5E3 iron specs

[rzenc]

Hi gentlemen!

I was asked by a friend of mine to build him a 5E3 + tremolo - he played one that I built around 3 years ago - minus tremolo - and loved it. AFAIR it had a H.T. secondary of 300 - 0 - 300 VAC rectified by 5Y3WGTA - Philips Black Plates - but I don't remember how much current it could supply. Looking at this chart - http://www.tubebooks.org/tubedata/HB-3/Receiving_Tubes_Part_2/6V6-GTA.PDF - it is suggested that @ 285VDC, loaded @ 8k ohms it would ask 92mA + 13,5mA at max signal conditions. So I guess 150mA DC would be plenty for the power supply. I should add 3mA per triode, so V1 (12AY7) - both triodes connected in parallel = 6mA's, P.I. 6mA, tremolo is based on Hoffman's bias vary tremolo and would drag more 6mA's whole bottle???
So adding all current demands 150mA's + 3*(6mA's) = 168mA rounded to 170mA's???

It will have a choke (shielded) between plates and screen in accordance to the amp he played.

Thanks in advance

Best Regards
Rzenc

[Geezer]

Original 5E3 PT is ~~100mA, so 125-150mA will be OK & then some....

[rzenc]

Original 5E3 PT is ~~100mA, so 125-150mA will be OK & then some....

Thanxxxxxxx!!!!!!!!!!!

Do you think the tremolo will be "weak" considering lower voltages?? I have build 5 AB763's with voltages from 380VDC to 446VDC... the effect seemed to be quite the same... but 300VAC rectified with 5Y3 might yield ~300VDC...

I attached the trem section modified to cathode bias operation.

Thanx in advance

Best Regards

Rzenc

[HotBluePlates]

I was asked by a friend of mine to build him a 5E3 + tremolo...

Do you think the tremolo will be "weak" considering lower voltages??

There is a way to be certain you will have perfect tremolo. Build a 5E9 Tremolux! The name literally comes from "Deluxe, with tremolo." The linked schematic is for a 5E9A, and I don't think a schematic was ever drawn for the 5E9 (I've never seen one anywhere).

Anyway... I used to own a '55 5E9 Tremolux. It's tremolo can get very swampy, if that's what your friend wants (and if he wants trem, then he probably does). The only difference between the 5E9 and 5E9A that I saw was the location of the switch to turn the tremolo on/off. The switched pot may be difficult to source; if it is, make sure to look for both the 2M pot with switch and the 250k pot with switch. The 5E9 had the switch on the Depth pot (250k) instead of one the Speed pot (2M).

The big noticeable difference between the Deluxe and Tremolux (other than trem) is the cab size. The Tremolux had a much bigger cabinet. I didn't measure mine, but I have seen various sites that suggest the Tremolux used the cabinet for the tweed Pro, which is plausible. If you are build or buying, use the dimensions for the Pro, as it makes a big difference. If you are buying, people probably won't list a Tremolux cabinet, just the Pro. If so, make sure you contact them ahead of time to specify a 12" cutout in the baffleboard instead of 15".

Of course, you can use Deluxe power and output iron.

[phsyconoodler]

300v after a 5Y3 will yield about 330v at the plates.
  The original Tweed Deluxe specs are 81ma and a 650v center tapped primary.That will give closer to the correct voltages.
This is from the Hammond site. www.hammondmfg.com
  They have perfect Tweed amp transformers.I've used them with great results.

[FYL]

Build a 5E9 Tremolux! The name literally comes from "Deluxe, with tremolo."

Old Deluxe then: the Tremolux uses a paraphase PI 5D3-style, not a cathodyne like the 5E3.

Great amp BTW.

The big noticeable difference between the Deluxe and Tremolux (other than trem) is the cab size.

Yup. Fender used 16.75 x 20 x 9.5" cabs for the 5E3 (a few early '55 versions were slightly smaller at 16.5 x 18 x 8.75"), the first 5E9's used an 5E3 cab with an enlarged panel cutout but Fender switched to a more comfortable 20 x 22 x 10" after a very short while. Same cab as the narrow panel Pro, different baffle (12" vs. 15" cutout).

