DIY Audio Projects Forum
http://diyaudioprojects.com/Forum/

First DIY amp FINISHED - 300B SET - works!
http://diyaudioprojects.com/Forum/viewtopic.php?f=9&t=1932
Page 2 of 9

Author:  cbj591 [ 17 May 2010, 07:41 ]
Post subject:  Re: First DIY amp FINISHED - 300B SET - works!

No offense at all, I'm just not sure why we do it like we do. It doesnt make sense to me either. :up:

Take care

Brian

Author:  sampleaccurate [ 17 May 2010, 07:48 ]
Post subject:  Re: First DIY amp FINISHED - 300B SET - works!

azazello wrote:
I mean in Europe /in Bulgaria/ 1 big transformer /in building/ between some avenue and all cables are closed under ground never mind in towns or villages /sorry for off!/.

I can answer that. It's cheaper to put it up on poles.

Overhead high voltage lines are much much cheaper than underground cable, and if the poles are there already you can use them to hold cheap transformers up off the ground and keep all that stuff up high, bringing only the secondary voltage from the transformers down to the customers.

In downtown business districts there are usually underground systems, and almost all new urban residential development is mandated by the government to have underground electric. The differences in electric distribution are interesting across different nations. A coworker used to have that picture above on his desk, either that pole or one that looked identical.

I worked for electric utilities as an electrical engineer for 14 years.

Why does this blue glow on my 300Bs keep coming and going? It's there, it disappears, it reappears. What's up with that?

Author:  cbj591 [ 17 May 2010, 08:06 ]
Post subject:  Re: First DIY amp FINISHED - 300B SET - works!

The blue glow must be from the 3-D wiring :P

Author:  tombethe [ 17 May 2010, 08:12 ]
Post subject:  Re: First DIY amp FINISHED - 300B SET - works!

Hi sample...

How many volts are on the 300B plates??

Maybe it's some kind of overvoltage / overload that results in gas / plasma glow...

Author:  cheap-Jack [ 17 May 2010, 08:35 ]
Post subject:  Re: First DIY amp FINISHED - 300B SET - works!

sampleaccurate wrote:
a single ended triode 300B stereo amp.
I used SMPSs for the heaters,

Hi

What power supply is a "SMPS"?

c-J

Author:  sampleaccurate [ 17 May 2010, 09:27 ]
Post subject:  Re: First DIY amp FINISHED - 300B SET - works!

cheap-Jack wrote:
What power supply is a "SMPS"?

SMPS - switched mode power supply - same thing used in the oddwatt. It's a really economical and lightweight way of powering heaters. I used a 12 volt DC SMPS to power the two 6SN7 heaters in series and a 5 volt SMPS to power each of the 300B heaters.

B+ is only 320 volts. I might take it to about 400 and see what happens.

BTW, this is the circuit but DC heaters and a SS power supply were used:

Image

Author:  azazello [ 17 May 2010, 10:10 ]
Post subject:  Re: First DIY amp FINISHED - 300B SET - works!

When blue cloud is more?....Lets I know?....Maybe in pauses ? Maybe I have some explanation ?

Author:  cheap-Jack [ 17 May 2010, 11:24 ]
Post subject:  Re: First DIY amp FINISHED - 300B SET - works!

sampleaccurate wrote:
switched mode power supply

HI.

That exactly what I thought it is. I just want to you to confirm to me.

The last PS I would use to power any audio amps is switch mode, a hugh generator of RFI, let alone heating tubes.

Here what I am using to power the 6.3V tube heaters of my tube phonostages:- a digital power pack comprising a 6V sealed lead acid cell, rechargeable by a 7.5V SMPS.

Yes, I've chosen SMPS for its constant regulated voltage O/P, extremely efficient, cool running & very small size. I scrapped the SMPS board from a redundant charger sleeping in my parts bin & used it to build an small outboard 6.3V heater pure DC power pack for my phonostages.

So pure DC heating means no hum from the tube heaters/filaments, which is crucial for DHT like 300B & the likes. I have the heater circuit floated from the phonostage circuit to ensure zero ground loop from the PS.

Knowing SMPS is a well-known RFI generator, it must be 100% isolated from any audio circuitry, including their AC powerlines. To ensure no RFI generated from the digital power pack affecting my auido rig, I've so design/built this digital heater power pack that when the SLA cell inside the power pack is heating the tube heaters when I am playing LPs, the digital charger is always switched off & electrically 100% isolated from the SLA cell.

Under no circumstances the digital charger & the SLA cell work at the same time by proper switching circuitry incorporated in the power pack, which is built in a small plastic equipment box, 7.5" x 3.5" x 2.5". Thanks to the miniature 7.5V 4ADC digital PS board, only 2.5" x 2". which permitted me to build the entire PS (digital charging board + 6V SLA cell + all switching gears, LED indictors & voltage measuring points etc etc) in such a small box !!!!

To further ensure no RFI leaking via its AC powre cord & battery DC cables hooked up to the phonostages, they both have RFI ring suppressor snapped on.

I enjoy the pure DC heating sound let alone cute looking of the small power pack, which sits right beside my super-upgraged Dynaco PS-2 pre-amp.

c-J

PS: IMO, you are playing with (RFI) fire !

Author:  tombethe [ 17 May 2010, 12:16 ]
Post subject:  Re: First DIY amp FINISHED - 300B SET - works!

320Volts is OK. Then it's a fluorescent glow.

The electrons from the cathode hit some cobalt (i.e.) particles on their way to the plate.
That causes the cobalt atoms to emit visible blue glowing photons. Don't care...

PS - 400V is still OK...

Have fun ;-).

Author:  Bennybuis [ 17 May 2010, 13:57 ]
Post subject:  Re: First DIY amp FINISHED - 300B SET - works!

Hi eberybody,

my coke bottle KT88 from Sovtek, who ever may make them (probably Reflector Corp, Saratov), have a slight blue glow as well, only visible at night. They did that from day one, nothing to worry about. I find it very beautiful.

Page 2 of 9 All times are UTC - 6 hours [ DST ]
Powered by phpBB® Forum Software © phpBB Group
http://www.phpbb.com/