DIY tube amps

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bob p
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Re: DIY tube amps

Post by bob p » Wed Feb 26, 2014 8:24 pm

Not having taken measurements on your amps, I would have to guess at what is going on with your builds. I still don't see the reason for bypassing the caps with zeners.

I always manually bias a cathode biased amp using method A. Properly tuning an amp for the tubes in use eliminates the need for trial and error, aka "tube rolling."
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Re: DIY tube amps

Post by angelod307 » Wed Feb 26, 2014 8:39 pm

Tube rolling is a whole different subject. My buddy mark weiss just recently promoted that a tube is a tube and if they sound different, something wrong with the tube he said loosely. Well, i feel that quality is something you might share then. What do you think bob , do tubes have a unique sonic signature?
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Re: DIY tube amps

Post by angelod307 » Wed Feb 26, 2014 8:43 pm

Back to my curiosity, is there a safer way to power the tubes? When bob designed the amp, he assumed all 6bq5 tube were in fact the same. Sadly we all learned not. Too late though as the expensive transformers are bought. I have considered buying all new power transformers, but i lack the knowledge of who, what and were. 325 is what we have, 300 is what i think may work. What say you bob?
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mbskeam
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Re: DIY tube amps

Post by mbskeam » Wed Feb 26, 2014 8:58 pm

Angelo,
Bob p is talking about the bias circuit

this is Bob C take on his DC restore that he builds into his big amps.
I only built as shown.... :D
I can barely tie my own shoes.
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bob p
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Re: DIY tube amps

Post by bob p » Wed Feb 26, 2014 8:59 pm

Am I correct in understanding that the hand-drawn Zener-Cap Bypass Thingy is NOT part of the Bob Carver amp design? It came from someone else as an add-on, and not from Bob Carver?
Carver Preamps: C-1, C-2, BillD's JVD-modded C-4000, C-9
Carver Amplifiers: BillD's C-500, M-1.5t (4) PM-1.5 (4) M-500t (2)
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Re: DIY tube amps

Post by angelod307 » Wed Feb 26, 2014 9:23 pm

bob p wrote:Am I correct in understanding that the hand-drawn Zener-Cap Bypass Thingy is NOT part of the Bob Carver amp design? It came from someone else as an add-on, and not from Bob Carver?

No, that is the autobias that bobs amps are famous for, the first application was hit or miss, then joe, the master of manufacturing bobs amps brought this forward at our request. Still bobs design though. Instead of two diodes parallel, three different values in series.
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Re: DIY tube amps

Post by mbskeam » Wed Feb 26, 2014 9:25 pm

no this is from Bob, the original print had a different zener set up, so I drew this as the add on, these are my notes thats all
Mbskeam

SILVER 7's
Amazing Line Source
2 SVS PB16 SUBS
#1 BLACK BEAUTY's made by the man, the myth, the legend Bob Carver
CARVER: TFM-75, TFM-45(3), SD/A-490T
SUNFIRE: Tube pre
WTL Amadeus GTA+DV DRT XV-1t
2 sets of ALS'3, set of SILVERS, set of PLATS
AUDIOCONTROL: phase coupled activator
KENWOOD: BASIC M2a (2)

“Youth ages, immaturity is outgrown, ignorance can be educated, and drunkenness sobered, but stupid lasts forever.”
― Aristophanes

The only thing I'll feel......will be the RECOIL
Necronomicon Ex-Mortis....... Klaatu Barada Nikkto
"We should seek the greatest value of our action"

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mbskeam
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Re: DIY tube amps

Post by mbskeam » Wed Feb 26, 2014 9:27 pm

No, that is the autobias that bobs amps are famous for, the first application was hit or miss, then joe, the master of manufacturing bobs amps brought this forward at our request. Still bobs design though. Instead of two diodes parallel, three different values in series.
wrong place Angelo.... :D
Mbskeam

SILVER 7's
Amazing Line Source
2 SVS PB16 SUBS
#1 BLACK BEAUTY's made by the man, the myth, the legend Bob Carver
CARVER: TFM-75, TFM-45(3), SD/A-490T
SUNFIRE: Tube pre
WTL Amadeus GTA+DV DRT XV-1t
2 sets of ALS'3, set of SILVERS, set of PLATS
AUDIOCONTROL: phase coupled activator
KENWOOD: BASIC M2a (2)

“Youth ages, immaturity is outgrown, ignorance can be educated, and drunkenness sobered, but stupid lasts forever.”
― Aristophanes

The only thing I'll feel......will be the RECOIL
Necronomicon Ex-Mortis....... Klaatu Barada Nikkto
"We should seek the greatest value of our action"

angelod307
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Re: DIY tube amps