 

[tubeswell]

Or upgrade to a 5G9 - tweed front end, LTP, bias-vary trem/fixed bias - I promise he won't be disappointed - although its got a bit more bite and headroom than a 5E9A (or 5E3) (and that's to do with the fixed bias) the trem is so hypnotic it'll slam you into the middle of next week. Mine uses 300-0-300@150mA, 6.3V@4A, 5V@3A and a 50V bias winding

On the 5E9 I think the tube compliment used a 5U4GA instead

[HotBluePlates]

...but Fender switched to a more comfortable 20 x 22 x 10" after a very short while.

It was very short. Where Tubeswell's pic shows "serial number" my amp said "production number" and was #45. Built by Eileen. 

But the big cab is handy for all the stuff you shouldn't throw in the back of the cabinet. Cords, pedals, etc.

[rzenc]

I was looking at 5E9-A tremolo section and noticed that there is a 250K pot on cathode of tremolo tube, which connects to cathode on paraphase P.I. and I was thinking that it might get scratch sounding due to DC flowing through it. And it also occuredme that fender changed the desing to have only A.C. present on pots - expect for point #11 on schematic I posted - derived from Hoffman's bias vary trem - which receives bias voltage on fixed bias amps.
So considering 5E9-A schemo I thought about using a 12 positions radiowave selector in order to accomplish the value - 250K ohms - and going deeper on thoughts and smoke I realised that a logaritmic scale would fit better, due to earing perception. What you guys think?

Thanks in Advance

Best Regards

Rzenc

[HotBluePlates]

You are right about the possibility of noise due to d.c. on the pot. But in the one I owned, there was no noise that I recall when adjusting the pots. I don't think a change is necessarily warranted.

It is ideal to have no d.c. on the pots. This particular pot has d.c. across it, but it is also not part of the signal path. At least not directly. I don't think adjusting this pot will cause any d.c. change at the phase inverter cathode, which would be the main way of coupling noise into the circuit. So again, I'm thinking no change needed.

Fender did avoid d.c. on pots where possible. But the change in the tremolo circuit would be more about a change in the location the trem is injected in the circuit. Fender moved away from the paraphase inverter shown (for various reasons), and had to change their method of adding trem without pumping noise. In fact, this specific trem circuit in this specific amp was patented by Leo Fender as a way to add trem without undue noise. But the evolution went to bias-vary and then opto-coupler trem.

[rzenc]

You are right about the possibility of noise due to d.c. on the pot. But in the one I owned, there was no noise that I recall when adjusting the pots. I don't think a change is necessarily warranted.

It is ideal to have no d.c. on the pots. This particular pot has d.c. across it, but it is also not part of the signal path. At least not directly. I don't think adjusting this pot will cause any d.c. change at the phase inverter cathode, which would be the main way of coupling noise into the circuit. So again, I'm thinking no change needed.

Fender did avoid d.c. on pots where possible. But the change in the tremolo circuit would be more about a change in the location the trem is injected in the circuit. Fender moved away from the paraphase inverter shown (for various reasons), and had to change their method of adding trem without pumping noise. In fact, this specific trem circuit in this specific amp was patented by Leo Fender as a way to add trem without undue noise. But the evolution went to bias-vary and then opto-coupler trem.

Thanks for the answer! i will give this a try and see what happens, then, it is also possible to modify it to concertina P.I. and try the bias vary trem.

I also liked the idea of 5G9, it is pretty straight forward, long tail P.I., fixed bias and bias vary trem. actually it would be the power section of a AB763 with 6V6 and p.i. plus trem - except presence and feedback loops - however I haven't built paraphase P.I. and would like to hear one of those.

Regarding tremolo circuits, opto-couplers sounded ok to me - I have 2 amps with them, both 4x6L6GC ~ 100W - but I have built 5 AB763 with bias vary trem and they sounded very nice to me, I mean, more natural, less sudden, althought when really crancked, the trem effect was kinda to subtle... even performing mods to increase trem effect, but this amps were 6L6GC, which needs big drive to roar. 6V6 needs much less.And there is the possibility to use El84 with those THD adapters - which requires even less drive, and this tells me that trem effect should be stronger with tubes needing less signal on their grids.

