Thanks, accepted 😀😀😀!
Is has to be assumed that Hohner, a German company located in the Black Forest, designed these amplifiers around typical TV tubes for rather pragmatic reasons: Tubes like PL84 and PL509 etc. used to be very very common in the heydays of tube TV sets here in Europe. Every TV repairman had them in his service suitcase or at his shelves. Thus, a musician never needed to look for a specialist in musical instrument amplifiers, instead he brought his broken Hohner amp to the next TV service shop where he could expect instant help.
Best regards!
I used to be a member on the Aussie Guitar Gearheads forum, and I heard the same thing about Australian guitar amps from the valve era - many were built around TV tubes, particularly sweep tubes. They were easily available, very rugged, very reliable, and probably less expensive than the ones being used in American and British valve designs of the time.
There is another, less politically correct, way to look at it. Leo Fender was an accountant with a minimal technical understanding of electronics - he had to lift his circuits straight from the back of the RCA catalogues, because he had no idea how to actually design his own. And he was cheap, so he probably lifted the cheapest circuits he could.
Similarly, Jim Marshall's hired technician blindly copied Fender's Bassman at first - either he was told to, or he or his employer lacked either the knowledge, or the confidence, to create their own original designs.
Meantime, designers in Germany, Australia, and Canada all seem to have gone their own ways, designing genuinely original circuits using components that were locally available. To me, that suggests that these designers were probably more technically skilled, and certainly more confident in their ability to pull off their own original designs.
-Gnobuddy
The thing about these EL86/6CW5 TV Vertical Deflection Tubes and the TV Horizontal Deflection (Sweep) tubes (like 6CM5/EL36, 6DQ6 etc) is that the published anode power ratings are for those TV set duties.
For use in a Class AB Audio power amp the max anode dissipation is 1.5 to 1.7 times higher.
For example:
The 6DQ6A sweep tube data lists anode power dissipation as 15W max. The Sydney Australia AWV factory which made these (in Oz) published operating points for their use in a Class AB PP Output Amp and recommended running them at 20W Anode dissipation with a limit of 25W not to be exceeded. 2 of those give 60W Output very easily and operating points in that published data included one entry offering 86W from a pair.
See 3rd page of this for that published data.
https://frank.pocnet.net/other/AWV_Radiotronics/Radiotronics_1962/1962_03_AWV_Radiotronics_27_03.pdf
Cheers,
Ian
For use in a Class AB Audio power amp the max anode dissipation is 1.5 to 1.7 times higher.
For example:
The 6DQ6A sweep tube data lists anode power dissipation as 15W max. The Sydney Australia AWV factory which made these (in Oz) published operating points for their use in a Class AB PP Output Amp and recommended running them at 20W Anode dissipation with a limit of 25W not to be exceeded. 2 of those give 60W Output very easily and operating points in that published data included one entry offering 86W from a pair.
See 3rd page of this for that published data.
https://frank.pocnet.net/other/AWV_Radiotronics/Radiotronics_1962/1962_03_AWV_Radiotronics_27_03.pdf
Cheers,
Ian
Last edited:
> Leo Fender was an
His circuits are 90% generic; not from RCA. His 12AX7 values are from GE tables. He did invent a tonestack. He also made "mistakes" which caught on (5F6a tone driver and output NFB). His reverbs were better than many others. He *listened* to musicians and tried to do good by them.
He didn't do TV tubes because through the 1950s, TVs used audio tubes (top-cap on 6L6 guts was the standard H-sweep), and by that time he had done his best work, had sellable circuits, and crates of his common tubes.
It was into the 1960s, when Leo had health issues, when TV tubes began to improve. 3rd-generation TVs had to be smaller/cooler/cheaper. Now we get the very high purveyance V-sweep bottles adopted by late-1960s designers.
For a guy with so little electronics, and no guitar, he sure did good when he sold-out to CBS.
> power ratings are for those TV set
A switch-mode H-sweep circuit working RIGHT has low losses, but if it gets a little wrong the losses go up radically. And at the time there was no simple way to know how much power was being dissipated. (Temp-sticks were common.) So the published limits allow a large factor of safety. Audio amps are more predictable and measurable, so you can go some higher.
His circuits are 90% generic; not from RCA. His 12AX7 values are from GE tables. He did invent a tonestack. He also made "mistakes" which caught on (5F6a tone driver and output NFB). His reverbs were better than many others. He *listened* to musicians and tried to do good by them.
He didn't do TV tubes because through the 1950s, TVs used audio tubes (top-cap on 6L6 guts was the standard H-sweep), and by that time he had done his best work, had sellable circuits, and crates of his common tubes.
It was into the 1960s, when Leo had health issues, when TV tubes began to improve. 3rd-generation TVs had to be smaller/cooler/cheaper. Now we get the very high purveyance V-sweep bottles adopted by late-1960s designers.
For a guy with so little electronics, and no guitar, he sure did good when he sold-out to CBS.
> power ratings are for those TV set
A switch-mode H-sweep circuit working RIGHT has low losses, but if it gets a little wrong the losses go up radically. And at the time there was no simple way to know how much power was being dissipated. (Temp-sticks were common.) So the published limits allow a large factor of safety. Audio amps are more predictable and measurable, so you can go some higher.
