Dumble clone SE

[adamG]

Hi Guys,

Please, advice me in this issue
http://ampgarage.com/forum/viewtopic.php?t=16545&start=0&postdays=0&postorder=asc&highlight=ods+single+ended
Actually, I recently assembled above one with 6L6 onboard. It is really great baby. I gives me a lot of joy.
My version of it is 8 pots on front faceplate ,which is as attached below.
I am as much encouraged as I decided to bild another one with KT88 or 6550 to get approx.18-20W. Because, why to straggle with P-P,when I can receive same output power with less tubes;)
Do you think it does make sense?
Thank you in advance.

Regards,

Adam

[shooter]

Do you think it does make sense?

Yes, to some of us  , most however prefer PP, Me I like building KT88 SE, I've used them with 3 different preamp sections and they take whatever you throw at them.  Other options with more tubes;
PSE 6L6, or quadSE EL84's.  The plus side for PSE, with a new OT and a few minutes re-work, walla PP!

[Willabe]

as I decided to bild another one with KT88 or 6550 to get approx.18-20W. Because, why to straggle with P-P,when I can receive same output power with less tubes;)
Do you think it does make sense?

A major factor to consider is SE OT's are much larger, weigh more and cost more than PP OT's of the same power output.

And SE amps sound/react/play different than PP amps. Like Shooter said some like SE, some prefer PP. 

[adamG]

A major factor to consider is SE OT's are much larger, weigh more and cost more than PP OT's of the same power output.

Thank you Willabe.
OT ,a bigger one is not an issue for me.
Fortunately, I wire them by myself. For this amp I assume OT with EI84 laminations, which is a 28x29,5 tongue that may be enough, right?
After 12-13 PP amps, I focused on SE ones. Some believe that SE circuits have very unique tonal character that I agree with.

Another question. I intend to extend TS from Princetone for Bandmaster that is bass and treble.
Do you think I might reduce preamp signal gain (clean tube)?

Regards,

Adam

[adamG]

Yes, to some of us  , most however prefer PP, Me I like building KT88 SE, I've used them with 3 different preamp sections and they take whatever you throw at them.  Other options with more tubes;
PSE 6L6, or quadSE EL84's.  The plus side for PSE, with a new OT and a few minutes re-work, walla PP!

What HT did you provide?
I assume 400V. Would it be ok or too high?

Regards,

Adam

[shooter]

most of my B+ has been on the "lowish" side, 340ish, but 400 on a 88 should be just fine.

Do you think I might reduce preamp signal gain (clean tube)?

Do you mean will the TS cause more gain loss as a 2 knob, or you need to reduce tube gain because of a 2 knob?
I'm using a "James" style 2 knob in my current build that I'm tweaking, I have found it will roll off or "boost" highs or lows a lot more than I expected, although the TS calculator does indicate this.

[PRR]

> KT88 or 6550 to get approx.18-20W

SE tube amp is at-best 40% efficient.

Or the idle plate dissipation is 2.5X the desired output power (Sine RMS).

18W-20W out leads to 45 or 50 Watt tube plate rating.

In extended experiments with 6550 working at 37W-41W Pdiss I was able to show 13W pretty clean and 17W "guitar rating" (bent but not seriously kinking).

I was working at 530V-600V to see what was possible. This seriously increases power supply cost and danger. In retrospect 400V is a much better target.

40W idle dissipation from 400V supply is about 100mA (0.1A).

As a ballpark, tube at 400V 0.1A should be loaded in 400V/0.1A= 4K impedance.

When you add B+ filtering and cathode bias (ALWAYS use cathode bias when you can, especially when working at 99%-101% of rated dissipation), you may end up nearer 440V-450V. 450V filter caps may be marginal.

You could instead run two 6L6/EL34 at 25W Pdiss each, which is not quite full rating. (Old EL34 said 25W but it is clear all new ones will take more.) Point is that replacement 6L6 or EL34 are available in every town, while 6550/KT88 may not be. Also you can limp-through on one tube if the other blows. I'd like to come down from 400V, so 350V and 50W is 0.14A plate current and a 2.5K load.

[adamG]

40W idle dissipation from 400V supply is about 100mA (0.1A).
s a ballpark, tube at 400V 0.1A should be loaded in 400V/0.1A= 4K impedance.

When you add B+ filtering and cathode bias (ALWAYS use cathode bias when you can, especially when working at 99%-101% of rated dissipation), you may end up nearer 440V-450V. 450V filter caps may be marginal.

Accordingly to above, I would'n like to lead the amp to overload and overheat tube at 99-101% if its diss. It's not wise.

I'd like to come down from 400V, so 350V and 50W is 0.14A plate current and a 2.5K load.

