ECL84 push-pull amp - Help!

[blackcorvo]

First of all, hello there!

I've got a couple ECL84s here, and I'm trying to build a push-pull amp with them. I looked around and saw some circuits with these tubes, and I really wanted to try using them.
What I have so far is basically a Marshall 18W circuit, using a 12AX7 for V1 and the same values of the original schematic for everything - except for the output pentodes. I have their G3 connected together going to B+ thru a 390R resistor, the common cathode resistor is 220R, the caps from the inverter are 2,2nF, and the grid stoppers are 15k.

The problem is that I'm getting a really bad, fuzzy distortion, apparently from the phase inverter, and I don't know how to fix it.
If anyone here can help me, I'd be really thankful. I can even make a sample of it, if that can help identify my problem.

I really like the sound of the 18W, but I want to maybe use the 12AX7 as 2x cascade gain stages instead of one. But first, I wanna fix this problem so I can get to test that later.

Thanks ahead for any possible help.

[tubenit]

I built this ECL84 amp.  I originally tried more common values with the components, but the distortion was intolerable to me & I had waaaayyy too much of it. I think initially (prior to the tweaks) the pentodes were being overdriven way too much.

Take a look at this schematic and especially at the areas I indicate in red. The amp has a sweet tone, very touch sensitive, smooth sustain and nice harmonics in my opinon.

Maybe something from the schematic will be helpful to you. You can also do a search on the "enhance" cap to get some additional information.

With respect, Tubenit

[blackcorvo]

I built this ECL84 amp.  I originally tried more common values with the components, but the distortion was intolerable to me & I had waaaayyy too much of it. I think initially (prior to the tweaks) the pentodes were being overdriven way too much.

Take a look at this schematic and especially at the areas I indicate in red. The amp has a sweet tone, very touch sensitive, smooth sustain and nice harmonics in my opinon.

Maybe something from the schematic will be helpful to you. You can also do a search on the "enhance" cap to get some additional information.

With respect, Tubenit

I'll try it, thanks! I just need to get a dual potentiometer so I can test that circuit.

And one more thing: how big are the 1k5 resistors going to the screen grids? There's no indication of how many watts they're supposed to handle. I'm guessing 2w ?

[tubenit]

I think I used Doug's 2w resistors which is what I usually do for power tubes.

Regarding the PPIMV,  I typically have it dialed around "7", but use it from 5-10 (all of which sound good to me).  When I have measured wiper to ground, I have been surprised at how low of a resistance there is compared to the typical 220k to ground grid resistors.  And there is still plenty of volume. The SoLow Watt does a great job of sounding big for a small amp and the bass response is quite good, IMO.

with respect, Tubenit

[blackcorvo]

I give up.
I tried literally EVERYTHING to make this work.
Tried different values, concertina instead of long-tail PI, series resistors to reduce the signal level... but either I get that damn fuzzy distortion, or I get an irritating high-pitched oscillation!
I thought that maybe the output voltage swing from the preamp was driving the output too hard, so I used a 100k resistor in place of the 3k3 resistor to reduce the voltage, but... I still get that damn distortion.

I really don't know what to do anymore, and I'm getting pissed off at this project. Might as well just trash everything.

This is the only reason I HATE tubes: EVERYTIME I try to do something using them, it either sounds like crap or it doesn't work at all... and I'm losing my faith in trying to build my own tube circuits because of that.

[tubenit]

Doesn't sound like it's working out for you & that it's gotten really frustrating to you.

If you're not enjoying it, maybe it's time to walk away from it and put your energy and passion into other things?

And later, if you want to give it another shot,  post a schematic and photos & we'll see if we can offer something else to consider trying.

With respect, Tubenit

[John]

Blackcorvo, Tubenit is right (as he usually is) if you're not having fun, then the end result will never be worth it. I'm still pretty new at all this myself, but I enjoy every aspect of it - working out schematics, drawing them up, re-drawing them when my mistakes get pointed out  and figuring out where I went wrong. The only part I don't is wiring the heaters.

