NAD - Ashdown CTM15

[dannybuoy]

My Orange Terror Bass bit the dust recently, so I dropped it into PMT in Cambridge for them to send back to Orange for a repair. Whilst I was there I tried out a couple amps to use a replacement.

I almost went with the Ashdown MiBass 2.0, it had a great grindy sound very similar to a Catalinbread SFT pedal. But then I tried and fell in love with the little all tube CTM15 and ended taking one home!

I'm not currently in a band so a practice amp is all I need, and this fits the bill perfectly, perched aloft my pair of Ampeg SVT210AVs!

I've noticed a couple of issues though that I didn't notice when playing the demo unit in the shop:

- When I first turn it on there's quite a lot of crackling that disappears after 30 secs to a minute. It sounds like the crackling you get when turning a dodgy old potentiometer. It's not as bad today as it was yesterday so maybe this is improving the amp burns in?

- It's pretty noisy, not bad with the gain all the way off, but as soon as you nudge it up the hissing gets very loud.

- The sound with the gain all the way off is warm and bassy, I can crank the master volume and be happy the sound this. However, as soon as you increase the gain, it seems to really over-emphasise the treble. Clank city, which can only be dialled out by turning down the middle and treble controls on the amp or the tone control on my bass almost all the way down!

I've tried replacing the 12AX7 preamp tube with a Gold Lion reissue I had lying around, which seemed to make a small improvement to the sound but not to any of the issues listed above. Would the amp need re-biasing if I replaced the EL84s and if so is this something I could easily do myself with a multimeter?

I'm thinking of popping back to the shop to compare it to their demo unit again to see if these issues are real and not just down to the wiring in my house etc, but it's quite a drive away from here. If anyone has any advice here it would be much appreciated - anyone here with Ashdown CTM amps suffer from the same problems?

Edited December 31, 2013 by dannybuoy

[BruceBass3901]

The CTM 15 is said to be a little 'treble heavy' and clanky sounding. I have not tried the CTM 15 myself but I have the CTM 300 which can do trebley and clanky but also beautifully round and full sounding. The clanky sound may just be the nature of the CTM 15 though.

I believe walbassist got to play with the CTM 15 quite a lot so he may be an authority on this little amp

[franzbassist]

[quote name='BruceBass3901' timestamp='1388655029' post='2324334']
I believe walbassist got to play with the CTM 15 quite a lot so he may be an authority on this little amp
[/quote]

Hi guys

Here's my tuppence worth.

1. I didn't notice any crackling pots on my head.
2. Mine wasn't hissy at all with the gain knob fully ccw, but it did increase as you turned the gain up. Not so much to be unpleasant though.
3. I [i]loved[/i] the tone with the gain knbob fully ccw, but the moment it was turned up the tone seemed to change quite dramatically. As you say, it becomes much more upper-mid and treble orientated. I guess that's just the way it is.
4. Not sure about swapping out the EL84s for something else, certainly no idea about re-biasing. I tried a set of JJs in mine (12AX7 and 5751s in the pre, EL84s for the power) and they sounded good, but certainly didn't change the core tone to any extent.

Cheers

Gareth

[dan670844]

Sounds like a dodgy output valve to me a squealer, replacing The EL84 in a LB30 CTM15/30 is a chinch, just change them, the amps are cathode biased, with a clever little addition to the circuit. You Dont need matched valves. But take it back to the shop, why should you pay for replacement valves!
It a great little amp btw.

[RandomBass]

Re the re-biasing, this and the LB30 use cathode biasing which means they do not require any re-biasing when you change valves. You can almost consider this method like auto-sensing and it lets you plug-and-play different EL84 output valves without fear.

EDIT: dan670844 beat me to it on the cathode biasing bit - I must learn to type faster lol

Edited January 2, 2014 by RandomBass

[dannybuoy]

Just to confirm, I don't have crackly pots, it's just the amp sounds like crackly pots are being turned whilst it's warming up.

With gain and master maxed, the noise it creates is unbearably loud, even with no bass plugged in. Hardly any with gain set to minimum though, which is where it sounds best. I may well pop back to the shop tomorrow to try their one out again!

Edited January 2, 2014 by dannybuoy

[franzbassist]

[quote name='dannybuoy' timestamp='1388664223' post='2324454']
Just to confirm, I don't have crackly pots, it's just the amp sounds like crackly pots are being turned whilst it's warming up.