One thing is for sure, tweed - 12AY7 - 2 knob preamp, parallel plates and grids with different cathode resistors and caps. P.I. and trem circuit for now will be 5E9-A, let's hear what happens.

I will start this in a couple of weeks and will report back.

Thanks for the insights and help!!!! Much appreciated.

One question that keeps coming up, would a LOG pot be "better" suited for this task? I mean intensity pot, not speed pot.

Thanks

Best Regards

Rzenc

[rzenc]

This is kinda of topic but since it has to do with this amp...

I'm drawing a point to point wiring for it and for some simplicity of layout I would use one triode for P.I. and the other for tremolo. I need 2 triodes for P.I. and 2 triodes for tremolo. So, according to my arrangment, I would use 1 triode inside each bottle for trem and the other for P.I. Could this result in leakage from one triode to another inside the glass bottle???
I will draw it to show whaty I'm asking more clearly...

Thanks in Advance

Best Regards

Rzenc 

[tubeswell]

I'm drawing a point to point wiring for it and for some simplicity of layout I would use one triode for P.I. and the other for tremolo. I need 2 triodes for P.I. and 2 triodes for tremolo. So, according to my arrangment, I would use 1 triode inside each bottle for trem and the other for P.I.

Huh? Why not just use one bottle for the PI and the other for the trem? There are plenty of proven layouts that work that way

[HotBluePlates]

Use a linear pot for the Intensity pot, Reverse Audio for Speed (the standard 3M Rev Audio pot is fine).

[rzenc]

I'm drawing a point to point wiring for it and for some simplicity of layout I would use one triode for P.I. and the other for tremolo. I need 2 triodes for P.I. and 2 triodes for tremolo. So, according to my arrangment, I would use 1 triode inside each bottle for trem and the other for P.I.

Huh? Why not just use one bottle for the PI and the other for the trem? There are plenty of proven layouts that work that way

It would be neatier... functional I don't know, yet

The word I was looking for while typing the above paragraph is internal crosstalk - within the glass container - and also from adjascent pins... I would like to know these figures...

Use a linear pot for the Intensity pot, Reverse Audio for Speed (the standard 3M Rev Audio pot is fine).

Thanks for the advice! I will give it a try. Actually I got pretty curious about how a 5E9-A may sound.

Best Regards

Rzenc

[rzenc]

HPB, did you happen to look inside your tremolux? I`m curious to know if the schem matches your amp.

http://www.schematicheaven.com/fenderamps/tremolux_5e9a_schem.pdf

Thanks in Advance

Best Regards

Rzenc

[HotBluePlates]

I sold that amp back in 1998. I wish I kept it, but needed money.

But my '55 Tremolux exactly matched the schematic except that the switch for the tremolo was on the Depth pot instead of the Speed pot.

I'm drawing a point to point wiring for it and for some simplicity of layout I would use one triode for P.I. and the other for tremolo. I need 2 triodes for P.I. and 2 triodes for tremolo. So, according to my arrangment, I would use 1 triode inside each bottle for trem and the other for P.I. Could this result in leakage from one triode to another inside the glass bottle???

I would strongly recommend, if you want to build the 5E9, to just use Fender's proven good layout. There's only 1 thing that I'd advise against doing the way Fender did it: use 2 wires for the heater circuit instead of just 1 wire and grounding the opposite leg of the heater. They're not shown on the layout (because they were "not needed with a grounded heater leg), but use a heater CT (if available) or the artificial center-tap of 100 ohm resistors.

[tubeswell]

HPB, did you happen to look inside your tremolux? I`m curious to know if the schem matches your amp.

http://www.schematicheaven.com/fenderamps/tremolux_5e9a_schem.pdf

Thanks in Advance

Best Regards

Rzenc

[rzenc]

I would strongly recommend, if you want to build the 5E9, to just use Fender's proven good layout. There's only 1 thing that I'd advise against doing the way Fender did it: use 2 wires for the heater circuit instead of just 1 wire and grounding the opposite leg of the heater. They're not shown on the layout (because they were "not needed with a grounded heater leg), but use a heater CT (if available) or the artificial center-tap of 100 ohm resistors.

