FAQ  •  Register   •  Gallery •  Login

It is currently Sat Dec 20, 2014 5:15 pm

Update from Bob

<<

Toy Maker

User avatar

Puppet Master

Posts: 6589

Joined: Wed Oct 08, 2003 1:26 am

Post Wed Oct 26, 2011 12:08 am

Update from Bob

Hi Carverfest tube amp builders,
 
As you may remember, the amps we built were flawed because the tubes were not reliable, and the bias regulator zener diodes blew up about half the time. So I just cut them out and built the amps without them. Since I did not have good tubes with me, We tested the ones I did have and the ones that seemed okay were the ones we used.
 
These desperate decisions yielded an amp that was okay, but not as spectacular as it should or can be!
 
Here is the latest:
 
I tested lots of output tubes and found out something I did not know. I found out that some EL84/6BQ5 tubes are rated for 550 volts, and others are rated for 300 volts.
Most American 6BQ5 tubes are good for 300 volts. I thought a 6BQ5 was a 6BQ5 and good for 550 volts. Not true. This amp runs at 425 volts, and if you use a 300 volt tube, they tend to run away and glow cherry red. Not good! Amperex are the best, and can easily take even a thousand volts, whereas the ones we used at Carverfest are good for only 300 volts. Even the great Telefunken tubes are good for only 300 volts. So don't use them. You will be tempting fate. Mullards are good for 550 volts.
 
The tubes to use are the brand new Sovtek 6BQ5/EL84 tubes sold by Electro - Harmonix. I have tried them for extended time periods, fifty of them to be exact, without a single failure. That compares with about one in three failures for the Red Army tubes (300 volts) that I got for a buck or so. These EH tubes sound great and are superb tubes. You can get a matched quad for about $29 dollars, or about $7.25 dollars each. They are almost as good as Amperex. Buy them for your Carverfest amp! eBay item number 290613742187.
 
The next item is the bias regulator. Get a single 15 volt, 5 watt zener and install it across the 220uf/35 volt cathode bypass capacitor. This capacitor is in the cathode circuit of the four 6BQ5 output tubes. Solder the cathode end (the band) to the + end of the capacitor and the anode end to the - end of the capacitor. The schematic you have may show two 7.5 volt zeners, or I might have erased your copy. In any event, the circuit should be a 15 volt, 5 watt zener across the 220uf cap.
 
Buy it at any on-line place like Parts Express or Mouser. The brand is Micro - commercial, part number 1N5352B - TP, 5 watt zener. Cost about 55 cents.
 
These changes will make the amp sound the way it should. The bias regulator especially!  Without it the bias floats all over the place and the amp sounds mushy. With the regulator working the amp gets a better soundstage, greater depth, sweeter imaging; even the presentation will be wider and more detailed. I wish the ones I brought to Carverfest had worked. They got to me the day before I left, and I did not have the time to try them, but I thought they would work. Oh well.
 
Bob Carver
Whatever you do in life will be insignificant, but it's very important that you do it... because nobody else will.

‎~You think Einstein walked around thinkin' everyone was a bunch of dumb shits?~

SHUT UP AND ENJOY THE MUSIC!
╭∩╮(︶︿︶)╭∩╮

Image
<<

frenchguy

SILVER-7t

Posts: 1741

Joined: Fri May 14, 2010 11:53 pm

Location: wisconsin,home of the Green Bay Packers!

Post Wed Oct 26, 2011 12:23 am

Re: Update from Bob

James, Alex posted this a few days ago if you are not aware of this? otherwise nevermind as probably best to be in its own thread!! :D
Carver M-4.0t & Rollandized tfm42, ct-6 & ct-17, sda390t, jolida jd 100A & JBL L96,s Modified JBL 4401,s W/Ribbon Tweeters, Carverfest vacuum tube amp & CF Linestage, Dared SL-2000A tube preamp, Carver AL3 Amazing speakers in natural oak, Carver Cinema 5.1 subwoofer & Douglas connection cables
<<

kingman

User avatar

(pair of) SILVER-7 TUBE AMPs

Posts: 5770

Joined: Sun Nov 30, 2008 2:10 pm

Location: Upstate South Carolina

Post Wed Oct 26, 2011 6:55 am

Re: Update from Bob

That's what a "relationship" can do for ya... :lol: :lol: :lol:
In reality, it only matters what it sounds like to YOU!!!
<<

Chauss

User avatar

(pair of) SILVER-7t's

Posts: 2350

Joined: Tue Mar 22, 2011 4:35 pm

Location: In my own little world.....