Do you mean a pair of EL34/6L6 at 350V and 50W?
There's the topic that was not successfully ended...
http://el34world.com/Forum/index.php?topic=9150.100
You remember, when Geezer tried the idea of parallel 2x6L6 and after all He gave up with this or I do not get it right?
Extra gain stage was needed to power output tubes.

Thank you PRR!

Regards,

Adam

[adamG]

Do you mean will the TS cause more gain loss as a 2 knob, or you need to reduce tube gain because of a 2 knob?

I mean not to loose preamp gain (clean tube) because of second knob/dividing TS on two knobs - bass and treble.
My concern is to keep tonal character of Princeton TS, but to get more flexibility with bass and treble.
I prefer less bass maintaining treble on its level.
As far as I know, another high or low filter may reduce whole preamp signal gain, right?

Regards,

Adam

[adamG]

40W idle dissipation from 400V supply is about 100mA (0.1A).
As a ballpark, tube at 400V 0.1A should be loaded in 400V/0.1A= 4K impedance.
When you add B+ filtering and cathode bias (ALWAYS use cathode bias when you can, especially when working at 99%-101% of rated dissipation), you may end up nearer 440V-450V. 450V filter caps may be marginal.

Maybe ,I did not put the HT level ,clearly. Sorry. I planned DC voltage (400V/B+) after filtering.

Regards,

Adam

[Lindsay]

AdamG,

I'm very interested in this thread. Are you winding your own output transformer? If you did I'd be most interested to know how you went about it and what low frequency you were targeting.  I just wound one myself for a SE KT88 project. I used EI96, 1"1/2 stack.

[adamG]

I'm very interested in this thread. Are you winding your own output transformer? If you did I'd be most interested to know how you went about it and what low frequency you were targeting.  I just wound one myself for a SE KT88 project. I used EI96, 1"1/2 stack.

Yes, I do make them by myself. Fortunately, on this forum
http://www.diyaudio.com/forums/tubes-valves/109165-opt-design-assistante-el84.html ,
I found very fundamental formula how to design PP OTs.
The key issue is enamel and isolation...
Very similar design approach is to SE OTs.
Famous OT Producers will not testify that the most of replacements for Marshall and Fender are acc.to above forum link formula;)
Of course, there are different frequences and other design details, but fundamental formula/winding desing is almost same for all.

The low frequency of guitar amps OT's is 82Hz. I am pretty sure that Gurus on this forum confirm that.
So, my OTs are dedicated to above figure. Therefore, It does not make sense to provide lower Hz for guitar circuit/amp.
I assume EI84 for KT88. Anyway, I'll double check that before winding OT.

Regards,

Adam

[terminalgs]

Because, why to straggle with P-P,when I can receive same output power with less tubes;)

A big benefit of PP is cancellation of hum/buzz in heater supply.   For even a small 3 tube 5W build, I'd be tempted to use 2 6v6s in PP sans a dedicated PI tube.

[adamG]

A big benefit of PP is cancellation of hum/buzz in heater supply.

My SE that started this topic has no hum ,at all. I provided solid filtering ,which is five nodes. Three of them has 47uF cap and another two 22uF. Chassis is JTM AL accomodation with effective grounding points.
So, the amp is damm quiet ;)
My intention is to simplify the future amp with two 12A_7 and one KT88.
Yesterday ,I was send with front faceplate. Tomorrow morning I'm gonna fix it into chassis. Then ,I'll take photos.

Regards,

Adam

[terminalgs]

My SE that started this topic has no hum ,at all. I provided solid filtering ,which is five nodes.

I was thinking more about AC heater supply introducing hash/buzz etc from the plug on the wall, like light dimmers, fan motors, etc...


If your SE build doesn't have any of that, great.

[PRR]

> benefit of PP is cancellation of hum/buzz in heater supply

No. P-P cancels B+ hum, not heater hum.

[Lindsay]

I'm very interested in this thread. Are you winding your own output transformer? If you did I'd be most interested to know how you went about it and what low frequency you were targeting.  I just wound one myself for a SE KT88 project. I used EI96, 1"1/2 stack.

Yes, I do make them by myself. Fortunately, on this forum
http://www.diyaudio.com/forums/tubes-valves/109165-opt-design-assistante-el84.html ,
I found very fundamental formula how to design PP OTs.
The key issue is enamel and isolation...
Very similar design approach is to SE OTs.
Famous OT Producers will not testify that the most of replacements for Marshall and Fender are acc.to above forum link formula;)
Of course, there are different frequences and other design details, but fundamental formula/winding desing is almost same for all.

The low frequency of guitar amps OT's is 82Hz. I am pretty sure that Gurus on this forum confirm that.
So, my OTs are dedicated to above figure. Therefore, It does not make sense to provide lower Hz for guitar circuit/amp.
I assume EI84 for KT88. Anyway, I'll double check that before winding OT.