You probably should walk away from the project for a few days, the solution might occur to you. When I did my first build, I spent at least a week off and on trying to figure out what was wrong. When I saw what I had done wrong it was so very obvious I couldn't believe it!

But definitely, download the SchExpress program and mess with it. It's helped me to visualize how I'm going to lay stuff out as I'm doing the schematic, and also lets me keep track of each tweak as I do it. Cheers!

[blackcorvo]

I just sat down to listen the sound samples of Tubenit's amp, and I heard the distortion I was talking about in it! Not as pronouced as in my case, but still there.
I guess it's just how the ECL84 distorts... but I really don't like it, so... I'm thinking of trying another model of pentode-triode I have here, the 6AW8, and maybe that one is gonna work the way I want it to.

If not, I guess I'll just try something else. Sorry for earlier, but I was really frustrated and sad for this project not sounding anything like I wanted it to. I'm really sorry, and thanks for everything.

[tubenit]

I just sat down to listen the sound samples of Tubenit's amp, and I heard the distortion I was talking about in it! Not as pronouced as in my case, but still there. I guess it's just how the ECL84 distorts

Yes, the amp does has some distortion in the overdrive. However, the overdrive has a very clear and transparent tone, IMO. I don't think it's a muddy OD tone at all.   And I can dime all the controls on my SoLow Watt & there is NO oscillation at all.  This soundclick was done PRIOR to adding the two enhance caps that the amp still has.

http://www.soundclick.com/player/single_player.cfm?songid=11184770&q=hi&newref=1

Having said that, I can sure appreciate that the ECL84 tone may not be what you want. I have gotten rid of every EL84 amp I've owned. Never could get into them for some reason.

With respect, Tubenit

[tubenit]

You might want to check out this thread where there is some discussion that the 6AW8 tube "might not be suitable for audio"

http://www.el34world.com/Forum/index.php?topic=12263.0

However, there is a data sheet and schematics for low watt push/pull tube amps here:
http://www.el34world.com/Forum/index.php?topic=12526.0

There is a chance that the distortion you hear in your amp that you don't like is from the oscillation and IF that were resolved, perhaps you'd like the amp tone?

With respect, Tubenit

[blackcorvo]

The distortion I'm talking about is really sutile in your soundclip. Sounds a but buzzy, and it's easier to hear it when you play low notes, mostly driving the PA into distortion. I dunno, it just sounds really bad to my ears, like a misbiased transistor booster or something. It's irritating as hell.

Anyway, I thought of trying other power tubes, but I'd need at least 2 of each, because the PT I'm using only has 12v for filaments.
The power tubes I have here are 3x 6AS5, 3x ECL84, 1x ECL85, 2x 5AQ5 and 1x 6BQ5.
My OT can handle a max of 30mA thru it's primary, wich is my biggest worry.


What I'm looking for in this amp is something that doesn't go much over 3W. I get yelled at for playing my strat unplugged, so I really doubt I'd ever be able to crank a 5W Champ without getting hit in the head by a broom afterwards...

That's why I added a switch to reduce the B+ on this prototype, so I could reduce the power. I have to use a voltage doubler to get the 250v for this circuit - wich actually gives me almost 300v -, so I used this little trick to be able to reduce the B+ to 150v:


Open switch: 150v. Closed switch: 250v.

I have everything hooked up in 2 pront-o-labors, with every part of the circuit as spaced out as possible. I can't post pictures because I lost my camera.

I really don't know what to do. It's really bad to go and buy things for a project that won't work the way you'd like it to.

I'll try to record a clip and post it here.

[Ritchie200]

I hear that disturbing tone in 'Nits clip too, but I think it might be the guitar.  The muffled sound?  Isn't that the guitar too?...just sayin'...

Corvo, 'Nit has done more with this tube than anybody I know.  You are talking to the right guy!  But what sounds good to one person, might not to another.  I have yet to find a cranked 6L6 amp that sounds good to me.  Others would not buy or build anything but.  Don't give up!  There are all sorts tubes to try!  So little time!

