Super Single-Ended Project

capohk

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Seriously, why are your diodes backwards? Trying to blow up some capacitors?

Thanks - was copied over from a previous drawing where my PS went right to left. Forgot to flip over the orientation of the diode bridge.
 

NTC

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Seriously, why are your diodes backwards? Trying to blow up some capacitors?

Seriously, why are your diodes backwards? Trying to blow up some capacitors?

Thanks - was copied over from a previous drawing where my PS went right to left. Forgot to flip over the orientation of the diode bridge.

That was bothering me throughout reading the thread. So what IS that 5th diode for? I don't see a need for it.
 

printer2

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Seriously, why are your diodes backwards? Trying to blow up some capacitors?

Thanks - was copied over from a previous drawing where my PS went right to left. Forgot to flip over the orientation of the diode bridge.
Been there done that.
 

Mongo Park

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I don’t think parallel 6V6 will be much louder than one 6V6. Much richer harmonics would be expected. With separate cap and resistor on the cathode you can bias each tube separately. So perfectly the same or a little out one a bit hot and one a bit cool, which is the way I would go. Following to see how it all comes out.
 

chas.wahl

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The same concept was done, with some simplification, by Dave Hunter in his book "The Guitar Amp Handbook", apparently 10 years later than the Angela circuit (of which I was unaware). It has no choke, no double rectifiers, different plate and cathode resistor values on the first preamp tube, but has the same BRT/DEEP switch. Power tubeage claimed: 2x6V6 or one 6L6 or EL34. Maybe worth a look -- no schematic, just a layout (not to scale, really). Not a home practice amp unless you have a few acres around you.
 
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capohk

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I am saying add another filter cap, then position the choke, then another filter cap for the plates, and on with the rest of the power supply. The current choke position can replaced with a small value / high wattage resistor so your plates and screens remain close in voltage.
OK. Let's see if this makes sense.

What values do you suggest for the power supply filtering. The original 5F2a has 16/16/8/8
The Angela scheme has 40/16/16. There is an upper preferred limit dictated by the rectifier tube, but with diodes, is this still a factor? In any case, I'm looking to stay pretty close to the 5F2A tone, so don't need to go big.

What value resistor before the choke?

I re-drew the schematic to make better sense of how the power section and preamp connect.

1652334455733.png
 

capohk

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The same concept was done, with some simplification, by Dave Hunter in his book "The Guitar Amp Handbook", apparently 10 years later than the Angela circuit (of which I was unaware). It has no choke, no double rectifiers, different plate and cathode resistor values on the first preamp tube, but has the same BRT/DEEP switch. Power tubeage claimed: 2x6V6 or one 6L6 or EL34. Maybe worth a look -- no schematic, just a layout (not to scale, really). Not a home practice amp unless you have a few acres around you.
I have the Dave Hunter book and the schematic I found looks exactly like what I need. No choke though, and only 3 filter stages. It does have NFB and the switchable cathode bypass cap on V1a, but no cathode bypass on V1b. It also has a separate cathode bias for each 6V6 as suggested earlier. I'll go back and read Dave Hunter tonight and see where I get to.

DhkB2IyzJFIkdZ7CIQh9MeXi8ep6hETfSYiKTvm2i6F_g9_Fd-_f1EQEAgPzq2iufc8miA6XzjhOJmOwPSiYtks5CfPqG4fYG1UOMeKLbWHo7KSWOv_UZxGwD2Zjaxx-lurnuN1AbKRU_yKLNQ
 

andrewRneumann

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OK. Let's see if this makes sense.

What values do you suggest for the power supply filtering. The original 5F2a has 16/16/8/8
The Angela scheme has 40/16/16. There is an upper preferred limit dictated by the rectifier tube, but with diodes, is this still a factor? In any case, I'm looking to stay pretty close to the 5F2A tone, so don't need to go big.

What value resistor before the choke?

I re-drew the schematic to make better sense of how the power section and preamp connect.

View attachment 982314

99F330FF-B267-46D7-8ECE-A0EBCF3B904A.jpeg


Just a suggestion based on first hand experience. I’m well aware other people didn’t do it like this. I did it like other people too and my amp rippled like Lake Michigan. The choke made it dead silent.

Reservoir cap and choke first, then rest of power supply. How about 40-40-16-16. The screen dropping resistor could be 470-Ohms or even less. I installed screen grid stoppers too, but that’s another topic altogether.

