Ultralinear Deluxe reverb ?

[Toxophilite]

Anyone ever built a ultralinear amp based around pushpull 6V6s?

I love my ultra linear super. I have built deluxes (3) vibroluxes etc and they are succesful and great sounding but my ultralinear super remains the prettiest sounding amp I have. Could be the 4 x 10s but I'd like to try ultralinear in a 6V6 pushpull
Seems like a fun experiment
Has anyone done it?

I've heard all the disparaging remarks about these amps and silverface amps in general, mostly via the internet , forums etc.
In fact I never knew my amp was bad sounding till I read it was on the all-knowing internet 
Humourously all the people (many of them guitarists) who came up to me after shows to compliment me on my sound didn't realize my amp was supposed to sound like %$#%^
I'm not chasing early break up, a 'sweet spot', the woman tone, nor do I want to sound like SRV or Santana etc.
I want beautiful clear cleans and my ultralinear super does that like nothing else.


I know they'll give up to 70 watts with 6L6GCs
Does anyone know the math on what is possible with 6V6s..or even El84s?

[shooter]

Does anyone know the math on what is possible with 6V6s..or even El84s?

Yup, the more you use, the more you get

I have a UL PP with'34's, she sings great and you can drive it right to grungy too

I'm getting ready to build a SE with kt88, UL.  The breadboard version spec'd at 39.6W for a heater, and 23ish for audio

[Toxophilite]

hmmm
maybe what I should ask is;

Can one achieve louder cleaner operation with a 6V6 pushpull amp using an ultra-linear OT ?


I'm glad to hear people are doing it though

[shooter]

achieve louder cleaner operation

UL puts you somewhere between pentode and triode operation
my educated  guess now, triode is typically less audio power but "cleaner", happy class A
so to get louder, you need more tubes.
I "design" my clean more on how much I want the PA tubes to distort, I typically shoot for 20%, leaving me with 80% clean PA.  The UL builds I've done seem to help make the PA section more "predicable" than giving it a PS tap and R, so I can focus more on where to lose or gain preamp signal to get "that spot"

[jjasilli]

KT-88 specs show typical or UL operation can make 100W.  Conclusion is that UL does not produce more power. 

[PRR]

I would not expect a huge difference. Not to justify a new OT.

UL will lower below-clipping THD from 4% to 2%. That's important for hi-fi specs.

UL *may* have advantages in reliability when you push tubes HARD. A 70W 2-6L6 straight amp may be possible in the lab, but will self-destruct with mis-connections and extreme abuse. Yet the 70W 6L6 Fenders seem to hold up OK.

Tubes are cheap. If you want more clean 6V6, run four.

[Toxophilite]

Interesting.

My Ultralinear super reverb is rated at 70 watts.
It's as loud and clean as I could ever need and more.
And has been dragged around North America (and looks it) and has few if any problems (usually of my own making)

Maybe it's not a significant advantage after all

[DummyLoad]

Interesting.

My Ultralinear super reverb is rated at 70 watts.
It's as loud and clean as I could ever need and more.
And has been dragged around North America (and looks it) and has few if any problems (usually of my own making)

Maybe it's not a significant advantage after all

UL requires more drive (Vpk swing) than pentode operation and likely why you have more headroom. overall sensitivity with a UL output stage with the preamp unchanged will have more "headroom". 70W/100W difference is negligible with added decreased sensitivity you have have greater perceived headroom.

70 UL fender is a two tube 6L6GC circuit with 500V B+ to the plates: THAT is how you are getting 70W out of a pair of 6L6GC. IIRC, the tubes don't last long in those amps: typically <500 hrs. they are taking a beating. also i recall that NOS tall bottle sylvania 6L6GC work best in that circuit. do not modify the balance circuit. if you copy it, copy the bias and balance circuits. when you install a new pair of tubes, re-balance them for best results and longest life.

schematic attached is probably your amp. it states pro reverb, but the bandmaster, pro, and super were the same circuit in that era. see the speaker option notes in the schematic.   

--pete

[Toxophilite]

Thanks
I've actually been using that amp live , in the studios and at rehearsals for the past 28 years or so
it actually hasn't shown any tendency to eat power tubes
For the first bunch of years i was playing for a living so it saw a lot of road etc.
Pretty well bulletproof and I never had a problem changing tubes etc.
the only problem I ever had was a heat sensor fuse thing inside went and turned the amp off mid show on tour!
A local tech removed it, that was probably 26 years ago. no problems since other than the occasional upkeep. Still has the original speakers.
Still sounds great

[DummyLoad]

the only problem I ever had was a heat sensor fuse thing inside went and turned the amp off mid show on tour!

that was a thermal cutout switch. in the schematic, it's the symbol to the left of the 2-1/2A SB main fuse.

