Output transformer for 807s?

[billraymond]

I am working to build an amp using 807s in push-pull with an output of about 20-25 Watts. I have 2 output transformers "on the shelf" as it were. I'd like to use one of them if possible, rather than purchasing a new OPT. These are an Acrosound TO-300 and a Dynaco A-420. The Acrosound is recommended for 6L6 class and EL34s with a max. plate current of 75 mA per tube. (However, I have seen circuits published using the TO-300 with 807s.) Consequently, I'm thinking that the TO-300, although possibly workable with 807s, might not be an ideal choice. The Dynaco is also specified as recommended for 6L6 class and EL34s, but there is no mention in the literature of max. plate current. The Dynaco catalog does say, though, that "units are conservatively designed and can handle twice the d c current of the tubes recommended for use...overloads...will [not] harm the transformers." This would suggest to me that the A-420 might be usable with the 807s. What do you all think?

 

[Tubelab_com]

Both of these transformers will work good for your application......maybe a bit too good. These transformers were designed for high fidelity. If you are building a guitar amp they may not be the best choice if you like to turn it up to 11 and get nasty. If you want something clean, then go for it.

 

[gingertube]

Acrosound themselves showed an application circuit TO-300 with 807 - See page 8
http://www.clarisonus.com/Archives/Trans/Acro55.pdf

The circuit shown is a HiFi Circuit, see Tubelabs comments above, but it shows that the TO-300 is quite suitable for a pair of 807.

For 807 Application Data See here;
http://www.retrovox.com.au/STC807.pdf
Everything you ever wanted to know about using 807.

Cheers,
Ian

 

[billraymond]

Thanks guys, that's just what I wanted to hear. I'm going for clean--like the 25L15.

 

[gingertube]

Ah - so it is a Guitar. Amp
When you mentioned 807 I as going to suggest you look at the Standel 25L15. Probably the best known 807 Git Amp.
To get that exact sound (if that is what you want) you will need a 15" JBL, I can never remember if it was a D130 or a K130.
Maybe someone can advise which and whether there are suitable alternatives.
Do you have/need the 25L15 schematic?
Cheers,
Ian

 

[billraymond]

Ian, I have a D130 that I am planning to use and I've copies of the various schematics posted in the thread "I have finished my Standell [sic] 25L15 clone" and taken note of the various comments in that thread on the schematics. I believe I can get close enough to the Standel circuit for my purposes, as I'm not trying to "clone" it, just trying to get close.

 

[bparnell57]

Interesting, I am not very familiar with 807's in guitar amps, I will have to research that more, are there any notable models I should look into?

 

[gingertube]

The Standel 25L15 is the best known 807 Amp. It was popular with Country Players, quite clean. This is understandable as the 807 is a forerunner to the 6L6. Think of it as a 6L6 with an anode top cap.

Here are some links to guys who have made clones etc.
Standel 25L15 Inspired Amp - Hoffman Ampifiers Guitar Tube amp forum

Adnd to Ted Weber who has or did have a kit for the amp and the cabinet.
http://www.tedweber.com/schematics/jp25_schem.jpg

Cheers,
Ian

 

[bparnell57]

Oh, thats right, it is basically a 6L6 with an anode cap. Thanks for the info

 

[Kay Pirinha]

The Standel 25L15 is the best known 807 Amp. It was popular with Country Players, quite clean. This is understandable as the 807 is a forerunner to the 6L6. Think of it as a 6L6 with an anode top cap.

Sorry, Ian, but no! The 6L6, introduced in 1936, was the very first beam power valve. The 807, which came in WWII, was a derivative of it. Nevertheless, your conclusion is quite right. Any schematics, any output tranny, designed for a 6L6 application up to a plate dissipation of 25 watts, will do well for the 807, too.

Best regards!

 

[gingertube]

Thanks for the correction on the 6L6 / 807 timeline. I should have got this right, last tube purchase was a box of 12 NOS Amperex 807. Also the current restoration job I'm doing for a local collector is a Healing "Church Chimes" PA Amp built here in Adelaide. It runs PP 807, phase splitting transformer driven by triode strapped 6J7 with a couple more 6J7 in pentode mode for teh Mic and PU preamps.
I've been interested in the Standel for a while as I wanted to try the 807s. Currently trying to talk a friend into selling me a JBL D130 he has stashed away or at least get it included as part of the purchase price of the 6V6 PP Guitar Amp I'm designing and building for him.
Cheers,
Ian

 

[Tubelab_com]

Sorry, Ian, but no! The 6L6, introduced in 1936.....Thanks for the correction on the 6L6 / 807 timeline

I thought it was 1939 but I could be wrong.

The 807, which came in WWII, was a derivative of it.

The original 807 was a rebased 6L6GA with some RF shielding added around the lead frame on the bottom. As the need increased in WWII there were several versions of the 807 made. Some were nothing more than a 6L6GB with a different base and a top cap. The 6BG6G was a 6L6GA with a top cap and a different pin out for TV sweep tube duty. Any of these can be used in ANY schematic that calls for a 6L6, 6L6G, 6L6GA or 6L6GB. None have the screen grid voltage or plate dissipation capability for use in a circuit designed for a 6L6GC.

There is also the 6BD5 which is a 6V6GT sized tube with 6L6GA guts stuffed inside. The dissipation rating is lower for fear of melting the glass. It has a different pinout.

As the war ended and demand dwindled there was some creative glass stuffing by some tube companies, especially Sylvania and Philips ECG. I have seen 807's that contained 6L6GC guts, and 6BG6GA's that contained 7027A guts.