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Old 26th October 2014, 04:25 AM   #1
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Default The hardest part about a DIY tube amp is.....

Finding a design to build! I have looked and looked and do not know enough about all the classics to know if an old Eico or Marantz would fill the fill, so I want to get some input. I am a tinkerer and a solder slinger but I am no designer. I wanted something that could (if possible) get by with just point to point wiring and no PCB's.

Anyone know of an amplifier that would include the following? Obviously, not everything is included here but this is in very general terms what I have been looking for.

Integrated amplifier design
Capacitor coupled
Push-pull

4 x KT88 or EL34

2 power transformers
1 psu chokes
2 anode chokes
2 Output Transformers

Pre-amp controls
- Line Input Selector - 4 sources 4 sets of RCA Inputs
- Stepped Volume Control
Speaker taps - Main L / R 8 ohm only

Last edited by Soothsayerman; 26th October 2014 at 01:58 PM.
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Old 26th October 2014, 04:30 AM   #2
iko is offline iko  Canada
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Really good power supply. Period.
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Old 26th October 2014, 04:42 AM   #3
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I see you have 2 Anode Chokes listed, are you considering a Balanced Parafeed design?

I love point to point construction.

The Pre-Amp design is just as important, to say the least. What kind of input are you going to use? And will this Pre-Amp be on board this chassis? Or do you already have something doing the Pre-Amp duty? Regulated Power Supply is Key. What about negative feedback, distortion %'s?

I'm exactly where you're at. And reading as much as I can.

Regards, Doug
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Old 26th October 2014, 07:06 AM   #4
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Quote:
Originally Posted by Soothsayerman View Post
Finding a design to build! I have looked and looked and do not know enough about all the classics to know if an old Eico or Marantz would fill the fill, so I want to get some input. I am a tinkerer and a solder slinger but I am no designer. I wanted something that could (if possible) get by with just point to point wiring and no PCB's.

Anyone know of an amplifier that would include the following? Obviously, not everything is included here but this is in very general terms what I have been looking for.

Integrated amplifier design
Capacitor coupled
Push-pull

4 x KT88 or EL34

2 power transformers
2 psu chokes
2 anode chokes
2 Output Transformers

Pre-amp controls
- Line Input Selector - 4 sources 4 sets of RCA Inputs
- Stepped Volume Control
Speaker taps - Main L / R 8 ohm only
Good idea!
Why do I need "2 psu chokes" ?
Separate anode power - very good.
Output and power transformers have already purchased?
What the rest of the tube you wish to use?
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Old 26th October 2014, 09:46 AM   #5
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Quote:
Originally Posted by Andreas AVM View Post
Good idea!
Why do I need "2 psu chokes" ?
Separate anode power - very good.
Output and power transformers have already purchased?
What the rest of the tube you wish to use?
I am guessing it if for two monoblocks.

For the OP, keep in mind that any of designs that have global feedback, the compensation networks are for the specified output transformer only.
You need a >10Mhz scope to fine tune the compensation if you use a different output transformers

Point to point is certainly possible, maybe have a look in the Photo Gallery thread.
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Old 26th October 2014, 01:59 PM   #6
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Quote:
Originally Posted by costis_n View Post
I am guessing it if for two monoblocks.

For the OP, keep in mind that any of designs that have global feedback, the compensation networks are for the specified output transformer only.
You need a >10Mhz scope to fine tune the compensation if you use a different output transformers

Point to point is certainly possible, maybe have a look in the Photo Gallery thread.
Oops,

I changed it back to just 1 psu choke. It's a single chassis.
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Old 26th October 2014, 04:32 PM   #7
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Quote:
Originally Posted by iko View Post
Really good power supply. Period.
AMEN!

If the OP is willing to add the 7591 to the list of potential "finals", a variation on the "El Cheapo" theme is a possibility. Fisher, Scott, Sherwood ... took full advantage of the fact that small signal circuitry used with "12" W. O/P tubes requires no change to drive 7591s. Obviously, the "trick" is available to anybody that cares to use it.

FWIW, "El Cheapo" was designed so the builder needs only a decent DMM to complete the project. A brute force method of phase compensation is available. Connect a small cap. from the "hot" leg of the O/P trafo to ground. The cap. shorts the NFB loop out above a freq. of at least 80 KHz. The better the O/P "iron", the smaller the cap. becomes.
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Old 26th October 2014, 05:24 PM   #8
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Quote:
Quote:
Originally Posted by Andreas AVM Click the image to open in full size.
Good idea!
Why do I need "2 psu chokes" ?
Separate anode power - very good.
Output and power transformers have already purchased?
What the rest of the tube you wish to use?


Quote:
Originally Posted by costis_n
I am guessing it if for two monoblocks.

For the OP, keep in mind that any of designs that have global feedback, the compensation networks are for the specified output transformer only.
You need a >10Mhz scope to fine tune the compensation if you use a different output transformers

Point to point is certainly possible, maybe have a look in the Photo Gallery thread.
Thank you.
But I do not need help.
I talked to starttopic post1.

Last edited by Andreas AVM; 26th October 2014 at 05:38 PM.
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Old 26th October 2014, 06:25 PM   #9
RajkoM is offline RajkoM  Bosnia and Herzegovina
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The hardest part about a DIY tube amp is........ diy BOX CASING
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Old 27th October 2014, 04:09 AM   #10
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Quote:
Originally Posted by RajkoM View Post
The hardest part about a DIY tube amp is........ diy BOX CASING
Thats easy, so many places that will provide enclosures or just get two plates and have a wood sides!
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