Post Wed Oct 26, 2011 7:52 am

Re: Update from Bob

Is anyone here willing to /going to make a "group buy" (ie qty) and postal mail these out so everyone does not have pay $10 shipping charges for $1 worth of parts?
Image
Good sound—like good music, good wine and good fellowship—is meant to be shared.
"The difference between genius and stupidity is that genius has its limits" Albert Einstein
<<

engtaz

User avatar

"TAZ"

Posts: 5253

Joined: Sat Jun 30, 2007 1:43 pm

Location: Tampa, FL

Post Wed Oct 26, 2011 8:29 am

Re: Update from Bob

Actually, it so you don't have to find it in another thread.
engtaz


Carver M4.0T in front channels to Caver AL VI's in SACD & 2 Channel setup
C 16, PT 2400, Slim Device, Carver TX-8, 490T and Rega TT w Grado Gold cart in the 2 channel setup
Bogen SRB20 is computer amp
Carver PM-350 donated for youth church use
<<

Toy Maker

User avatar

Puppet Master

Posts: 6589

Joined: Wed Oct 08, 2003 1:26 am

Post Wed Oct 26, 2011 2:32 pm

Re: Update from Bob

Whatever you do in life will be insignificant, but it's very important that you do it... because nobody else will.

‎~You think Einstein walked around thinkin' everyone was a bunch of dumb shits?~

SHUT UP AND ENJOY THE MUSIC!
╭∩╮(︶︿︶)╭∩╮

Image
<<

angelod307

SILVER-7 TUBE AMP

Posts: 2735

Joined: Sat Jun 06, 2009 10:56 pm

Location: manning, sc

Post Wed Oct 26, 2011 7:05 pm

Re: Update from Bob

let me know, as i will get them and send out.
CarverFest: I just go for the arts and crafts
<<

angelod307

SILVER-7 TUBE AMP

Posts: 2735

Joined: Sat Jun 06, 2009 10:56 pm

Location: manning, sc

Post Wed Oct 26, 2011 7:07 pm

Re: Update from Bob

never mind, i will get a bunch. pm the address they will go to.
CarverFest: I just go for the arts and crafts
<<

Don

User avatar

(pair of) SILVER-7t's

Posts: 2170

Joined: Tue Oct 28, 2008 10:46 am

Post Wed Oct 26, 2011 7:25 pm

Re: Update from Bob

angelod307 wrote:never mind, i will get a bunch. pm the address they will go to.



PM sent
To argue with a person who has renounced the use of reason is like administering medicine to the dead.
— Thomas Paine


"Try not to become a man of success, but rather a man of value" Albert Einstein

"Politicians are the only people in the world who create problems and then campaign against them". Charlie Reese

"The problems we face today exist because the people who work for a living are outnumbered by those who vote for a living." Brad Shurett


"Kindness is a language that the Deaf can hear and the Blind can see." Mark Twain

RIP Bill D.
<<

angelod307

SILVER-7 TUBE AMP

Posts: 2735

Joined: Sat Jun 06, 2009 10:56 pm

Location: manning, sc

Post Thu Jan 12, 2012 11:59 pm

Re: Update from Bob

any new news on the tubes for the amps? i sent a pm to the store bob mentioned for 8 quads pricing. anybody else need some ? maybe i can get a better price on them right.
CarverFest: I just go for the arts and crafts
<<

angelod307

SILVER-7 TUBE AMP

Posts: 2735

Joined: Sat Jun 06, 2009 10:56 pm

Location: manning, sc

Post Fri Jan 13, 2012 3:34 pm

Re: Update from Bob

so, the price is 5% off with a shipping charge of 20.43 for a total of 240.75. next i asked how many do i need to order to get a 20% discount, and we will see. $30.09 per set shipped. almost free shipping.
CarverFest: I just go for the arts and crafts
<<

hewlew1

"You Fuckin' Fucks"