I was considering to elevate heater reference since we have a cathode follower on the trem tube and pin 3 is marked 205V. The question is how much should it referenced to???

HPB, did you happen to look inside your tremolux? I`m curious to know if the schem matches your amp.

http://www.schematicheaven.com/fenderamps/tremolux_5e9a_schem.pdf

Thanks in Advance

Best Regards

Rzenc

Thanks for the pic...It will be of great help.

Best Regards

Rzenc

[FYL]

I was considering to elevate heater reference since we have a cathode follower on the trem tube and pin 3 is marked 205V. The question is how much should it referenced to???

Easy:

What are the rated and actual heater to cathode voltages?

Rated = 180V for a 12AX7, actual = 205V (let's forget heating voltage), you need at least 25 V, shoot for 35 V or more just to be on the safe side.

What kind of 12AX7 are you going to use?

Some Russian 12AX7's such as the Sovtek and it's derivatives are very weak when it comes to cathode isolation and don't last long with more than 100V heater to cathode voltages. Use another 12AX7 for the CF.

How to derive the reference?

Just add a voltage divider, preferably after the screen filtering node, R1 from B+, R2 to ground in // with a > 10 µFdecoupling cap, I routinely use 47 µF.

R1 > 200K in order not to waste too much power in the divider and R2 < 100K to keep heater to cathode resistance at acceptable levels.

Both resistors should be flameproof models, at least 1-watt models just to be on the safe side.
 
Vout = Vin * (R2/(R1+R2)

With Vin = 300V, R1 = 220K and R2 = 47K, Vout = 52.8 volts. Good.

Where should it be connected?

Either to the 6.3 V center tap, if available, or to the junction of the two 100R balancing resistors across the heaters (virtual center tap).

[rzenc]

Many thanks FYL!!!!!!!!

V1 preamp - probably - E.H. 12AY7;
V2 P.I. JJ ECC803S or TAD 12AX7A - I think JJ has smooth response, TAD being more agressive.
V3 TREMOLO - I only tested JJECC803S and TAD 12AX7A - JJ had more impact.

V4 & V5 JJ 6V6-S which I have 2 quads on hands.

V6 I still don't know if I shoot for 5U4GB or 5Y3WGTA... suggestions ??? 

Power tubes and small bottles will have different heater windings from P.T.

I like 6V6 at lower voltages - at least on 5E3 amps - but I have never heard a 5E9-A so... I don't know what to expect from it... althought I guess it won't sound to different from 5E3... ah... forgot to tell...this will be a head version. Cab is to be decided yet as well as speakers... I guess he is aiming at Celestion Blue or Greenbacks... don't know... I have just bought him 4x12" EV12L BLS... cabinet is being made out of solid mahogany, baffle too.

Thanks in Advance for your kind attention.

Best Regards

Rzenc

[rzenc]

Is the oscilattor switch a simple SPST switch to turn on/off the tremolo? It is shown on potentiometer and I was wondering if I could just install a switch intead of buying a pot to do so... or is there something that I'm missing here??

Thanks in Advance

Best Regards

Rzenc

[FYL]

Is the oscilattor switch a simple SPST switch to turn on/off the tremolo?

Yes.

[rzenc]

Is the oscilattor switch a simple SPST switch to turn on/off the tremolo?

Yes.

thanks FYL,

So, is it necessary to be turned on in order to make the footswitch to work?? I guess so...

Thanks in advance

Best Regards

Rzenc

[FYL]

Of course.

 

[tubeswell]

So, is it necessary to be turned on in order to make the footswitch to work?? I guess so...
Rzenc

Hi Rzenc

The trem will also work without the footswitch or course; - but you just might not be able to dial it all the way off, depending on how much slam the LFO circuit sends to the 1st PI cathode.

[rzenc]

There is a way to be certain you will have perfect tremolo. Build a 5E9 Tremolux! The name literally comes from "Deluxe, with tremolo." The linked schematic is for a 5E9A, and I don't think a schematic was ever drawn for the 5E9 (I've never seen one anywhere).

