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6SL7, 6L6x2 amp....

knockbill

knockbill

Lunatic Member
Think a Motorola THS1078A PS can power this amp? I'll be building two, for stereo, on the Moto chassis,,,

I have a Moto schematic for a HS-1198 chassis which is very similar to the THS1078A chassis I have,,, B+ to the OPT is 320V, and 300V to the 6V6 plates and screens... I can probably raise teh B+ some, by adjusting the resistors... The first 3 caps in the Moto filter are 40uF, only 20uF in this amp....

nijnkonijn.nl/machmat/schema/power/ppp/acro205b.gif

I'll try to find a copy of the Moto schem...

Regards,
John
 
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Thanks for the info,,,

I'd like to keep it all tube, the Moto has a rebuilt PS ,,,,but I see your point....

The Moto chassis uses a 5U4, ( trans puts out 315-0-315V)... It which seems inefficient compared to 5AR4...
I said changing caps, (as in the 6L6 schem), however, if 5AR4 will work, it uses the caps that are in the PS now...

Biggest question I have is, will the Moto PS power this amp x2... Or should I forget about using the 6L6GC's, and just build a Maggy clone, of some kind, with this chassis?

Regards,
John
 
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A little math tells me the stock output stages combined use 175ma, plus another 22ma to the 12ax7's and preamp. Call it 200ma in use on the B+ line. By the datasheet, you're looking at around 100ma per pair of 6L6's, so a stereo channel would use all you have. Add in the phase inverters and you're probably going to need at least 225ma of current available. You'd also want to add up the heater current used and see if its enough. Looks like you do have a second heater winding for the preamp, so that can be used for something too.

You might have more luck with a 6BQ5 amp. They'll use a little less current than 6L6's do.
 
Thanks Gadget,,,
I've been searching to see if I could find the specs on the Moto PT,,, kinda figured it would be a wash... This trans is perfect for a PP pair of 6V6's,, not enough nads for 6L6's, I guess... Its got a good 1/4" or more lams than the Maggy PT, so it should run pretty cool ....

I'll look into a nice 6V6 stereo amp... Lots of Maggy clones out there,,,
I like the sound of my Maggy 185 better than the HK I just went thru,(6BQ5)
Actually, I like the little 6AQ5 amp better than the HK!!!

Can't think of any other tubes to try with this PT, PS and chassis....

I'll build something out of the Moto....

Regards,
John
 
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6AQ5 is pretty much a 6V6 in a small package, so it makes sense that if you like one, you'd like the other.

An oddball cheap tube that might be fun to build around is a 6P15P. Its kind of like a de-rated 6BQ5, but I find them to be somewhat brighter than a 6bq5 is. You can get new quads of the things for like 15 bucks.
 
gadget73 said:
6AQ5 is pretty much a 6V6 in a small package, so it makes sense that if you like one, you'd like the other.

An oddball cheap tube that might be fun to build around is a 6P15P. Its kind of like a de-rated 6BQ5, but I find them to be somewhat brighter than a 6bq5 is. You can get new quads of the things for like 15 bucks.
Click to expand...

Here's a nice, simple 6BQ5 , modded Maggy amp, I was thinking of building last spring... Then I got the Mag 185, and the HK,,, This may sound better than the HK, its a lot cleaner, and would fit the Moto chassis easily...
http://wkinsler.com/radios/7tubeamp1.html ....

I'll look for schematics for 6P15P...
I wanted to try to build something with the tubes I just got,,,, I was thinking of 6F6 or 6K6, as I got a lot of them..... Less power than 6V6,,, but, its something different... Regardless, I'll need OPT's, just have one 8K from teh Moto...

