More sag please... Weber Copper Caps?

[Structo]

When I have visited the London Power site before, I got tired real quick of it because O'Connor refers to his books in just about every thread of the forum and in his FAQ's.

It's like, I could tell you the answer to your question but I'll just refer to my book so you will buy it.

[d95err]

I had never heard of london power. Just spent half the afternoon trolling around their site. Pretty cool... Which of the sus kits would I need for the ceriatone?

From their site:
SUS-1 can be used with any non-Power Scaled fixed-biased amplifier.

SUS-2 can be used with any cathode-biased amplifier, regardless of whether the amp is Power Scaled.

SUS-3 is for fixed-biased amplifiers fitted with Power Scaling.

I'm thinking sus-2. Are these pretty easy to install? I'm sure they have a layout, I'm just not clear on where I would put it in the amp. Thanks for the link. Wheels are turning steady now.

For your Dumble-clone you need SUS-1 since it's fixed bias.

It should be fairly easy to install if you have a little experience in modding amps and can find your way around the components inside the amp.

[d95err]

When I have visited the London Power site before, I got tired real quick of it because O'Connor refers to his books in just about every thread of the forum and in his FAQ's.

It's like, I could tell you the answer to your question but I'll just refer to my book so you will buy it.

I understand your frustration, but I think Kevin intends his forum to be mainly a support site for his kits and books. I'd rather see a more open discussion there too, but there are other great forums for that (here for instance...).

[bluesfendermanblues]

When I have visited the London Power site before, I got tired real quick of it because O'Connor refers to his books in just about every thread of the forum and in his FAQ's.

It's like, I could tell you the answer to your question but I'll just refer to my book so you will buy it.

I understand your frustration, but I think Kevin intends his forum to be mainly a support site for his kits and books. I'd rather see a more open discussion there too, but there are other great forums for that (here for instance...).

+1

Kevin's business is selling books...let the man eat
(I have most of the TUT's and they are worth every penny IMHO)

[renshen1957]

Take that Fender 5B6 PTP amp I built with octal pre that sucker sounds fantastic right out of the chute with low volume sustain. But the trade off is your not going to bring the house down unless its miked and your only style of music for the night is playing blues. Which isn't all that bad to me.

What the hell exactly is sag (rectifer) sag (transformer)? Resistor based sag such as in some 18w Marshall type builds?

Since the thread has already mentioned London Power, you might want to check out Kevin O'Connor's Super-Scaler which is mentioned in Volume 4 The Utimate Tone (along with Sustain/Sag, what it is and how to this option to an amp) or Volume 5 (actually amps with schematics and circuits). A Super Scaler is a class B Amp which is driven by a lower power amp (a 5B6 for example) and makes it louder without changing the tone.

Sag has more to do with the power supply and voltage drop than rectifier or transformers, although both these are a factor being part of the power supply. On the other hand, AC 30s are Cathode Biased and have a rectifier, but the Bias is so high on the Power tubes that it is essentially pre-sagged. The AC 30 is Class A up to 22 1/2 watts when it slips over into class AB. Subsitute a 5y3 tube for the GZ34 tube and you may lower the B+ voltage, but you don't achieve any additional. Substitute a 5u4 tube in a AC30 and you will over heat the 5Volt winding.


(The Ultimate Tone Volume 6 has a chapter on the Dumble Amps.)

A lot of the above is discussed on www.powerscaling.com, a amp building forum hosted and populated by a mix of Professional and Amateur amp builders.

Best Regards

[dartanion]

The AC 30 is Class A up to 22 1/2 watts when it slips over into class AB. )

Not true at all. The definition of class of operation has not changed, so what you are doing is perpetuating a myth.

Class A is achieved by output tube plate current flowing for 360 degrees of the input cycle at maximum unclipped output. Thus, class of operation does not change when you crank up the volume. As well, the AC30 is well known to be operating in class AB.

As far as KOC is concerned, his books are okay at best. You'll learn more by reading an old tube manual or RDH4.

[jelle]

As far as KOC is concerned, You'll learn more by reading an old tube manual or RDH4.

This is certainly true for the Dumble Chapter which I read two weeks ago. I did not learn a thing, actually I was more confused after reading it.

I really dig RDH4.

[bluesfendermanblues]

As far as KOC is concerned, You'll learn more by reading an old tube manual or RDH4.

This is certainly true for the Dumble Chapter which I read two weeks ago. I did not learn a thing, actually I was more confused after reading it.

I really dig RDH4.

You guys are perhaps not the target group of the DUmble chapter in TUT6. My guess would be that many people on this site have more knowledge on Dumble amps than KOC.

Let it go. Kevin is trying to make an honest buck selling book. I respect that. - Lets talk amp sag instead.

[jaysg]

When I have visited the London Power site before, I got tired real quick of it because O'Connor refers to his books in just about every thread of the forum and in his FAQ's.

I just asked a question over there and got a reference to his latest $72 book. In my case, I can buy a custom PT for about $110 and take care of the issue directly.

I've built the power scaling + sag circuit into my liverpool, and the sag works as promised. The newer thing is a side chain compressor setup. He indicated somewhere that the sag circuit didn't do much in cathode biased amps like the liverpool, because they're already running close to their dissipation limits...louder doesn't mean more average current. I find that it is nice just to get the attack a tad chewier. I'm glad I built it.