'Nits biggest fan!
Jim

[blackcorvo]

Well, a friend of mine sent me this schematic for the power section that he calculated, and I just got the components to try it out.


The values between parentheses are a second option to be tried out.

I'll get back to the bench and see what happens.

[blackcorvo]

Ok, here's a demo of the amp built just as in the schematic I posted. Only thing I did was add a 100pF cap between the plates on the PI - to prevent oscillations, even thought I haven't gotten any -, and drived this power with 1/2 12AX7. This gain stage is the same from the 18W circuit, but with only one triode instead of 2 in parallel.

http://www.4shared.com/mp3/704dbRLF/ECL84PP_18w_input_haflvolume.html

The volume is at half. The mic I used is not very sensitive, so the volume of this sample is a little low, but you can head the weird distortion I'm talking about. It's easier to hear it when I play using my fingers instead of using a pick.

[tubenit]

you can head the weird distortion

That indeed sounds rather odd.  I don't think it's the ECL84 tube (given the success of the SoLow Watt amps built)?

With respect, Tubenit

[blackcorvo]

you can head the weird distortion

That indeed sounds rather odd.  I don't think it's the ECL84 tube (given the success of the SoLow Watt amps built)?

With respect, Tubenit

I really don't know... these are Miniwatt ECL84s. They're supposed to be pretty decent. And the store I bought them from is very reliable - they don't sell tubes with less than 80% of transcondutance, no matter if they're new or used tubes.

I'll try to change them around, and try the third ECL84 I have here in place of the other two I was using for the amp, and all that swapping goodness.

Right now, I should get ready for college.

[Ritchie200]

What does the front end of this amp look like?  It sounds like a bit of old fashioned blocking distortion to me?  Can you post the entire schemo?

Jim

[blackcorvo]

What does the front end of this amp look like?  It sounds like a bit of old fashioned blocking distortion to me?  Can you post the entire schemo?

Jim

This is what I'm using right now:


I'm using a Halogen Lamp transformer (12v 50W), using half of the primary connected to the mains and the other half is my HV secondary.
The filaments are connected in series (duh).

My friend told me he got the curves for the triodes and is gonna try to re-design the whole thing.
I know NOTHING about tube amp designing... I just build based on pre-made schematics, basically.

[PRR]

You are using a 220V (110-0-110) power transformer for an Output transformer?

With a 200V B+?

It will distort bad on 50-60Hz. It will distort 82Hz, lowest guitar note. It may distort all tones below 200Hz.

Dogs are sleeping so I can't hear your MP3.

[blackcorvo]

You are using a 220V (110-0-110) power transformer for an Output transformer?

With a 200V B+?

It will distort bad on 50-60Hz. It will distort 82Hz, lowest guitar note. It may distort all tones below 200Hz.

Dogs are sleeping so I can't hear your MP3.

No, that's just a suggestion from my friend as a temporary test-only OT.
The output transformer is an 8k - 4R / 8R push-pull OT for 3W max output.
It's supposed to be specifically designed for the *CL84 tubes.

I bought everything from an online store here in Brazil called AltanaTubes. They're the only store speciallized in tubes we have here.
I know the owner, so if it's anything about the OT or the tubes, I can certainly have a talk with him about it.

And the B+ going to the OT is around 280V.

[Willabe]

It sounds like a bit of old fashioned blocking distortion to me?

Tubenits got 56K as the grid stopper for the ECL84 and you show only 8K2, that's a big difference. I didn't read the whole thread, but have you tried bigger grid stop resistor values?

Is the heater wind really 12v with 2x390R as the artificial ground ? Most guys use 100R. I've never used an ECL84 but don't they have a 6.3v heater?


                 Brad
                        

[blackcorvo]

It sounds like a bit of old fashioned blocking distortion to me?

