100W Stoneham valve amp - small footprint, lighter weight

[lidl e]

i'm very interested in this...

 

will keep an eye out.

[JapanAxe]

3 hours ago, Stoneham said:

I've had an idea of changing the way the standby circuitry works - so while on standby, which removes high voltage to the power valves, there would still be power supplied to preamp and enable the DI out to function as well as rest of preamp.

Then, if a valve pops during a gig (which normally stops the amp from working at all)  you can at least get a DI signal out of it.  Very minimal cost or complexity to do this

Excellent!

[Merton]

4 hours ago, Stoneham said:

I've had an idea of changing the way the standby circuitry works - so while on standby, which removes high voltage to the power valves, there would still be power supplied to preamp and enable the DI out to function as well as rest of preamp.

Then, if a valve pops during a gig (which normally stops the amp from working at all)  you can at least get a DI signal out of it.  Very minimal cost or complexity to do this

Nice, smart idea!

[BassmanPaul]

9 hours ago, Stoneham said:

I've had an idea of changing the way the standby circuitry works - so while on standby, which removes high voltage to the power valves, there would still be power supplied to preamp and enable the DI out to function as well as rest of preamp.

Then, if a valve pops during a gig (which normally stops the amp from working at all)  you can at least get a DI signal out of it.  Very minimal cost or complexity to do this

The standby switch could switch out the output tube cathodes or even their screen supplies.  Switch on the centre tap of the OPT is yet another.

[Quilly]

23 hours ago, Stoneham said:

I've had an idea of changing the way the standby circuitry works - so while on standby, which removes high voltage to the power valves, there would still be power supplied to preamp and enable the DI out to function as well as rest of preamp.

Then, if a valve pops during a gig (which normally stops the amp from working at all)  you can at least get a DI signal out of it.  Very minimal cost or complexity to do this

I understand Ampeg have some sort of function for their 20 and 50W tube amps that allows them to be used without a load, dont ask me how they do that.    

[Matt P]

I'm really liking the idea of being able to use the amp as a preamp for recording or Di into a desk, would it be possible to have 2 switches not a single 3 position one? for me it would limit the chances of accidently switching it to fully on without a cab connected.

 

Matt

[JapanAxe]

3 hours ago, Quilly said:

I understand Ampeg have some sort of function for their 20 and 50W tube amps that allows them to be used without a load, dont ask me how they do that.    

I had the Ampeg PF-50T and there are some ceramic resistors inside to form a dummy load, plus a ventilation grille. I wouldn’t like to play it hard that way though.

[Gypsyfolk]

I think if this amp ever happens & manages to satisfy all the contributors it should be called the unicorn!!!

[Beer of the Bass]

On 06/04/2023 at 13:21, JapanAxe said:

I had the Ampeg PF-50T and there are some ceramic resistors inside to form a dummy load, plus a ventilation grille. I wouldn’t like to play it hard that way though.

 

Yep, the ratings of the resistors used add up to 45 watts, which feels a little marginal given the claimed 50 watt output!

[Quilly]

On 06/04/2023 at 12:51, Matt P said:

I'm really liking the idea of being able to use the amp as a preamp for recording or Di into a desk, would it be possible to have 2 switches not a single 3 position one? for me it would limit the chances of accidently switching it to fully on without a cab connected.

 

Matt

Maybe it’s possible to design some sort of failsafe that if the power section doesn’t see a load it shuts off and just leaves the preamp values on? I’m no engineer and I’ve no idea it that’s possible .

[Stoneham]

Hi everyone, after a very challenging year I'm now picking this project up again.  A prototype (built onto a YI200 chassis) will be ready in next few working days.  Been really struggling with the coffee maker attachment!

The easiest thing would be to combine 2 x 6550/KT88 with a high voltage supply, say 650V.  Most high power valve bass amps use this.  It works, but high voltage is a valve killer.  I've been working on increasing efficiency so I can use a regular 500V supply and prolong valve life.

I've got a bit further to go but have just obtained 90 watts from 2 x KT88 with a 450V power supply which I'm excited about.  This first prototype will put out about 90 watts, until I get a custom transformer set wound.

[JapanAxe]

2 minutes ago, Stoneham said:

Hi everyone, after a very challenging year I'm now picking this project up again.  A prototype (built onto a YI200 chassis) will be ready in next few working days.  Been really struggling with the coffee maker attachment!

The easiest thing would be to combine 2 x 6550/KT88 with a high voltage supply, say 650V.  Most high power valve bass amps use this.  It works, but high voltage is a valve killer.  I've been working on increasing efficiency so I can use a regular 500V supply and prolong valve life.

I've got a bit further to go but have just obtained 90 watts from 2 x KT88 with a 450V power supply which I'm excited about.  This first prototype will put out about 90 watts, until I get a custom transformer set wound.

I’m liking the sound of this!

[warwickhunt]

3 minutes ago, Stoneham said:

Hi everyone, after a very challenging year I'm now picking this project up again.  A prototype (built onto a YI200 chassis) will be ready in next few working days. 

 

Is the YI200 chassis quite a large chassis?  

[Stoneham]

27 minutes ago, warwickhunt said:

 

Is the YI200 chassis quite a large chassis?  

No it's 17.5" wide, happy I can get this down to 16" 

[Merton]

Very cool 😎 

[Merton]

FWIW, the original request I sent to Martin was same width as the Ashdown Little Bastard, which I believe is 15-3/4” wide, so 16” is bloody marvellous.

[Matt P]

exciting news! looking forward to hearing (and hopefuly testing out) the prototype.

 

Matt

[BassmanPaul]

It IS fun when a new project starts to come together.  I wish you good fortune with the amp.

 

[Quilly]

I think this will be a hit, a compact 100w tube amp for bass! . Kinda holy grail stuff. 

[dmccombe7]

10 hours ago, Quilly said:

I think this will be a hit, a compact 100w tube amp for bass! . Kinda holy grail stuff. 

Agree and the fact its built in UK is a huge bonus.

Looking forward to seeing and hearing the completed amp.

Dave

[Geek99]

Maybe I’m missing something- are there pictures ?

 

i ask as a total tube amp newbie 

Edited August 17, 2023 by Geek99

[Quilly]

16 minutes ago, Geek99 said:

Maybe I’m missing something- are there pictures ?

 

i ask as a total tube amp newbie 

Probably all you'll see at this point is a bunch of electronic components on a hacked down chassis as its still a WIP. But If you check out the old style Ashdown Little Bastard 30W head you'll get an idea of the final dimensions. To get a 100W valve head to this 16" or thereabouts footprint is a fair achievement. Usually a 100W valve head is a big beast.

[warwickhunt]

3 minutes ago, Quilly said:

Probably all you'll see at this point is a bunch of electronic components on a hacked down chassis as its still a WIP. But If you check out the old style Ashdown Little Bastard 30W head you'll get an idea of the final dimensions. To get a 100W valve head to this 16" or thereabouts footprint is a fair achievement. Usually a 100W valve head is a big beast.

 

Alternatively search on BC for Handbox WB100.

[Downunderwonder]

Iirc the Handbox uses toroidal transformers which keeps the weight down compared with the  trad iron core boat anchors. See also Traynor amps.

[Quilly]

1 hour ago, warwickhunt said:

 

Alternatively search on BC for Handbox WB100.

Still smaller than the WB120, in addition the manufacture of this is sporadic, but I think they're back up and running again. Great amp by all accounts, I think they're using 4 6L6 tubes. The project here is to use 2 * KT88s, similar to the Ashdown CTM100, but much tidier.