6CG7 in my RB T10

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6CG7 in my RB T10
« on: 17 Mar 2023, 05:37 pm »
As I've posted previously, this preamp sounds so good pared with the SET 120.
But, I've been having a LOT of noisy / bad tube issues with the 6922's in my T10.  Starting off with EH's and there was a whining static sound from one of them...then it got new JJ's and they sounded really good! but ...one of them developed this weird chirping sound .  Yes it followed the tube when I switched them around in the preamp.  Then I purchased some used , but high testing (apparently) vintage Amperex BB tubes.  And, guess what, one of them is super noisy and microphonic.  The noise comes and goes but the preamp sounded so nice and sweet with them.  Recently I can't get the noise in that one channel to cease. 

After reading that, in general, 6922's are prone to being microphonic, I decided to purchase some matched 1960's NOS, but shopworn, RCA 6CG7 clear-tops from Brent Jesse which are considerably less expensive than 6922's...nos, vintage or reproduction.  I think I paid $24 ea.

I've been listening to them this morning for a few hours and I imagine they may settle in, but so far it's a very nice experience.
They present as maybe more relaxed than the 6922's   They do seem to show that tube-like sweetness and are maybe slightly less linear than the 6922's.  Not sure.  The bass is just ever so much softer (less articulate / palpable / fast) but not to its detriment.  Just trying to compare.   The actual low frequencies are there in spades.  The highs are also probably just slightly more recessed than the previous tubes, but still present and detailed.  The stereo image still psychedelically floats between my speakers just like with the previous tubes ...especially the Amperexs'.  Probably due to such a smart and simple circuit the RB10 has.

I believe I read in these pages somewhere that Frank said that while the 6CG7's are a straight swap in this circuit , they do run hotter or pull more current...which in the long run, could be a mark against them. 
But... for the price and the more mellow, liquid thing they are doing to my streamed music right now I'm pretty happy with the switch.

Is anyone else running 6CG7's in their T10 RB?


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Re: 6CG7 in my RB T10
« Reply #1 on: 22 Mar 2023, 09:07 pm »
Thanks for posting this. I was not aware 6CG7s were an option. I also found from doing a bit of searching in the AVA Circle that 6N1Ps will also work in addition to the standard 6DJ8s and 6922s. I just recently picked up a used T10 and may be trying some of these variants.


Re: 6CG7 in my RB T10
« Reply #2 on: 24 Mar 2023, 11:54 am »
I like the JJ ECC88 tubes in the T10 RB preamp.