So uh is there a guide to getting this guy to 30-40 watts (id be running at 20-25 watts but want some head room) without global feedback and decent distortion numbers? Also at around what point does it leave class A when you mod it for double the power or more?
board is on its way!
So 6HJ5 and an antek AN-4T360 Should be good for 40 watts before i go insane due to the 500v cap restriction?
What do i do about the -60 bias? antek is a ghost town in that department. I could hook a AN-0225 up in series.
So 6HJ5 and an antek AN-4T360 Should be good for 40 watts before i go insane due to the 500v cap restriction?
What do i do about the -60 bias? antek is a ghost town in that department. I could hook a AN-0225 up in series.
Small 115:12.6VAC out transformer hooked up backwards to the 6.3V winding giving 58VAC out. You don't need much current for the bias supply.
Got any idea on output transformer impedance for 30-40watts? Ive seen anywhere from 1.5k to 6k.
I think George made a comment about using a 3.3K P-P. When my 6HJ5's arrive, I was going to try a 3.3K with ~500v on the plate.
Hmm... Well i guess i could pull the old put the 8 ohm load on the 16ohm tap and get some
CXPP50-MS-6.6K
CXPP50-MS-6.6K
I forget, how much power are we thinking with the 6HJ5's? I know I can peak at 200 or so watts with 26HU5's.
http://www.diyaudio.com/forums/tube...-new-p-p-power-amp-design-45.html#post2234905
It seems you just sacrifice dampining factor by going to lower ohm primaries in exchange for higher output. so it looks like 3-4k gets you 100 watts at 450-500v. Question is when does it stop sounding good and start sounding like a guitar amp? Or does it only sound good at full output and stink and normal listening levels if you make it for 100-200watts using the same setup others are runing 30-50 watts.
AKA lets push this 100 volts over = 450volts b+
then start lowering the primary impedance
6k 50 watts
3k 100 watts
1.5k 200 watts
That seems to be what im reading. Im more interested in making it sound good with head room. Which primary impedance is the more HIFI?
http://www.diyaudio.com/forums/tube...-new-p-p-power-amp-design-49.html#post2292543
So:
50watts from 6GV5
100watts from 6HJ5
200watts from 35LR6
It seems you just sacrifice dampining factor by going to lower ohm primaries in exchange for higher output. so it looks like 3-4k gets you 100 watts at 450-500v. Question is when does it stop sounding good and start sounding like a guitar amp? Or does it only sound good at full output and stink and normal listening levels if you make it for 100-200watts using the same setup others are runing 30-50 watts.
AKA lets push this 100 volts over = 450volts b+
then start lowering the primary impedance
6k 50 watts
3k 100 watts
1.5k 200 watts
That seems to be what im reading. Im more interested in making it sound good with head room. Which primary impedance is the more HIFI?
http://www.diyaudio.com/forums/tube...-new-p-p-power-amp-design-49.html#post2292543
So:
50watts from 6GV5
100watts from 6HJ5
200watts from 35LR6
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Well I thought I would pull this amp out of the box I put it in when I moved and actually finish it up. One thing I realized when getting it out is I don't think I ordered the mosfets for Q1 and Q2. Since I am planning on using the antek 4t360 transformer for my HV supply I was curious if I should be finding some mosfets with greater dissipation? The stock mosfet that Pete has in his BOM is a Fairchild FQPF8N60C. I like the idea of using the full pack mosfets, makes mounting just a bit easier to the top plate..a little transfer paste and a nut and bolt.
Other than that I think I have just about everything to get my 6HJ5 version up and running. R21 I am planning to change out to a 25k ohm 50watt chassis mount resistor that I have, should take some stress off the screen regulator
Other than that I think I have just about everything to get my 6HJ5 version up and running. R21 I am planning to change out to a 25k ohm 50watt chassis mount resistor that I have, should take some stress off the screen regulator
You should be fine, the fets are good for 7.5 amp 600v. one is just a ripple filter so its not doing much. The other is just going to drop some more voltage then normal due to running 450v into it instead of 350 stock. but the current is almost nothing. stock can eat 50 watts, if you get the same animal in a slightly different (electrically conductive) package its good for 150watts. its called the FQP8N60C and is a plain jane to-220 package like a lm317. SHould be easy to find a thermal pad/shoulder washer kit for it.
