Peavey Delta Blues 210 and tube changes
I realise that this is probably a really common question but I'm looking for some advice on changing the tubes on my amp. I've recently bought a Peavey Delta Blues 210 and I'm finding I can't turn the volume up to more than about 2 or 3 without feeding back. The amp has 4 power tubes (EL84's) with a 12AX7 driver and two further 12AX7 pre-amp tubes.
I know virtually nothing about amps other than what I've learned from this site. Would you recommend swapping the 12AX7s for 12AU7s or something in between? Should I only swap the driver or do all the pre-amp tubes need to be changed? Is it just a question of trial and error, and is there any possibility of damaging the amp?
Any help and advice is much appreciated.
Many thanks Skip. This is my first all valve amp, my previous amp being a Marshall solid state not great for harp at all. I was starting to have trouble being heard over the rest of the band and I saw the Delta Blues going for a good price at my local store. It's the 2 x 10'' model rather than the 1 x 15'' and I'd read some other harp players who recommended it. I basically got carried away and bought it so now want to try and make it work for me.
I've ordered a couple of 12AU7's so hopefully they'll help.
Thanks for your advice.
I've just got back from my latest band rehearsal, the first with my new Peavey Delta Blues. I swapped the 12AX7s in positions 1 and 3 for 12AU7s and I'm pleased to report my feedback problems are now a thing of the past (unless I try to crank the volume up above 8 or 9).
To my ear, the amp sounded great and the rest of the band were pretty positive as well. I could even hear myself clearly (most of the time).
Thanks again for the advice.
Hello Adam- Well, ya done good! Be sure to experiment with the full range of the tone controls. Treble, middle, and bass controls often dramatically affect over-all volume. Save the deep reverb for home use in general.....too much reverb at a gig can reduce your amp's ability to "cut" through the band.
Skip Simmons
Hello Adam- Thanks for writing. Yes, that is a very common question and there is already a LOT of information online.
I will try to summarize my thoughts on the subject!
You can't hurt the amp at all by experimenting with preamp tubes, but leave the power tubes alone. Take some time to practice pulling the tubes in and out. It is VERY easy to bend the tube pins or mangle the socket in the amp, so don't rush.
There is no hard and fast rule about which position to try a lower-gain tube, but I would start with the socket that is closest to the input jack. You may be happy with just one tube swap, or you may like having more than one low-gain tube in the amp. The goal is to make the amp more usable for YOU.
Don't sweat the tonal differences between various brands of the same tube or go crazy spending big dough for vintage tubes. it's the lower gain that really makes the difference. By the way, nice used American-made 12AU7s are pretty easy to find.
Here is a list of the common subs and their "amplification factor" from high to low:
12AX7 - 100
12AT7 and most 5751s -70
12AY7 - 40
12AU7 -20
Of course, in the back of my mind I'm thinking that you could really use a smaller, more harp-friendly amp!
Skip Simmons