Ashdown CTM 15 vs Ampeg pf20t

[Joseph Lavallo]

I wanted to throw this out for discussion. I'm considering these 2 amps. I will be primary using it with an eminence 2x10 cab. From watching all video available on line I prefer the sound of the Ashdown. Having been an ampeg user most of my life I am surprised about that. This will be used for practice and studio with an occasional gig. I have other amps and pre amps at home.

 

[ahbass2500]

What sound are you after?

I have the PF50T and the CTM15. PF50T does the Ampeg fliptop sound really well and stays clean to edge of breakup doing it. EQ section is more powerful on the PF50T than the CTM15. Noting that the PF20T and PF50T have some differences, but should sound fairly close to each other.

CTM15 does overdrive really well, but can be set clean. Gain knob on it is basically a dial in your level of grit knob. It has a nice sound even when set clean, but it does not shift much (other than level of grit) from its core sound. EQ section on the CTM15 is not very powerful. If you want to make significant shifts in EQ, then you need to change what you are feeding it. I typically add a touch more low end using a Broughton Studio One before the CTM15.

I run both heads on either a single Phil Jones Bass Compact 2 or a pair of Phil Jones Bass Compact 8 cabs. I find the CTM 15 needs a little help adding low end when it is paired with the Compact 2 (likely due to the cabinet voicing). I do not have to run low end heavy input when running the CTM15 on the Compact 8s.

 

[klattman]

I’ve used both and kept the ashdown. The ctm 15 breaks up fairly early but sounds good doing it. The ampeg is cleaner to start and has more eq shaping.

In terms of power there’s no meaningful difference. Through a 2x10 they will both sound good but won’t keep up with drums if you need that. Pick the one you like the sound of better.

The built in loads are nice so you can go straight to PA or desk and not need a speaker load like most tube amps. I use the Ashdown essentially as a preamp often or even practicing through headphones.

 

[Joseph Lavallo]

I tend to run some degree of OD on my sound. Definately not as dirty as the ctm 15 gets with the gain knob past 3 o'clock My live rig consists of a di 2112 and for convenience I will typically pair it with a Hartke Kb12 for some back line. We are on in ear monitors so I don't need to beat out a drummer.

My general impression from the limited video out there is the Ashdown will get dirty like Geezer Butler. It definately has a classic rock metal vibe to it.

The Ampeg seems very clean. Clickity/Clankity. I have an svt micra vr as a practice rig and sounds great with a preamp in front of it. But it definately needs more compression or drive.

As far as eq I have a collection of bases. Most have active eqs. The only passive bass I own is a P bass and that mid range honk tends to sound good through anything.

 

[ahbass2500]

I tend to run some degree of OD on my sound. Definately not as dirty as the ctm 15 gets with the gain knob past 3 o'clock My live rig consists of a di 2112 and for convenience I will typically pair it with a Hartke Kb12 for some back line. We are on in ear monitors so I don't need to beat out a drummer.

My general impression from the limited video out there is the Ashdown will get dirty like Geezer Butler. It definately has a classic rock metal vibe to it.

The Ampeg seems very clean. Clickity/Clankity. I have an svt micra vr as a practice rig and sounds great with a preamp in front of it. But it definately needs more compression or drive.

As far as eq I have a collection of bases. Most have active eqs. The only passive bass I own is a P bass and that mid range honk tends to sound good through anything.

Given this info, I agree with your original post... the CTM 15 is likely the one for you.

 

[Joseph Lavallo]

I was leaning that way. Even with the gain knob off on the CTM there's a nice amount saturation and grit.

Do you run a compressor with the CTM 15 or do the tubes do enough?

 

[ahbass2500]

I was leaning that way. Even with the gain knob off on the CTM there's a nice amount saturation and grit.

Do you run a compressor with the CTM 15 or do the tubes do enough?

I run a compressor. Broughton Omnicomp when it is hooked up to the PJB C2 cabinet. Effectrode LA-1A and/or Empress Bass Comp when it is hooked up to the PJB C8 cabinets.

 

[Joseph Lavallo]

I was leaning that way. Even with the gain knob off on the CTM there's a nice amount saturation and grit.

Do you run a compressor with the CTM 15 or do the tubes do enough

 

[DuluthDank]

I wish Ashdown would do a lower power tube head that didn't use a Fender tonestack, as they are just too limited for my tastes. The funny thing is a lot of their non-tube heads have the most versatile EQ's on the market. There must be some technical reason for this or something.

 

[induction]

CTM15 does overdrive really well

The ctm 15 breaks up fairly early but sounds good doing it

Interested in the CTM15 too. Is the overdrive/break-up coming from the EL84 power stage tubes, or is something pushing the ECC83 preamp tube to give the the overdrive? I have never played through an all tube head and am curious to experience the power stage tube break-up I have read so much about.

 

[ahbass2500]

Interested in the CTM15 too. Is the overdrive/break-up coming from the EL84 power stage tubes, or is something pushing the ECC83 preamp tube to give the the overdrive? I have never played through an all tube head and am curious to experience the power stage tube break-up I have read so much about.