Regards,
John
 
You won't find much of anything, but its very nearly a 6BQ5. It works pretty nicely in a Stromberg-Carlson ASR-433, which originally ran 6BQ5's but fairly conservatively. they actually minded the datasheet, unlike a lot of other manufacturers. Basically if you build a 6bq5 amp but keep the screen voltage down a bit you can run one. You may find something for SV83, which is apparently another designation for it.
 
gadget73 said:
You won't find much of anything, but its very nearly a 6BQ5. It works pretty nicely in a Stromberg-Carlson ASR-433, which originally ran 6BQ5's but fairly conservatively. they actually minded the datasheet, unlike a lot of other manufacturers. Basically if you build a 6bq5 amp but keep the screen voltage down a bit you can run one. You may find something for SV83, which is apparently another designation for it.
Click to expand...

Found a few schems for 6P15P,, I'd rather use vintage tubes, I have a bunch of 6V6's and 6SL7, 6SN7's... Really wanted to try out teh 6L6's, guess a mono amp is all the power available...I have all teh parts to build one channel... Maybe something else will pop up and help the cause...

Regards,
John
 
You could do a Williamson type with 6V6 tubes. That would involve a pair of 6SN7's and a pair of 6V6's per channel. Lots of options using those tube types depeding on how many you have and what transformers you want to run.
 
gadget73 said:
You could do a Williamson type with 6V6 tubes. That would involve a pair of 6SN7's and a pair of 6V6's per channel. Lots of options using those tube types depeding on how many you have and what transformers you want to run.
Click to expand...

Good idea,,, I have many 6SN7's and 6V6s,,, The OPT's must be found for what ever I build I only have teh one Moto bass channel PP trans...
Is it much different than a 6V6 Maggy amp?

I'm dug out of teh snow, spend teh PM, looking at Williamson schems,,, sure should be plenty...
Thanks
Regards,
John
 
don't really know. I've never owned a 6V6 Magnavox, or a 6V6 Williamson for that matter. The only Williamson I had ran 807 tubes, which are kind of like a 6L6GC in a fat coke bottle with a plate cap.
 
Well. I'd highly recommend one!!! I'll try to compare teh ckts... The Williamson amps are KT66, w/ 6J5 drivers... I guess I'm looking for a Williamson "type" amp...

I have some old coke bottle tubes w/plate caps,,, however, they probably need 6L6 Power transformers... I'll keep reading, and searching, some thing should pop up...

Regards,
John
 
Tentatively decided to build a slightly modified Maggy 175 amp with the Moto chassis,,, going to use 6SL7 drivers, as I have them, and they sound pretty good,,,, with 6AQ5's, anyways!!
The chassis is laid out pretty funky, that may be the biggest challenge, but I want to reuse it...

Since I have all the parts for the original plan, (PP 6L6 amp),,,I'll tack one channel together, just to see how it sounds....or, possibly, one channel of a Williamson, however, it seems to want pretty high end OPT's... I'm still entry level!!

Regards,
John
 
The original Williamson was intended as a hifi amp. The later variant with the ultralinear transformer also worked out well, but with nearly double the power of the triode-strapped design of the original. The transformers were quite big and are still not real cheap.
 
gadget73 said:
The original Williamson was intended as a hifi amp. The later variant with the ultralinear transformer also worked out well, but with nearly double the power of the triode-strapped design of the original. The transformers were quite big and are still not real cheap.
Click to expand...

That's what I found,,, The transformers are the biggest expense, don't think I'm in that league, yet... Maggy's are a good bang for the buck,,, and the transformers are cheaper!

Really appreciate your input... Learned a few things doing the research....

Regards,
John
 
you can probably come up with a couple console pull transformers for not much, or one of the various Edcor offerings.
 
gadget73 said:
you can probably come up with a couple console pull transformers for not much, or one of the various Edcor offerings.
Click to expand...

Sounds like a plan,,, Going to mock up one channel, and try the Moto 3rd channel OPT, to see if its capable of wide range,,,, I'm guessing the Moto bass channel wiring, is filtering the highs...
I had a lead on a pair of SE OPT's for teh 6AQ5 amp,, but it didn't pan out....

Will have to try some Edcors, at some point,,,

Regards,
John
 
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