Single Ended Amps - Opinions

[Littlewyan]

I've been toying with the idea of building a single ended amp for quite a while, but I've never come across a demo of one that sounded good with distortion. I realise they'll never sound like a Push Pull amp but they just always seem to sound so grating with no definition. The only one that sounded ok was the Marshall SL5, but I suspect that's because it's a Master Volume amp and they're not actually driving the power section. Look at the Vox AC4C1 however and it sounds likes a trebly fizzy mess. Same for the Marshall Class 5, absolutely no definition, just fuzzy mess.

What are your thoughts? Can single ended amps sound good with distortion? Or are they better kept clean.

[pompeiisneaks]

I don't know the answer myself, but I do know that often the tone of the singled ended amps like the champ are often the super small speaker. If you put it into a big 12" with great response it sounds a lot better. I might have to give that a try with my champ into my EVM 12L ;D Right now I'm mid selling my home and moving so they're all packed up... but some day!

~Phil

[xtian]

Yes, they can sound awesome! Check out my builds:

Black Butte Desktop (10w): https://ampgarage.com/forum/viewtopic.php?t=33171

Black Butte (2w): https://ampgarage.com/forum/viewtopic.php?t=32876

[Stevem]

If your ok with the sound of preamp distortion in which every tube is in fact single ended then, why don't you think that a amp with a single ended output stage can't sound good?

That being said there output stage does allow different harmonic overtones to be produced since there is no phase canceling going on at all.

[Synchu]

Of course you can, it simply takes a bit more effort.
This is all SE EL84 with a Tele:
https://soundcloud.com/synchu/thewrongk ... -the-third
To my ears it doesn't sound fizzy, I think.
What I found, though, is that most designs are (for one reason or another) fit with undersized either power or output (or both) transformers and saggy power supplies.
You have to be also delicate with gain staging and frequencies to avoid blocking distortion which is another frequently seen problem with SEs.
Speakers used in small SE combos are a whole other story.

Niki

[R.G.]

Single ended amps can sound simply beautiful. Fizzy distortion is more an issue of which stage distorts and how much - I've heard a lot of push-pull fizzy amps.

The one amp I deeply regret not having any more is one I made myself from a Magnavox-brand hifi (not stereo...) furniture-grade home entertainment center I found in a used-furniture store. It used a single 6AQ5 output stage and I cobbled a two-12AX7 preamp/driver to it. I deliberately limited the amount of overdrive to the output tube and to intermediate stages to keep things from being massively overdriven at each stage along the way. This let it have a lot of gain/distortion on tap with the volume control, but a smooth and wide slide into distortion without being harsh at any level.

Sigh. The lost loves of our youth.

[Littlewyan]

Thanks for the responses guys. The amps sounded great Xtian and Synchu. You have all convinced me! My idea is to have 2 x 12AX7s with an EL34 output stage setup for high gain (Trainwreck Express high gain, not 5150 high gain). Not based on any existing designs really, I was just going to get a basic layout done and start experimenting. I just wanted to make sure it was worth doing before going to all the effort! So thank you all!

R.G. - We all have that one amp we regret getting rid of. Mine is a Marshall 1987xl.

[xtian]

Ryan (is that right?), don't forget the Pi or CLC filtering arrangement--that extra reservoir filter is helpful for cutting the hum common in SE builds.

[Littlewyan]

It is Ryan

I will be using a CRC filter before the output stage to bring the voltage down a bit anyway. The PT I'll be using is one I bought years ago for a 20W 6V6 amp.........before I really knew how to spec a transformer. It has a 250V Non CT Secondary that can only handle 120mA. Not enough for a 6V6 or EL84 push pull and slightly too high voltage for a single ended Class A. If I bring the HT down by 40V I can just about get away with running an EL34 with it.

[Colossal]

Yes, they can sound awesome! Check out my builds:

Black Butte Desktop (10w): https://ampgarage.com/forum/viewtopic.php?t=33171

Black Butte (2w): https://ampgarage.com/forum/viewtopic.php?t=32876

I completely agree. SE gets a bad rap because the baseline in Guitar Amp World is usually the worst pile of crap assembled to make a sound for the least amount of money. If you use good parts, properly sized transformers, and good power supply design (CLC is a must), you get a great sounding amp. You want loud? Go parallel single-ended.

[wpaulvogel]

I’m in the process of building a single ended 6550 amp. I wound a power transformer that will produce about 400 volts on the plate and 220 volts on the screen by having two windings feeding 2 stacked full wave bridge rectifiers. I wound a 3k to 4, 8 and 16 ohm output transformer. I just ordered the faceplate and rear panel. It’s going in an aluminum Marshall 50 watt style chassis. It’s got 2 12ax7 preamp tubes with cathode follower first stage to handle the load of the tone controls and a cathode follower second stage for pushing the 6550. The data sheet says it’ll make 20 watts. I’m not so sure it’ll make that much power but the transformers are stout and should have no sweat with the current and voltage demand. Pictures coming soon.

[thetragichero]

yeah single ended is great!
even a lowly champ can sound great if it's been taken care of

[statorvane]

You want loud? Go parallel single-ended.

Ditto. Best amplifier I ever built.

PSE103_Schematic.pdf

f521790688.jpg

[Synchu]

^ I have the feeling, I might have asked in another topic, but are there any sound clips from this one?

Niki

[Phil_S]

...The PT I'll be using...has a 250V Non CT Secondary that can only handle 120mA. Not enough for a 6V6...

Not trying to talk you out of building a SE amp...I'd think 120mA is more than enough for a pair of 6V6 push pull. Plates and screens need about 75mA. That leaves over plenty for preamp tubes. Also, remember that a PP amp cycles from on tube to the other so that both are not running full tilt at the same time. This one might handle a pair of 6V6 in SE Parallel configuration (maybe a 10W amp) and quite possibly one EL34. Well, good luck with your build, whatever you choose!