18 watt TMB with 6V6's.

[DG45]

I've heard some positives about 6v6's in place of EL84's in this Marshall circuit. I'm not very tech savvy so can someone point me to what changes need to be made in order to run 6V6's. Transformers, passive component changes, etc. I've read a couple things saying that it's not too complicated but cant find specifics. If it's too detailed to post here, maybe someone can point me to a specific link (that isn't too technical). I'd appreciate it.

Thanks

[danman]

You would need to remove the 9 pin sockets for the EL84's and install 8 pin octal sockets for the 6v6's. Power transformer would likely be ok if your happy with the plate voltage it provides. There would be a few other components that would need to be changed such as cap and resistor values. It really isn't that difficult if you are familiar with tube circuits but otherwise it might be best to have a tech make the swap.

[DG45]

I would be doing the build, probably from a kit and making the mods myself. Unless the optimum transformers are different between the two tube types and I don't have the option to swap iron for the kit. I'm capable of the build, but I would need the specifics on component changes. Tube sockets are a given, I'm dumb but not that dumb.

[danman]

If I am not mistaken, the specs for both OT's are pretty close. Both tube types will operate happily with an OT in the 8k range so it should not be a problem to use the OT supplied with the EL84 kit. Check out the layouts at "Trinity Amps". I believe they have an 18 watt kit with the option of using EL84 or 6v6 power tubes. You should be able to figure out the different component values needed for the 6v6's by comparing both layouts.

[romberg]

I would be doing the build, probably from a kit and making the mods myself. Unless the optimum transformers are different between the two tube types and I don't have the option to swap iron for the kit. I'm capable of the build, but I would need the specifics on component changes. Tube sockets are a given, I'm dumb but not that dumb.

If this is the first amp you are going to build (it usually is never just one , then I'd recommend the following:

1) drill out the power tube socket holes for octal sockets.

2) Get a pair of these: http://www.mojotone.com/amp-parts/TubeA ... et-adapter

3) Build the kit as stock with el84s and the the above plates to mount the 9 pin sockets.

4) After you have a working and debuged amp, then switch to 6v6s.

El84s like to see an OT primary load of around 4-6k. And 6v6s like 4-5k. So, The output transformer should be fine with either.

I'm guessing the thing you will most need to tweak is the bias circuit for the tubes. The el84s are probably cathode biased. Are you planning on doing the same thing with the 6v6s? Most likely you will need to adjust the value of the bias resistor as I doubt the two tube types will draw the same idle current or want to see the same bias voltage.

Tweaking the above will be easier to deal with after you have a working amplifier. Especially if you are doing it all for the first time.

Mike

[DG45]

Romberg ... no, not my first build. Would be my second full guitar amp build and I've fixed a couple. I've also built several amps, pre-amps and phonostages for home audio.

Helpful advice. Thanks Danman and Romberg.

I'll look over those layouts.

[neikeel]

I will start off by saying I have never made a 6V6 amp but variations on EL34, EL84, KT66, 6L6 etc.

The advice you have had so far is, IMO, spot on although you could use yellow jackets or similar instead.

The usual -139 OT (JMP50) is 3.4k primary and the -103 OT (8k) but as you are going low wattage the 18w type OT has 8k primary too.

Do you have a particular OT in mind?

[DG45]

I will start off by saying I have never made a 6V6 amp but variations on EL34, EL84, KT66, 6L6 etc.

The advice you have had so far is, IMO, spot on although you could use yellow jackets or similar instead.

The usual -139 OT (JMP50) is 3.4k primary and the -103 OT (8k) but as you are going low wattage the 18w type OT has 8k primary too.

Do you have a particular OT in mind?

No, nothing specific. Just browsing some kits and thinking out loud. I'd probably go with a lower cost kit, which probably means Classic Tone iron (which I'm fine with). But, I'm not 100% committed to the build at this point either. Some kit suppliers will allow you to swap out parts which is why I mentioned the transformers but it's becoming apparent that an 8K OT for el84 will also accommodate 6V6. So, that question appears to be answered.

[Haze13]

I have 2 OT's from the Musical Power Supplies the OT19PP and the OT10SE. 8k 22VA Marshall type transformer and the Single Ended 5-7k 12VA. I like them very much and I think for the price there is nothing better. They are USA maid too. So before you go with ClassicTone (Used it in 2204 build and it's a Killer OT) check them too. Just my 0.02$
With OT19PP you can try a EL34 in Triode mode too. 380 as a B+... Good for cleans, no NFB needed, 45mA for bias per tube and like 24 volts of p-p headroom. More than a El84 of 6V6 can give.