Not an expert on how the CTM15 is set up, but from what I have read it has a solid state preamp that pushes the ECC83 for overdrive. You are ultimately trading off gain and volume knob to get breakup/total output dialed in, so you could push the output section. My experience is that the gain knob/preamp breakup sounds better on this particular head.

Several good demos out there if you want to get an idea of what it sounds like. Sweetwater has one on their product page and there are a few others on youtube.

 

[Joseph Lavallo]

Interesting question. The Ecc83 is the brittish version of a 12ax7. I have used amps with single 12ax7 in the pre amp like the Hartke h3500 and 2 notes. By themselves you don't get that much OD from them.

 

[Wasnex]

Interested in the CTM15 too. Is the overdrive/break-up coming from the EL84 power stage tubes, or is something pushing the ECC83 preamp tube to give the the overdrive?

There are different variants of the CTM15. The original had a solid state front end on the preamp. The consensus seemed to be it was better for guitar than bass. The lows were thin and it did not have enough headroom for bass.

I believe the Volume control was at the end of the preamp. So any drive you get from turning up the volume occurs in the phase inverter or output tubes. Not sure if you can force the preamp into drive with a clean boost or buy cranking the tone controls.

The current CTM15 has a Gain and Volume control. I haven't read anything about it.

 

[Joseph Lavallo]

When you compare the Ampeg pf20 to the ctm15 the ampeg has 2 12ax7 tubes in the pre amp section. The difference between the 2 amps are the power tubes. The el84 tubes in the Ashdown are likely the main reason why they sound so different.

 

[Wasnex]

The Ecc83 is the brittish version of a 12ax7

ECC83, ECC803, 12AX7, 7025, CV4004 etc are current variants of the tube type. There are additional (obsolete) designations as well, for example 6681 and 7729. AFAIK these all have an amplification factor of 100mu.

5751 is a current low gain variant. It biases very much like a 12AX7 but amplification factor is 70-80. Some people really like 5751. I have rolled them a few times and so far I have preferred the standard 100mu tubes.

 

[Wasnex]

The el84 tubes in the Ashdown are likely the main reason why they sound so different.

I believe it has more to do with designer choice and the way each amp is voiced.

 

[ahbass2500]

I believe it has more to do with designer choice and the way each amp is voiced.

Certainly huge difference in the EQ section setup. The Ampeg EQ significantly impacts the resulting output. The CTM15 might as well not have an EQ section (large swings in the settings has minimal impact on output).

 

[induction]

Good to know about the different variants of the CTM-15. Of my two favorite video demos of it: one is 10 years old and has white colored knobs, the other is 1 year old and the knobs look the amp picture currently on Ashdown's website.

I just emailed Ashdown to ask wether the overdrive is coming from the power stage tubes getting pushed, or whether something is pushing the preamp tube.

The other thing I am interested in is the concept of "a tube amp pushing back" and "3D sound qualities" which I have read and heard about in reviews/discussions of various all tube heads.

Any thoughts on these aspects of playing through the heads? General cork sniffing, maybe real but not possible with their wattage, or yes both provide a noticeable touch response and quality to the sound?

 

[Wasnex]

The other thing I am interested in is the concept of "a tube amp pushing back" and "3D sound qualities" which I have read and heard about in reviews/discussions of various all tube heads.

These are definitely common characteristics people associate with tube amps. Both of these qualities tend to manifest when amps are pushed near their clean power limits. Both the preamp and output section are responsible for the qualities, but IMHO the output section is usually most responsible.

The problem is people tend to talk about "tubey goodness" as if it's one quality that all tube amps have. The reality is "tubey" is comprised of a mix of multiple qualities that different models of amps possess in different ratios. So each model of tube amp has it's own personality and the personalities of different tube amps can vary over a wide range.

Another factor is taste varies from one person to the next. What I like and want may be very different from what you like and want.

In particular I think the PF20T and CTM15 are likely to be very different. You may perceive them both as tubey, but in different ways.

Part of my collection includes: Ashdown LB30 Mk1, LB30 Mk2, CTM30 Little Stubby, and Ampeg PF50T. They are all different. The LB30 Mk1 and CTM 30 Little Stubby are the most similar, but there are differences in their voicings, how they transition into overload, and how their controls respond to inputs. I would say the LB30 Mk2 is the least tubey.

 

[induction]

The problem is people tend to talk about "tubey goodness" as if it's one quality that all tube amps have. The reality is "tubey" is comprised of a mix of multiple qualities that different models of amps possess in different ratios. So each model of tube amp has it's own personality and the personalities of different tube amps can vary over a wide range.

This is very helpful. In my case, in addition to tone, I am interested in three qualities: drive from power tubes, "feeling the amp pushing back", and "3D sound". The amp is just for home practice so no volume needs. I was recently considering the same two amps as the OP and, based on the driven sound and the voicing, was leaning toward the Ashdown. Regarding drive, I have a Broughton P15 which sounds great though sometimes want more and different breakup than I can get from it Regarding drive and voicing, I have an Ampeg SCR DI sitting on a shelf not getting use, and a Broughton Scorpion I really like. Besides sound, I was hoping a little tube amp would let me experience "tubey goodness" qualities. It is good to learn that different tube amps exhibit the qualities differently: I can constrain my search and not try to find an amp with everything.