The higher (more negative) your negative bias supply is, the hotter the cathode 10M45 (U1) will be, since it dissipates most of it as heat. The other 10M45's are fed by the board B+, so their temperature depends on that voltage.
The life expectancy of sand state critters is affected by their operating temperature, with zero lifetime at around 150C internal die temperature. So, if they are too hot to touch, I would look into a bigger heatsink. You can also reduce their dissipation by adding a resistor in series with the drain (anode) lead. I did this on the SSE board. Some say the added resistor improves the sound, but I never heard a difference when I jumpered the resistors.
My little red board has the same small heat sinks that I use on the SSE attached to each 10M45. U2 starts smoking when the B+ gets cranked to 600 volts, so I now have 2 heat sinks on that one. They are still much too hot for long term reliability.
I have seen Bendix, and Cetron with a metal base, and "USN" (US Navy, no clue who actually made it) with a brown phenolic base. The 5 new ones that I bought had no name at all, but have the newer metal base. All have Bendix style ceramic spacers instead of mica with metal spring clamps touching the glass.
They are hard to find, so you just have to check with the tube sellers that you deal with. VaccumTubes.net has them listed at $35 each, but I don't know if they actually have any.
I got lucky and found some in a bin at a local electronics store.. ebay claimed to have a bunch, but when I further inquired about them, they were just B's, not WB's.
I did see them at one or two online vendors, as tubelab mentioned, but they were more expensive than kt-88's, so don't bother.
Thank you, tubelab.. as always...
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Finally posted details about the PPP 807 amp (using this driver) on the web page. Still a few things missing (like a BOM) but most of the info is there:
"807" Push-Pull amp
I'm thinking of asking Edcor to make a power transformer for this amp with multiple taps for B+. Something that would be more "universal" for different output tubes or to drive the 807's harder. Any recommendations or requests for voltages?
I've found this classictone tx relatively versatile. Under 500v w/ the 120v taps, and about 600 w/ the 110v taps. The heater is unfortunately either a little under voltage or a little over voltage, w/ my mains. Personally, if I could have one more output, it would be lower so I could use tubes that like 350ish volts.
Heard back from Edcor the other day. Apparently they won't make a drop-in replacement for the Classic Tone pwr xfmr Pete used, seems it's an odd size for them. They can make a similar vertically oriented xfmr, but they only like to fit 2 taps through the hole in the end bell. Since the Classic Tone has the higher voltages covered pretty well, I think I'll go with 350v and something lower as wicked1 suggested. Thinking 275v. Any comments?
Also, they said it would be just under $70 per unit with 120/240 v primaries and secondaries like the Classic Tone.
Also, they said it would be just under $70 per unit with 120/240 v primaries and secondaries like the Classic Tone.
I got a new multimeter, and my voltages are all different now.. High voltages are lower, and low voltages are higher!
Only one I'm really concerned w/ is the heater. My new meter is saying it's 7.5v.
Should I drop that w/ a resistor? (I'd probably do 2, one on each leg to share the power dissipation)
Or, are there better ways, or would you not worry about it?
Pete, if you see this and have a minute... If you're using the 100v taps, could you measure your heater? My mains are 119.5ish volts and heater is 7.5v w/ my new meter. 2 old meters show a different reading (6.9v), but this new one is supposed to be calibrated.
Thanks
Only one I'm really concerned w/ is the heater. My new meter is saying it's 7.5v.
Should I drop that w/ a resistor? (I'd probably do 2, one on each leg to share the power dissipation)
Or, are there better ways, or would you not worry about it?
Pete, if you see this and have a minute... If you're using the 100v taps, could you measure your heater? My mains are 119.5ish volts and heater is 7.5v w/ my new meter. 2 old meters show a different reading (6.9v), but this new one is supposed to be calibrated.
Thanks
my meters tend to display higher reading when the batteries are about to drain out, you can check that the 9 volt battery is 9 volts, anything less, replace the battery with fresh ones...
i have a bout 5 dmm's 2 of which are Fluke 87's, i use the Flukes as reference for the other less expensive dmm's...
i have a bout 5 dmm's 2 of which are Fluke 87's, i use the Flukes as reference for the other less expensive dmm's...
New meter is a fluke.. New battery.
It's True RMS, and the old cheap meters are not. That shouldn't make a difference for measuring the heater voltage, should it?
As I said the new meter SHOULD be calibrated, and better at reading low AC voltages, but I've tested it w/ three 'cheap' meters, and they all say 6.9v, while the new calibrated fluke is the only one that says 7.5v.
It's True RMS, and the old cheap meters are not. That shouldn't make a difference for measuring the heater voltage, should it?
As I said the new meter SHOULD be calibrated, and better at reading low AC voltages, but I've tested it w/ three 'cheap' meters, and they all say 6.9v, while the new calibrated fluke is the only one that says 7.5v.
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Pete, being all too generous, loaned me his new amps for a while so I've taken some measurements for you. He's using the 120 V tap (brown wire on the classic tone) and my line is at 121.6 v right now. Heaters are at 6.5 v. I calculate that on the 100 v tap this would give 7.8 on the heaters. Sounds like you're right on with the 7.5 you're measuring.
Since Pete was generous enough to loan me his new amps, I thought the least I could do was leave some comments on how they sound. So I'll offer what meaningful info I can. I'll preface by saying that even though we built the enclosures for the amps, I'm not trying to play them up just to sell more boxes - take it for what you will.
