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Millett "Starving Student" hybrid amp - Page 449

post #6721 of 6782
Quote:
Originally Posted by Greystoke View Post
 

What are people using for the internal case wiring for these amplifiers?  I see references to "silver wire," is that better for wiring up circuits?  I'm still putting together the parts for one of these projects, and wanted to make sure I had everything on hand.

The wire that most people use are solid core silver plated copper or plain old copper for the internal wiring inside amps.  If you want you can invest in silver wire but that is going to be very very expensive and honestly I don't think it will make a difference.  If you want something that is cheap and easy to use get some wire from navships on ebay.  Even though its stranded it will work wonderfully. 

post #6722 of 6782
Quote:
Originally Posted by Zashoomin View Post
 

The wire that most people use are solid core silver plated copper or plain old copper for the internal wiring inside amps.  If you want you can invest in silver wire but that is going to be very very expensive and honestly I don't think it will make a difference.  If you want something that is cheap and easy to use get some wire from navships on ebay.  Even though its stranded it will work wonderfully. 


I appreciate the lead for Navships' store!  I was looking at the OFC from vt4c, but if I can get something similar without the long shipping time that sounds preferable.  

post #6723 of 6782
Quote:
Originally Posted by Greystoke View Post
 
Quote:
Originally Posted by Zashoomin View Post
 

The wire that most people use are solid core silver plated copper or plain old copper for the internal wiring inside amps.  If you want you can invest in silver wire but that is going to be very very expensive and honestly I don't think it will make a difference.  If you want something that is cheap and easy to use get some wire from navships on ebay.  Even though its stranded it will work wonderfully. 


I appreciate the lead for Navships' store!  I was looking at the OFC from vt4c, but if I can get something similar without the long shipping time that sounds preferable.  


I don't like to be contradictory with a very helpful post, but stranded is all I've ever used or heard recommended for hookup wire.  Then again, maybe PTP is different than just "hookup" wire.

 

As for Navships - agree 100%.  The best is 22ga SPC multi-strand.  It tends to be a little stiff, but not nearly as much as a solid variety.  I've used it on everything I've built for years and years.  It's outstanding stuff and the insulation won't shrink and pull back from a solder joint.

post #6724 of 6782
Solid wire is good for hookup or P-t-P because it can be 'dressed' into corners or otherwise shaped and it'll stay put.

We use 'trirated', a stranded wire rated for high voltage , to wire mains-voltage instrument panels with coiled strain reliefs, which also serve to allow replacement of a breaker or instrument in the event that a wire should need to be stripped back. Stranded is good in looms.

w
post #6725 of 6782


I'm not sure anyone was talking about switchgear. ;) 

 

Quality stranded is still best for DIY-ing small stuff, which is just about everything in do-it-yourself audio equipment.  Stranded is its own strain relief, whereas solid can easily break, torque loose less-than-perfect solder joints, and generally create a stiff mess for casing up the typical DIY amplifier.  Yes, solid will stay where you put it and it may be adequate for PTP, but you can still do the same with stranded and probably have safer joints.  JMHO. 


Edited by tomb - 2/14/14 at 9:34am
post #6726 of 6782
No experience of wire-wrap, tomb? http://en.m.wikipedia.org/wiki/Wire_wrap

There is a reason why solid, insulated wire is made. Your humble opinion notwithstanding, users should think about which type of wire will give best service in their particular application, rather than trying to apply some Procrustean rule-slicing to make stranded hook-up wire fit your class of DIY items.

I understand the Bottlehead tube amp and preamp kits are all supplied with solid wire for hookup.

I always use solid wire when wiring tube equipment PtP (except when I don't). I keep a supply in various colours for just that purpose. Try it, it's easier.

w
post #6727 of 6782
Quote:
Originally Posted by wakibaki View Post

No experience of wire-wrap, tomb? http://en.m.wikipedia.org/wiki/Wire_wrap

There is a reason why solid, insulated wire is made. Your humble opinion notwithstanding, users should think about which type of wire will give best service in their particular application, rather than trying to apply some Procrustean rule-slicing to make stranded hook-up wire fit your class of DIY items.

I understand the Bottlehead tube amp and preamp kits are all supplied with solid wire for hookup.

I always use solid wire when wiring tube equipment PtP (except when I don't). I keep a supply in various colours for just that purpose. Try it, it's easier.

w


Nope.

post #6728 of 6782

Hi just wondering if anybody could please help out with a first time build that has been 3+ years in the making.

 

One of the tubes does not light.  I have tried the following:

- checked wiring

- changed mosfet

- tested voltage points (19v and 63v), both ok

- swapped tube

- swapped out capacitors

 

I have trawled the thread for any other solutions and think that a total rebuild may be brewing.

Before I do so can anybody suggest any other courses of action?

Are there any other voltage points I should test to isolate the problem?  My electronics knowledge is limited so I have been paranoid about too much prodding in case I destroy a 19j6 as they are pretty rare/expensive nowdays.

I have been told that it is very unlikely, but is there any chance of a dud resistor?

 

Sorry about the curt-ish post, I did type an elaborate more detailed post earlier but for some reason the browser refreshed and I had to start this one again.

Thanks for reading and I hope somebody can lend a hand. 

post #6729 of 6782
Quote:
Originally Posted by the_Samurai_chicken View Post
 

Hi just wondering if anybody could please help out with a first time build that has been 3+ years in the making.

