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(one more) ALEPH P 1.7 clone

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#682
You can use Goole language tools http://www.google.com/language_tools?hl=en and put the site name in and select German to English. Not great, but acceptable.

The TKD CP2500 pots are very good, but expensive. Not as expensive as Penny and Giles, but still pricey. In the US, Michael Percy Audio carries stereo versions of these, as well as Partsconnexion. These run around $60 USD. Thel is the only place (other than TKD) that I have seen more than a 2-deck TKD pot.

I attached a parts list that I used. The Dale RN60s are a bit big for the board... RN55s would fit much better and be high enough rating for most of the resistors. The zeners are 1/2 watt. Panasonic TSHA would be the choice for caps, IMHO. I haven't gotten a transformer, etc. for mine yet... just have the boards built and waiting.
 

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#684
understanding Dissipation and current of circuit

T3 and T7 (IRF 9610) provides 30mA of current to T2 and T9(main gain devices IRF610) while T1 and T8 (IRF610) sinks 20mA of current to ground?

Therefore T2 and T9 are biased at 30mA?

What is the dissipation of the mosfets?

And consequently, what is the VA of the transformer needed to power 2 channels?

Regards
zenesh
 
#685
on Veteran´s boards you can ealily put a profile of aluminum to mount the transistors and give them some means of heatdissipation although the original Aleph P with the same amount of bias current did not use any heatsink...your choice...

I used a standart 120VA transformer (leaves you with 60VA per channel which is plenty)as it fittet nicely with the powerrequirements of my Pearl, Aleph P and X-ONO-projects.
 
#688
It seems more interesting for Zenesh to understand exactly what minimum power is required from the powersupply and how much each MOSFET dissipates.

It's easy to determine the voltages at the drain and source intersection of the three MOSFETs from the resistors between the devices.
Anyone can tell how much dissipation results from 60VDC regulated times 30mA.
(I don't have the schematics in front of me either, i dream about this stuff at night)
 
#692
Yes jacco trying to learn the maths behind the circuit.

R25/R26 is large in resistance so almost no current is sourced there?

T1 requires 20mA so about 10mA goes through R23?

Therefore about 30mA passes through T2. Using max 60VDC max dissipation is 60 * 0.03 = 1.8W

Max dissipation for 1 side is
60 * 0.02 = 1.2W(T1)
60 * 0.03 = 1.8W(T2)
60 * 0.03 = 1.8W(T3)

Total (T1+T2+T3) = 4.8W
1 Channel = 4.8*2 =9.6W

So even 60VA is way more then enough for 2 channels?
 
#693
Zenesh,

there's only one 60VDC rail, the current is flowing to ground.
At 30mA flowing in, the total dissipation of all three devices can not be higher than 1.8Watt.

Without a signal present, assuming identical behavior of top and bottom half, the voltages at the sources of the gain devices are the same=> no current flowing through R23.
(R23 sets the gain of the circuit)

Means the difference between 30 and 20mA flows through R25/R26 to ground.
For the powersupply, it doesn't matter whether the current goes to ground through semis or resistors.
R25/R26 are 4,75K and 10K, i think, equivalent of ~3.2K.
That gives the voltage at the source of the current device.

There's also a MOSFET in the powersupply, regulating from nearly 84 volts down to 60VDC.
Total power take-off is 84 Volts times 30mA ~ 2.5Watts for each section = 5 watts per channel.
A standard rule at this forum is using a transformer with a VA rating of at least three times the power requirement, so 30VA or higher.
Most use something bigger because the price difference between 30 and 50VA is not staggering.

I wind my own transformers for pre-amp use, the kind of transformer that is also favored by Mr Curl.
Winding a 30VA is cheaper and also saves me some time.
 
#695
Hi guys,

as I pointed out, the 120VA transformers I use are used because I baught a large volume of these magnetically shielded, and in epoxy molded tordials...and I remember mentioning that for the Aleph P 60VA per channel is plenty and I meant plenty!

The pod is more than a handful. I had the blue and the bigger black ALPS-pod and they are nothing like the CP2500.

Also the good conductive plastic pod from Panasonic does not match up the CP2500 (only my lonesome expertise...)
 
#700
There are a transformers at farnell singapore that are suitable, though smallest is 63VAC. I intend to head to sim lim tower and see what i can find.

With regards to the pod Tod. how much is it? I am still searching for some sort of volume control.
 
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