WOW mental note, they say solder at 300c for 5 sec or less. I normally solder sensitive so8 at 325...
Not to highjack this thread...
Does anyone have some tips on how to get this combo going that i just bought?
steve red board
6hj5
2 of the 10 pounder transformers
I know i need to swap g1 and g2 on the board, and upgrade the electrolytics to handle the voltage. If im shooting for quality do i want 6k or 3.3k primaries(im only looking for 50 watts or less due to output iron cost)?
I think tube lab said just wire 1 transformer normal to the board and then wire the other transformer, rectified/filtered in the same way, i series to the power tubes to double the voltage.
Do i have to upgrade any parts on the red board? swap anything to a higher wattage?
WOW mental note, they say solder at 300c for 5 sec or less. I normally solder sensitive so8 at 325...
Not to highjack this thread...
Does anyone have some tips on how to get this combo going that i just bought?
steve red board
6hj5
2 of the 10 pounder transformers
I know i need to swap g1 and g2 on the board, and upgrade the electrolytics to handle the voltage. If im shooting for quality do i want 6k or 3.3k primaries(im only looking for 50 watts or less due to output iron cost)?
I think tube lab said just wire 1 transformer normal to the board and then wire the other transformer, rectified/filtered in the same way, i series to the power tubes to double the voltage.
Do i have to upgrade any parts on the red board? swap anything to a higher wattage?
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Give me a week or two. I have exactly the same combo in mind, but some experiments are needed first to determine the load needed for the B+ voltage 2 of these transformers will generate. I'm guessing that a load in the 6600 ohm range will be capable of over 100 watts on a B+ of 650 to 750 volts.
My wife has been spending much of her time 1200 miles away caring for her mother who has cancer. She got three weeks at home, so no Tubelab for 3 weeks. My other life will resume late next week.
Quote:
Do i have to upgrade any parts on the red board? swap anything to a higher wattage?
Some resistor values are changed, and the feedback resistors need to be made from a series connection of 2 or 3 resistors since they will see over 1000 volts on signal peaks.
I will post the build up of this amp in this thread when it resumes.
Sounds like the stock ones will be just fine. Good thing as I did find them in another box...have to love unpacking after months of living some where and not realizing where everything is.
Forgot to ask...has anyone tried any of the substitutes for the 6cb6. I found a handful that are exact substitutes just wondering if they performed as well as the 6cb6 but at a fraction of the price. I think I have around 3 6cb6s of unknown condition in my stash of stuff...I thought I had quite a bit more but unfortunately I was thinking of my mountain 6al5s😡
I finally read through the entire thread and I have to say I would definitely be interested in building this amp if it can get around 100-120 wpc in a stable and documented build.
WOW just got my board. EVERYTHING is onboard right down to the ground loop isolator. I can also fit 3 sizes of audio caps in it. It never occurred to me that i needed 4 6cb6 drivers for this thing...
I stuffed many of the different driver tubes that I listed in the post above into my board. Most worked, but my favorite has been the 6GU5. It results in a very low distortion and provided a bit more gain for driving big tubes. I got a bunch from AES cheap when they had a 50% off sale a few years ago. 6CB6's were as common as dirt in the 1950's so they shouldn't be hard to find cheap.
The board can be pushed to 250 WPC, but I am not sure that I would call that stable or reliable. I cranked over 150 WPC with the 6HJ5's, but I will document a build in the 100 WPC range when I return to the bench. I have found a bunch of tubes that will work at that level, but the 6HJ5 seems to be preferred by several builders due to the lack of plate cap.
hey-Hey!!!,
For scaling I'd consider moving the finals off board. None of the bigger sweeps will need lots of g2 voltage and some 9-pins are useful. I'd like to see just a front end board, but I like the E-Linear aproach; same effect but simplified circuitry. Dependant on primary tap location, but with custom winds it isn't so difficult.
cheers,
Douglas
For scaling I'd consider moving the finals off board. None of the bigger sweeps will need lots of g2 voltage and some 9-pins are useful. I'd like to see just a front end board, but I like the E-Linear aproach; same effect but simplified circuitry. Dependant on primary tap location, but with custom winds it isn't so difficult.
cheers,
Douglas