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6CB5 in triode PP?

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#21
Something like this maybe?

C0C4D460-5653-4021-9427-ADB3E240CB0C-6853-000005282E6C0B09.jpg


No values because I don't know if these are the tubes I will use yet. I added the gain stage on the input in case the first triode of the 6GF7A is not sufficient. Should those stages be cap coupled?

Thanks!

Blair
 
#23
I have little fingers around the house, so I'm going to try to keep the top caps under the hood. There is adequate venting above and below the bulbs in this old chassis from a Proceed preamp. The Ecdors will fit in here as well as long as I stick with the 60W outputs.

You think I will need a "whisper fan" to circulate around the output tubes?

Is there enough room to build an amp in the chassis without too much crowding? This is one of the reasons I want to use the 6GF7A as a single tube driver.

8EBDB0EA-C3B5-4B5F-B361-F14D00568F4C-9087-000006C382681EC1.jpg


Thanks!

Blair
 
#24
How much voltage swing is necessary to drive a pair of these 6CB5s? The 6GF7A is essentially a 13EM7 in a novar bottle. First section gain is 64 and second section is 5.4.

Will I need an additional gain section in front of these 6GF7As to get full drive voltage?

Thanks!

Blair
 
#25
Miles Prower said:
Forch, I saved all the original notes. Loadline (attached) Do keep in mind that this particular project never got built, so it's very much a preliminary design.

With an Rl= 635R/phase, you'll need ~2.54K (P-2-P) A 3K3, 60W Edcor should be just fine here, and the somewhat lighter plate load will drop the output a bit, and maybe the distortion as well (though it doesn't look like you're gonna get very much of that anyway).

Even though these H3 estimates are rough, and high-side errors, they do correlate somewhat to sonic performance. However, in the final analysis, you still have to spend some time listening to the open loop performance to see how that distortion sounds, and what's likely to be necessary to correct for those sonic defects. If the 6CB5 is like the 6BQ6, all it'll need is enough gNFB to take the "edge" off. There shouldn't be any of that "pentode nastiness".
Click to expand...


I may have found a pair of 1650T Hammonds which are 1.9K and 120W. Is that way too low for a pair of the 6CB5 tubes?

Thanks,

Blair
 
#27
Hi,

He did by stating that the optimal load would be 2.54K, but 3.3K would suffice at the cost of a little power. 1.9K is less difference to 2.54K than 3.3K, so I am asking if it would be an OK plate load to use 1.9K vs. 2.54K.

Will the 1.9K load cause excessive distortion?

So, yes, miles did answer the question.
 
#33
deicide67 said:
Hi,

He did by stating that the optimal load would be 2.54K, but 3.3K would suffice at the cost of a little power. 1.9K is less difference to 2.54K than 3.3K, so I am asking if it would be an OK plate load to use 1.9K vs. 2.54K.

Will the 1.9K load cause excessive distortion?

So, yes, miles did answer the question.
Click to expand...

as a rule of thumb, i always prioritise SQ over power ratings.....😀
in your case i will choose 3.3k, you can connect the 8 ohm speaker to the 16 ohm tap is you wanted more power...
 
#34
🙂 nope. They are fully passive and dynamic as almost any box speaker I've heard. The bass drivers are Acoustic Elegance IB15, midrange Peerless 830883, and the BG Neo3PDR with back cup removed for the tweeter.

I'm playing with the sweeps for fun because I cannot afford the tubes for my big amps yet😉
 
#35
AJT said:
as a rule of thumb, i always prioritise SQ over power ratings.....😀
in your case i will choose 3.3k, you can connect the 8 ohm speaker to the 16 ohm tap is you wanted more power...
Click to expand...

I will see about the pricing difference between the Edcors and the guy with the Hammonds.

We will see. I'm actually curious about the sweep tubes. I've never tinkered with them before.
 
#37
Don't feel shamed. I use a Emotiva 175W amp to drive my speakers right now. I'm looking for tubes that will nail my drivers with the same authority🙂

My other project is a PPP KT120 amp. That should do it!

As for the 6CB5, I'm thinking that maybe I should go with monoblocks using PPP since I have two power transformers.

Again, speculative on the hammond pricing.
 
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