I just received a used CTM 100 from GC and the two ECC832 tubes do not glow after I followed the correct warm-up procedure. Are these two tubes used just for the DI or are they just bad tubes or might there be a bigger problem? I did remove and reseat the tubes.
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OFFICIAL ASHDOWN CLUB
- Thread starter Presto2112
- Start date
Some tubes have really dim heaters. Does the amp pass signal? If yes, both tubes are working.
The ECC832 tubes are V1 and V2. Both sections of V1 are in the signal path. Half of V2 is in the signal path and the other half drives the DI.
The schematic is not complete. A DC filament supply is shown, but it's not clear if it is used for all of the small signal tubes, or just some. There is also a 6.3V AC filament supply. This may serve only the output tubes, or it may serve some of the small signal tubes.
If the amp does not pass signal, you could try different tubes in V1 and V2. If you have a local GC, see if they will fix it or ask for a return.
The problem could be as simple as a loose connection, or some component may have failed.
Thank you for the informative and speedy reply! The amp does pass signal. The nearest GC is a five hour drive from where I live so I'm stoked that the amp isn't broken.
Be careful about opening up and touching things inside tube amps as they retain enough magic invisible stuff to give you a good jolt. That energy must be dissipated first.
Yes true.
As long as he is only removing the back panel to access the tubes (and isn't sticking anything in the tube pin holes,
) he'll be fine. 
Pulling the chassis out of cabinet, then you're getting into the potentially fatal voltages, even when unplugged.
Yes, thanks for expanding the thought more fully. I am not tech by any means.Yes true.
As long as he is only removing the back panel to access the tubes (and isn't sticking anything in the tube pin holes,
Pulling the chassis out of cabinet, then you're getting into the potentially fatal voltages, even when unplugged.
I watched a video of a professional tech once with an ABM and he showed that the two heatsinks in the back if touched carried a wallop as well because they were energized. Even when "off" there was some voltage. I think he said they should have been isolated IIRC. Anyway, he cautioned about pulling the chassis out as you mentioned and unintentionally touching things, and they aren't full tube heads. He even mentioned getting zapped doing something around the preamp tube. It was an EVO III and the design may have changed by now.
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Question for ABM users. I'm not sure if this is normal or not and need insight. When I run mine at home with an Ampeg 212 or a Fender 115 I can get some tube grind and break up more easily than when using my Ampeg Heritage 410 live. At home I still have to run the input at ~3:00 or more and the tube drive at ~2:00 to get some grit, depending on the bass. When using the other cab live or at rehearsal I basically need to max the input and go to 3:00 or more on the tube drive. Just seems the grit is much less noticable and achieved when not at home and at higher volumes (but nothing crazy). Is that typical or is it possible the tube (Eden 7025) is getting weak? It's well over 10ys old.
Changing cabs has no impact on how a preamp tube works.
Most likely this can be attributed to differences in the way the cabs are voiced. Also when playing live, you may need a more saturated sound because the distortion is being masked by the other sound sources.
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Thanks you for the comment. Maybe I should have worded that better, but I didn't mean to imply the cab would affect the preamp or tube. The 410 is definitely bigger sounding, and is in bigger rooms. Yet I'm noticing the lack of break up when no one else is playing as well. I think you are right about the voicing of the cabs may be the biggest part of it. I guess it's normal to have the input and tube drive set that high and just shows up differently given the cab and context. Thanks again for the insight.
Yeah, may be the room or the cab voicing. I know it comes down to individual drivers, but I have typically noticed that 12s and 15s for some reason seem to break up more noticeably. That or the power handling and the voicing combined?
I’ve had the same experience during live performances: the tube grind gets lost in the mix. For the music I play, 50-70s R&B and blues, this works perfectly. I also use a distortion pedal (Bass Juice), which similarly gets lost in the mix. I’m fine with this, but if you need a modern grind, consider getting a Darkglass.
Thanks for the reply. The 115 is the lowest rated cab, the other two have the same rating. I'm really leaning towards voicing, and just being in a bigger room that at home is really playing a significant part.
Yes, indeed. I am contemplating that. I have some pre tubes somewhere--unless they got tossed when we moved 3 yrs ago.....
I emailed Ashdown because I was considering tubes and some youtubers said to be careful because some amps use cathode followers and some tubes don't work well. Dave Green replied in less than 10 minutes and said there was way too much rubbish on the internet. Any 12ax7 tube would work fine with Ashdowns. He also recommended JJ ECC83s for it.
I haven't looked back to the specific question**, but as for the ECC83 and the equivalents to that tube would be a 12DW7 or 7247. The design of that tube is essentially the first half's triode is a 12AX7 type, while the second half's triode is a 12AU7 type. (Warning, do not conflate the JJ ECC832, with the JJ ECC823, on which the triode halves have been reversed for use in other applications.)