So...I talked to my friend and he agreed to build a 5E9-A  :evil4:

I went to check the pdf but there is no P.T. or O.T. numbers, no A.C. voltages also... the only clue left is 395VDC at reservoir cap and lower voltages downstring:
unkown A.C. voltage + 5U4GA + 16uF(395VDC) + [2500+16uF(370VDC)] + [22Kohms+16uF(290VDC)]
I'm trying to figure out how much A.C. I need to arrive at these figures.
However, since pdf of 5E9-A quotes 5E9 using 5Y3 recto instead of 5U4GA I did a search but found no schem for 5E9. Then I tried 5G9 and it also uses 5U4, but GB instead of GA version. I found the following A.C. secondary voltages:
300 - 0 - 300, yielding 370VDC at reservoir cap, which is 2*20uF instead of 16uF.
395/370=1,067. So I should ask for 300*1,067=320-0-320VAC.
5U4GB quotes maximum current capability, with cap input and 320VAC per plates as 150mA's DC per plate.
Working backwards:
370-290=80VDC
80VDC/22Kohms=0,0036A (3,6mA) for 3 small bottles,
395-370=25VDC
25VDC/2500=0,01A (10mA), but 3,6mA is flowing to preamp bottles, so:
10mA - 3,6mA = 6,4mA's for a pair of 6V6 G2. 
This leaves 150mA - 10mA = 140mA for 6V6 pair.
I did not found data regarding 6V6 at this higher voltage. According to RCA 6V6GTA, each tube can dissipate 14W while operating at 350VDC plate and 315VDC at G2.
I found JJ 6V6-S datasheet which quotes their 6V6 at 14W too. At 395VDC on plates, each tube will be eating 35mA’s. 395*0,035=13,825W.
Total current would be 2*0,035 + 2*0,0032 + 3*0,0012 = 0,07+0,0064+0,0036=0,08A. I would feel more confortable letting a 20% more current, so 0,1A (100mA’s).
Then, comes the question:
First, does it makes sense??? 
Do I need a H.T. secondary of 320 – 0 – 320 VAC @ 0,1mA DC???

I attached the datasheet I used to arrive at this conclusions.

Thanks in Advance,
Best Regards.

Rzenc

[rzenc]

The trem will also work without the footswitch or course; - but you just might not be able to dial it all the way off, depending on how much slam the LFO circuit sends to the 1st PI cathode.

Both cathodes and connected together on 5E9-A P.I.

but you just might not be able to dial it all the way off

The footswitch will allow tremolo to be disconnected if it is switched on thru pannel switch.

I'm actually wondering how this switch is supposed to be hooked.

Thanks for the response!
Best Regards

Rzenc

[tubeswell]

Both cathodes and connected together on 5E9-A P.I.

Indeed they are

The footswitch will allow tremolo to be disconnected if it is switched on thru pannel switch.

I'm actually wondering how this switch is supposed to be hooked.

The switch on the speed pot is not necessary in the stock amp because it merely shorts the 220k tapering resistor to the input side of the pot anyhow - which is the same thing as turning the wiper to that side of the pot.