Tubenits got 56K as the grid stopper for the ECL84 and you show only 8K2, that's a big difference. I didn't read the whole thread, but have you tried bigger grid stop resistor values?

Is the heater wind really 12v with 2x390R as the artificial ground ? Most guys use 100R. I've never used an ECL84 but don't they have a 6.3v heater?


                 Brad
                         

I'm using a Halogen Lamp transformer (12v 50W), using half of the primary connected to the mains and the other half is my HV secondary.
The filaments are connected in series (duh).

100Rs would need to be of a higher power value. With 390, I can stay at 1W - also, I had a whole bunch of them here, and I only have 2x 100Rs, wich I'm using for the screen grids.

I tried grid stoppers as high as 220K, and still had the same distortion issue.

[sluckey]

The filaments are connected in series (duh).

But you have three tubes. Are you saying all three are in series? If so, you need to redo that because the 12VAC is not distributing equally across 3 tubes. Measure the voltage across each tube filament and you may find some underheated tubes. That may be a factor in your distortion, but I'm just guessing. I have no experience with starved heaters.

To properly heat those three tubes with 12VAC you could connect the two ECL84s in series and connect the 12AX7 pins 4 and 5 across the 12VAC, leaving pin 9 disconnected.

EDIT... Those pin numbers on the ECL84s look like pin numbers for a 12AX7 PI and EL84 PAs. You did use the correct pin numbers when you wired it up, right?

[Willabe]

What speaker are you using? I don't see it listed.

Have you tried different speakers?


                Brad

[blackcorvo]

The filaments are connected in series (duh).

But you have three tubes. Are you saying all three are in series? If so, you need to redo that because the 12VAC is not distributing equally across 3 tubes. Measure the voltage across each tube filament and you may find some underheated tubes. That may be a factor in your distortion, but I'm just guessing. I have no experience with starved heaters.

To properly heat those three tubes with 12VAC you could connect the two ECL84s in series and connect the 12AX7 pins 4 and 5 across the 12VAC, leaving pin 9 disconnected.

EDIT... Those pin numbers on the ECL84s look like pin numbers for a 12AX7 PI and EL84 PAs. You did use the correct pin numbers when you wired it up, right?

If I put ALL filaments in series, I'd have killed the 12AX7 because the ECL84s drain 750mA @ 6v each, while 12AX7 drains 300mA @ 6v or 150mA @ 12v (wich is what I'm using).

The pinout is marked wrong because it's just the 18W schematic and I was too lazy to change the pinout to the correct one.

I'm using a generic 8", 8 ohms speaker from an old Philips stereo, with a ceramic magnet. I found this speaker in the street and sent it to be repaired.
I don't have any other speakers, and I'm pretty sure it's not the speaker because I used it with many other circuits and it sounded really good.
Not as loud as a proper guitar speaker, but still sounds pretty good.

I just don't know how to design tube amps, but I did study electronics.

[Willabe]

I know this has been frustrating for you, but I still think your gonna find what's wrong.


               Brad

[sluckey]

If I put ALL filaments in series, I'd have killed the 12AX7...

I didn't do the math before but here goes... As you say, the 12Ax7 operates at 6.3V/.3A and the ECL84s operate at 6.3V/.72A (according to Duncan). This means the 12AX7 resistance is 6.3/.3 = 21Ω and the ECL84s resistance is 6.3/.72 = 8.75Ω. If the three were connected in series the total resistance would be 21 + 8.75 + 8.75 = 38.5Ω and the total current would be 12/38.5 = 0.312A.

So, the 12AX7 operating at .312A is only slightly hotter than the norm. Voltage across it would be .312 x 21 = 6.55V, hardly enough to kill it. These tubes will operate at 7VAC without complaining. However, the ECL84s would be operating at that same current of .312A, less than half what it requires. The voltage across each ECL84 would be .312 x 8.75 = 2.73V. The ECL84s might work to some degree at that current but I suspect the operation would not be anywhere near optimum. That's why I said 'starved'.

