My first home audio amp.

Tim Wyatt · 8th November 2004, 05:06 AM

What do you think so far. Nothing is wired yet and it is still mounted to my "work stand"

.

rcavictim · 8th November 2004, 07:39 AM

Looking good! I like the layout. I would have left more room between the output xfmers and the output tubes though. Are those 6BQ5's?

I don't quite understand how you are going to use one choke between two 5Y3 rectifier tubes though, or am I missing something?

Tim Wyatt · 8th November 2004, 01:41 PM

Yes 6BQ5s with 12AX7s (Bugle boy) and 5Y3GTs. As for spacing of the output tubes from the output trasformer, what problems may I have? Feedback, Oscilations or other? Would a small shield between them help? I am using the rectifiers in parallel to double the current handling. Thanks.

rcavictim · 8th November 2004, 03:27 PM

Tim,

Nothing to worry about. My concern is a generality and it is about the IR heat thrown off by the output valves. It will cause the output xfmers to get warmer than they otherwise would but probably not so hot as to worry about. Just something to think about next time.

The reflection off the chassis in your photo makes the spacing of the output tubes to the xfmers look too close, but I see this is an optical illusion. If you have an inch here you are OK. There is lots of airflow to cool things since this amp is not in a small tight covered box like a Heathkit or Eico using similar circuit and tubes. Those little Eico's (HF-12) run HOT!

resident · 8th November 2004, 03:29 PM

Quote:

As for spacing of the output tubes from the output trasformer, what problems may I have?

Output tubes will get to hot the OPTs.They're too close!
I don't think you will have other problems.

Sch3mat1c · 8th November 2004, 06:32 PM

For the rectifier, you'll use a paralleled 5Y3 for each half, feeding the choke?

Tim

Tim Wyatt · 8th November 2004, 06:39 PM

The power tubes have at least an inch between them and the transformers. The angle of the picture and the shine of the base make it hard to see. The 5Y3s are in parallel feeding half the cap, B+ and the choke. Then the choke goes to the other half of the cap for the preamp section. Both sides run off of both rectifiers and choke. Funny that the Eico HF-12 was brought up. I used two of these for this amp. The power section was salvaged from an old frequency shifter monster sized test thing.

Sch3mat1c · 9th November 2004, 04:06 AM

Er, that big fat choke is only for the preamp?

Tim Wyatt · 9th November 2004, 05:04 AM

Quote:

Originally posted by Sch3mat1c
Er, that big fat choke is only for the preamp?

Should I go Cap-Choke-B+ to power tubes, resistor, Cap to preamp? Most schematics I have seen have the choke after B+ to the power tubes, That's why I was going that way. Would it be better to run everything after the choke? Thank you for your help.

SHiFTY · 9th November 2004, 08:10 AM

Depends on the rating of the choke. If it can handle the entire current of the amp, then definitely use a CLC filter where the second C feeds the output tubes, then an RC for the preamp where the C feeds the preamp tubes.

Your + rail will look then like this: CLCRC

The first C should be no more than 20uF or so, otherwise you will stress the 5Y3s.

Most classic audio amps use a similar design, eg Leak TL12

8th November 2004, 05:06 AM	#1
Tim Wyatt diyAudio Member Join Date: Mar 2004 Location: Wichita,KS	My first home audio amp. What do you think so far. Nothing is wired yet and it is still mounted to my "work stand" .

8th November 2004, 07:39 AM	#2
rcavictim diyAudio Member Join Date: Jun 2004 Location: Cool end of a soldering iron NW of Toronto	Looking good! I like the layout. I would have left more room between the output xfmers and the output tubes though. Are those 6BQ5's? I don't quite understand how you are going to use one choke between two 5Y3 rectifier tubes though, or am I missing something? __________________ I.Q.Test. Have you ever purchased a recreational snowmobile?

8th November 2004, 03:27 PM	#4
rcavictim diyAudio Member Join Date: Jun 2004 Location: Cool end of a soldering iron NW of Toronto	Tim, Nothing to worry about. My concern is a generality and it is about the IR heat thrown off by the output valves. It will cause the output xfmers to get warmer than they otherwise would but probably not so hot as to worry about. Just something to think about next time. The reflection off the chassis in your photo makes the spacing of the output tubes to the xfmers look too close, but I see this is an optical illusion. If you have an inch here you are OK. There is lots of airflow to cool things since this amp is not in a small tight covered box like a Heathkit or Eico using similar circuit and tubes. Those little Eico's (HF-12) run HOT! __________________ I.Q.Test. Have you ever purchased a recreational snowmobile?

8th November 2004, 06:32 PM	#6
Sch3mat1c diyAudio Member Join Date: Jan 2003 Location: Milwaukee, WI	For the rectifier, you'll use a paralleled 5Y3 for each half, feeding the choke? Tim __________________ See my Electronics webpage -- the home of Vacuum Tube Drag Racing. The key to being a successful Audiophile: "I reject your reality and substitute my own!"

9th November 2004, 04:06 AM	#8
Sch3mat1c diyAudio Member Join Date: Jan 2003 Location: Milwaukee, WI	Er, that big fat choke is only for the preamp? __________________ See my Electronics webpage -- the home of Vacuum Tube Drag Racing. The key to being a successful Audiophile: "I reject your reality and substitute my own!"

8th November 2004, 01:41 PM	#3
Tim Wyatt diyAudio Member Join Date: Mar 2004 Location: Wichita,KS	Yes 6BQ5s with 12AX7s (Bugle boy) and 5Y3GTs. As for spacing of the output tubes from the output trasformer, what problems may I have? Feedback, Oscilations or other? Would a small shield between them help? I am using the rectifiers in parallel to double the current handling. Thanks.

8th November 2004, 06:39 PM	#7
Tim Wyatt diyAudio Member Join Date: Mar 2004 Location: Wichita,KS	The power tubes have at least an inch between them and the transformers. The angle of the picture and the shine of the base make it hard to see. The 5Y3s are in parallel feeding half the cap, B+ and the choke. Then the choke goes to the other half of the cap for the preamp section. Both sides run off of both rectifiers and choke. Funny that the Eico HF-12 was brought up. I used two of these for this amp. The power section was salvaged from an old frequency shifter monster sized test thing.

9th November 2004, 08:10 AM	#10
SHiFTY diyAudio Member Join Date: Jul 2002 Location: New Zealand	Depends on the rating of the choke. If it can handle the entire current of the amp, then definitely use a CLC filter where the second C feeds the output tubes, then an RC for the preamp where the C feeds the preamp tubes. Your + rail will look then like this: CLCRC The first C should be no more than 20uF or so, otherwise you will stress the 5Y3s. Most classic audio amps use a similar design, eg Leak TL12

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