There are some NOS (New Old Stock) tubes available, but as far as I've seen only two current production tubes, the JJ ECC832 (made in the Slovak Republic) and the Electro Harmonix 12DW7/7247 (made in Russia).
**I read it just after it was published it, I just haven't went back to reread it today.
There are some NOS (New Old Stock) tubes available, but as far as I've seen only two current production tubes, the JJ ECC832 (made in the Slovak Republic) and the Electro Harmonix 12DW7/7247 (made in Russia).
**I read it just after it was published it, I just haven't went back to reread it today.
Thanks Jack. I was leaning towards a JJ ECC803. But that was just a thought. Currently is has an Eden 7025 in it. One source said there were hand picked Rubys. I can't confirm.
What would you say would be the advantage with the tube types you suggested as opposed to a ECC83s? You have me interested. (I prefer to avoid Russian made anything-not that they are not good.)
sorry it's so long.Direct subs for 12AX7 types include ECC803, ECC83, 7025, etc. There are also some obsolete designations like 6922 if you are interested in old stock. 12AX7 types have an amplification factor of 100 and bias the same in the circuit. A lower gain option that is considered a direct sub is 5751. A 5751 biases like a 12AX7 type, but has a gain factor of only about 70.
12AT7 has a gain factor of about 45 and 12AU7 has a gain factor of about 19. 12AT7 and 12AU7 bias different than 12AX7 types. 12AT7 wants to pull more current than 12AX7. 12AU7 wants to pull more current than 12AT7.
Ref: Preamp Tube Gain Factors And Substitution Chart – 300Guitars.com
12AT7 and 12AU7 can usually be safely plugged into a 12AX7. In many cases optimal performance will require switching a few components so the tube biases in the proper range.
So I don't generally consider 12AU7 a direct sub for 12AX7. This also goes for 12DW7 as it includes one 12AX7 section and one 12AU7 section. You can certainly try though.
If you want an Ashdown that runs 12DW7, consider CTM 100, CTM 200, or CTM 300. V1 and V2 are both 12DW7 types. AFAIK, the 12AU7 part of V1 is the input buffer. The 12AU7 part of V2 drives the DI, so it has no impact on the signal that runs through the amp.
The other common amps that run 12DW7 are vintage Ampegs. Channel one of vintage SVT runs three 12DW7 and the two channels are summed in a 6C4 which is essential 1/2 of a 12AU7. Channel 2 in a vintage SVT is comprised of a single 12AX7.
In the middle of the MTI era Ampeg converted 12DW7 circuits to 12AX7. In some cases they simply swapped in a 12AX7. In other circuits they replaced a few resistors.
Some people prefer lower gain tubes in amps like the Orange Terror Bass, Orange AD200B, and Aguilar DB359.
A common complaint with the Terror Bass and AD200B is the perception that the preamp has excessive gain. This makes it impossible to get a clean signal unless the Gain control is set fairly low. Using a lower gain tube makes it possible to turn the Gain control up higher before the onset of distortion, but it doesn't necessarily increase the amount of available clean headroom.
I have never played a Terror Bass. I own an AD200B, but I don't know what preamp tubes it's running. It sounds great so I have not bothered to open it up. I also own a DB359. This amp came to me with a 5751 in V2. I rolled tubes and preferred 12AX7 types. The experiment included rolling a variety of 5751 in both V1 and V2. To me 12AX7 types felt more lively, responsive, and musical. I selected JJ ECC803S for V2 and Mullard ECC83 for V1. I have tried 5751 in a couple of other amps, and so far I have always preferred a 12AX7 type.
The only circuit where I have preferred a different tube type is the reverb driver circuit of my Fender Showman Reverb. The original tube is 12AT7. A common swap is 12AU7. This mellows out the reverb a bit and also makes the control work better. With a 12AT7 the control in my amp has a dead spot where it would normally be adjusted (just barely on). With 12AU7 the control is adjusted above the dead spot.
If you want current production tubes, your only choices are JJ, Chinese, or Russian. Psvane seems to have taken over for Shuguang, which I believe may be gone forever. Reviews suggest Psvane may have some quality control issues in the MI series tubes. Various venders recently restocked Shuguang, but I believe they were essentially NOS tubes. I stocked up on 12AX7B from Ruby (Magic Parts). They are sold out now. AES still has stock: Invalid Link Removed
JJ offers three 12AX7 variants: ECC83S, ECC803S, E83CC. All three are offered in standard or gold pins.
