DIY Audio Projects Forum
 NEW  Matt presents bias and operation data for the 6V6 tube in SE operation - 6V6 Single-Ended (SE) Ultra Linear (UL) Bias Optimization.

DIY Audio Projects Forum

Welcome to the DIY Audio Projects Message Forum. Use these forums to discuss Hi-Fi audio and to share your DIY Audio Projects. Registration is free and required to post messages and view the file attachments. Registration will only take a minute and registered users do not see any advertisements. After you have completed the online registration process, check your email (including spam/junk folder) for the verification email to activate your account. New members are under moderation - so your posts will not be visible until approved by a moderator. See the Read Me 1st, Forum RULES and Forum FAQ to get started on the forum.

It is currently 16 Dec 2019, 04:48

All times are UTC - 6 hours [ DST ]




Post new topic Reply to topic  [ 524 posts ]  Go to page Previous  1 ... 4, 5, 6, 7, 8, 9, 10 ... 53  Next
Author Message
PostPosted: 18 Oct 2010, 23:50 
Offline
Project Author
User avatar

Joined: 06 Jun 2008, 18:23
Posts: 5151
Location: Australia
Suncalc wrote:
An interesting issue has arisen with the power supply.

The combination of the high DC voltage (454v) and the moderately high current (196mA), giving rise to an equivalent load of only 2.31kΩ, while using a vacuum tube rectifier (5U4) means that the effective Edc/Em is only about 0.74. This means that I need a transformer secondary voltage of 1226VCT. I can get a 700 series Hammond transformer with a 1250VCT, 200mA secondary (it's an 8 pound beast) but it has no filament windings. This means that I'm thinking about a dual secondary Hammond u-bracket transformer for the 300B DC heaters (to remain hidden inside the chassis) and an Edcor dedicated filament transformer (XPWR28) for the 5U4 and 6SN7 filaments.

It looks like the power supply itself is going to be more complicated then the rest of the amp. I'll get the details of the design decisions and the resultant schematics posted as soon as possible.

I can make this a feature, not a work-around.

_________________
Projects: "Precision" - 300W Class AB Holton power amp | "retro2308" - chip based headphone amp | ”Calibre 834” - tube phono MM preamp |


Top
 Profile  
 
PostPosted: 19 Oct 2010, 07:48 
Offline

Joined: 18 Jun 2010, 12:46
Posts: 284
Location: Northern VA
According to the datasheets I'm reading the 5U4GB is limited to a 1100 Volt Plate to Plate AC voltage and that's with a choke input supply. It's 900 Volts for a cap input supply

Were you planning on a choke input or cap input power supply?

You may need to go with Damper Diodes, and with damper diodes the voltage drop is much less than a 5U4, so you could get away with a lower voltage transformer, they are also cheaper.
Suncalc wrote:
An interesting issue has arisen with the power supply.

The combination of the high DC voltage (454v) and the moderately high current (196mA), giving rise to an equivalent load of only 2.31kΩ, while using a vacuum tube rectifier (5U4) means that the effective Edc/Em is only about 0.74. This means that I need a transformer secondary voltage of 1226VCT. I can get a 700 series Hammond transformer with a 1250VCT, 200mA secondary (it's an 8 pound beast) but it has no filament windings. This means that I'm thinking about a dual secondary Hammond u-bracket transformer for the 300B DC heaters (to remain hidden inside the chassis) and an Edcor dedicated filament transformer (XPWR28) for the 5U4 and 6SN7 filaments.

It looks like the power supply itself is going to be more complicated then the rest of the amp. I'll get the details of the design decisions and the resultant schematics posted as soon as possible.


Top
 Profile  
 
PostPosted: 19 Oct 2010, 08:32 
Offline
Project Author
User avatar

Joined: 08 May 2009, 08:20
Posts: 918
Location: Duesseldorf, Germany
Hi Matt,

just a little question:

What about using an hybrid rectifier setup (i.e. Graetz bridge with 2 diodes in front and the 5GU for the voltage output)?
IMO - that could also be more effective.. Thus you'll have the current transformer in series (no CT) and nearly double the voltage.

Just my :2c:.

Have fun ;-).

_________________
Cheers,
Tom.

Some of my projects: TDA2050 Chip Amp, the LM3886 Gainclone Thread and the Szekeres Headamp Thread.


Top
 Profile  
 
PostPosted: 19 Oct 2010, 09:24 
Offline
Project Author
User avatar

Joined: 06 Apr 2009, 10:08
Posts: 1596
Location: US Pacific Northwest
Rock4016;

You are entirely correct in the limitations of the 5U4GB. The PIV is 15550V but the max AC per plate is 450VAC/550VAC (cap/choke). I can't used damper diodes because the current draw is too high and even the 35Z5GT in a hybrid topology won't help me here. I may have to revert to solid state diodes in the HV supply.

