DC30 Clone OT Question

[milkyBK370]

Hi folks,

I have exhausted all possible avenues in my bid to answer a couple of questions I have on the DC30 clone I'm building. I hope the the good folks here could put my mind at ease!

I'm using Ceriatone's layout but sourced all the parts, etc myself. http://ceriatone.com/images/layoutPic/m ... iatone.jpg

I'm using Hammond trannies. They are the Vox vintage replacement set. I'm fine with the PT wiring but have a couple of questions about the OT. On the Ceriatone layout the OT primary is labelled P - CT - P. Here's the Hammond data sheet for the OT which include the wiring diagram. http://www.hammondmfg.com/pdf/EDB1750V.pdf

The primary has Yellow - Red - White wires. I'm guessing the CT is the red wire but am unsure where to connect the other two primary wires. The layout is labelled Q and S which are connections to pin 7 of two of the power valves.

I'm not sure if it matters which way round the yellow and white wires go. Surely the voltages present at pin 7 on the valves are the same so it shouldn't matter??? I'm stuck!

Any help would be greatly appreciated.

Thanks,
Gary

[jestaudio]

Hi folks,

I have exhausted all possible avenues in my bid to answer a couple of questions I have on the DC30 clone I'm building. I hope the the good folks here could put my mind at ease!

I'm using Ceriatone's layout but sourced all the parts, etc myself. http://ceriatone.com/images/layoutPic/m ... iatone.jpg

I'm using Hammond trannies. They are the Vox vintage replacement set. I'm fine with the PT wiring but have a couple of questions about the OT. On the Ceriatone layout the OT primary is labelled P - CT - P. Here's the Hammond data sheet for the OT which include the wiring diagram. http://www.hammondmfg.com/pdf/EDB1750V.pdf

The primary has Yellow - Red - White wires. I'm guessing the CT is the red wire but am unsure where to connect the other two primary wires. The layout is labelled Q and S which are connections to pin 7 of two of the power valves.

I'm not sure if it matters which way round the yellow and white wires go. Surely the voltages present at pin 7 on the valves are the same so it shouldn't matter??? I'm stuck!

Any help would be greatly appreciated.

Thanks,
Gary

Makes no differnce, as long as the centre tap is correct the other 2 wires are essenciatly the ends of a ciol.

[epis]

Hi Gary,
no, it doesn't matter, your amp doesn't use nfb, so go for it, finish your amp and enjoy it.Cheers

[milkyBK370]

Thanks for the replies fellas. I felt a bit stupid for asking but wanted to be sure before I lit her up.

[milkyBK370]

In true Columbo style: just one more thing. The rectifier sockets each have 2 diodes and a 0.01uf ceramic disc. I was wondering what these are for. The layout calls for them but I've seen pics of various builds, including the example of Ceriatone's site, and they are left out. Also, I was unsure which diodes to buy as the layout doesn't mention any values. I got 1N4007 diodes from Amp Maker for it but don't really know if I need to use them.

[overtone]

OK Columbo, they not really needed. But I do do the diode thing.
They are a cheap insurance in case your rectifier valve goes pear shaped.
I guess the capacitors are extra extra insurance against any kind of "switching noise" from the diodes.
Have you checked the Minimum Limiting Resistance for the rectifier and PT combination that you have chosen?
For that & about your 1N4007s try reading this site from Merlin for more information than I can give you right now:
http://www.freewebs.com/valvewizard/fullwave.html
http://www.freewebs.com/valvewizard/bridge.html
Amp Maker hints to me that you are located in the UK right?
Best, tony

[M Fowler]

50/50 chance the amp will squeal on power up. Cut those OT primary wires long in case you have to swap from side to side.

I'm attaching transformer information on the Ceriatone Dizzy 30 just in case any one wants it.

Mark

[overtone]

Mark, isn't the 50/50 chance of the squeal from hell only with a NFB loop involved?
Best, tony

[M Fowler]

Tony,

The heck if I know

I never thought about the why of it all. I'll let the more knowledgeable characters respond to that.

Mark

[overtone]

I forget the reasoning too... well anyway, it is certainly very good advice to leave the leads long at first. I try to keep the over-lengths bunched up outside the chassis.

[dass101]

It can only squeal in NFB amps, because if you wire it the wrong way the negative feedback becomes positive feedback - instead of feeding back an inverted signal you feed a normal signal - and positive feedback means oscillation of the respective stage.

The above is a bit of generalization, because you actually feed back a normal signal, but insert it at the inverting input of the PI. You get the idea...