So...I talked to my friend and he agreed to build a 5E9-A  evil4

I went to check the pdf but there is no P.T. or O.T. numbers, no A.C. voltages also... the only clue left is 395VDC at reservoir cap and lower voltages downstring:
unkown A.C. voltage + 5U4GA + 16uF(395VDC) + [2500+16uF(370VDC)] + [22Kohms+16uF(290VDC)]
I'm trying to figure out how much A.C. I need to arrive at these figures.
However, since pdf of 5E9-A quotes 5E9 using 5Y3 recto instead of 5U4GA I did a search but found no schem for 5E9. Then I tried 5G9 and it also uses 5U4, but GB instead of GA version. I found the following A.C. secondary voltages:
300 - 0 - 300, yielding 370VDC at reservoir cap, which is 2*20uF instead of 16uF.
395/370=1,067. So I should ask for 300*1,067=320-0-320VAC.
5U4GB quotes maximum current capability, with cap input and 320VAC per plates as 150mA's DC per plate.
Working backwards:
370-290=80VDC
80VDC/22Kohms=0,0036A (3,6mA) for 3 small bottles,
395-370=25VDC
25VDC/2500=0,01A (10mA), but 3,6mA is flowing to preamp bottles, so:
10mA - 3,6mA = 6,4mA's for a pair of 6V6 G2.
This leaves 150mA - 10mA = 140mA for 6V6 pair.
I did not found data regarding 6V6 at this higher voltage. According to RCA 6V6GTA, each tube can dissipate 14W while operating at 350VDC plate and 315VDC at G2.
I found JJ 6V6-S datasheet which quotes their 6V6 at 14W too. At 395VDC on plates, each tube will be eating 35mA’s. 395*0,035=13,825W.
Total current would be 2*0,035 + 2*0,0032 + 3*0,0012 = 0,07+0,0064+0,0036=0,08A. I would feel more confortable letting a 20% more current, so 0,1A (100mA’s).
Then, comes the question:
First, does it makes sense???  huh
Do I need a H.T. secondary of 320 – 0 – 320 VAC @ 0,1mA DC???

I attached the datasheet I used to arrive at this conclusions.

Thanks in Advance,
Best Regards.

Thanks for the response!
Best Regards

Rzenc

working on a rough approximation for a 5U4 type tube to get a B+ of 395, your HT secondary ought to be 325-0-325 @ 150mA IMO.  Heater winding 3A min, Rectifier winding also 3A

OT anywhere between 5k and 8k5, with 6k to 7k5 getting a nice tone (due to the higher plate voltages). I think the stock one would've been 8k. I built my 5G9 using 5k and it sounds really sweet.

[PRR]

> I'm trying to figure out how much A.C. I need to arrive at these figures.

You cited the Limits curve for 5U4.

You want the Characteristics. You hope for 400VDC and estimate 100mA. Draw lines at these points. The intersection of these lines with the slanting "VAC" lines tells you what V AC to use. This case comes between 350V and 300V, closer to 350, perhaps more like 340VAC.

Note that 5U4 can carry a 300mA load. It's over-size for a 100mA load. Two 6V6 would usually be powered with 5V3/5V4. Oddly this too seems to say 330V-340V... we'd expect the smaller tube to have higher loss, even at this low current. I won't try to explain this, because in fact many "5V4" sold today are a USSR military rectifier with "better" performance than an old-school 5V4.

But why are you doing math? A Fender two-6V6 amp is a standard product. And you can't beat it, nor would you want anything less. Use the standard transformer.

[rzenc]

The switch on the speed pot is not necessary in the stock amp because it merely shorts the 220k tapering resistor to the input side of the pot anyhow - which is the same thing as turning the wiper to that side of the pot.

Thanks for the info! 
I was thinking that it might create a thumb in order to get the tremolo started...

But why are you doing math?

Because I must specify this to the factory which supplies me irons.. gotta tell them how much voltage and current I need on secondaries and they build them accordingly. For instance, to this project i will be ordering a P.T. with 125VAC + triple shielding and secondaries for H.T. 340 - 0 - 340 @ 100mADC, 5 volt @ 4A to feed recto heater, 3,15 - 0 - 3,15 @ 2A for 6V6 heaters, 3,15 - 0 - 3,15 @ 2A for preamp heaters - I want to elevate preamp heater reference to avoid arcing between electrodes and also avoid hum. Not sure about a choke (10H @ 50 ohms @ 40mA's - shielded), maybe a switch for choke or 2500 ohms resistor between reservoir cap and second filter cap.
I was checking 6V6 spec sheet and got curious about the load/power/distortion/plate current/screen current.... I believe it's based on S.E. power out since watts are low.. 5W max figure shown..
When power dissipation reaches max point (4,6W), distortion also reaches lowest point (5,3%T.H.D.), G2 current (between 7mA and 8mA @ 250VDC), plate current (46mA @ 250VDC), effective load resistance ~6K ohms. How could this be translated to higher voltages? I mean, keeping T.H.D. somewhat low and dissipation high?? I have built 5E3 types with 8Kohms O.T. primaries and multi secondaries - 4 - 8 - 16... and it seems to be pretty standard to load 6V6 amps with 8K~10K primary O.T... i don't want to reinveint the wheel here, just want to getter better understand of how this mathemagic happens...

