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Eric Barbour's Brute force regulator mods

58.106.134.107
Posted on February 24, 2015 at 08:04:55
amnesiac
Audiophile

Posts: 717
Joined: August 21, 2002
 Hi I have been using this regulator in my preamp for at least 8 years now without ever touching it or changing a tube even. I want to use it in the driver stage of my new 814 amp.

I need to drop from 650 volts of my output supply to 300volts for the driver. Is this possible with this reg?

I am trying to avoid another power supply.

Thanks

 

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Youch! Don't do it inside the reg, posted on February 24, 2015 at 08:56:55
Chip647
Audiophile

Posts: 2651
Location: The South
Joined: December 24, 2012
 If your driver is drawing 10mA, the regulator may need 5mA itself

You will want around 325 volts feeding the regulator and 300 volts output. This is a much kinder load on the reg and it will need to dissipate a little more than 25 * 0.015 = 0.375 watts. (Dropping 350 volts in the reg will have it dissipating +5.25 Watts.

Just use a dropping resistor before the regulator (and add a cap to ground). To drop 325 volts with 15mA you can use a 22K resistor, You will need a 20 watt rated resistor as you will be passing 5 Watts. Then all is golden.

 

RE: Eric Barbour's Brute force regulator mods, posted on February 24, 2015 at 09:12:27
danlaudionut
Audiophile

Posts: 5480
Location: Schenectady
Joined: June 6, 2002
 No because the 6AS7G only handles 250V max.
You need to use another tube then yes.
What current is the driver needing?

DanL



 

RE: Eric Barbour's Brute force regulator mods, posted on February 24, 2015 at 11:14:35
Caucasian Blackplate
Industry Professional

Posts: 8313
Location: Seattle
Joined: June 18, 2004
 I'd imagine your driver could be tweaked to run on 400V.

You'll need to bias up the heater winding to +115V, be sure the rest of the tubes on that winding aren't going to mind.

A big dropping resistor to shave off 100V before the regulator would probably be enough to keep you out of trouble and get you back into a more reliable design.

 

RE: Eric Barbour's Brute force regulator mods, posted on February 24, 2015 at 12:52:12
JKT
Audiophile

Posts: 612
Location: Midwest
Joined: November 26, 2002
 If you would be interested in a shunt regulated supply instead of series regulation and are not SS phobic K&K Audio sells a kit that consists of a CCS and shunt reg. on one board. I did the beta testing for this and use it for the input and driver stages of my mono-blocks (122V & 434V). If you are using it with a single-ended stage the shunt current should approximately equal the current draw of the circuit so the heat sink on the shunt devise should be appropriately sized. The CCS needs to see ~50V across it, so dropping the raw voltage down to 350V with RC filter first is a very good idea. Shunt reg. the input and driver stages of my amps greatly improved their sonic presentation.


"It is better to remain silent and thought a fool, then speak and remove all doubt." A. Lincoln

 

+1 (nt), posted on February 24, 2015 at 13:51:56
Tre'
Industry Professional

Posts: 17302
Location: So. Cal.
Joined: February 9, 2002
 .
Have Fun and Enjoy the Music
"Still Working the Problem"

 

RE: Eric Barbour's Brute force regulator mods, posted on February 25, 2015 at 02:05:08
amnesiac
Audiophile

Posts: 717
Joined: August 21, 2002
 So can I set these and they will stay set for ten years? This amp will be so heavy I don't want to remove it much once it installed.

I have 4 salas regs that will not likely be built. I am concerned if I have the ability to see if they are unconditionally stable and if they will stay that way.

Are the K&K regs easier then salas regs? I thought the salas had a ccs too? how long have you had them running in your amp?





 

RE: Eric Barbour's Brute force regulator mods, posted on February 25, 2015 at 04:47:01
amnesiac
Audiophile

Posts: 717
Joined: August 21, 2002
 I haven't even decided on the tube yet. Thats the fun part. All the options. I might do something like a srpp direct coupled to a 6f6 . I was thinking if I go that way. I can elevate the driver tube and get a little closer to the b+.

This is my interstage from Silk audio.

I-511SD
5.0K
30mA (36mA)
1:0.5+0.5
55H
1.25K+1.25K
20Hz - 75KHz
SE to PP or A2 drive circuit. It has a 400volt rating

A 46 or 47 is another option.

4e27 is option 2 for output tube. Almost identical op point.

7k Tribute output trans.

 

RE: Eric Barbour's Brute force regulator mods, posted on February 25, 2015 at 09:07:48
Caucasian Blackplate
Industry Professional

Posts: 8313
Location: Seattle
Joined: June 18, 2004
 If you have the interstage transformers, consider using an output tube that needs them. (805, 811, 211, 845, 3C24, 861-A, etc)

 

RE: Eric Barbour's Brute force regulator mods, posted on February 25, 2015 at 10:13:13
JKT
Audiophile

Posts: 612
Location: Midwest
Joined: November 26, 2002
 I've had the regs in my amps, line stage and phono pre for over two years. There are some considerations you need to be aware of if you decide to install. If the heat sink the shunt FET is mounted on is not able to safely dissipate all the heat generated with zero load (all current from CCS is shunted) it will fail. So, no operating the PS without tubes. If a tube fails, ditto. Kevin's version of the Salas reg. uses a small reference CCS (~1mA) in series with a resistor to derive the reference voltage. The version that he sells with the kit uses a JFET as a 2 terminal CCS and a trim pot so that the reg. voltage is adjustable. There is a temperature coefficient at play here. The adjustment needs to be done when the amp has reached thermal equilibrium. At start up the voltage will be lower and then rise to the reg. setting. The driver stage of my amp with a reg. voltage of ~430V had a +- 20V swing with a 20 degree change of ambient temperature (60-90degrees). That said, the regulators that I am now using have a more sophisticated zero tempco cascode reference CCS and a fixed resistor. They come up to voltage within 30s and stay put. Kevin doesn't sell them this way because he believes DIYers want the adjustability and he doesn't want to stock a bazillion Rset resistors. Unless you have direct coupled stages where tight control of voltage is crucial, having the voltage drift a little probably is not a big deal. I did have a reg. fail on the input stage of my power amp once when a tube went whockey (small heat sink). It was easy to fix. Hope this helps you decision. I do have 11 of these throughout my system. Adding them improved sound staging, front to back separation, back ground silence and speech intelligibility. Adding them to the driver stage of my power amps noticeably improved bass definition.


"It is better to remain silent and thought a fool, then speak and remove all doubt." A. Lincoln

 

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