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
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
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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
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
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.
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.
Attachments
Thats easy, so many places that will provide enclosures or just get two plates and have a wood sides!
Thats very interesting. I'm not married to anything really. Every time I settle on something, I run across a piece of information that changes my mind. Right now I am waffling on choke filtered or cap filter powered supplies. Clearly cap filtered is cheaper and more efficient, but if choke sounds better then I want choke. If I wanted efficiency I would build a solid state amp. :-D
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Choke I/P filters are inherently well regulated and, in their own way, efficient. When choke I/P filtration is employed, it is possible to access the full VA capability of the power trafo rectifier winding. Due to I2R heating effects, only about 1/2 of the rectifier winding's VA capability is available, when cap. I/P filtration is used.
Choke I/P filters are current rich and voltage poor. Cap. I/P filters are voltage rich and current poor. High value cap. I/P filters are reasonably well regulated, but introduce other issues. Scan the archives for my posts about "hash" filters.
Keep the Laws of Physics firmly in mind and select a rational setup. Sweat the details and a good result will be obtained. Compromises are inevitable, with cost, space, and weight being obvious factors.
+1 for the El Cheapo - even a hacked together variation with some changes to suit on-hand parts can sound very musical - built a couple with EL84s and salvaged terminally ill Scott amps a while back, and one is still sounding too good to risk transplanting to an all new chassis
Second hardest part about a DIY tube amp after the power supply, is probably affording the output iron to deliver the bandwidth you're hoping for - which is were the Scott LK48 OPT came in hand - one pair found a home in TubeLab Simple P/P
Second hardest part about a DIY tube amp after the power supply, is probably affording the output iron to deliver the bandwidth you're hoping for - which is were the Scott LK48 OPT came in hand - one pair found a home in TubeLab Simple P/P
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