But this is a moot point since you have the filaments wired correctly. Your statement "The filaments are connected in series (duh)." was not clear to me.

I just don't know how to design tube amps, but I did study electronics.

I seem to have hit a nerve. I do that a lot. Sorry, that was not my intent. You clearly know what you're doing.

[blackcorvo]

I just don't know how to design tube amps, but I did study electronics.

I seem to have hit a nerve. I do that a lot. Sorry, that was not my intent. You clearly know what you're doing.

no, I am sorry. The frustration over this project, plus some other things bothering me, made me get a little too irritated. You didn't know how much knowlegde I have of electronics, so it's not your fault. Thanks for trying to help me.

I'm still waiting my friend contact me again with his results. I even asked him to send me the curves with operation points marked, and the math stuff as well.
I'll probably have it this weekend or next week. Everybody will get a week off because of Carnaval, so I believe he'll have enough free time to work on it.

And now that I haven't touched the circuit in a couple days, I'm thinking this distortion is possibly from the PI, because I used grid stoppers as big as 220k and I still had the same weird sounding fuzziness with no change in it what-so-ever.
Maybe I shold use the 12AX7 for the PI, and use the ECL's triodes for the preamp? Maybe even use them in a SRPP/cascoded stage for a pentode-ish sound?

I really don't know what else to try. I'm completely lost in all this.

I'll probably make it a parallel SE thingie if nothing can fix the weird sound.

[sluckey]

I'm using a generic 8", 8 ohms speaker from an old Philips stereo, with a ceramic magnet. I found this speaker in the street and sent it to be repaired. I don't have any other speakers, and I'm pretty sure it's not the speaker because I used it with many other circuits and it sounded really good. Not as loud as a proper guitar speaker, but still sounds pretty good.

I'd rule out the speaker. Most hifi speakers just don't cut it for guitar use.

[blackcorvo]

I'm using a generic 8", 8 ohms speaker from an old Philips stereo, with a ceramic magnet. I found this speaker in the street and sent it to be repaired. I don't have any other speakers, and I'm pretty sure it's not the speaker because I used it with many other circuits and it sounded really good. Not as loud as a proper guitar speaker, but still sounds pretty good.

I'd rule out the speaker. Most hifi speakers just don't cut it for guitar use.

Well, I have asked the guys that repaired it to follow my specification - thin paper cone and small aluminum dust cover -, and it sounded pretty good with other projects before this one.
I'm pretty sure it can handle the power. From what I could find, this baby can take up to 30W. And from the size of the magnet and diameter of the coil, it surely is rated for above 10w.
Also, it would probably just not have the right TONE because of the speaker being for hi-fi, instead of having that crappy, fuzzy sound. It's NOT the speaker.
Here is a sample of the same speaker used with a 2w single-ended circuit I worked on long ago: http://www.4shared.com/mp3/sucWFa4a/12ax7_6as5_amp_sample.html


I just can't buy real guitar speakers. I live with my parents, and they'd probably have a heart attack if I showed how much a guitar speaker costs... the lowest price I've found was about twice the price of my guitar. Ouch.

But I do remember finding some vintage tube radio speakers selling for really cheap on mercadolivre (the brazillian version of e-bay, but it's usually not as reliable).
To be more specific,
this one and this one are the speakers I found. I've heard some guitar speakers are actually based on old radio speakers, so.. maybe these could work?
Apparently, the dealer seems to be honest. I still have no money ATM to buy anything...

[sluckey]

I just listened to your sound clip again. The fizz I hear could certainly be caused by pushing a guitar through a hifi speaker, especially a cheap one. In my early days, I ruined some good hifi speakers by playing guitar through them. And they all sounded fizzy in just a short time. There's a big difference between guitar speakers and hifi speakers.  The more I learn about your speaker, the more I'd want to rule it out.

