I'm lookimg for 6v6 PP amp schematics that uses 6.6k OT

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M Fowler
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Re: I'm lookimg for 6v6 PP amp schematics that uses 6.6k OT

Post by M Fowler »

Either Ampeg B15N uses 6k6 OT with 6L6's and the Standell 25L15.
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roberto
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Re: I'm lookimg for 6v6 PP amp schematics that uses 6.6k OT

Post by roberto »

kagliostro, you are referring to the user of the italian forum, I guess.

AFAIK he has around 250V B+ and 6k6 on the 6V6s, cathode grounged through a 220R//(some uF) in common.

He noticed low output power even with 30Vpp on the grids of the 6V6s.
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Kagliostro
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Re: I'm lookimg for 6v6 PP amp schematics that uses 6.6k OT

Post by Kagliostro »

Ciao Roberto

Yes, of course

I think the voltage is adequate for the 6aq5 tubes, but is low for the 6v6

and I asked about other circuits using 6v6 and 6.6k OT as to give a look to

the level of B+ used as to confirm my idea about a weak voltage

---

@ Stevem

The PT has a 225v-0-225v AC so no problem for the ez81 rectifier

@ M Fowler

Thanks but I was asking about 6v6 and 6.6k OT, not 6L6

anyway thanks

K
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jazbo8
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Re: I'm lookimg for 6v6 PP amp schematics that uses 6.6k OT

Post by jazbo8 »

Kagliostro wrote:Ciao Roberto
and I asked about other circuits using 6v6 and 6.6k OT as to give a look to
the level of B+ used as to confirm my idea about a weak voltage
The low B+ does not explain why the output power is so low. As you saw from the datasheet, with B+ = Eg2 = 250V and Ra-a = 10k, you can still get 10W from a pair of 6V6GT.
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Kagliostro
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Re: I'm lookimg for 6v6 PP amp schematics that uses 6.6k OT

Post by Kagliostro »

Yes, but with 10k load, not 6.6k load

So I mean there is a low B+ with respect to the OT impedance, or, if you look to this thing from one other perspective, there is a too low primary impedance of the OT for that B+

K
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jazbo8
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Re: I'm lookimg for 6v6 PP amp schematics that uses 6.6k OT

Post by jazbo8 »

Kagliostro wrote:Yes, but with 10k load, not 6.6k load

So I mean there is a low B+ with respect to the OT impedance, or, if you look to this thing from one other perspective, there is a too low primary impedance of the OT for that B+

K
Yes, you can get more power from a 10k OPT, but you still have not found out why the amp was only putting out 3.5W when it should be closer to 7W... looking at other schematics is not going to help you fix the problem that you have with the existing amp.
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Kagliostro
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Re: I'm lookimg for 6v6 PP amp schematics that uses 6.6k OT

Post by Kagliostro »

Right

K
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roberto
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Re: I'm lookimg for 6v6 PP amp schematics that uses 6.6k OT

Post by roberto »

With 250 V B+ you can have 250 Vpp maximum (hideally) on the primary winding.

With a 6600 to 8 Ohm transformer, you will get no more than 8,7 Vpp on the secondary, so 4,7 Wrms. I've suggested to connect a 16 Ohm speaker to the 8 Ohms tap.
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Kagliostro
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Re: I'm lookimg for 6v6 PP amp schematics that uses 6.6k OT

Post by Kagliostro »

And that seems a good choice

K
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jazbo8
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Re: I'm lookimg for 6v6 PP amp schematics that uses 6.6k OT

Post by jazbo8 »

roberto wrote:With 250 V B+ you can have 250 Vpp maximum (hideally) on the primary winding.
Don't you mean 500Vpp or 250Vp?
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roberto
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Re: I'm lookimg for 6v6 PP amp schematics that uses 6.6k OT

Post by roberto »

I'm selling a "p". Anyone interested please call 555-U-R-RIGHT.

Thanks.
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Structo
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Re: I'm lookimg for 6v6 PP amp schematics that uses 6.6k OT

Post by Structo »

Interesting tube choices on the schematics posted earlier.

The 7 pin pentode 5654 has a Mu of 2550

And the EF86 Mu is 5000

Does someone have a pile of 7 pin tubes? :D
Tom

Don't let that smoke out!
billyoung
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Re: I'm lookimg for 6v6 PP amp schematics that uses 6.6k OT

Post by billyoung »

Can anyone explain impedance and loadline when you use a VVR on B+.
how can it work properly with a fixed impedance. Everyone seems to hold to using plate voltage and load line to determine correct ot primary imedance ?

so when B+ is wildly variable what happens to all the formulaes for proper design ? I must be missing something ?
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martin manning
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Re: I'm lookimg for 6v6 PP amp schematics that uses 6.6k OT

Post by martin manning »

billyoung wrote:Can anyone explain impedance and loadline when you use a VVR on B+.
how can it work properly with a fixed impedance. Everyone seems to hold to using plate voltage and load line to determine correct ot primary imedance ?

so when B+ is wildly variable what happens to all the formulaes for proper design ? I must be missing something ?
The screen voltage is reduced along with the plate voltage, so the match to the load impedance stays roughly the same. Voltages scale together, and current scales like voltage to the 3/2 power (Child-Langmuir law).
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