A couple of questions

a 3W single ended EL84 amp for home, work & school

A couple of questions

Postby GrahamJ » Sun Jul 26, 2015 12:10 pm

Hello,
Before I order a pcb I would please appreciate a some advice.
I have a pair of Edcor GXSE15-8-5K output transformers and I was wondering if their 5K input, instead of the 5.5K noted in the parts list, would be satisfactory?
Also, I have a Hammond 157Q choke (3.5H, 98 ohms) that I would like to use instead of the Triad C24X (1H, 50 ohms)? I am a learner, my thoughts are are to lower R20 from 100 to 47 ohms which should take care of the combined resistance but I am unsure what effect the additional 1.5H will have?
Thanks
Graham
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Re: A couple of questions

Postby GrahamJ » Wed Jul 29, 2015 9:42 am

Hello,
As there has been no advice forthcoming, I have decided to opt for the Triad choke, as detailed in the parts list.
Surely my 5K Edcor outputs will be fine?
Graham
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Re: A couple of questions

Postby cdmawolf » Wed Jul 29, 2015 11:46 am

You actually have a better transformer set than is spec'd. As for mounting, you are on your own. Good Luck!!
p[
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Re: A couple of questions

Postby GrahamJ » Wed Jul 29, 2015 3:09 pm

Thanks cdmwolf,
I'll be making my own case as I need plenty of room.
Not good at working in confined spaces.
Time to get my PCB ordered.
Graham
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Re: A couple of questions

Postby GrahamJ » Wed Jul 29, 2015 3:22 pm

Hello again,
I just tried to order the budgie se pcb and found out that there are currently none available.
Anyone please know if and when there will be any new stock ready for sale?
Thanks,
Graham
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Re: A couple of questions

Postby cdmawolf » Wed Jul 29, 2015 8:05 pm

Where are you looking?

parksaudiollc.com
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Re: A couple of questions

Postby GrahamJ » Thu Jul 30, 2015 2:47 am

Hi cdmawolf,
I tried the announcements thread at the top of the budgie se forum. There is a PCB purchase link beneath the parts lists that takes you to an ordering page, paypal etc.
If you know of another option, I will try again.
In the meantime, I'll keep looking.
Thanks,
Graham
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Re: A couple of questions

Postby cdmawolf » Thu Jul 30, 2015 10:11 am

I believe Shannon might be in the middle of a move, but here is the link I was referring to:

http://parksaudiollc.com/budgiese.html
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Re: A couple of questions

Postby GrahamJ » Thu Jul 30, 2015 11:20 am

Hi cdmwolf,
Thanks for the link, unfortunately same result.
I'll wait until Shannon is back up and running.
Graham
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Re: A couple of questions

Postby TomMcNally » Mon Aug 03, 2015 10:49 am

Did you look in this forum ? Look under "purchase"

http://www.diytube.com/phpBB2/viewtopic.php?f=21&t=6547
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Re: A couple of questions

Postby GrahamJ » Mon Aug 03, 2015 11:12 am

Hi Tom,
Yes I've tried that link many times.
Just now however, I followed your advice, and the link is back in business. I have placed my order.
Shannon must be over the worst.
Thanks Tom
Graham
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Re: A couple of questions

Postby GrahamJ » Fri Oct 02, 2015 8:12 am

Hello,
The Budgie is up and running and sounding SUPERB! Nice design and fun to put together.
Big thank you to Shannon.
I am using Edcor GSXE15-8-5K output transformers and a Hammond 369JX power transformer. I have a couple of Russian 6P14P outputs and a nice old Brimar ECC83 driver.
All else is as recommended in the parts lists.
I have one small query which concerns the voltages being a little low. For example. the driver anodes are at about 150/142v and the output anodes are 247/249v. Even the heaters do not exceed 5.6v.
I was expecting that the slightly higher specification Hammond 369J would have driven the voltage a little higher. Using an online bias calculator these voltages mean that the Budgie is running at about 7W(29 mA) dissipation, which is a little cool.
I was hoping for some advice as to how best to proceed and if it would improve the amp further. Perhaps reducing R20?

I'll post a picture after I have discovered how to reduce the photo size on my Chromebook.

Thanks,
Graham
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Re: A couple of questions

Postby GrahamJ » Fri Oct 02, 2015 9:13 am

Hello again,
I managed to reduce the file size of my photograph by using an onlne resizing site.

Graham
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Re: A couple of questions

Postby TomMcNally » Sat Oct 03, 2015 6:50 pm

The amp looks nice ! The Hammond 369JX has two primaries with multiple taps, make sure you have it connected properly. I don't know where you are, so I can't suggest what you need to do. The windings are in series for 200-240 and paralleled for 100-120. Maybe you are tapped too high ?
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Re: A couple of questions

Postby GrahamJ » Sun Oct 04, 2015 9:47 am

Hi Tom,
Thanks for getting in touch. I am in England, UK and out of interest I have just checked the mains voltage. Bang on 240 volts.
Regarding both primaries on the Hammond 369JX, I have joined the middle wires, brown and black and I am using the blue and white for my supply. I'm pretty sure this is correct. The following link is for the above power TX.
http://www.hammondmfg.com/pdf/EDB369JX.pdf

I was not expecting this problem as it appears that this transformer is a little better specified than the Edcor. At least if I haven't made a silly mistake, this issue is handy for Shannon to be aware of.
Would you think that by lowering the first power supply resistor this could resolve the low voltage issue without upsetting the power supply stability and also by running the valves a little hotter, further improve the sound?

Thanks,
Graham
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