Surely you know someone that would let you plug your amp into their guitar cab just for a test. Then you would know for sure. Maybe even be able to quit beating your head on the floor. You could probably take your amp down to a music store and try it out on some nice cabs, especially if the salesperson thought you were in the market.

[Willabe]

What about the guy you know where you bought the tubes? Does he have a guitar speaker/cab you could try?


                    Brad     

[blackcorvo]

I just listened to your sound clip again. The fizz I hear could certainly be caused by pushing a guitar through a hifi speaker, especially a cheap one. In my early days, I ruined some good hifi speakers by playing guitar through them. And they all sounded fizzy in just a short time. There's a big difference between guitar speakers and hifi speakers.  The more I learn about your speaker, the more I'd want to rule it out.

Surely you know someone that would let you plug your amp into their guitar cab just for a test. Then you would know for sure. Maybe even be able to quit beating your head on the floor. You could probably take your amp down to a music store and try it out on some nice cabs, especially if the salesperson thought you were in the market.

No. I don't know anyone that owns a cab. That stuff is really expensive down here and only professional - or really rich - guitarrists have that kind of stuff.
The amp is put together on 2 solderless protoboards, connections as spaced as possible, power supply on one board and the amp on the other board, so I can't take it anywhere. Even if I had it properly soldered all together, I don't have an enclosure for it...
Still, if I HAD it on a box and all, the music store guys would NEVER let me use a cab. They sometimes won't even let you touch the guitars, what to say connect an unreliable black box into  one of their products. What if the circuit went bad and blew up the speakers? How the heck would I pay for that?! And what would happen to the dude that let me plug it in?
No, I prefer to keep my luck with what I've got in hands. At least if something goes BOOM, I'll be the only one losing something.

What about the guy you know where you bought the tubes? Does he have a guitar speaker/cab you could try?


                    Brad     

Nope. He just sells tubes because of the audiophiles and Ham radio people. Only recently he got in contact with the DIY comunity that works with guitar stuff. But even if he did have something I could use, he lives and works on the other side of the state.

[blackcorvo]

Ok, my friend sent me the new values for the PI:
100K for both plates, 470R for the cathodes and 15K for the tail resistor.

Still the exactly same sound.

I even tried my combo's speaker, but all it did was sound louder and with more highs. The weird distortion was still present, so as I suspected, it's NOT the speaker.

I tried swapping between the 3x ECL84s I have here in all imaginable combinations, but they all sounded the same.

I really don't know what to try next...

[PRR]

Do you have a Volt Meter?

[blackcorvo]

Do you have a Volt Meter?

I have a Digital Multimeter. It's not true-RMS, though.

[PRR]

Obviously it would be good to post plate grid cathode DC voltages on PI and the stages before and after it.

And probably a link to the plan you are working from (not all "18W Marshalls" are the same).

I can never think of a need for 'true' RMS in audio work.

[blackcorvo]

Obviously it would be good to post plate grid cathode DC voltages on PI and the stages before and after it.

And probably a link to the plan you are working from (not all "18W Marshalls" are the same).

I can never think of a need for 'true' RMS in audio work.

Here is the latest schematic with all the voltages:

[DummyLoad]

just a suggestion from my perspective; it seems like the LTPI is grossly over-driving the output pentode grids.

this should help tame the LTPI output - see attached .GIF.

--DL

 

[darryl]

I would suggest a grid stopper on the input of the phase inverter - in the spot marked with a red arrow below:



The value can be quite high - anywhere from about 220k up to 1meg.

The grid stoppers on the pentode sections may benefit by being increased from 8.2k to at least 15k. Any value up to 47k is fine.

All the grid stoppers should be soldered directly onto the appropriate pins on the valve socket, so the lead length from the grid to its grid stopper is as short as possible.

[PRR]

> it seems like the LTPI is grossly over-driving the output pentode grids.

I figure it is capable of delivering 13X to 16X what the output grids need.

> tame the LTPI output

Going to have to turn-down a LOT.

I think the LTP stage could run on 40V (instead of 245V).

