[audionut]

Well I've since contacted Jeff at GJA, and he's using the J511's for CRD1 in his kits, and is considering offering them with the PC boards since the 1N5313's are so hard to source now. I ordered 2 of the J511's today from him today, and will start my build sometime next week. I had PM'd Alex on the 1N5314 for a possible sub, but he hasn't responded as of yet. I know he's extremly busy with his Liquid Fire, which is totally understandable.

 

[gurubhai]

 
Hi people, the recommended output mosfet IRF540/9540 have disappeared from the market around here. Retailers here are offering a IRF540N/IRF9540N as replacement.
Is it ok to use them as a substitute ?

 

[cfcubed]

Maybe you'll get a more specific answer for this application but a quick search turned up these thoughts:
http://www.diyaudio.com/forums/car-audio/161985-irf540n-place-irf540-mtx-thunder-2300-a.html
http://www.diyaudio.com/forums/car-audio/186332-mtx-4202-irf540z-irf540n.html
and you've probably seen 'em.

 

[gurubhai]

Yes,I have seen them. The N versions are supposed to be newer & better but some of the posts seem to suggest that they may not work well in some circuits. So, I was hoping for a more specific answer for ehha.
 

 

[iamthecheese]

I'm pretty set on the EHHA as my summer build, but I have a few questions.
 
I'm planning on ordering one of the glass jar audio kits, and someone please correct me if I'm wrong but they are inclusive except for wiring, casework, and chassis jacks(aka the additional stuff i need to buy).
 
I'm considering housing the transformers and power supplies in a separate box and stacking since on my desk I have more space vertically than horizontally, how much extra money would this design cost and is it even worth considering?
 
I'm likely going to order this iron: http://circuitspecialists.com/prod.itml/icOid/9747 or similar for the project, to replace my basic weller I did my minimax build with.

 

[funch]

The kit comes with two boards, all components to populate them, and two transformers. You supply everything else.
Be sure to inventory everything when it arrives and let Jeff know if there is anything missing.
 
I have this station http://circuitspecialists.com/prod.itml/icOid/7307. It's not what you would call 'heavy duty', but
works well and is cheap to replace. Easy for me too, as the shop is 40 minutes from my home. I'm not familiar
with the one you linked, though. It seems to be a new line for CS.

 

[jdkJake]

Are you considering stacking the amp chassis on top of the transformer chassis? That would not be recommended due to the emission characteristics of a toroidal transformer. Not that people do not do it anyway....

Unless you are going to locate the transformers physically away from the amp, the stacking concept will actually have the potential to degrade overall performance.

 

[iamthecheese]

Quote:

Are you considering stacking the amp chassis on top of the transformer chassis? That would not be recommended due to the emission characteristics of a toroidal transformer. Not that people do not do it anyway....

Unless you are going to locate the transformers physically away from the amp, the stacking concept will actually have the potential to degrade overall performance.

I was just thinking as a potential space saving design, but it it causes interference I can easily toss out the idea. I had just seen a ton of DIY amps with the PSU stacked underneath.

 

[flynhawaiian]

I've decided to undertake this project and had a few questions, and hoped some of you might steer me in the right direction.
 
(1) I assume the BJT setup is better than the mosfet as far as sound goes?
(2) If so which transistors might you recommend?  I have heard going with the Toshiba 2238/968 pair is the way to go.
(3) If I use the pair, how is it wired?  Ie, Is the Q10BJT = 2238 and Q11BJT = 968
(4) Which power supply should I use?  The board power supply or is there another recommendation such as the R-Core?
 
Thanks Again

 

[jdkJake]

I've decided to undertake this project and had a few questions, and hoped some of you might steer me in the right direction.
 
(1) I assume the BJT setup is better than the mosfet as far as sound goes?
(2) If so which transistors might you recommend?  I have heard going with the Toshiba 2238/968 pair is the way to go.
(3) If I use the pair, how is it wired?  Ie, Is the Q10BJT = 2238 and Q11BJT = 968
(4) Which power supply should I use?  The board power supply or is there another recommendation such as the R-Core?
 
Thanks Again

1) Not necessarily. The MOSFET sounds mighty fine. I think only a couple of folks have built BJT versions (sachu and cobaltmute come to mind). I think sachu is in the position to directly compare the two versions, so, hopefully he will chime in.

2) There are multiple BJT's that can be used. The Toshiba's you mention are but one of them. Lot's of folks have opinions on the sound characteristics of the various devices available. So, it really comes down to sound preference. The build is actually designed for a different set of BJT's, so, be aware, the pin outs of the various devices may be different and needs to be accounted for appropriately.

3) Q10 is the NPN device and Q11 is the PNP device.

4) The Rev A includes a power supplies that are more than sufficient for both the amp and tube heaters. The rcore you mention is a transformer, not a power supply per se. You will need a set of transformers to feed both the amp and tube heater supplies. There are multiple ways you can go with regard to transformers. A search through the thread will yield many recommendations.

 

[gurubhai]

Quote:

I've decided to undertake this project and had a few questions, and hoped some of you might steer me in the right direction.
 
(1) I assume the BJT setup is better than the mosfet as far as sound goes?
(2) If so which transistors might you recommend?  I have heard going with the Toshiba 2238/968 pair is the way to go.
(3) If I use the pair, how is it wired?  Ie, Is the Q10BJT = 2238 and Q11BJT = 968
(4) Which power supply should I use?  The board power supply or is there another recommendation such as the R-Core?
 
Thanks Again

I used BJT(2238/968) for my EHHA  build & mosfets for rev.A, so I shall try to answer a couple of your questions.
 
1) They are both excellent sounding & share the common EHHA sound sig.The differences are there, but are rather subtle.
The mosfets are a little harder to find the sweet spot though since the bias setting varies quite a lot.
The BJTs, otoh, are much easier to bias right.
 
3)Like JdkJake said, check the npn/pnp status. One thing I must add that the pinouts of 2238/968 are inverted from those of stock BJTs. If you  use the rev. A board, you can simply use the mosfet holes for 2238/968s.
 
 
 

 

[nullstring]

I would also like to hear Sachu's opinion has he made the MOSFET's first and the BJT's second.
I wonder if that changes anything.

 

[iamthecheese]

Does anyone have the dimensions of the Rev A boards? I can't seem to find them on the Cavalli website.

 

[Sathimas]

Boards are 107mm wide
 
Heater supply is 20mm long
Power supply is 44mm long
Amp board is 83mm long
 
Hope that helps

 

[iamthecheese]

Quote:

Boards are 107mm wide
 
Heater supply is 20mm long
Power supply is 44mm long
Amp board is 83mm long
 
Hope that helps

Thank you very much, that it does.