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Old 8th July 2012, 04:57 AM   #71
Variac is offline Variac  United States
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I've asked np to take a look
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Old 8th July 2012, 07:00 AM   #72
Zen Mod is offline Zen Mod  Serbia
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not much of a difference
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Old 8th July 2012, 07:22 AM   #73
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Soldersucker, I suggest you take a look at: http://www.planet10-hifi.com
Dave offer drivers, plans, flat panels for the Frugal horn and is working on new flat panel set for other of his designs.

I once had the Fonken with modified Fostex drivers from Dave. It was truely great.

I had several other speakers using bigger 8" Fostex drivers (also modified Fostex drivers) and they made my ears bleed...
So stick to the small ones but be aware that it will not be a party speakers but they can play pretty high in a small room.

Happy building to your daughter.
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Old 8th July 2012, 10:14 AM   #74
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Wow , what a nice little amp project .
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Old 8th July 2012, 10:47 PM   #75
Variac is offline Variac  United States
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This article we have from Morgan Jones seems to be perfect for an easy to build speaker that's efficient and easy to drive.. and would fit in a dorm room.

Arpeggio Loudspeaker

np mentions in a comment on the article that it would work well with a small amp he's designing, however that was back when the article was published,
no reason to think that our amp is the same one, but I suspect it has similar needs and issues..


Here's the driver but its a slightly newer model. We should compare the specs of old and new.. :

Madisound Speaker Store

Last edited by Variac; 9th July 2012 at 11:17 PM.
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Old 9th July 2012, 08:48 AM   #76
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Quote:
Originally Posted by Variac View Post
This article we have from Morgan Jones seems to be perfect for an easy to build speaker that's efficient and easy to drive.. and would fit in a dorm room.

Arpeggio Loudspeaker

np mentions in a comment on the article that it would work well with a small amp he's designing, however that was back when the article was published,
no reason to think that our amp is the same one, but I suspect it has the same needs and issues..


Here's the driver but its a slightly newer model. We should compare the specs of old and new.. :

Madisound Speaker Store
That's good , I am very tempted to buy it . It seems also the FE206 has been emproved ...
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Old 9th July 2012, 12:51 PM   #77
Variac is offline Variac  United States
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Here's the old model to compare. There are differences, but I wonder how significant they are...

Europe Audio
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Old 9th July 2012, 06:14 PM   #78
LBHajdu is offline LBHajdu  United States
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Default A nice accessible amp for first time builders

The real neat thing about this amp that makes it unique from many other pass designs (not counting non-passLabs\FirstWatt commercial work) is the low power consumption. If compared to the F2 it uses the same gain device has the same output power and similar distortion numbers but the dissipated power goes from ~75 watts/channel to ~20watts /channel. Obviously there are some caveats, feedback Mu-Follower… but non-the less it’s an archetypal pass amp. Perhaps it should have been called the pass-eco-amp.

But is this a teaching tool or is it an amp you could listen to for a few years? I would love to know from some of the builders how it sounds into full range drivers (reviews). I would like to know if it could beat my current class-D demo board for an ADAU1592 with diy power supply to drive my Fostex full range speakers (all subjective I know).

One thing that I think would encourage more people to "jump in the pool", If the parts to populate the PCB are provided. To my everlasting shame I have purchased some PCB’s I have never populated, and will most likely never do so. However I am happy to say that I have built every kit I have ever purchased (mostly headphone amps) where the parts to populate the PCB were provided. This is what Glass Jar Audio does.

Questions?
I have a bag of 2SK170. I have measured the drain currents (Idss) of each of these using a 9v battery a resistor and a multi meter and I have attached a sticky tag to each with the current labeled. I don’t have a distortion analyzer, but I was wondering if there is a way this information could be used to pick the 2SK170 which will yield the lowest distortion in this amp. I have a guess at how to do this based on the B1 article, but I am just guessing you could measure the gate threshold voltage of the MOSFET Q1, then figure out how much voltage would be flowing across R9 and select the JFET with the Idss closest to that. Is that correct?

An upgrade path is always nice and gives people more of an encouragement. So I was doing simulations in LTspice to see how well a SJEP120R100 would work in this amp (I am just assuming it would improve things). That would make it an all JFET amp. I didn’t have a model for it so I just put a 3.5V voltage source on the source of an IRFP240 to model the lower turn-on gate voltage threshold of 0.75v – 1.25v. The amp was not happy. The solutions I could find were to connect P1 and R9 to a -3.5v voltage source (which I did not like because it needs an external supply). Or to decuple by use of a cap the JFET stage from SJEP120R100. This required many changes. I also tried putting a diode (to act as a voltage source) under the source pin of the SJEP120R100, which introduce funny harmonics, but worked, at least in simulation. Any ideas as to how this could be easily done. After all we want to keep SemiSouth sales healthy so they will keep producing power JFET for years to come.

Leve
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Old 9th July 2012, 07:26 PM   #79
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Quote:
Originally Posted by LBHajdu View Post
I have a bag of 2SK170. I have measured the drain currents (Idss) of each of these using a 9v battery a resistor and a multi meter and I have attached a sticky tag to each with the current labeled. I don’t have a distortion analyzer, but I was wondering if there is a way this information could be used to pick the 2SK170 which will yield the lowest distortion in this amp. I have a guess at how to do this based on the B1 article, but I am just guessing you could measure the gate threshold voltage of the MOSFET Q1, then figure out how much voltage would be flowing across R9 and select the JFET with the Idss closest to that. Is that correct?

An upgrade path is always nice and gives people more of an encouragement. So I was doing simulations in LTspice to see how well a SJEP120R100 would work in this amp (I am just assuming it would improve things). That would make it an all JFET amp. I didn’t have a model for it so I just put a 3.5V voltage source on the source of an IRFP240 to model the lower turn-on gate voltage threshold of 0.75v – 1.25v. The amp was not happy. The solutions I could find were to connect P1 and R9 to a -3.5v voltage source (which I did not like because it needs an external supply). Or to decuple by use of a cap the JFET stage from SJEP120R100. This required many changes. I also tried putting a diode (to act as a voltage source) under the source pin of the SJEP120R100, which introduce funny harmonics, but worked, at least in simulation. Any ideas as to how this could be easily done. After all we want to keep SemiSouth sales healthy so they will keep producing power JFET for years to come.

Leve
Surely you haven't checked here: SS 120R085 Depletion Mode Jfet
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Old 9th July 2012, 08:51 PM   #80
pidesd is offline pidesd  Canada
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i ve build one channel of this amp and did not compare directly to other pass amps i built (aleph j,f5,sit ccs sony fets) but when i use bf862 jfet and 2n4401 as bjt, it is amazing to me, with lowthers.

Last edited by pidesd; 9th July 2012 at 09:09 PM.
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