If the driver makes more than the output tubes need, the positive peak is distorted and the average grid bias shifts from zero to a negative voltgae. That's normal in overdriven guitar. But if the driver makes more-than-twice what the output grids need, the bias-shift tends to shut the output tubes OFF, with slow recovery, a pretty brutal sound.

No good single answer.

Try changing the 6K8 to something like half the grid-leak, about 100K, so the bias-shift is less.

If you can stand less gain (if you never really need the Volume at Max), try 100K or 33K from plate to plate on the PI.

Raise the PI tail resistor a lot. Like 50K or 100K. But don't let the cathodes go above 200V, the limit heater-cathode voltage rating of this tube.

Leave the tail-resistor around 15K-50K, but raise the 470r to 4K7 or 22K to choke the PI. The goal is to get the plates very close to the (C) voltage so the swing is less.

[tubenit]

Please compare my schematic to yours. Note that I have ALOT more gain in my amp, yet there are no oscillation issues at all. The amp has great sustain, sweet harmonics and is very touch sensitive. It sounds like a "huge" amp at 3-4 watts when I crank it.

IF you go back and look at the early post of the SoLow Watt you will see numerous things that I did to lower the gain from the LTPI into the output pentodes.

I have indicated those with blue arrows.  They work for me quite well and the amp sounds good. I can dime all controls and have NO oscillation at all.

Note with the PPIMV that there is a total grid resistance to ground around 100k and I am only dialing the PPIMV to around "5-7" about 95% of the time. It works fine on "10" with no oscillation also.

With respect, Tubenit

[DummyLoad]

the bias-shift tends to shut the output tubes OFF, with slow recovery, a pretty brutal sound.

similar to the tone on neil young's hey-hey my-my...

NEIL YOUNG & CRAZY HORSE - Hey Hey, My My (Into the Black)

[PRR]

> similar to the tone on neil young's...

Yes, but who has Neil's fine finger control?

[DummyLoad]

> similar to the tone on neil young's...

Yes, but who has Neil's fine finger control?

right-o. the point i was making is that such brutal distortion can be made into music - you need to beware of the maker tho. :D

--DL

[blackcorvo]

I'll put this project aside for now. My friend said he'll soon build the amp as he designed, and then we'll see if I just happened to be unlucky of getting bad tubes / OT, or if it is indeed a design issue.

For now, I'll work on something more simple... probably a small SE amp. I got a 5k - 8R OT here taken from an old tube radio. I've tested it before, and it works.

I have plenty of tubes to play with:

3x 6AS5 - one by Admiral, the other two made in USA, no brand
1x 6AU6 - made in USA, no brand
1x 6BZ6
1x 6BA6 - russian
2x 5AQ5
1x 6BQ5 - made in Brazil, taken from that old tube radio
1x 12AX7 - Sovtek
1x 6BZ7
2x 6AW8A
1x unamed twin-triode - 12A*7 pinout, plates twice as tall as the 12AX7's. It was in that old radio too.
2x EF184
1x EF183

and some others I can't remember right now.

Thanks for all the help.

[sluckey]

right-o. the point i was making is that such brutal distortion can be made into music - you need to beware of the maker tho. :D

No way! That was pure noise! I'm a huge NY fan but I can't stand that Crazy Horse crap, except for maybe a half dozen songs. Love all his D-45 stuff though. 

I know, just an opinion...

[DummyLoad]

No way! That was pure noise!

bah! :p

[DummyLoad]

1x 6BQ5 - made in Brazil, taken from that old tube radio I got a 5k - 8R OT here taken from an old tube radio...

match made in heaven. use the 12AX7. :-)

--DL

[blackcorvo]

1x 6BQ5 - made in Brazil, taken from that old tube radio I got a 5k - 8R OT here taken from an old tube radio...

match made in heaven. use the 12AX7. :-)

--DL

I followed this "holy match" you pointed, and I have built a prototype.
I'll probably create a new topic for it. Don't wanna go too off-topic on this topic here.