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Old 24th February 2003, 09:32 PM   #761
gpapag is offline gpapag  Greece
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And these are the resistors that were tested. End of wire. Sign-off
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Old 25th February 2003, 12:01 AM   #762
Guiness is offline Guiness  United States
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Thanks for helping me understand. And thank goes out to JDEV for the power supply schematics. I appreciate it. So I am almost convinced to build one for myself. A couple more questions:

Peter Daniel, what are the Volts & Amps of the hexfred diodes you are using on your power supply with the Plitron (22-0-22 @400VA) power transformer? And where did you order them from. I am looking at digikey but am not sure which ones would be the best to use. If possible an order number would be very helpful.

Next question is, I really do not want a potimeter on these amps. I will be running them with a tube preamp that I have built. So can I just replace the 50K pot with a 50k .5W resistor? Or is there another value that would be better?

Peter thanks for the inspiration, you do great work. And you can use standard aluminum bar stock as heatsink with the LM3875T? That gives alot of creativitivy to enclosure design.

Thanks again everyone
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Old 25th February 2003, 02:01 AM   #763
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Quote:
Originally posted by Guiness
what are the Volts & Amps of the hexfred diodes you are using on your power supply with the Plitron (22-0-22 @400VA) power transformer? And where did you order them from. I am looking at digikey but am not sure which ones would be the best to use. If possible an order number would be very helpful.

I'm just testing today 6 different diode types for discreet bridges. I'll post later today my findings. As to a pot, I think you are correct.
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Old 25th February 2003, 02:29 AM   #764
moe29 is offline moe29  United States
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Peter,
I think you should sell a few thousand first,
then be in the position to give one away!

btw, do you have a name for your "company".

Not that i even know if you'll ever come to the point of
making one available for purchase... i was thinking though,
if the Gain Card sells for $3,500 (that's USD) what the
hell will one of yours be worth??? at least $7K


- - more importantly you've inspired me to try putting one
together (i put in a sample request last night!)


m.
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Old 25th February 2003, 03:49 AM   #765
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Actually I'm in a proccess of building a first batch of 20 amplifiers. I still didn't come up with a name. They will be available at the Montreal show (if I'll make it on time).
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Old 25th February 2003, 03:59 AM   #766
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So I spent 4 hours today comparing different diodes. This is the choice I used:

MUR1620 (hexfred) $1.66
HFA08TB60 (hexfred) $2.17
8ETH03 (ultrafast) $1.00
15ETH06 (ultrafast) $1.39
MUR820 (schottky) $1.08
MUR1520 (schottky) $1.71

Beside are the prices in CAD for quantity 10 and more. All available from Digi-Key. And here's my test setup.
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Old 25th February 2003, 04:17 AM   #767
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This was the first time I really compared dides and I have to admit that in some cases the difference in sound was comparable to placing different capacitors in a circuit. I also noticed that diodes (like resistors) are directional .

I was looking for a natural sound, something that draws my attention and don't allow me to get bored fast. I didn't want the mechanical sound.

The choice wasn't really easy, because all of those diodes are decent quality and supposed to be better then standard rectifiers.

First one to be put aside as least appealing was 15ETH06. Thet's the one I liked the least. The other one that was definitely different from the rest was MUR1520. This diode sounded most natural and grabbing attention. It had very good detail and resolution, probably because it softened highs a bit. Also the voice was very laid back, but sounding very narural, without the glare and harshness that other diodes provided.

I didn't test MUR1620, because being common cathode diode, it didn't fit my circuit.

The 3 other types were pretty close together, with MUR820 close to MUR1520 in character, without softening the trebles so much though. I thought that this might be good substitute for 1520, yet I found it less engaging.

The 8ETH03 was also nice sounding and it was probably the second after 1520 that was drawing my attention to music. The HFA08TB60 being the most expensive of the bunch was also at the end of my list. Actually I couldn't find nothing wrong with it, it seemed to be most neutral, but I thought it was also most mechanical sounding from the group.

So here it is, the quick overview of some of the diodes. It is only the first impression I got and more lengthy listening sessions are in order, but as they say, the first impression is usually correct. Also that choice is probably very dependant on the rest of the system and listening preferences and may vary. My choice for today is MUR1520.

I'm always open for other suggestions and ready to try more. Next thing I will try, is how the umbilical cord from PS to the amp affects the sonics.
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Old 25th February 2003, 04:22 AM   #768
BrianGT is offline BrianGT  United States
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Quote:
Originally posted by Peter Daniel
diode testing....
You should try some of those Fairchild Semi Ultrasoft, Hyperfast ones, and see how they compare.

--
Brian
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Old 25th February 2003, 04:24 AM   #769
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I will try them tomorrow. What I found is that the same type diode with different amps rating sounded different. Ussually higher rating exaggerated the sonic character of the diode.
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Old 25th February 2003, 04:27 AM   #770
JDeV is offline JDeV  South Africa
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Do you guys stay up late or wake up early. I just started my 06:00 AM shift.
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