Pictures of your diy Pass amplifier

[AndrewT]

No, you don't. The 240V version uses a single CL-60, as shown in the schematic and as properly made on his PCB.

I have explained this to the 110/120Vac users a few times.
A single CL60 does not give sufficient current limiting during start up to prevent a close rated fuse from rupturing.
230Vac users need a correctly rated Thermistor on EACH 115Vac primary
or
a double resistance Thermistor on the 240Vac primary.

 

[drpro]

ya da ya da

 

[AndrewT]

ya da ya da

You can choose, and now you have expressed your choice.

 

[6L6]

Andrew - in general, I agree with having the additional thermistor.

In this case, it's drawn and utilized exactly as Papa builds (and sells) with the FW products, so there's good evidence that this is sufficient.

 

[Zen Mod]

230Vac mains , 800VA Donut , one CL60 after 4A Sloblo, 8pcs of 33mF in cap bank

works like charm , didn't had one fuse replaced in several years

 

[carpenter]

A couple just after completion...

Such clever cosmetics! I love your retro, Buck Rogers theme....

 

[xrk971]

http://www.diyaudio.com/forums/head...e-class-headamp-without-heat.html#post4920666

 

[Soundhappy]

@ Xrk972

Great build congratulations

 

[xrk971]

@ Xrk972

Great build congratulations

Thanks Soundhappy, one of my few "boxed" amps.

 

[cosmo61]

In my case with 240Vac primary and 600Va trafo (fuse 2,6A)
i blow fuses before i put two CL60 in serie,

I have explained this to the 110/120Vac users a few times.
A single CL60 does not give sufficient current limiting during start up to prevent a close rated fuse from rupturing.
230Vac users need a correctly rated Thermistor on EACH 115Vac primary
or
a double resistance Thermistor on the 240Vac primary.

 

[AndrewT]

2.6A is a close rated fuse for a 600VA 230Vac transformer.

Are you confirming that a single CL60 blows this fuse after a few cold start ups?
and
Are you confirming that two series connected CL60 have so far reliably allowed many cold start ups?

 

[cosmo61]

Yes i confirming with one CL60 i blow fuses after a few cold starts up.
When i switched to two CL60 i don't got this problem any more.

 

[Zen Mod]

so it's simple - less is better

if one doesn't work ,it's just too much of less

then add second one

 

[AndrewT]

so it's simple - less is better

if one doesn't work ,it's just too much of less

then add second one

it's a case of using sufficient added resistance to limit the peak current that passes into the transformer at start up.

Double the mains voltage needs double the added resistance to limit to the same current as from 115Vac. But @ 230Vac the fuse is halved so one needs four times the added resistance to limit the current peak to match the lower value of the close rated 230Vac fuse.

It's simple arithmetic.

Yet we still see replies like this

No, you don't. The 240V version uses a single CL-60, as shown in the schematic and as properly made on his PCB.

ya da ya da

 

[nar]

it's a case of using sufficient added resistance to limit the peak current that passes into the transformer at start up.

Double the mains voltage needs double the added resistance to limit to the same current as from 115Vac. But @ 230Vac the fuse is halved so one needs four times the added resistance to limit the current peak to match the lower value of the close rated 230Vac fuse.

It's simple arithmetic.

Yet we still see replies like this

You're right dear Andrew,
since I use 2 CL60 in series on my Aleph J mono-blocs, 400VA donut in each mono-bloc, no blowing fuses

I use 2AT on 230V mains
2 diode bridge per amp
182.000 capacitor bank per mono-bloc
Original bias figure

Regards,

nAr

 

[vdi_nenna]

ACA Pictures

Some pics of my ACA build.

The transformer has 4- 15v outputs. They were not labeled. Its 286VA or so. Had to use a variac to find the polarity of the secondary. Primary only has two leads for 120v. They were easier to detect correct connections.
Secondary pairs are in parallel.

The case is a 3U mini-dissipante from the store.

Power supply used 60k uF CRC per channel. Blue cap is the same size, voltage and temp capacity as the black filter caps. 21V unloaded and 17.9v loaded power supply output.
Used irfp140 mosfets. I first mistakenly installed irfp9140 on Q2. I checked 3 or 4 times before installing but got confused anyway. Once the washers went on, there was no more checking... the power resistors burned and had to replace them and both mosfets on both channels.
The input and output caps are bypassed with Vishay/Roederstein 1uF caps.
Used standard bridge.

Vince

 

[Dennis Hui]

Bravo Vince!

 

[vdi_nenna]

Thank you Dennis. Without your tip, I wouldn't have looked under the washers!

 

[Zen Mod]

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(picture of my B1 )

 

[vdi_nenna]

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(picture of my B1 )

What's the point?