That 5th diode on your ground return to the rectifier is going to cut off your HT completely. I’m curious where that came from? Possibly a previous design with a Zener to drop additional voltage?
 

capohk

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That 5th diode on your ground return to the rectifier is going to cut off your HT completely. I’m curious where that came from? Possibly a previous design with a Zener to drop additional voltage?
I 'borrowed' the power supply from Barry Ampmaker's WF-55 schematic which was the very first kit I built years ago. It's the scheme that's used in my little desktop champ.

Screenshot 2022-05-12 at 5.49.42 PM.png


Although now I look at it, I have left out the R13 resistor to ground.
 

NTC

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So the 5th diode is a Zener. They do have a different symbol - as shown in your example. Do you need one in your design?

It is also good practice to show the Zener voltage and power rating so others (and your future self) know what you were doing.
 

andrewRneumann

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I 'borrowed' the power supply from Barry Ampmaker's WF-55 schematic which was the very first kit I built years ago. It's the scheme that's used in my little desktop champ.

View attachment 982336

Although now I look at it, I have left out the R13 resistor to ground.

I’m all for borrowing. And I’m all for presenting a design here for input. That particular Zener diode is there to reduce the HT voltage. Unless you have a reason to reduce HT voltage, leave it out. If you select the right transformer, it shouldn’t be necessary.
 

Mongo Park

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I think you are receiving good advice. With that advice you are moving in the right direction. The original amp you started with has little of what you want, as in parallel 6v6 and a preamp. So I think it is best to move on the the other example which have more of what you want. I find the super A a complicated amp to slim down from a Nubie point of view. Working out the power supply is a great place to start a happy B+ is a good thing. Having to go back and change this once the amp is built is more of a compromise.
Look at this calculator it may help

I would also add in a tone pot
 
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capohk

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I think you are receiving good advice. With that advice you are moving in the right direction. The original amp you started with has little of what you want, as in parallel 6v6 and a preamp. So I think it is best to move on the the other example which have more of what you want. I find the super A a complicated amp to slim down from a Nubie point of view. Working out the power supply is a great place to start a happy B+ is a good thing. Having to go back and change this once the amp is built is more of a compromise.
Look at this calculator it may help

I would also add in a tone pot
Screenshot 2022-05-13 at 9.54.34 AM.png

Looks about right for B+?

The 2-stroke also specs for around 330 - 360VDC on the output tube plates. The transformer I am looking at is 275v for 240V, we have around 227V at the wall in HK so should be a little lower. Adding a choke will also bring it down a little. Seems my choice of PT is good?

I'm re-reading the 2-stroke project in Dave Hunter's book. It does seem to be very similar, along with Dennis Cornell's Romany/stinger amp. As previously discussed, there doesn't seem to be any sonic advantage to tube rectification for a SE amp so a diode rectified 2-stroke would achieve my aims too. I do like the idea of being able to run different tubes in both preamp and output sections.
 

Mongo Park

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Yes many have stayed the 5y3 in a SE amp is a waste of a tube. Go for SS you won’t look back. Also running various tubes complicates things. If you could run various tubes I think you would settle on one combination that sounded the best and that would be it.
 

2L man

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Loadline might look close to this but where the B+1 settle change it some. Because of high B+1 the Operating Point comes to the right and low so linearity is poor and there comes lots of 2nd harmonics already on low power. This headroom of 250V produce about 5W and more than 10% distortion. I understand this is how Tweed Champ are traditionally set :)

This loadline use 6k/reactive because when two parallel tubes are used to drive 3k OT they share the load and it comes half. Plate voltage is about g1 voltage loss less than PS B+1 when Cathode Biasing is used. Screen voltage has some effect to Cathode current/Bias voltage.

What is your OT max bias current?

If it is higher than 75mA you can change OP more left and up improving PS filtering installing few more RC or RCR stages. I think electrolyts is better investment than Choke when Solid State rectifier is used.

Obviously SS diodes pass higher current peak than tube rectifier and it make Choke electromagnetic "pulse" stronger and it increase Hum when it transfers to OT inductively. I have come to this conclusion because oscilloscope show smoother DC voltage but SE amp still hum more than using better filtered PS using multiple RC filters

Choke was favored when electrolyts were proportionally much more expensive and Choke did also lengthen Rectifier tube operating life.
 

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Mexitele Blues

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Second, the 5F2A and 5F1 both have 22k negative feedback. The Angela schematic deletes the NFB. Why?

I suspect it has to do with the designer's desired Vox vibe. NFB will damp the chime, in so many words.

