Advice needed on new 6L6 ro 6V6 SE or SET build

[GloBug]

Hi everyone, I have:

- a pair of 5K:8ohm Telefunken OPT's
-574V CT 1.26A (5V@4A, 6.3V@4.6A) Power transformer. (Magnavox salvage, if hooked up as original AMP142 schematics yields around 270DC.(2 x 5Y3, 1HY choke)

I have already built myself a PPP 6V6 stereao amp and I love it. Now I want to try my hand at a Single Ended build, see what all the fuss is about.

I'm not looking for crazy power, my other amp is pretty decent in that department. I don't really want a flea amp either. My understanding is that if I run a 6V6 or 6L6 in class A or triode or tetrode brings the power output down as compared to pentode mode.

I do have efficient speakers, and can play around with the ohms, if I need to reflect a change back to the amp (4,6,8 ohm etc) I can change or purchase speakers for it down the road, although it would be nice if I could have 8ohm taps.

I also notice the 6L6 requires around 280V in that scenario. I thought this might work well with my power transformer. Also notice it can use my 5K opt's

I worry if I run a single 6V6 SE and start playing around with tetrode or triode that it might be too shy on power, thus the 6L6 appeals to me.

I am trying to learn to use Duncans PSUD, aside from that I should be able to play with my voltage a bit. I have 5U4, 5Y3 or solid state diodes. (Also have less common rectifiers in my box.) Could even use a 6volt if needed.

What do you guys think 6V6 or 6L6? Looking for quality. I think the 6V6 might be the nicer sounding tube, maybe just to quiet- thus the 6L6 comes into play. I'm thinking I need around a 5w amp although I'm willing to try a little less for quality's sake.

Once I get that sorted out I have some small signal tubes here like: 6GH8,6SN7,6CG7,12**7, 6C4 etc.

AL

 

[GloBug]

Maybe I asked a common question. I'm starting to get some good results with some deeper googling.

Something along the lines of RH807 or a Tubelab ish SE sound good?

 

[leadbelly]

Don't assume that your OPT's, which in the other thread you state are intended for 6BQ5 etc., can handle the extra DC current needed to get power out of a 6L6 or 807. Test this with a non-permanent setup first. If you want to play conservative then go for the 6V6's.

 

[GloBug]

OK thanks for the advice.
From the data sheets I see around 1.2 watts for class A triode SE connection. (6L6)

Do you think that setup would stress them too much?

My logic if it could handle a 6V6 at around 5w I should be OK with a low voltage 6L6.

I'm about 70/30 leaning towards the 6L6, just to build with a different tube and because I have a very beefy PT. Now I just remembered I have a PT from a 6V6 PP mono amp I may be able to use.

 

[leadbelly]

My logic if it could handle a 6V6 at around 5w I should be OK with a low voltage 6L6.

OK, well you're definately not getting the message, because if you bias the 6L6 for a lower plate voltage/higher cathode current operating point, you are making the situation worse and increasing the likelihood of OPT DC saturation. Maybe do a bit more reading up on the basics first.

 

[GloBug]

......and here comes the thread brake.

Well as I said I have various power supply options, up to about 425V.

Let's just relax, I'm just eyeballing the datasheets to get a game plan.
From some of the reading I have done it seems doable, no need for panic.

Do you have and schematics for an amp based on my first post?

 

[vinylkid58]

Why not try something like the RH84, just sub in the 6V6 and bias accordingly.

jeff

 

[aardvarkash10]

^ +1

 

[GloBug]

+3 votes for 6V6 then.

Actually that's were I started. lol Full circle.

So would be looking at around 2 watts with the RH84 I think?

I suppose it's worth trying maybe a 6SN7/6V6 RH84 on a board and see how it sounds.

I strayed away from it just due to so many "needs very efficient speakers" and " a little bass shy" comments. I guess the only way to find out is to try it.

I do understand by the nature of SE it's bass shy vs. PP etc. Thought I might have been able to avoid that using the 6L6, and just go ahead and build the chassis etc. and tinker with it later.

Seems apparent I will have to try some stuff on a board first.
Maybe I'll start a thread on it. Thanks!

AL

 

[aardvarkash10]

If you want to stay octal, 6SL7 and 6V6. The SL will give a better characteristic for the plate to grid feedback scheme

 

[GloBug]

It doesn't look like I have any of those.

It would be nice to stay octal, but I'm not that vein.

What else would be good for the signal tube, I have some NOS 6GH8,6SN7,6CG7,12A*7, 6C4 etc. I have lot's of other tube if you have any other suggestions, I might have it.

 

[brucetassin]

I have a 6SN7 / 6V6 SE posted on this site.
I also have a 6SL7 /6V6 SE.
Advance search on my name and look at the schematics.
Both sound very good but will not knock down walls or anger the neighbors.
I may be totally out of the park but are your Telefunken OPT's SE types?

 

[GloBug]

Yes they are SE opt's... Unless I really missed something! lol You can see a picture of them and tell me what you think here, it has the windings wrote on it http://www.diyaudio.com/forums/tubes-valves/200506-anybody-know-telefunken-se-transformer.html

I will check out your drawings, Thanks Bruce.

AL

 

[GloBug]

So I put the meter on two candidates for the PT.

If I use the beefier PT I could go up to a 5U4 rectifier if needed/wanted or parallel 5Y3's. Other then that it might be a waste of iron for such a small amp. I will however use it, if the voltage suits the project. I am going to attempt to model them in PSUD to see what kind of final voltages I can get between the two.

Here are the voltages measured with nothing attached @118vac.

"Bigger PT"
305-0-305. 65ohm secondaries.
Originally powered Magnavox AMP142 6V6 PPP

"Suitable PT"
327-0-327 220ohm secondaries.
Originally powered 12ax7/6av6/12AU76V6 PP mono amp with 5Y3.
It has a separate heater tap going to the first preamp tube. <Is this of much use?

Any winner with regards to the secondary ohms? I'm assuming less is better

 

[Wavebourn]

If you already heard 6V6 I would suggest you to forget about 6L6. Try something better than 6L6.

Edit: or you can experience for yourself how parallel feedback across curved tube can make it sound well. In such case you would need pentoge stage to drive it. 6AC7, for example.

 

[GloBug]

Ya 6V6 is the plan now. I should have implied 6V6 use between the two.
I figured the 30volt difference between the two could be useful to get a desired B+.

 

[aardvarkash10]

what signal level pentodes have you got?

 

[GloBug]

NOS 6GH8,6SN7,6CG7,12A*7, 6C4- these are what I have tested anyways.

Also on my list of untested used and NOS are 6CB6,6CS7,6GW8, 12BH7,12BY7,6BH6,6BC5 plus more, I'm just throwing numers at you.

 

[brucetassin]

Funny you should ask!

Just a few days ago, I rolled several Rec. tubes in my 6V6SE.
with a 5R4 the B+ was 259vdc.
with a 5Y3 the B+ was 277vdc.
with a 5U4 the B+ was 297vdc.
All conditions were the same except for the rec tube

 

[GloBug]

Did you find a preference?

My last amp I built with SS I would like to try tube rectifier, although I'm in the camp that rectification type is not that important, so long as it's built well.