With gain and master maxed, the noise it creates is unbearably loud, even with no bass plugged in. Hardly any with gain set to minimum though, which is where it sounds best. I may well pop back to the shop tomorrow to try their one out again!
[/quote]

Definitely doesn't sound right. Take it back.

[Cosmo Valdemar]

[quote name='dannybuoy' timestamp='1388514311' post='2322969']
Clank city[/quote]

This is a place I would like to visit.
I'm surprised the MiBass gives good grind though, I always imagined they would be specimens of zing and cleanliness. Perhaps I should try one out.

[dan670844]

Thats defo one of the output valves, The valves arcing, you can see this if you turn the amp on in a dark room, you will see the dodgy EL lighting up.
Obviously only for a minute or so with a speaker cab contected.
I have a vast collection of Ashdown Valve amps haha! one thing they all have in common is they are silent. My CTM you can max everything and there is very little audible noise. They are made like hifi amps. Although made in china this one is no exception. Any audible his or hum will come from the amps surrounds like house wiring, dimmer switches and phones. Valve quality is paramount. I would try and get the shop to change the output valves. But you will ditch the supplied valves anyway, while ok the stock ruby are not the best sounding or the most robust. A pair of electro harmonix EL84 Mil specs are what you need thick glass and big spacers. EL84's are prone to mechanical damage when hot, need to let the amp cool for 5 mins before moving. Then they are fine, and in my opinion very reliable. I play bass for a living and exclusively now use a ctm300 and a lb30. In two years hard use neither of them, touch wood have missed a beat. I dont even carry a backup amp!!!! just a couple of fuses and valves..

Until the amp / Valves have burnt in and it has got decent power valves, rather than the broken ones! . You cant really judge the tone, this will take a good few hours. The preamp valves will change the tone considerably, if there is to much high end for you, consider changing the pre to jj' s the ecc83s is much deeper and darker sounding
cheers

Edited January 2, 2014 by dan670844

[dannybuoy]

Yeah, the MiBass was a very dirty amp with the gain past noon, but in a good way. Like I said, it instantly reminded me of the SFT which is my favorite drive pedal.

I'll return the amp either this afternoon or tomorrow morning depending on when the wife returns with the car! Definitely seeking a replacement CTM15 though as I'm very happy with the sound.

[disssa]

[quote name='walbassist' timestamp='1388657531' post='2324369']
1. I didn't notice any crackling pots on my head.
2. Mine wasn't hissy at all with the gain knob fully ccw, but it did increase as you turned the gain up. Not so much to be unpleasant though.
3. I [i]loved[/i] the tone with the gain knbob fully ccw, but the moment it was turned up the tone seemed to change quite dramatically. As you say, it becomes much more upper-mid and treble orientated. I guess that's just the way it is.
4. Not sure about swapping out the EL84s for something else, certainly no idea about re-biasing. I tried a set of JJs in mine (12AX7 and 5751s in the pre, EL84s for the power) and they sounded good, but certainly didn't change the core tone to any extent.[/quote]

Yepp, that is true. I found out, that the CTM15 dont like high output active basses. I play a Music Man Reflex with high output and the CTM15 with gain full ccw. With only a litte bit of gain the sound goes more middle and treble way...
With no gain and master, there is a little hum, but not dramatically.

On page 7 at the [url="http://ashdownmusic.com/files/product/file/user_manual_20130911060258_28463.pdf"]manual[/url] are the info, that it is a "Automatic BIAS for Plug&Play Easy Valve Replacement"... I dont know exactly, what the preamp valve do for a job.:



Is the only 12ax7 (on pic "V1") valve a phase inverter? It seemed, that the preamp is SS, not tube driven... Or what?

Edited January 2, 2014 by TraceAmp

[eude]

[quote name='dannybuoy' timestamp='1388673721' post='2324626']
Yeah, the MiBass was a very dirty amp with the gain past noon, but in a good way. Like I said, it instantly reminded me of the SFT which is my favorite drive pedal.[/quote]

This has got me very interested in the MiBass 2.0, although I might hang fire to see what they announce at NAMM first.
OK, back on topic

Eude

[RandomBass]

Nice clear upskirt shot there Interestingly there is an unused valve location on the PCB, between the two EL84s.

[Musicman20]

I've heard that Ashdown have quite a lot coming out for NAMM this year...who knows! I do quite like the fact they are releasing a lot of valve amps!