Fellow parallel-6V6 fan checking in here, I referenced the Angela schematic many times while drawing up my Gibsonette build. It had no NFB stock, which results in a thick woolly sound that's out of control by 3:00 on the knob. I added a 3-way NFB switch, found where I liked it best, and left it there.

I think the PT you linked above, in combination with your wall voltage and a bridge rectifier will put your B+ at about 330V, a nice place to be. The SS rectification will also allow you to fit everything into a 5F2 chassis.
 

Joeyboy951

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Buoyed by my recent success with re-building my 5f1 using PTP and a small chassis, I am planning my next build. I have been listening to The Truth About Vintage Amps a bit too much and settled on the parallel SE 6V6 project that Steve Melkisethian first posted in the Angela catalogue in 1996. It's basically a 5F2 with a bigger OT and 2 6V6s in parallel single-ended configuration. I'm hoping there are some folk here who are familiar with the circuit as I'm right at the limit of my understanding with some of this stuff.

I am progressing my learning by trying to draw out the schematic for what I want to do, which is use a solid-state rectifier instead of the two 5Y3s, partly to reduce cost but also because I like the simplicity of it. I already have what I think is a good PT and OT in mind from Primary Windings UK. The specs are here:

PT
Primaries - 2 x 120V
Secondaries - 0 – 190V – 275V @ 160mA
Heater winding 6.3V at 3A centre tapped.

OT
Primary - 3000 Ohms, Inductance 2.5H at 1KHz, Leakage inductance 6mH
Secondaries - 4 Ohm, 8 Ohm and 16 Ohm
Power rating - 15W

Initial questions:

A choke is suggested for the first filter stage.
In the notes for the single 6V6 amp that Steve outlines, he suggests anything between 2- 10H with at least 120mA but no more that 100 ohms DC resistance.


Primary Windings also sell a couple of chokes and it would be good to get the iron all from the same place. However, the specs for the two that look reasonable are:

10H at 100mA, DC resistance 130 Ohms

Or

10H at 180mA, 200 Ohms DC resistance

Which specs are important and why?

Second, the 5F2A and 5F1 both have 22k negative feedback. The Angela schematic deletes the NFB. Why?

I'll follow up with my somewhat completed schematic and the Angela schematic for reference. Super appreciative of any feedback as always. The resistor and capacitor values for the SSE differ in several places from the 5F2 that it is based on. I'm leaving those blank on my schematic until I can work out why and what should be there.

Finally, Angela Super Single-Ended Guitar Amp Solid State Rectified has quite the catchy acronym. Maybe in future posts I'll just use that.

Matt
my previous post I talked about building my Class A single ended amp after reading a book by Dave Hunter ( UK ) Guitar Amp Handbook. My tube configuration is 5Y3, KT66 and 12Ax7.
speakers are Jensen 16 ohms for 10” and 8 “ speakers
this amp can rattle the windows on compress you chest when
turn it up or be mellow and soft. Speakers can be played in pair
or single with a two phase switch.
 

capohk

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I suspect it has to do with the designer's desired Vox vibe. NFB will damp the chime, in so many words.

Fellow parallel-6V6 fan checking in here, I referenced the Angela schematic many times while drawing up my Gibsonette build. It had no NFB stock, which results in a thick woolly sound that's out of control by 3:00 on the knob. I added a 3-way NFB switch, found where I liked it best, and left it there.

I think the PT you linked above, in combination with your wall voltage and a bridge rectifier will put your B+ at about 330V, a nice place to be. The SS rectification will also allow you to fit everything into a 5F2 chassis.
Ha - I just finished reading your Gibsonette thread. I'll have a closer look at your schematic for the GA-8.

I was just looking at Jesse Quitslund's version which he calls Lulu I think. He says he first built it in 1996 while he was working for Steve Melkisethian at Angela, so I'm guessing it's the ASSEGAP.

I have the first edition of the Hunter book in which the Two-Stroke project is parallel 6V6. Apparently in later editions, he changed the power section to just one power tube as they thought it sounded better.

The more I read, the more likely I am to get option paralysis, so I think I'm going to build the Two-Stroke pretty much as stock and then try experimenting. I like to find the sweet spot for an amp or an effect and then leave it there. Any switches and pots for NFB, cathode bypass would likely be just in a prototype and then deleted in the final build. I need this to be as simple and robust as possible really, as it'll be a jam/small gig tool hopefully.

Looking at chassis, I like the Hammond style die-cast boxes - aluminium, pretty rugged and easy to work. The other option might be a BF Champ, with the third hole used for some other adjustable.
 




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