--pete

[Toxophilite]

Yes that what it was. I haven't the schematic in front of me. Likely it was there for a reason. But it wasn't needed since and there hasn't been a meltdown
Funny thing about the UL amps.
I often wonder about how many people that deride these amps have actually played one?
I think many of them might be pleasantly surprised.
I also haven't heard about any having any problems. they seem to be as bulletproof as the rest of them.

[DummyLoad]

acrosound published UL HI-FI amplifier that uses 6V6 coupled to 8Ka-a OT with UL taps. see attached. should help simplify your design - plagiarize this one.


scrap the floating paraphase inverter and replace with AB763 preamps. bump B+ up to 380V-400V and increase Rk of 6V6 from 250R to 300R or thereabouts: e.g., a value that sets idle current so that plate dissipation between 60-70% of maximum plate dissipation. 


--pete 

[DummyLoad]

Yes that what it was. I haven't the schematic in front of me. Likely it was there for a reason. But it wasn't needed since and there hasn't been a meltdown
Funny thing about the UL amps.
I often wonder about how many people that deride these amps have actually played one?
I think many of them might be pleasantly surprised.
I also haven't heard about any having any problems. they seem to be as bulletproof as the rest of them.

i have a fender PA135 that sounds wonderful, however, the reverb is a bit too noisy so i don't use the reverb. it's in really rough shape and doesn't get much use anymore, so i need to flip it or scrap it and salvage the transformers. 

mid 70's to late 70's era fender stuff tends to be "brighter" overall.

--pete

[PRR]

> Pretty well bulletproof

What I was trying to say. Non-UL 2*6L6 can be goosed to 70W but may not last. Fender's UL amps seem to last OK, even in your long severe duty.

Pete- your first plan's 2K 10W WW resistor mod won't last a minute. I assume you got the image from elsewhere.

[DummyLoad]

yessir, PRR, it's a paste from acrosound catalog. download full ver. from pete millett's site.


i did not perform nodal analysis. good to know. i would believe 100r there at 10w.


--pete

[sluckey]

Pete, look at reply #7, first pic. Someone drew in a 2K/10w WW resistor that's connected from the standby switch to ground. That's the resistor that's gonna light up like a sparkler.

[Toxophilite]

If I could ask another question about this
What would be the result of i took an existing single channel deluxe build built on a Hammond AO-43 chassis using the accompanying transformers (PT choke and OT).
and replaced the Ot with something like this and rewired the power amp properly to utilize the ultrlinear taps etc.
https://www.hammfg.com/files/parts/pdf/1650FA.pdf


I don't have it on hand so i can't try it right now. I just wonder if anyone had an idea what the result would be? If any?

[sluckey]

You would have a UL 6V6 amp. It might even sound like you want. You kinda lean toward the clean side and this just might get you there. Worth a try.

BTW, I have two original UL amps, Sunn Sceptre and Magnatone M10A. Both have a nice clean sound. I'll never part with either of those amps. The Sunn is also a very loud amp. The Maggie is more in line with your UL 6V6 idea. You can see both on my website.

[jjasilli]

You could drop 1/2 - 2 lbs with a smaller OT in that series:  http://www.hammondmfg.com/1608A.htm

[DummyLoad]

Pete, look at reply #7, first pic. Someone drew in a 2K/10w WW resistor that's connected from the standby switch to ground. That's the resistor that's gonna light up like a sparkler.

oh ok, thanks. yes, that hack. it's the only schematic i could find up until i found the second unaltered one that i attached in a later edit. looking at it again, i see what PRR means.


i'd use the 1650E.


--pete

[Ritchie200]

Toxo,

It appears we DO agree on something!  I too am a fan of the UL sound.  Are you talking about a stage amp that you will be hauling around the country?  The reason I ask is I wonder if you will get enough volume on stage to get any speaker/guitar interaction without getting into a little distortion with two 6V6's.  I know you like sparkling cleans.  Maybe I'm wrong, but I really wonder if that tube will give you sufficient clean volume without giving up - even in UL mode.

Here is a link about my beloved Marshall Major that everyone here dissected to the 'inth degree a couple of years ago!  Not a Fender circuit, but some good information.  I think a pair of KT88 would get you some beautiful clean tones - I know, I know, you don't believe in tubes sounding different.  However, these will give you loads of headroom and plenty of volume.  Set up properly, the KT88 will not mush or fuzz out on you when pushed, and they do sound so nice!  Maybe there is some information or even another option in the thread you can use.

http://el34world.com/Forum/index.php?topic=17548.0

Now all you have to do is obtain some of that rare cryogenically frozen camel turds for your baffle board!

Jim