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Old 10th November 2008, 05:53 PM   #11
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Thanks for the reply. However that's only 120 mA. Will that be enough?
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Old 10th November 2008, 06:07 PM   #12
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Is this for a stereo or mono amp? For stereo, 120 mA is too low! For EL84 or 6V6, go for 200 mA or higher. For 6L6, you will need at least 250 mA.
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Old 10th November 2008, 06:08 PM   #13
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Quote:
Originally posted by rockgardenlove
So, how does the Hammond 370 HX sound?
275-0-275
200 mA
6.3 v, 5v filament taps


Cheers!

The 370HX should work fine for a stereo EL84 amp (shared power supply)

I used the 270EX for monoblock baby hueys. I think they are 100ma each.

If you don't need universal input (115-240v) or the bias tap, you can look at the 270 series, they are equivalent without the above features, and are less cash.

Plan on your recified DC voltage to be 1.41 times your AC voltage depending on your PS design. Can be less depending on if you are using SS or tube rectification. If you do a choke input, you can adjust the first cap value to tune the B+ voltage.

Are you familiar with PSUDII?
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Old 10th November 2008, 10:00 PM   #14
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Yeah, it's gonna be a stereo amp.

I'm looking for a B+ of at 300 V or so. Does this sound right for PP EL84?

Boywonder...I was thinking 275-0-275 would work out to be around 300. According to you 1.41 rule though it works out to be 387.5. I'm planning to use a tube rectifier, so that'll bring it down a bit though, eh? But yeah, do I not need 275-0-275?

And what is PSUDII?

Thanks!
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Old 10th November 2008, 10:49 PM   #15
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Quote:
Originally posted by rockgardenlove
Yeah, it's gonna be a stereo amp.

I'm looking for a B+ of at 300 V or so. Does this sound right for PP EL84?

Boywonder...I was thinking 275-0-275 would work out to be around 300. According to you 1.41 rule though it works out to be 387.5. I'm planning to use a tube rectifier, so that'll bring it down a bit though, eh? But yeah, do I not need 275-0-275?

And what is PSUDII?

Thanks!

PSUDII is Duncan amps Free Power supply design software, super easy to use, and will give you a good feel for how your PS will work. The folks here can help you model the power supply with PSUD, but it is fairly straightforward to figure out. Highly recommended.

Download it here: http://www.duncanamps.com/psud2/index.html

300V B+ for PP84 is fine. My baby hueys are at 320V B+ with a 275-0-275 V 100 ma (each mono). They were originally running a B+ of 380V (and sounded rather good) but I re-did the PS as a CLC (per Gingertube's recommendation on the BH thread) so that I could tweak the 1st cap to get the voltage down. I think many production/classic EL84 designs run B+'s up to around 380V, so the tubes can take it, but it will reduce their life (but it also increases power output)

IIRC, Sy's Red Light District runs at around 380V B+.

Download PSUDII and play with it; to start, model a 275-0-275 xfrmr, Center tapped, the rectifier tube of your choice, then CRC or CLC (try both) with a 200ma constant current load. Once the model is set up look at the voltage at the constant current load. If you email me, I will send you a model of what a tube rectified CLC PS looks like (since I cannot figure out how to paste a pic in my posts)

PSUDII will let you know if your cap values exceed the current of your rectifier, and will also show AC ripple on your DC, and if your supply is underdamped (you'll see overshoot/ringing)
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Old 11th November 2008, 12:21 AM   #16
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What's CRC and CLC?

And isn't the supposed max plate voltage for EL84s 300 volts?

Thanks!
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Old 11th November 2008, 12:26 AM   #17
kmtang is offline kmtang  Canada
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Default Lundahl C-core OPT

I have really good experience with Lundahl's OPT. I built two 45 SE and one pair of 2A3 with them and they all sounds so good to me and my HiFi buddies.

I would like to build a PP amp with Lundahl's OPT as well. Even though I don't know how that sounds but I have confidence with Lundahl.

Johnny
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Old 11th November 2008, 12:28 AM   #18
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Hi,
Thanks for the suggestion. What's the price for something comparable? I'm trying to keep it pretty cheap.

Thanks!
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Old 11th November 2008, 03:51 AM   #19
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CLC=capacitor, inductor, capacitor

CRC=capacitor, resistor, capacitor

these are the passive elements after the rectifier (in order). They represent two different PS design topologies, yielding different B+ voltages and PS ripple performance.
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Old 11th November 2008, 03:59 AM   #20
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Hi,
I'm running into problems getting a high enough rectified B+ rail using a tube rectifier. Plotted here is the AC voltage vs the DC voltage. Any tips? Do I simply need a higher voltage transformer?

Cheers
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