Thanks for your kind attention
Best Regards

Rzenc

[PRR]

Sorry, I forgot you were in Brazil. The US has no industrial policy, so we let the Chinese build all our transformers. Maybe it would be better to have an at-home iron industry.... but we don't. Your country, probably wisely, encourages local production. It costs you more, but somebody in Brazil has work.

> 5 volt @ 4A to feed recto heater, 3,15 - 0 - 3,15 @ 2A for 6V6 heaters, 3,15 - 0 - 3,15 @ 2A for preamp heaters

5U4 only need 3A. 5Y3 is probably ample and just 2A. You might spec 3A just in case a 5U4 winds up in the hole.

Two 6V6 is 0.9A. You might spec 1.8A in case 6L6 wind up in the holes.

Three(?) 12AX7 is 0.9A.

The 6V6 and 12AX7 can use the same winding.

One 6V 3A winding should be ample.

Even if you don't want to pay import tax on standard Fender replacement iron, you can copy the specs. Or give the part-number to your winder. It is often easier to start from a known-good size and weight than to design completely from blank paper.

> 10H @ 50 ohms @ 40mA

50 ohms at 40mA is only 2V of DC drop. You use a choke because it has less drop than a resistor, but starting from 400V you can probably "waste" more than 2V. I would not mind 20V, a 5% drop. On the same core you could use 1/10th the copper. Or a wise choke designer could re-scale for maybe 1/3rd the iron and 1/3rd the copper. Don't over-specify: it adds weight and cost. Even if you have money, there's better places to spend it than by buying 0.5% screen drop.

> When power dissipation reaches max point (4,6W), distortion also reaches lowest point (5,3%T.H.D.)

That's an SE condition, which is somewhat different. In SE, low impedance load makes 3rd harmonic, high impedance load makes 2nd harmonic. There is a numeric optimum where they cross. That may not be the "ear optimum". And in push-pull, that 2nd harmonic does not exist.

In fixed-bias push-pull, if the tubes were able to deliver any current the load required, the maximum DC plate current is roughly 2*V+/Rl, where Rl is the nominal plate to plate load. Taking 400V and 8KCT we have 2*400/8,000 or 0.1A or 100mA. At 400V and 6K6 load, 120mA. The 6V6 won't deliver "any" current but it can pull 10KCT at low voltages and 6K6 at higher voltages. To this add 10% for screens. Your 12AX7 will not be running 3mA, more like 1mA-1.5mA each, and all together won't add much to the PT spec. 120mA-140mA ought to be ample.

[rzenc]

Many thanks for your kind attention!!!

I'm developing the layout for the board and while doing so, I have came across the need to relocate oscillator and C.F. to different pins, that is, from pin 8 to pin 3, pin 6 to pin 1 and pin 7 to pin 2. No, I did not change pin 9 to pins 4/5  although I will not use their practice of grounding pin 9. What concerns me is different plate and cathode specs on each triode.. althought RCA 6681/12AX7 quotes it as high MU twin triode... I guess I have just answered my question...

Also, after reading Merlin's book back and forth many times by now - very nice job!! Congratulations!!! - he advocates using grid stoppers to prevent blocking distortion, R.F., etc.. I would like to know how a stopper located on P.I. input 2 - second section / voltage divider - will affect performance and balance between each output signal being taken from plates...

Thanks ini Advance!!!!!!!!
Best regards

Rzenc

[FYL]

You may stick with the original schemo as paraphase PI's don't suffer from blocking - there's already a large R in series (here a 180K).

[rzenc]

Thanks FYL!!

Actually I have just reformulated my question:  How RGS2 will interact with the balacing resistors? It is effectively in series with grid leak resistor - 3K3 - to ground and also in series with load resistor - 180K... how should I treat it mathematically??? I was looking into Merlin's book but could not find it yet....