For bass I generally prefer the ECC803S over ECC83S (but YMMV). I haven't tried E83CC, but I recently added some to my stash.
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Thank you very much for the detailed response. Really good information. Thanks for taking the time to do that.
Direct subs for 12AX7 types include ECC803, ECC83, 7025, etc. There are also some obsolete designations like 6922 if you are interested in old stock. 12AX7 types have an amplification factor of 100 and bias the same in the circuit. A lower gain option that is considered a direct sub is 5751. A 5751 biases like a 12AX7 type, but has a gain factor of only about 70.
12AT7 has a gain factor of about 45 and 12AU7 has a gain factor of about 19. 12AT7 and 12AU7 bias different than 12AX7 types. 12AT7 wants to pull more current than 12AX7. 12AU7 wants to pull more current than 12AT7.
Ref: Preamp Tube Gain Factors And Substitution Chart – 300Guitars.com
12AT7 and 12AU7 can usually be safely plugged into a 12AX7. In many cases optimal performance will require switching a few components so the tube biases in the proper range.
So I don't generally consider 12AU7 a direct sub for 12AX7. This also goes for 12DW7 as it includes one 12AX7 section and one 12AU7 section. You can certainly try though.
If you want an Ashdown that runs 12DW7, consider CTM 100, CTM 200, or CTM 300. V1 and V2 are both 12DW7 types. AFAIK, the 12AU7 part of V1 is the input buffer. The 12AU7 part of V2 drives the DI, so it has no impact on the signal that runs through the amp.
The other common amps that run 12DW7 are vintage Ampegs. Channel one of vintage SVT runs three 12DW7 and the two channels are summed in a 6C4 which is essential 1/2 of a 12AU7. Channel 2 in a vintage SVT is comprised of a single 12AX7.
In the middle of the MTI era Ampeg converted 12DW7 circuits to 12AX7. In some cases they simply swapped in a 12AX7. In other circuits they replaced a few resistors.
View attachment 6987716
Some people prefer lower gain tubes in amps like the Orange Terror Bass, Orange AD200B, and Aguilar DB359.
A common complaint with the Terror Bass and AD200B is the perception that the preamp has excessive gain. This makes it impossible to get a clean signal unless the Gain control is set fairly low. Using a lower gain tube makes it possible to turn the Gain control up higher before the onset of distortion, but it doesn't necessarily increase the amount of available clean headroom.
I have never played a Terror Bass. I own an AD200B, but I don't know what preamp tubes it's running. It sounds great so I have not bothered to open it up. I also own a DB359. This amp came to me with a 5751 in V2. I rolled tubes and preferred 12AX7 types. The experiment included rolling a variety of 5751 in both V1 and V2. To me 12AX7 types felt more lively, responsive, and musical. I selected JJ ECC803S for V2 and Mullard ECC83 for V1. I have tried 5751 in a couple of other amps, and so far I have always preferred a 12AX7 type.
The only circuit where I have preferred a different tube type is the reverb driver circuit of my Fender Showman Reverb. The original tube is 12AT7. A common swap is 12AU7. This mellows out the reverb a bit and also makes the control work better. With a 12AT7 the control in my amp has a dead spot where it would normally be adjusted (just barely on). With 12AU7 the control is adjusted above the dead spot.
If you want current production tubes, your only choices are JJ, Chinese, or Russian. Psvane seems to have taken over for Shuguang, which I believe may be gone forever. Reviews suggest Psvane may have some quality control issues in the MI series tubes. Various venders recently restocked Shuguang, but I believe they were essentially NOS tubes. I stocked up on 12AX7B from Ruby (Magic Parts). They are sold out now. AES still has stock: Invalid Link Removed
JJ offers three 12AX7 variants: ECC83S, ECC803S, E83CC. All three are offered in standard or gold pins.
For bass I generally prefer the ECC803S over ECC83S (but YMMV). I haven't tried E83CC, but I recently added some to my stash.
I'm am currently leaning towards the JJ ECC803S (long plate tubes). From what I'm gathering is should be a step up from the ECC83S. I like a beefy tone, but with nice three dimensional character tubs bring to the party vs SS, so JJ's seem like a good option. Glassy and raspy I am not interested in. How that will compare to the at least 10 yr old Eden 7025 is anyone's guess (which was supposedly warmer than the stock tube). I was considering a Mullard, but opinions on tone are varied from good bass, little bass. Good mids, mids that don't work in some amps.
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Since sound quality is subjective, people will disagree on whether a given tube sounds good or not.
ECC83S and ECC803S sound significantly different in some circuits. Which is better will depend on what you like.
Beef is often associated with strong lows or strong low mids. The ECC803S tends to be a bit lean down low, and may increase clarity and focus.
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