Posts: 1324

Joined: Tue Feb 17, 2004 11:02 pm

Location: Northeast, Pa

Post Fri Jan 13, 2012 4:37 pm

Re: Update from Bob

keep us up to date Angelo I may want 4 quads if the price is right. This tube rollin shit is a bitch!
"Carver Audio, why settle for less, just ask my neighbors"
C1,C2,CT3,CT6,CT7/3,CT23,CT26,C4000,The Receiver,M500,M500T/6,M1.5T,TFM24/2,TFM/25/3,TFM35,TFM35X,TFM42/2,DTL200,TDR1700,DPL20,TX11/2, 5.2Center,5.1Sub/3,Original Amazings,Platinum Amazings/2,AL3'S,Polk SDA SRS, Polk SDA 1C's, Polk RTA11's, Polk Monitor 10's/2 ,Monitor 7's, Sunfire 300x2 /5, Sunfire pre, Sunfire MK2 Sub/2, 4 Carverfest monoblocks, Carverfest linestage preamp/2, Mapletree Audio Designs Tube Preamp,Phase Linear Andromeda III speakers, Phase Linear 4000 Preamp, Dahlquist DQ-10's
CERTIFIED AMPLE PLIERS EXPERT
Some of the best fuckings we get during our lifetime come from a relative!
I don't kiss ass, I dont take peoples shit, so dont expect it from me!
<<

basspig

User avatar

TFM-6cb

Posts: 271

Joined: Mon Dec 13, 2004 9:36 pm

Location: Connecticut, USA

Post Sat Jan 14, 2012 3:19 am

Re: Update from Bob

Good grief, it sounds like Bob is just 'guessing' instead of referring to the tube manual for design center and design maximum ratings. For heaven's sake, when you design a tube amplifier, you operate the tubes at their 'design center' values, or else the tube life will be GREATLY shortened.
The plate dissipation on this tube is ONLY 12 WATTS. Class AB1 operation, design center is 250V plate and screen grid. Cathode current is only 45ma.
Running this tube at 500 volts is foolhardy and, for a commercial product, downright irresponsible!!
Take care,

Mark & Mary Ann Weiss
http://www.basspig.com The Bass Pig's Lair - 16,500 watts of driving surround sound!

Business sites at:
http://www.ampexperts.com
http://www.mwhdvideo.com
-
<<

angelod307

SILVER-7 TUBE AMP

Posts: 2735

Joined: Sat Jun 06, 2009 10:56 pm

Location: manning, sc

Post Sat Jan 14, 2012 3:27 am

Re: Update from Bob

basspig wrote:Good grief, it sounds like Bob is just 'guessing' instead of referring to the tube manual for design center and design maximum ratings. For heaven's sake, when you design a tube amplifier, you operate the tubes at their 'design center' values, or else the tube life will be GREATLY shortened.
The plate dissipation on this tube is ONLY 12 WATTS. Class AB1 operation, design center is 250V plate and screen grid. Cathode current is only 45ma.
Running this tube at 500 volts is foolhardy and, for a commercial product, downright irresponsible!!


[-X

Most American 6BQ5 tubes are good for 300 volts. I thought a 6BQ5 was a 6BQ5 and good for 550 volts. Not true. This amp runs at 425 volts, and if you use a 300 volt tube, they tend to run away and glow cherry red. Not good! Amperex are the best, and can easily take even a thousand volts, whereas the ones we used at Carverfest are good for only 300 volts. Even the great Telefunken tubes are good for only 300 volts. So don't use them. You will be tempting fate. Mullards are good for 550 volts.



:-k

The bobfather has spoken. no one is perfect, just human. what i paid for the amp was a privilege for getting to hang out and talk shop. i tell you it was priceless although there was a amount that i spent. i would do it again.
CarverFest: I just go for the arts and crafts
<<

angelod307

SILVER-7 TUBE AMP

Posts: 2735

Joined: Sat Jun 06, 2009 10:56 pm

Location: manning, sc

Post Sat Jan 14, 2012 3:32 am

Re: Update from Bob

oh yeah, i may be a little biased though. :-"
CarverFest: I just go for the arts and crafts
Next

Return to CarverFest 20w Tube Amp

Who is online

Users browsing this forum: No registered users and 1 guest

Powered by phpBB © 2011 phpBB Group.