Thanks!!!!!!!!!!!!!!

Best Regards

Rzenc

[FYL]

The paraphase uses a voltage divider between the sections. Adding a series R after the divider w/o tweaking the divider would somewhat imbalance the stage.

[rzenc]

The paraphase uses a voltage divider between the sections. Adding a series R after the divider w/o tweaking the divider would somewhat imbalance the stage.

This is the reason behind my question... I would like to understand it better, how the grid stopper adds up to the load resistor and leak resistor too... and how all this should be taken into account when looking at A.C. load lines...

thanks in Advance

Best Regards

Rzenc

[rzenc]

Everything is finally here. I hope to put it up and running during the weekend.
Thanks for all help and support.
I will post pics and stuffs ASAP.

Best Regards,
Rzenc

[Shrapnel]

Sorry, I forgot you were in Brazil. The US has no industrial policy, so we let the Chinese build all our transformers. Maybe it would be better to have an at-home iron industry.... but we don't. Your country, probably wisely, encourages local production. It costs you more, but somebody in Brazil has work.

Sadly, I think there is an unwritten policy: let corporations do whatever they please to make their boards and stockholders richer [ even if they cut their own throats in the end. ]

I'm developing the layout for the board and while doing so, I have came across the need to relocate oscillator and C.F. to different pins, that is, from pin 8 to pin 3, pin 6 to pin 1 and pin 7 to pin 2. No, I did not change pin 9 to pins 4/5  although I will not use their practice of grounding pin 9.

A change like that is nearly inconsequential. All you seem to be doing is swapping triode halves around, so just remember that you did so as you do wire it up.

[simonallaway]

Sadly, I think there is an unwritten policy: let corporations do whatever they please to make their boards and stockholders richer [ even if they cut their own throats in the end. ]

If it's a publicly traded company then yes, that is exactly what their priority is..."maximise shareholder value".

[rzenc]

Hi Gentlemen,

Success!!!! The amp worked flawlessly from start-up!!! Nice feeling

My friend loved it even more then mine 5E3. His smile was from ear to ear 

I would like to thank all for your unvaluable help! HBP for suggesting such amazing circuit...
The tremolo is just suberb, wide range of control from subtle to very strong - highly recommended for trem - o - lo - vers -
The amp sounds very thick, not bassheavy, it has a great character.
I did the following mods:
GZ34 instead of 5Y3;
2.2uF instead of 25uF @ V1 cathode;
0.047uF instead of 0.1uF @ normal channel;
0.022uF instead of 0.1uF @ bright channel;
Add grid stopper to V2 pin 2 - 220K;
Add 470R/5W @ V4 & V5 screen grid;
10H choke instead of 2K5 resistor between power tube plates and screen nodes;
100uF instead of 25uF @ power tube cathodes;
22uF Solen Fast Caps instead of e-caps @ power supply rail.

A good friend who is a very good luthier will make the wood cabinet.
Here is a pic of it...

Thanks to all of you for your kind attention and support.

[HotBluePlates]

Excellent! You did a great job on the build! I'm also glad you enjoy the circuit.

I also think you did some very smart changes to the circuit.

[rzenc]

Excellent! You did a great job on the build! I'm also glad you enjoy the circuit.

I also think you did some very smart changes to the circuit.

Thanks HBP. It's a very nice, rich sounding amp, maybe tomorrow we will set side by side my 5E3 and his 5E9A and see what they can do...

Tremolo engages without any noise/thumb and when turned off it takes about 1 sec to shut off and the decay is perfect. It has sustain for days...]

I'm not sure about it but I guess the paraphase provides a beefier sounding stage then the cathodyne, at least some folks who played the amp said so...but they don't know about the amp innards...they where just comparing impressions...

Once again thanks, to all... I will take some pics of the inside and post some porn..

Best Regads

Rzenc

[samato]

...Once again thanks, to all... I will take some pics of the inside and post some porn..

Best Regads

Rzenc


That would be great.  When you do, please post them on the new gallery page:

http://www.el34world.com/Forum/index.php?action=gallery;cat=1

Thanks