If you're anything like me, you have a hard time deciding what to spend your time and money on with all the interesting projects out there. Having listened to Pete's amps for a while now, I will definitely be building myself a set. If you can duplicate Pete's effort, you'll have a great set of amps too!!
So far, I, and others, have listened to the amps with a set of large DIY 3-way horns (about 100 dB efficient), a set of Madisound full-range folded horns (BK-12m), a set of Vandersteen Model 3's and my old faithful Klipsch Heresy II's.
The large 3-way horns aren't anything to rave about, but they did reveal how quiet the amps are. With my head right next to the speaker, I can't hear any hum - none. There's a turn-on buzz for a second or so, but not very loud, and a distinct thump when you power down. Neither one is loud enough to make me think there's any risk of harm.
The little folded horns were a fun project, but mostly sit in the corner. I hooked them up and just had to listen for a while. I was impressed. They're light in the bass, as you might expect, but otherwise quite impressive. If I had these amps when I built them, they might not have wandered off to collect dust. No flowery words to describe the sound, they play music and it sounds like music (sorry, I'm not an audio reviewer).
The Vandersteen 3's: now this is an impressive combination. I can honestly say that I've never before had speakers as revealing or amps as good as these in my house. Everything is crystal clear. The sound is clean, fast, dynamic, etc. Vandersteen recommends 100 - 200 wpc, but these amps work! The owner of these speakers says they sounded a little fuller with his 200 wpc Counterpoint amp - but they self destructed years ago. I've listened to more records and cd's in the last couple of weeks than I usually do in months. Great recordings sound great, bad recordings sound bad. I never quite realized how much of a difference there could be between the two.
My old faithful Heresy's: I've listened to every amp I've had in my possession over the last 18 years through these speakers and have never heard them sound this good. I can put on a good record at a decent volume (yea, kinda loud) and instruments just jump out at you - I still laugh at the effect sometimes. I've never owned any high-end boutique amps, but have had numerous classic SS and tube amps, some home-made SE 2A3's, and random other amps that friends have sent my way. So again, nothing exotic to compare to, but quite a few amps nonetheless.
Hopefully you find my comments useful. These are my opinions and the opinions of others that have listened to Pete's amps.
If you're anything like me, you have a hard time deciding what to spend your time and money on with all the interesting projects out there. Having listened to Pete's amps for a while now, I will definitely be building myself a set. If you can duplicate Pete's effort, you'll have a great set of amps too!!
So far, I, and others, have listened to the amps with a set of large DIY 3-way horns (about 100 dB efficient), a set of Madisound full-range folded horns (BK-12m), a set of Vandersteen Model 3's and my old faithful Klipsch Heresy II's.
The large 3-way horns aren't anything to rave about, but they did reveal how quiet the amps are. With my head right next to the speaker, I can't hear any hum - none. There's a turn-on buzz for a second or so, but not very loud, and a distinct thump when you power down. Neither one is loud enough to make me think there's any risk of harm.
The little folded horns were a fun project, but mostly sit in the corner. I hooked them up and just had to listen for a while. I was impressed. They're light in the bass, as you might expect, but otherwise quite impressive. If I had these amps when I built them, they might not have wandered off to collect dust. No flowery words to describe the sound, they play music and it sounds like music (sorry, I'm not an audio reviewer).
The Vandersteen 3's: now this is an impressive combination. I can honestly say that I've never before had speakers as revealing or amps as good as these in my house. Everything is crystal clear. The sound is clean, fast, dynamic, etc. Vandersteen recommends 100 - 200 wpc, but these amps work! The owner of these speakers says they sounded a little fuller with his 200 wpc Counterpoint amp - but they self destructed years ago. I've listened to more records and cd's in the last couple of weeks than I usually do in months. Great recordings sound great, bad recordings sound bad. I never quite realized how much of a difference there could be between the two.
My old faithful Heresy's: I've listened to every amp I've had in my possession over the last 18 years through these speakers and have never heard them sound this good. I can put on a good record at a decent volume (yea, kinda loud) and instruments just jump out at you - I still laugh at the effect sometimes. I've never owned any high-end boutique amps, but have had numerous classic SS and tube amps, some home-made SE 2A3's, and random other amps that friends have sent my way. So again, nothing exotic to compare to, but quite a few amps nonetheless.
Hopefully you find my comments useful. These are my opinions and the opinions of others that have listened to Pete's amps.
a resistor or a thermistor, you know the types found on atx psu's, i use them to lose volts of 1volt or less...
thank you both! Dave for the confirmation of my voltage reading, and the review. I agree w/ all of it. I have been very impressed w/ this amp. I use different output tubes, and regulated some voltages, but I'd bet they sound the same. Pete's driver section is very well designed. Actually, for a bit of a review comment, I was listening to the amps w/ some friends, and we kept turning it up louder and louder, and finally realized we couldn't hear each other talking. It didn't seem loud in the traditional sense, because there was no distortion.. I'm used to concerts and clubs where loud = distorted, so am sort of preconditioned to thinking distortion=loud.
Tony, that's a great idea! I've been getting a lot of good parts out of old computer PSU's, but have never tried the thermistor. I'll get down to my scrap pile later and find one.
Otherwise, looks like I need a couple of .06 ohm 5w resistors.
Tony, that's a great idea! I've been getting a lot of good parts out of old computer PSU's, but have never tried the thermistor. I'll get down to my scrap pile later and find one.
Otherwise, looks like I need a couple of .06 ohm 5w resistors.
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