Mark; how do you feel about not having the 5U4 in the power supply? I could still use it for the 6SN7 and substitute the Edcor XPWR028 with one that has a high voltage secondary. Of course this may greatly increase the amount of filter iron in the amp. Or I can just substitute two diodes for the 5U4 and see where that takes me. It might also allow me to use an Edcor power transformer. Something like the XPWR073 or XPWR077 would fit the bill and also eliminate the dedicated filament transformer for the 6SN7.

I'm a little leery of the hybrid full wave bridge approach due to the much higher current rating required from the transformer. I'm not sure I could find a transformer with a high enough current rating at the required voltage.

Comments?

_________________
Matt
It's all about the Glass!
http://www.CascadeTubes.com
Cascade Tubes Blog


Top
 Profile  
 
PostPosted: 19 Oct 2010, 11:06 
Offline

Joined: 18 Jun 2010, 12:46
Posts: 284
Location: Northern VA
Most damper diodes can handle 150 mA each, the 6CM3 can handle 350 ma. And at 350 mA draw it only drops 10 volts. Thats quite impressive, also it's in a 9 pin envelop so it doesn't take up a lot of chassis room for a pair of 9pin sockets.

And they are affordable, and will have better bass than a 5U4 because of the much lower Rp.


Top
 Profile  
 
PostPosted: 19 Oct 2010, 15:45 
Offline
Project Author
User avatar

Joined: 06 Jun 2008, 18:23
Posts: 5151
Location: Australia
Matt:

Firstly I am happy to go with Hammond or Edcor power trannies. I'm Ok with a seperate filament transformer. I would rather tube rectifiaction over SS rec. and I want to use a choke. I realise if we go DC on the 300B filaments I would use diodes there.

These are only wishes and if it can't be done no big deal Whatever works Matt. I realise there are compromises in all designs. I leave it upto you.

_________________
Projects: "Precision" - 300W Class AB Holton power amp | "retro2308" - chip based headphone amp | ”Calibre 834” - tube phono MM preamp |


Top
 Profile  
 
PostPosted: 19 Oct 2010, 18:00 
Offline
Project Author
User avatar

Joined: 06 Apr 2009, 10:08
Posts: 1596
Location: US Pacific Northwest
Here's a good lesson for everybody. Don't rush your design and double check everything. In short, I messed up. :blush:

I was rushing the power supply design and failed to include a simple sqrt(2) factor in one of my equations. I don't need a 1250VCT transformer, I only need an 867VCT transformer. I kept looking at the GE 5U4 data sheet wondering why they could included a simple typical operation example with a 460v output and why I couldn't make my design do the same thing. :? Then I found my math mistake. OOPS!

Oh well. I guess I'll sharpen my pencil and try it again from scratch. The good news is that this should allow me to keep the 5U4 AND make the PS design a lot simpler.

I'll let everyone know how it goes.

_________________
Matt
It's all about the Glass!
http://www.CascadeTubes.com
Cascade Tubes Blog


Top
 Profile  
 
PostPosted: 20 Oct 2010, 07:42 
Offline

Joined: 18 Jun 2010, 12:46
Posts: 284
Location: Northern VA
mwhouston wrote:
Firstly I am happy to go with Hammond or Edcor power trannies. I'm Ok with a seperate filament transformer. I would rather tube rectifiaction over SS rec. and I want to use a choke. I realise if we go DC on the 300B filaments I would use diodes there.

These are only wishes and if it can't be done no big deal Whatever works Matt. I realise there are compromises in all designs. I leave it upto you.

Since this is going to be a "high end" performing amp, have you considered mono-blocks? The PS is not done you still have time to weigh that option.


Top
 Profile  
 
PostPosted: 20 Oct 2010, 15:57 
Offline
Project Author
User avatar

Joined: 06 Jun 2008, 18:23
Posts: 5151
Location: Australia
Not considering mono-blocks at this point. I've now been asked by the customer to seekout some high-end filter caps. Any suggestions?

_________________
Projects: "Precision" - 300W Class AB Holton power amp | "retro2308" - chip based headphone amp | ”Calibre 834” - tube phono MM preamp |


Top
 Profile  
 
PostPosted: 20 Oct 2010, 19:23 
Offline

Joined: 18 Jun 2010, 12:46
Posts: 284
Location: Northern VA
If you don't mind the size I'd use these for filter caps.
https://www.surpluscenter.com/item.asp? ... 5&catname=

If you are size restricted then these would do great.
http://www.partsconnexion.com/capacitor ... mtube.html


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 524 posts ]  Go to page Previous  1 ... 4, 5, 6, 7, 8, 9, 10 ... 53  Next

All times are UTC - 6 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 25 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Jump to:  
DIY Tube Projects :: DIY Tube Amp Kits :: DIY Speaker Projects :: DIY Solid State Projects :: DIY IC / Op-amp Projects :: DIY Phono Projects :: DIY Cable Projects :: Hi-Fi Audio Schematics
© diyAudioProjects.com - Terms of Service - Privacy Policy