 

One of the tubes does not light.  I have tried the following:

- checked wiring

- changed mosfet

- tested voltage points (19v and 63v), both ok

- swapped tube

- swapped out capacitors

 

I have trawled the thread for any other solutions and think that a total rebuild may be brewing.

Before I do so can anybody suggest any other courses of action?

Are there any other voltage points I should test to isolate the problem?  My electronics knowledge is limited so I have been paranoid about too much prodding in case I destroy a 19j6 as they are pretty rare/expensive nowdays.

I have been told that it is very unlikely, but is there any chance of a dud resistor?

 

Sorry about the curt-ish post, I did type an elaborate more detailed post earlier but for some reason the browser refreshed and I had to start this one again.

Thanks for reading and I hope somebody can lend a hand. 


Pics, pics, pics.

 

1. It's highly unlikely that you can destroy a tube, unless the heater voltage is way out of spec.

2. Chances of a dud resistor are indeed, extremely unlikely.

post #6730 of 6782

Good news! Only one of the tubes does not light.

 

This means that at least some of the other stuff is working.

 

You say 19J6, so I'm guessing that you have built this schematic:-

 

http://www.pmillett.com/starving.htm

 

It sounds like you have already tried most sensible possibilities, now we have to look for less likely possibilities.

 

Check that you actually have ~19V on pin 3 of the tube that doesn't light. Not 'at pin 3 of the tube socket', but actually on the pin. Most sockets will still let you access the pin from the bottom, or you'll have to try to get by pulling the tube partway out of the socket. On occasion corrosion can prevent a good contact.

 

Check for continuity between pin 4 (of the tube) and ground.

 

Check for continuity between pins 3 and 4 of the affected tube. 19V/150mA, you should have a resistance of ~123 ohms.

 

If you have these things, the tube will light.

 

Now - you can have ~19V showing at pin 3, and there still be a fault, if there is no continuity to ground (the tube is open circuit or pin 4 is not making good contact to ground), if there is a poor joint somewhere further up towards the PSU. This will result in there being ~19V measured (through a high impedance), but it will collapse when a good ground is made, so you need to be sure that the 19V is there when the tube is not O/C and pin 4 is securely grounded.

 

w

post #6731 of 6782

Gentlemen,

Thankyou both for your input.

 

Sorry tomb but I didn't have a photo taking device at time of post.  BUT I think that I have it sorted.  Ends up that the copper board I was earthing to had a plastic-y layer which melted/adhered to the solder and appeared okay solder.  But wasn't earthed....

 

Couldn't understand why I kept frying mosfets after torquing them down nicely.  Forum search reveals they have to be insulated... head slap moment.

SO assuming I can track down some silicon/mica insulation material. I think we are good to go!

 

 

 

Finally a question on the sound characteristics of this amp.  Admittedly I used a cheap pair of buds to test, but the sound was thin/tinny and detached. Kind of like a kids telephone (think can-string-can jobbie).  I used nichicon muse 220uf cap's and some other 0.1uf random film caps (limited choice). Would this be the culprit or some other gremlin?

 

Thanks again!

post #6732 of 6782
Quote:
Originally Posted by the_Samurai_chicken View Post
 

Gentlemen,

Thankyou both for your input.

 

Sorry tomb but I didn't have a photo taking device at time of post.  BUT I think that I have it sorted.  Ends up that the copper board I was earthing to had a plastic-y layer which melted/adhered to the solder and appeared okay solder.  But wasn't earthed....

 

Couldn't understand why I kept frying mosfets after torquing them down nicely.  Forum search reveals they have to be insulated... head slap moment.

SO assuming I can track down some silicon/mica insulation material. I think we are good to go!

 

 

 

Finally a question on the sound characteristics of this amp.  Admittedly I used a cheap pair of buds to test, but the sound was thin/tinny and detached. Kind of like a kids telephone (think can-string-can jobbie).  I used nichicon muse 220uf cap's and some other 0.1uf random film caps (limited choice). Would this be the culprit or some other gremlin?

 

Thanks again!


It's slightly possible that it was the earbuds.  If they are low impedance (16 ohms or less), the 220 uf caps are not going to be big enough to prevent cutting out a lot of bass.  However, "detached" and "can-string-can jobbie" sound pretty severe.  Based on your description above, it does not sound like you've listened to the amp yet with all components working, so I would not be concerned about what it sounds like until you get it all fixed.

post #6733 of 6782
post #6734 of 6782
Hi!

I've been pondering the power supply for a 12AU7 build (got a hold of some new Philips tubes, anybody try those out?).

I've found a cheap switched 48V 25W supply here in Sweden where I'm located.

Does anybody have thoughts on putting that inside a case together with this amp? Major source of noise? The supply itself comes in a metal casing with screw terminals for VAC in and VDC out. It would save me at least USD10 vs buying the spec.ed Cisco/Delta supply..

I've been simulating the amp with a 30V supply too. Seems to do fine in sim, but has anybody tried a lower anode voltage on a 12AU7? I read somewhere that the 12A7, IIRC, has the same low-voltage params as the AU7, in which case I'm guessing it should be fine...?

Lovely thread, lots of info, lots and lots of info. smily_headphones1.gif

Edit: Here's a link to the aforementioned psu: Linkedylink
Edited by swek - 2/18/14 at 3:43am
post #6735 of 6782
Edit: *facepalm* ...so it was being reviewed. Fry this.. Sorry
Edited by swek - 2/18/14 at 8:15am
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