...and, interestingly, never adopted by the post-Leo Fender Musical Instrument Corporation. They seem to have more or less stuck with the same old valve designs to this day, (with a minor foray into using another old valve type - EL84s instead of 6V6s - when the latter started to get thin on the ground before new production took off).
-Gnobuddy
Just grab one of those thousands of designs and Build Something!!
The easiest path in 110V land is 12AX7 + 2 EL84 + 100V PA tranformer + voltage mulitplier. in 220/240AV, 12ax7 and any pentode + halogen transformer. No expensive iron or rare parts.
If you've got a few $$$ then some Hammond/replacement-Fender iron and you've got a huge range of 12ax7 + SE pentode amps to chose from
But I already started to design my own schematics because there are thousands of them online, and they are usually just a rip off or some modification of some famous amp... I am already sick of 12AX7-s and others... Why not build something with EF89, ECC88, EL41, EL86, PCL82... I mean, don't get me wrong but a Mullard EL84 NOS costs 50-90$ (and they 're not even Blackburn) and on the other hand you have a EL86 Mullard, 1960's, Blackburn for 9$! And ECC88 from Svetlana (SED) with gold grid for 4$... I have built around 10 amps with EL84's parallel SE designs, old-style phase inverters and all that, but i feel all that has been overused...
Anyways, I am not doing any sort of verbal attack... just trying to say my opinion...
Anyways, I am not doing any sort of verbal attack... just trying to say my opinion...
Do it! And when you're finished, please share your schematics and your sonic impressions with us. Perhaps you might want to upload some audio Clips?
Best regards!
Best regards!
Okay... I think i came up with a plan...
I will use old radio power transformer that puts out 280v on each end and has a center tap, then I will rectify it through EZ81, then some VOX power section.
After that I will build something interesting, a parallel SE design with EL86's, and instead of one ECC88 i will use two of them to build a fake phase inverter stage for better gain (something like dvnator SEplex), and I will use a 12 watt output transformer from an old EL34 radio.
So, that's basically it...
(BIG thanks to all who replied and inspired me with that Orgaphon)
Cheers!
I will use old radio power transformer that puts out 280v on each end and has a center tap, then I will rectify it through EZ81, then some VOX power section.
After that I will build something interesting, a parallel SE design with EL86's, and instead of one ECC88 i will use two of them to build a fake phase inverter stage for better gain (something like dvnator SEplex), and I will use a 12 watt output transformer from an old EL34 radio.
So, that's basically it...
(BIG thanks to all who replied and inspired me with that Orgaphon)
Cheers!
Good idea! Be aware of the highish plate voltage you will expect from your PSU, and auto-bias your EL86's so that the plate dissipation rating of 12 watts/each will not be exceeded.
Best regards!
Best regards!
What he calls the fake phase inverter is just a normal gain stage... And "a 12 watt output transformer from an old EL34 radio" is likely ill-suited for the PSE EL86's.
My thoughts also - at first glance. But if he ran his amp from 280-0-280 Vac, after two-way SS diode rectifcation about 400 Vdc can be expected, after vacuum rectification still about 350-370 Vdc. So he has to bias his EL86's for lower plate current than usual to keep the plate dissipation ratings. Hence a higher plate load than usual has to be applied. Conclusion: Might fit 🙂.
Best regards!
Best regards!
Drew some load lines and the higher Ra seemed really off, very asymmetrical, may that's a good thing?
It's intended to be a guitar amplifier!
Main concern would be the restricted output power, though.
Best regards!
Main concern would be the restricted output power, though.
Best regards!
Not commenting on the rest of the circuit but the transformer might be spot on for this tube. EL34 calls for 2k while the EL86 asks for 2.5k.
To all those who have been following or participating in this thread . . . I don't know how many of you have noticed but this kid is only 15 years old.
I'm impressed!
Hats off to him 🙂!
I started building amplifiers at the age of about 12. Coincidentally, my very first one also used a PL84 (same tube as EL86, you know) that, together with it's output tranny, I had cannibalized from an old b/w TV set.
Best regards!
I started building amplifiers at the age of about 12. Coincidentally, my very first one also used a PL84 (same tube as EL86, you know) that, together with it's output tranny, I had cannibalized from an old b/w TV set.
Best regards!
Ditto!
Dr. Firebottle, please remember to be safe - working with hundreds of volts can be very dangerous. Safety first!
Somewhere about that age for me too (I was building some simple electronics at age 9). But the stuff I built then used PNP germanium transistors and ran off a 9 volt "battery eliminator" I had built. Not as scary or dangerous as the hundreds of volts in a valve amp, by a long shot!
-Gnobuddy
It all started when I was 11 yrs old... I wondered how my dad's Fender works, and at the age of 12 I built my first EL84 amp... My dad was proud but mom was scared of high voltages... So then I left all modern tech... And moved to the real analog stuff, gramophones, radios, schematic designs... And at age of 13 I could barley understand tube amp maths, biases, plate voltages and so on, but all i want to do is play guitar, play some real hammond organ, make amps... So there you have it... My whole life...
Last edited:
There will be a lot more to your life than just the first fifteen years, trust me on this! 🙂
-Gnobuddy
- Status
- Not open for further replies.