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Old 13th May 2007, 02:20 PM   #591
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If I could ask a question without going to far OT from this thread:

The last few post have directly dealt with transformer choices, mostly Plitron and Antek toroids. I have been planning my first diy Pass amps for a long time now. Grey, as you pointed out make a plan for each part and do the best you can. I have a very small budget which I have tried to solve by being resourcful, and planning. Both you (Grey) and Nelson have weighed in on the Plitrons, and Grey you seem to think that the Antek (at least) in this type of design would not be the best choice?

I have purchased 2 Antek torroids to build my 2 Aleph amps. 1 500VA 4x15 for my stereo miniA, and a 800VA 4x20 for my stereo Aleph 3. These will be used in a tri-amped speaker to power BG neo8/neo3 combo. I had previously figured that both toroids were rated enough to not be pushed to hard, and for my limited money these would be the best performance I could squeeze out. Now am I to think that these will give me problems? or leave me wishing that I had bought a different power supply?

thanks for for time in reading my post, and sorry to stray off topic.

Jase, the THICK fornt panel looks great! How many Pass amps do you have laying around your floor now?

Im sad that my WAF factor and 2 crazy boys will force me to "hide" most of my electronics

So mine will end up as the first Ikea/ furniture/ stealth built Aleph amps.
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Old 14th May 2007, 07:40 AM   #592
Skorpio is offline Skorpio  Denmark
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Quote:
Originally posted by Nelson Pass


There's a bootstrap in the amplifier?



The calculation goes 1.59A * 2 = 3.18A peak

3.18 * 3.18 *8 = 80 watts peak Class A into 8 ohms

and 40 watts peak into 4 ohms


If the midpoint between C3 and C4 are connected to output instead of ground the input resistance is bootstrapped and the input buffer can be left out. Also the value of c1 and c2 can be reduced....I have done that with a simular circuit with bipolars...have run superbly for years now...
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Old 14th May 2007, 05:30 PM   #593
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Quote:
Originally posted by HIPCHECK


Now am I to think that these will give me problems? or leave me wishing that I had bought a different power supply?


The first hint I had was when the UPS truck dragged bottom coming down the driveway.
The second hint was when I opened the box and saw that the Plitrons were nearly twice the size of similarly rated transformers from other manufacturers.
The third hint was when I measured the secondary voltage and found it to be a little high. (This is good. All transformer secondary voltages tend to drop as you increase the load. If it starts high, it's more likely to be within spec when you put a load on it.)
Plitron transformers are built tough. They deliver fully under loads that would cause an average transformer to sag. A less-than-average transformer? Don't ask.
I'm sure you calculated the transformer voltage you needed. You then went shopping based on price. The underlying assumption was that one transformer was as good as another transformer. Unfortunately, we're not buying a generic product like milk or paper clips.
To make a long story short, don't be surprised if your rail voltages come up short. The transformer may run warm, even hot.
This is the sort of situation the phrase Buyer Beware was invented for.

Grey

P.S.: Patrick, you need thicker interconnects...
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Old 14th May 2007, 05:44 PM   #594
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Quote:
It is true that Plitron is the best I've seen so far. The biggestdifference is in noise, which is crucial to high end product. Alsothe quality control and reliability are very high.
How about Avel-Lindberg? Do these rank at all? I've used several of their tranformers from Zen to Gain Clones. Am I getting my money's worth?

I can tell one thing about all of them- none have good websites to place orders.

Edit: Plitron updated their page, looks better now and easier to place an order.

Vince
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Old 14th May 2007, 05:46 PM   #595
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Quote:
Originally posted by vdi_nenna


How about Avel-Lindberg? Do these rank at all? I've used several of their tranformers from Zen to Gain Clones. Am I getting my money's worth?

I can tell one thing about all of them- none have good websites to place orders.

Vince
I have a few Avel trafos, and I have never had any problem. they are a good quailty trafo.
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Old 14th May 2007, 06:06 PM   #596
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My experience with Avel-Lindberg has been limited to low level circuits--preamps, crossovers, etc. With that caveat, I have been pleased. I don't believe they are as conservatively rated as Plitrons, but for low level circuits that's not a problem. They are, or were the last time I looked, somewhat more expensive than comparable units from Plitron. No, I haven't sat down and factored in customs charges on the Plitrons, that might change the balance--or might not.
I don't like cutting corners on transformers. I'm willing to part with an extra dollar or two to get a good one. Nelson has a warehouse/museum of all the things he's built and played with. I can't afford that luxury, either in terms of space or money. If I buy a hefty transformer, I can (and do) remove it from one circuit and put it into another, knowing that I'll get more good use out of it. If I use a Chinese cheapo, I'll end up with a door stop. Don't need more door stops.

Grey
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Old 14th May 2007, 06:10 PM   #597
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Quote:
Originally posted by Skorpio



If the midpoint between C3 and C4 are connected to output instead of ground the input resistance is bootstrapped and the input buffer can be left out. Also the value of c1 and c2 can be reduced....I have done that with a simular circuit with bipolars...have run superbly for years now...
And then short the junction of R1, R2 with the junction of C1,C2? Will this change take away the sound of the F4 which seems to be largely due to the JFET input stage? What about the output offset?

The Dracula amp posted earlier in this thread had an OPAMP input stage (while almost everything else resembles the F4) but no one reported anything about its sonic qualities. Just wondering because I am about to attempt the F4 with BF256B and 2N5461 JFETS in place of the 2SK/2SJ devices.
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Old 14th May 2007, 06:22 PM   #598
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Quote:
Originally posted by Samuel Jayaraj
The Dracula amp posted earlier in this thread had an OPAMP input stage
The BB-552 in the Drakul requires a minimum gain of 5, not the same.
You'll have to try it with a 551, even then not the same concept imo.

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Old 15th May 2007, 06:05 AM   #599
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Default F4

About Plitron's, wich range of products do you recommend for F4 ?
On the web site I've noticed 2 possible suitable categories :
1° - Standard Power Toroidal Transformers
2° - Low Noise Power Transformers for Solid State Amps
I suppose the second to be the right one

Regards.
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Old 15th May 2007, 06:08 AM   #600
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I wouldn't be afraid to use the standard series transformer.
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