[SripBoard Design] Starving Student Millett Hybrid Vacum Tube Amp - Page 6

the total price is pretty high. you cant order from mouser or digikey?

as for the caps, you definitely want wima for the output bypass caps, and they are good for the coupling position.

does the place your ordering from not carry nichicon capacitors?

and you kind of want a high quality potentiometer. if you think about it, its really the first component that comes into contact with the signal that could introduce noise. alps are good, but there are lots that are even better. 

as far as i can tell it looks correct. your getting 100 each for resistors? 

also its ok to use 1/2 watt resistors. you can get higher tolerances without a change in performance, you just cant get lower tolerances, for example 1/8 watt

Quote:

Originally Posted by TestSubject 

I wish someone would confirm that im following the right schematics... Also are the "Optional" components worth it SQ wise?

 

EDIT: The design is the same except for the "Optional" stuff and for the values of other components. I Havent bought anything yet. if the new one is better, where can i find a BOM?

 

Quote:

Originally Posted by TestSubject 

 

Hello,

 

I Havent been very well for the past week, but here is an update, I am about to order the components

 

A couple things are bugging me, for one, the price, 63 Euros, thats about 90$.

 

2) of all the recomanded brand for caps only wima was available, is it worth it sice i cant get the other good brands?

 

3) 33k Ohms resistors are only available at 1/2 watts

 

4) no 50 K available

 

5) MOSFETS IRF510 are not available, any alternative?

 

6) only stereo 50 K Pot is at 17 euros/ 25$ i mean really? looks good but...

 

The Psu and tube sockets are ordered.

47k resistor? I don't see it on the schematic.

There are lots of different kinds of Wima caps(I noticed you have a 1600v part in your cart, which will cost a lot more than something like a 63v part, which will work fine here). You can look for a cheaper one(any voltage rating 63v and higher) or just substitute something else, like Epcos or anything with close to the same uF/nF value. It doesn't need to be a box cap, it can be radial or axial leaded. You don't even need it at all and could omit it for now, and install one later if you want.

The half watt resistor for 33k will be fine.

The mosfets will be dissapatind around 5.5watts so they should have a fairly good heatsink. 

I don't know what to say about the volume control pot. Perhaps look at a Panasonic for some alternatives.

Quote:

Originally Posted by digger945 

47k resistor? I don't see it on the schematic.

 

testsubject said 50k resistors are out of stock at that shop

Quote:

Originally Posted by kchapdaily 

 

testsubject said 50k resistors are out of stock at that shop

I do not see 50k on the schematic either.

You could substitute an IRF610 if you can not find an IRF510 anywhere.

look right after the left and right rca input

Quote:

Originally Posted by kchapdaily 

look right after the left and right rca input

Oh. Those 50k 

At first glance I hesitate to say that they are necessary at all. 47k would be fine as a substitute.

Pierre, do you have TO220 insulator pads and screw mounting bushings for your IRF parts?

Insulator pads, etc. -> http://www.google.com/search?rlz=1C1GGGE_enUS357US359&sourceid=chrome&ie=UTF-8&q=to220+insulator#q=to220+insulator&hl=en&rlz=1C1GGGE_enUS357US359&prmd=ivns&source=univ&tbm=shop&tbo=u&sa=X&ei=QSE_Tq79F4-DsgKjx9AS&ved=0CFQQrQQ&bav=on.2,or.r_gc.r_pw.&fp=c15b6bc10f253e42&biw=1280&bih=709

Mounting bushing(part E or F to fit your part) ->  http://www.cpcares.com/pdf/1610.pdf

id say use mousers to220 mounting kit but thats out of the question. 

you definitely need a mounting kit that has nylon (or some other non-conductive material) shoulder washers otherwise your heatsinks may become attached to ground which could cause problems. just search whatever site your using for parts for a to-220 heatsink mounting kit.

@digger945

i think the 50k resistors help maximize the volume pots effectiveness. you could take them out and use an 100k pot but you would have to use the later 150degrees of rotation.

Quote:

Originally Posted by kchapdaily 

 

 

@digger945

i think the 50k resistors help maximize the volume pots effectiveness. you could take them out and use an 100k pot but you would have to use the later 150degrees of rotation.

Ah yes. So the pointer on the volume knob looks more presentable. I understand why some would like to see it at noon rather than 7 o'clock. 

I can send the mounting hardware if necessary. I will see if what I have on hand will fit the tab holes for the IRF parts.

EDIT: ... and yes, you are correct that you will have a little more precise setting on the volume control.

Pierre, good to see you are back.

I am at work so didn't really get a chance to review your circuit revision for correctness, but one thing I noticed right away was that your tube socket's traces are incorrect (bridging pin2 to pin7 and pin3 to pin8). If you look at the schematic again, the numbering is not in the right order from 1 - 8. It flips at #6. I'll check the rest of the traces tonight when I get home.

Also nice choice of headphones, I have been wanting a dt770 as well, I may pick one up too.

I just had a chance to review the latest revision. There are a couple things I spotted that needs to be looked over:

- R1 & R2 are not supposed to be connected to Q1's drain (pin2)

- I suppose you are not including caps 7 & 8?

- Also in my last comment, I mentioned the unordered socket pins on the starving student schematic... I do realize your schematic's socket only has 8 pins (instead of 9) as well. Maybe you intentionally drawn lines that way knowing that you can always cross the wires on the production model.

Hope that helps!

As far as pin9 goes, on the SS schematic it should be the dip in between pin4 & 5, which is not being used. I'm not exactly sure what it does though. If you look on my pcb design you can see how the traces are connected within the socket pins. http://www.head-fi.org/forum/thread/565483/12au7-starving-student-custom-pcb-drawing-critique-please#post_7653338

For caps 7 and 8, I would just put them in there. Dsavitsk and Tomb advised me to just go with all of the optional components since they are fairly cheap and will definitely help. And for the resistors, the larger the watt, the safer. You are just sacrificing a larger physical size.