[cdc3jj]

This might be a ittle off topic, but what would happen if I changed the PT? To something lighter like a 25 or 30w. Would that drop the B+ to where I could install a tube rectifier? I'm sure that would drop the output as well, but would I be hurting anything by doing that? How would the tone be effected? What other modifications would have to be done for such a thing?

[jaysg]

This might be a ittle off topic, but what would happen if I changed the PT? To something lighter like a 25 or 30w.

It really depends on what you're looking for in your amp collection. The Dumble isn't meant to be a saggy amp. This is why you'll find so many who prefer the 100W amps over his 50W and 6V6 amps. That said, the standard chassis for a 50W should have room for a rectifier tube in line with the output tubes. If the pt has an unused 5V tap, you don't need a different one. Using a tube rectifier brings B+ down because they're that way...~20V for a good GZ-34, more like 40V or 50V for the 5U4G.

[jelle]

As far as KOC is concerned, You'll learn more by reading an old tube manual or RDH4.

This is certainly true for the Dumble Chapter which I read two weeks ago. I did not learn a thing, actually I was more confused after reading it.

I really dig RDH4.

You guys are perhaps not the target group of the DUmble chapter in TUT6. My guess would be that many people on this site have more knowledge on Dumble amps than KOC.

Let it go. Kevin is trying to make an honest buck selling book. I respect that. - Lets talk amp sag instead.

I must add that I like his books in general. Since the comment was made that there is a Dumble chapter, I felt obliged to warn our fellow TAG members from buying it for this reason. I occasionally buy one of his books and generally I enjoy reading each chapter. As for the OT's topic...

Sag and Dumbles...try a 50W EL34 version with a 1K "choke' resistor and run the snot out of it. Wicked fun! Do not forget to keep the B+ low. Soft vaccuum tubes will feel very different in these amps.
Also a 5U4 straight bottle rectifier will do wonders in an amp like this if you like sag. Also, relatively low power speakers will reduce the headroom and contribute to the experience of sag.
Hope this helps,
jelle

[d95err]

Class A is achieved by output tube plate current flowing for 360 degrees of the input cycle at maximum unclipped output. Thus, class of operation does not change when you crank up the volume. As well, the AC30 is well known to be operating in class AB.

I think you're getting two different topics mixed up here. One is the old Class A hype discussion. I agree that for an amp to be called a Class A amp, it should be operating in class A at maximum rated output power.

But all class AB amps are operating in class A att some signal level below maximum output (otherwise it would be a class B amp). The point where the transistion between class A and class AB operation happens is a key issue when discussing sag.

[dartanion]

Class A is achieved by output tube plate current flowing for 360 degrees of the input cycle at maximum unclipped output. Thus, class of operation does not change when you crank up the volume. As well, the AC30 is well known to be operating in class AB.

I think you're getting two different topics mixed up here. One is the old Class A hype discussion. I agree that for an amp to be called a Class A amp, it should be operating in class A at maximum rated output power.

But all class AB amps are operating in class A att some signal level below maximum output (otherwise it would be a class B amp). The point where the transistion between class A and class AB operation happens is a key issue when discussing sag.

I understand that when you are varying the input level, yes, theoretically the amp is operating in a different class if you throw out the definition of class of operation, but you are totally missing the point. You are trying to re-define class of operation by saying, "But all class AB amps are operating in class A att some signal level below maximum output." Class of operation is determined at maximum unclipped output. What about that is not clear? If the output device is not conducting current throughout the input cycle, it's not class A. AC30s do not conduct current throughout the input cycle, and are thus not class A. They are class AB. If you don't trust me, maybe you should read Mr. Aiken's white paper on the subject. As well, Randall is a great guy and I'm sure would be willing to explain it to you here. Regardless, here's the link: http://aikenamps.com/VoxAC30classA_2.html


Back to the original topic, I have to agree that a saggy Dumble is kind of against the whole concept.

[cdc3jj]

I'm not really worried about what a dumble is or isn't. I'm just looking to make this amp that sounds great sound amazing (to my humble opinionated ears).

I really dig the cleans. I AB'd it with my twin and it blew the twin away. My gripe is there's not much sag/bloom happening on the OD channel (I use sag/bloom together because it seems to be a very simiar phenomenon... please correct me if I'm wrong before I order a 5u4 and a socket or one of LP's sag kits).

I haven't dug into it and checked voltages yet, as suggested in an earlier post, so I'm talking pretty hypothetically here. However, knowing the tiny bit I know and reasoning my way through things it would seem as though if a rectifier causes sag/bloom and this amp doesn't have a rectifier and lacks sag/bloom, perhaps adding the tube would be cool. If I do I will try it for a few days and decide whether I want to drill a hole and install a switch or just go back original.

Does sag typically only happen after breakup, when an amp is being pushed? Meaning can you have clean sag? Or is that bloom? That's what got me thinking about droping the PT wattage. Should I ask Nik about the install? Not knowing enough about his PT's I'll need someone to tell me exactly how to wire the tube in. (i.e. cut the red wires, attach them to pin 2 & 7 then run wires from 1 & 6 to the ______. yeah, I'm that green)

On a related topic if anyone knows a good informative book or website that could get me headed down the road to enlightenment let me know, but I can't afford KOC's $70+ books right now. Reguardless if it's worth it or not. Maybe in march once the road gigs start back up.

Thanks for all the information so far. I'm learning something new everytime someone posts. Thanks again.