Regards,

Adam

Thanks Adam,

I did have a look at that designer software some time ago but haven't tried using it. What I did was wind up 1000 turns and measure the inductance with the core material I had (non grain orientated 0.035mm) then worked my primary turns from that. The measured Inductance of the final product with a suitable air gap (HP meter at 120Hz) at 2.5K secondary gives me a low end of 80Hz. I  was worried that this wouldn't be suitable for dropped tunings so I substituted the core for M6 grain orientated that I had laying around. Dropped the low end to 60Hz. In hindsight I should have traded a bit of primary resistance for higher inductance.  Primary DCR  measured at 76R. I won't derail this thread any further but if you'd like to talk about transformers PM me.

Regards

Lindsay

[adamG]

I did have a look at that designer software some time ago but haven't tried using it.

Lindsay,

Search network for polish soft Amator 2000.
That is grafic lay on the previous .xls calculator file by a polish engineer near to my place.
It is easy available. You'll find it .When you get it ,write me PM, ok?
I'll translate it for you.
I am sure ,It's much more accurate than OPt_da for calculation, both of PP an SE OTs. The soft really works.
It gives everything you'll need to wire OTs, including gap distance, wires cross sections, turns, etc..
I veryfied that.
You do not need lams 0,35mm. The ennealed 0,35mm are more dedicated for PTs. IMO. I believe that they're more efficient ,when you need them for PTs, if needed in small shape for some reason. 0,5 ennealed are just fine for OTs.
Do not follow OPt_da. There're posts by an american guy, who very precisesly lectures how to overlay sections.
When you get that, then apply Amator 2000 :)

Regards,

Adam

[adamG]

Hi again,

Another question. Recently, I've swapped OD stage tube from 12AX7 to 12AU7, because 12AX7 was giving to much gain. I had to decrease Trim and Drive pots. But now, with 12AU7 OD tone is transparent, not too much saturated as with 12AX7.
Can you advice me how to increase OD signal level ,because the clean stage one is nearly on same level as with OD activated?
Level pot is on maximum, of course. Acc. to PP Dumblish version, when OD is activated, an amp overal signal is on huge level.

Thank you in advance.

Regards,

Adam

[kagliostro]

Return to the 12AX7 tube and put on the standard components values around it

then split the Plate Resistor testing various % till you reach the sound you like more

this preserves the "tone" of the stage and feed the following circuit with the right level of signal

http://www.blueguitar.org/new/articles/blue_gtr/amps/bp010629.pdf

---

Example



Ciao

Franco

[adamG]

Thank you very much. It looks interesting.
I've just read this article on blueguitar and I am facing to electronic store to purchase the pot;)

Regards,

Adam

[kagliostro]

Using a pot pay a lot of attention, there is B+ on it

use the pot to find the correct point

then measure it and use a pair of resistor

Ciao

Franco

[adamG]

Yes, I know it might be a dangerous operation.
That's why, I'll purchase 2W pot ,not to be electrocutioned.

Thank you.

Ciao ;)

Adam

[adamG]

Here are a couple of photos.

Regards,

Adam

[sluckey]

Classy looking amp, inside and out. Good job!

[kagliostro]

Out it is nice

Inside it is insane ... WOW I LIKE IT 

Franco

[BetterOffShred]

That's super beautiful!    I'd love to hear a little audio clip of that baby with an SG or Les Paul.

-Brett

[adamG]

Hi Guys,

Thank you very, very much!
I really like SE circuits. You know, I'm happy because, I wind those fomous OTs by myself and they do their job very well to my ears.
Anyway, the main thing is that this is only the amp and the real sound comes from our fingers. Don't you think?
 
Now, I am with the project of SE KT88 and TS as Bass/Treble solution.
Actually, I work on three of them at the same time. Crazy me;)
You must forgive me. I am not that brave to publish soudclips. I'm not a musician. Just occasional home playing. But ,I'll try.

Regards,

Adam

[kagliostro]

Ciao Adam

I'm curious, how did you solve the problem about 12AU7 vs 12AX7 use ?

Franco

[adamG]

I'm curious, how did you solve the problem about 12AU7 vs 12AX7 use ?

Hi,

Actually, I did not yet.
I am remained with...12AT7 ,what is resonable and the middle solution;)
Of course, I purchased pot, but after some time and 2-3 sounding tests ,I thought to keep as above. You know, I do not like raping out what is done. Another story is that I am a kind of perfectionist, who disire what is beyond his ability. 
Anyway, next one I'll try the splitting resistors during assembling and testing.

Regards,

Adam

[kagliostro]

You know, I do not like raping out what is done.

I can understand you very well !

Franco