Post by angelod307 » Wed Feb 26, 2014 9:34 pm

Oh yeah. You are very correct. I mis spoke . The three in a row is to drop voltage, while the two side by side are in the bias circuit. I simply confused my self as i often do.
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bob p
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Re: DIY tube amps

Post by bob p » Wed Feb 26, 2014 10:40 pm

I'm still not clear on what I'm looking at. It looks like:

a. somebody drew a schematic on a computer
b. somebody scratched out part of the bias circuit
c. somebody drew in another part of the bias circuit in the margin on the same page
d. somebody drew something else in the margin on another page, which looks like a voltage dropping adapter

I'm trying to figure out:

1. who drew the schematic in "a"
2. who crossed off something on the schematic as "b" and what did they scratch out
3. who drew that "c" stuff in the margin
4. who drew that "d" stuff on the last page. it looks like "d" is a kludge to fix an out of spec transformer.


It looks like there are at least 3 different revisions of the circuit all on one piece of paper. It's a mess to try to make sense of it. Can you help me out?
Carver Preamps: C-1, C-2, BillD's JVD-modded C-4000, C-9
Carver Amplifiers: BillD's C-500, M-1.5t (4) PM-1.5 (4) M-500t (2)
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angelod307
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Re: DIY tube amps

Post by angelod307 » Wed Feb 26, 2014 11:03 pm

Yes, alex is the man for the job as he drew a final release somewhere. I also have the original papers, but unlike facespace, i have to do a upload to photobucket first after i lay my hands on the papers. I will look for your email, and then i could simply send them direct.
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Magnaryder
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Re: DIY tube amps

Post by Magnaryder » Wed Feb 26, 2014 11:04 pm

bob p wrote:I'm still not clear on what I'm looking at. It looks like:

a. somebody drew a schematic on a computer
b. somebody scratched out part of the bias circuit
c. somebody drew in another part of the bias circuit in the margin on the same page
d. somebody drew something else in the margin on another page, which looks like a voltage dropping adapter

I'm trying to figure out:

1. who drew the schematic in "a"
2. who crossed off something on the schematic as "b" and what did they scratch out
3. who drew that "c" stuff in the margin
4. who drew that "d" stuff on the last page. it looks like "d" is a kludge to fix an out of spec transformer.


It looks like there are at least 3 different revisions of the circuit all on one piece of paper. It's a mess to try to make sense of it. Can you help me out?
Bob here's the deal. There were several changes made by Bob while we were in the middle of building the amps. Though it looks confusing...it was, 'specially for us noobs. Ask Alex Sauter to get you the link to his beautiful cad drawings. IIRC, they are the last word on the amplifiers' construction. There were some real pros helping us novices out during the build. Roy, Mike, Tom, Mark and I'm certain I missed someone, Bob sat at his desk scoping each one making sure it was operating up to snuff. Bob was a trooper. He kept some long hours.

I have 2 killer amps that I'm proud to let anyone give a listen.

ray
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angelod307
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Re: DIY tube amps

Post by angelod307 » Wed Feb 26, 2014 11:06 pm

The big cluster fuck was that bob was not aware most 6bq5 tubes are 300 volt, and not the 400 plus like the russian tubes, or i should say a good tube, maybe a tele or something that can take a higher voltage. So to ease the pain, 4 is a voltage drop as we also changed the 5 watt resistor to 6.8 k .
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Magnaryder
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Re: DIY tube amps

Post by Magnaryder » Wed Feb 26, 2014 11:14 pm

bob p wrote:OK, next question: why are you using zeners to bypass caps instead of resistors?
Mike correct me here but that's the DC restorer circuit, IIRC it eliminates the need for a bias pot because it does it automatically.
Bob applied it to audio from a video application.
ray
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Re: DIY tube amps

Post by bob p » Wed Feb 26, 2014 11:32 pm

Thanks for the help guys. I understand what the "DC restoration" circuit is all about and how it works. Bob didn't invent it, it's nothing new, and other people have already been using it in guitar amps for a long time (years). But that's not my point.

My concerns are that the schematics aren't clear and intelligible, and it's not clear who has made what incremental changes to the circuit; the drawings are a mess and there are no changelogs. Seeing all of the revisions made by people here, and hearing that nobody here can actually explain how it's designed to work, is making me wonder whether some mistakes may have mistakenly crept into the schematics with all of the revisions. So I'm trying to figure out what is supposed to be the "official" design. What I'm looking at is not at all clear to me.

thanks again.
Carver Preamps: C-1, C-2, BillD's JVD-modded C-4000, C-9
Carver Amplifiers: BillD's C-500, M-1.5t (4) PM-1.5 (4) M-500t (2)
Repair/Restoration/Upgrade expert for all of these components.

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