[eude]

[quote name='Musicman20' timestamp='1388680753' post='2324743']
I've heard that Ashdown have quite a lot coming out for NAMM this year...who knows! I do quite like the fact they are releasing a lot of valve amps!
[/quote]

I'd like to see some more 1x12 based cabs and more lightweight stuff personally, but regardless I like what they're doing at the moment, and it's nice that its all UK designed too

[BruceBass3901]

[quote name='eude' timestamp='1388679920' post='2324733']
This has got me very interested in the MiBass 2.0, although I might hang fire to see what they announce at NAMM first.
[/quote]

Likewise... Very interested to see what will appear at NAMM. The MiBass and the Drophead 15 are on my watch list for now

[VTypeV4]

Any joy? did they sort it for you?

[dannybuoy]

Going tomorrow!

[edstraker123]

Got a CTM-15 being delivered tomorrow so interested to hear how this problem pans out.

[Bigwan]

[quote name='TraceAmp' timestamp='1388678186' post='2324711']


Yepp, that is true. I found out, that the CTM15 dont like high output active basses. I play a Music Man Reflex with high output and the CTM15 with gain full ccw. With only a litte bit of gain the sound goes more middle and treble way...
With no gain and master, there is a little hum, but not dramatically.

On page 7 at the [url="http://ashdownmusic.com/files/product/file/user_manual_20130911060258_28463.pdf"]manual[/url] are the info, that it is a "Automatic BIAS for Plug&Play Easy Valve Replacement"... I dont know exactly, what the preamp valve do for a job.:



Is the only 12ax7 (on pic "V1") valve a phase inverter? It seemed, that the preamp is SS, not tube driven... Or what?


[/quote]

The opamps on the right of the first picture would certainly suggest that the ctm15 isn't all valve... That's a bit naughty, but I'll reserve judgement til I play one. Wouldn't put me off too much, especially with the drophead 15 looking so damn cute. More likely to be put off by the 10" speaker! Also confused/intrigued by the unused valve spot...

[RandomBass]

And there are at least four transistors in there, around the input stage area, near those ICs. Intriguing. Must find me a schematic....

[Beer of the Bass]

I'd expect some sort of SS stuff to drive the meter, but there just aren't enough preamp valves in there for a push-pull amp with a tone stack if it's going to have enough gain. Having said that, well designed SS stages aren't necessarily a deal-breaker. It could be single ended (i.e. no phase inverter needed), but then the 15 watt rating would be rather fanciful.
I wonder if the unused valve space on the board is there because it shares a board with one of the Hayden guitar amps and they just populate them differently for the two models? Certainly the tick boxes at the top of the picture would suggest this, since I think they have one built in the same size chassis.

[RandomBass]

[quote name='Beer of the Bass' timestamp='1388699362' post='2325142']
I'd expect some sort of SS stuff to drive the meter, but there just aren't enough preamp valves in there for a push-pull amp with a tone stack if it's going to have enough gain. Having said that, well designed SS stages aren't necessarily a deal-breaker. It could be single ended (i.e. no phase inverter needed), but then the 15 watt rating would be rather fanciful.
I wonder if the unused valve space on the board is there because it shares a board with one of the Hayden guitar amps and they just populate them differently for the two models? Certainly the tick boxes at the top of the picture would suggest this, since I think they have one built in the same size chassis.
[/quote]

Very good point about the Hayden connection, well spotted Sir. They have a 'Mofo' range - and that word can be clearly seen on the tickbox at the top of the picture.

EDIT: And having had a quick Google, the Hayden Mofo 15W clearly shows another valve between the two EL84s, which would explain the spare location in the pictures above. Also, the Mofo 15 can be switched to 2W mode - perhaps this additional valve does this, taking the EL84s out of circuit.

Edited January 2, 2014 by RandomBass

[disssa]

I got a really quick answer from the Ashdown Support:

[i]"The Preamp on the CTM15 is solid State driving a tube back end[/i]..."

[quote name='RandomBass' timestamp='1388701767' post='2325179']
EDIT: And having had a quick Google, the Hayden Mofo 15W clearly shows another valve between the two EL84s, which would explain the spare location in the pictures above. Also, the Mofo 15 can be switched to 2W mode - perhaps this additional valve does this, taking the EL84s out of circuit.
[/quote]

It is only a "Magic Eye Indicator"-Tube, maybe a EM84 between the two EL84:

Edited January 3, 2014 by TraceAmp

[Beer of the Bass]

Shame they didn't use the magic eye on the CTM15. As a gimmick, it would be a lot cooler than the Ashdown VU metre IMO!