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New AD30r, tube substitutions good and bad

Posted: Thu May 02, 2019 7:28 am
by JJJ

Picked up an old ad30 reverb combo recently... had some adventures trying to get it working properly. Now that it is, I have found a preamp substitution I thought worked really well for anyone who feels their ad30 compresses too much, clips too easily or doesn't play nice with drive pedals.

The amp was a basket case when I got it. It worked, but it lacked volume and power. The previous owner said it had blown fuses a lot on him and he had got it serviced/repaired. Well, the 'repair' was a 5y3 rectifier tube, I assume to lower the voltage. I also found a 12au7 in the phase inverter and after a service from my own trusted tech, that they were putting the wrong fuses in it.

The tube substitutions, if anyone is wondering about them and googling away, effectively castrated the amplifier. No power, no dynamics. The tone was there, but the amp felt terrible. I am sure I can attribute this mostly to the 5y3, as Orange told me these "lower the voltage too much" and as far as I can read up on the net the only thing you really achieve is reliably killing 5y3 tubes. With a 5ar4 back in place and the correct fuse, the amp worked fine but the 12au7 seemed to choke back volume and harmonics still. I am not sure how suitable a substitution something like that is either, from a technical perspective. I would say this tube alone reduced the volume nearly half and sucked the punch right out. I think if you're looking to tame power in an amp like this there are much more effective ways like external attenuation or a v1 swap, as I will come to.

With the correct tubes types all back in place the thing needed to be wound up quite loud to achieve a decent gain tone. I noticed it could be pretty fizzy and depending on what you plugged in, much of the gain available was kinda useless. It definitely had the old school orange character I was after, but it seemed pretty hard to tame. I noticed that it was so ready to clip, that aside from a clean boost, it didn't like any sort of drive in front of it.

I have since replaced v1 with a 12ay7. The difference is like night and day. The amp has all of the dynamics and harmonics it had before but it seems less compressed and the top end is much less brittle. I would describe the amp now as "smooth". It accepts the dirtiest, heaviest fuzz and drive pedals I have now without complaint. I can crank the gain control on the amp without it becoming too fizzy compressed. Unlike what you read with other amps, this 12ay7 did not significantly reduce the gain, just the character of it. I would say the volume difference is not significant, rather the master volume control has a more linear range. This does not reduce power per se, but it means you can also use the amp at lower master volumes without it sounding awful.

The gain control is a lot more responsive and useful now. The cleans are cleaner, the dirt is smoother, it does everything I need to now and sounds just how I had intended when I bought it. This is an off the shelf electro harmonix 12ay7 - I cannot recommend these enough, if anyone is looking to tame an ad30 (or, ironically, run it a bit heavier with a fuzz or really dirty drive). The vendor I bought it from says they test quite consistently.

Also a general thumbs up for all ehx branded tubes. Aside from the reverb driver and sovvie 5ar4 it's all ehx branded new production tubes, and in my other amps I have had nothing but good experiences with them. I cannot say the same about plain old sovteks, JJs, or shuguangs and their related rebrandings.

Anyway, hope that helps someone. When I was googling around for pre substitutions myself, I found people trying 5751s, 12at7s, and other tubes but nothing specifically about the 12ay7 in this amplifier.

I would add - this tube has also made me like the vintage 30s that the amp came with. They were very spiky before, but with this swap the amp sounds incredible and they will be staying

Re: New AD30r, tube substitutions good and bad

Posted: Thu May 02, 2019 10:26 pm
by Les Paul Lover
Good to hear you got your amp sorted.

I take it it doesn't pop fuses anymore?

As for the harsh treble you mentioned with some valves, it depends more on the valve manufacturer than the valve type itself.

I've got an AD15 and an AD5. I run them both with the standard valve complement. I've tried JJ (Ok, but lack treble), Chinese (OK), Harma retro 7025 (I believe rebranded EH) which is pretty nice, though slightly noisier, and and ruby selected sovtek something which is my favourite in terms of new production valves.

I've tried RFT ECC83, very nice, fuller sound than any new stock, with more low end, and sweeter treble too. It breaks quite early and quite hard too.
Then I settled on a 60s welded plate Tungsram ECC83, which sounds fuller still, has incredibly sweet rich top end as well as lovely full low end. A remarkably full sounding and balanced valve, with lovely smooth break up.

As for power valves, I've got some Russia NOS 6P14P EV valves. Equivalent to EL84, but military grade, rated for 5000h use and sounds really lovely. Fuller bass, again sweeter top end. It really makes a lovely difference when cumulated to the Tungsram ECC83.

I think my rectifier us a JJ.
NOS rectifier are super hard to find.

Re: New AD30r, tube substitutions good and bad

Posted: Fri May 03, 2019 1:05 am
by JJJ
Nup. They had 500mA fuse in it but it wasn't marked slow blow. With the right fuse it's been fine. I am glad that appears to be a user error problem rather than an issue with the amp.

Yeah I happen to really like the sound of the chinese preamp tubes, I just can't seem to get my hands on any that will last. For some reason they short out or just die after a little while. I have one single shuguang 12ax7b that won't die but it's a horrible match for the orange - too much gain and high end. The ehx stuff always seems to do the job for me and never needs replacing. I did try some tung sol stuff from the same factory that sounded nice.

As far as the power tubes I just stick with the ehx el84s because I have had such good luck with them. All I need them to do is work, so I don't really want to roll dice on nos stuff only for one to perish early or something. Same goes for the recs... man those are expensive now. The cheapy sovteks I bought tested within like 2v of eachother in the amp and seem to work fine, so I will stick with those for now. I guess as long as you buy tested recs you should be okay.

I did put a jan tube in the reverb driver because it had the factory orange brand shuguang in there which looked... tired. So hopefully that will last as long as I do