRFP150,
P1 is 25K.
V+ is 20V, 24V in, CxMx, then CRC with 15mF-0.05ohm-15mF.
Not sure what am I doing wrong. The current through the FET sits at 4A no matter how many turns I turn P1 either CW or CCW.
The FET is hot to the touch, but it tolerates the current (being bolted to a massive heatsink), there is no smell or smoke from burnt components.
Will be great if someone can point to the error I've made.
Below are some photos.
Thank you.
I need some help with the MoFo I'm building on a proto board - I can not bring the current down, it stays at around 4A.
The choke is a microwave transformer @200mH, 1.9 ohm (measured with my cheap LCR meter).
FET is IRFP150,
P1 is 25K.
V+ is 20V, 24V in, CxMx, then CRC with 15mF-0.05ohm-15mF.
Not sure what am I doing wrong. The current through the FET sits at 4A no matter how many turns I turn P1 either CW or CCW.
The FET is hot to the touch, but it tolerates the current (being bolted to a massive heatsink), there is no smell or smoke from burnt components.
Will be great if someone can point to the error I've made.
Below are some photos.
Thank you.
Attachments
OK, I should have been more specific.
This is the second channel and the FET is not soldered, just plugged in there for the photo.
Otherwise the boards are identical.
I am just working on one channel and ironing out possible wiring and other faults, e.g. found that P1 was 200K, also there was no GND connection to the bottom of the choke.
The worrying part is the Pot has no influence on the bias through the FET and I don't know why, everything is wired according to the diagram on p.4 of the original MoFo file.
This is the second channel and the FET is not soldered, just plugged in there for the photo.
Otherwise the boards are identical.
I am just working on one channel and ironing out possible wiring and other faults, e.g. found that P1 was 200K, also there was no GND connection to the bottom of the choke.
The worrying part is the Pot has no influence on the bias through the FET and I don't know why, everything is wired according to the diagram on p.4 of the original MoFo file.
Look at the soldering of the FET itself circled two dry joints!
View attachment 683598
That might be the cause.
Hi formantjim, you'll might be pleased to know that you were very close to the mark.
Turned out that the channel under test had a broken track between the gate of the Fet and its gate stopper resistor, although both are probably 1 mm apart.
Thank you for the lead in the right direction.
Once repaired all went fine - adjusted bias to 1.6A, stays steady, monitored for an hour.
Tomorrow will test the other channel, hope will be good from the start.
Some photos of the one under test.
Attachments
Big-MoFo in action.
Finished construction (added SMPS MeanWell LRS-200-24 and related IEC connector and 193V inductor)...look this post
fixed the bias to 2.4A for 24V. In static mode the heatsinks now heat up more but my hand can leave it without bother ... I do not want to measure.
A dear friend made me available the pre john curl (a clone kit by Jim'sAudio) ... the JC-2 .... with excellent components. And so obviously I tried it.
I sincerely say that coupled with BigMofo the result was very good.
But .... poor JC-2 ... when he came back into action my KISS with the 6SN7 has just disappeared. With the tubes comes into action a great sound .... wonderful performance .... the power, the dynamics, the detail, the soundstage reach an incredible quality level.
BigMoFo = A MASTERPIECE .... I do not know how to define it better and at this point it emerges that the preamp is a good project with the tubes.
All this of course IMHO
Finished construction (added SMPS MeanWell LRS-200-24 and related IEC connector and 193V inductor)...look this post
fixed the bias to 2.4A for 24V. In static mode the heatsinks now heat up more but my hand can leave it without bother ... I do not want to measure.
A dear friend made me available the pre john curl (a clone kit by Jim'sAudio) ... the JC-2 .... with excellent components. And so obviously I tried it.
I sincerely say that coupled with BigMofo the result was very good.
But .... poor JC-2 ... when he came back into action my KISS with the 6SN7 has just disappeared. With the tubes comes into action a great sound .... wonderful performance .... the power, the dynamics, the detail, the soundstage reach an incredible quality level.
BigMoFo = A MASTERPIECE .... I do not know how to define it better and at this point it emerges that the preamp is a good project with the tubes.
All this of course IMHO
Exactly
I'm glad I'm not the only one that thinks so!
Lent mine out and starting to miss it.
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I'm glad I'm not the only one that thinks so!
Lent mine out and starting to miss it.
Simple solution. Build another and when your first one returns,
you can run the pair balanced.