would anyone be intrested in this kind've thing?

[umph]

essentially i eventually want to go into building valve amps commercially (within the next year or so) i've finished the design of my 200watter and now i'm going to start work on a smaller amp.

The smaller amp is going to be a class A all valve amplifier around 5 - 10watts depending on what valves you put in it. It's going to be cathode biased so you can switch between 6v6 / 6l6 / el34 / 6ca7 / kt66 / kt88 or any other valves with the same pinout and primary impedence at will for different clean / overdrive sounds.

Heres the bit thats a bit out of the ordinary, it's going to have an inbuilt dummy load and post power amp line out so that you can run it directly into a power amp or straight into the desk for recording and i'm going to aim to keep the weight of the amp to under 20pounds / 9kg probably a bit lighter if i compramised a bit more on the output transformer. But essentially you'll be able to get great valve tone without the weight, well thats the plan anyway.

The preamp i havn't 100% decided on yet, but i was thinking of keeping it simple, gain, bass, treble and volume, but since this would be a bit of a studio amp would a more flexible preamp be ideal? If you have any input on this it would be greatly apprieciated!

Edited January 5, 2010 by umph

[Happy Jack]

Just pretending for a second that I'm an electrical/electronic ignoramus who thinks that electricity drips out of wall sockets:

1. The dummy load is to fool the valves into thinking that they're driving a speaker (even though they're not)?
2. The post-power amp line-out allows a tone-rich signal to be fed to a SS power amp?
3. There will be a valve pre-amp sitting in front of all this, presumably using ECC83's or whatever?

[ashevans09]

extremely interested would be my response...

[umph]

[quote name='Happy Jack' post='702003' date='Jan 5 2010, 07:21 PM']Just pretending for a second that I'm an electrical/electronic ignoramus who thinks that electricity drips out of wall sockets:

1. The dummy load is to fool the valves into thinking that they're driving a speaker (even though they're not)?
2. The post-power amp line-out allows a tone-rich signal to be fed to a SS power amp?
3. There will be a valve pre-amp sitting in front of all this, presumably using ECC83's or whatever?[/quote]
aye your correct about the dummy load and the post power amp line out, will be like the ones fender use except i'll add a balanced line out aswell.

For the preamp i'm not 100% just yet for the one i've been testing on the bench i've been using a 6sl7 (bit darker sounding than an ecc83 but essentially the same with lower gain) but i may use ecc83s for the proper thing just because they're easier to get.

For the preamp though, would you guys prefer it kept simple ie 4 knobs or would you like more direct control over the mids and other things?

[fatgoogle]

I would be for a really nice practice amp, how loud would a 5-10 watt valve bass amp be?

I would prefer a simple preamp myself, maybe gain, bass, mids, treble, master sort of like those fender tv combo's.
Would the ohms be 16,8,4 or similar?

[JTUK]

EQ is the thing. I like the idea of keeping it simple, uncluttered and if it sounds good, then fine..but I think you'd do well to add some comprehensive mid EQ, personally as just loud bass is just flooding the bass freqs. Gtrs might get away with less knobs, but I can't see bass working that way.

My preference on any amp is a parametric 4 way band, FWIW.. as per the SM400

[fatback]

[quote name='JTUK' post='702651' date='Jan 6 2010, 11:44 AM']EQ is the thing. I like the idea of keeping it simple, uncluttered and if it sounds good, then fine..but I think you'd do well to add some comprehensive mid EQ, personally as just loud bass is just flooding the bass freqs. Gtrs might get away with less knobs, but I can't see bass working that way.

My preference on any amp is a parametric 4 way band, FWIW.. as per the SM400[/quote]

Sounds tasty.

Fretless guys like a parametric mid to hit that 700 mwah.


fatback

[BassBod]

Im always interested in these sorts of designs, and I could use a low wattage valve head for a lot of my work. I've used an old Alembic F2B (twin channel fender/RCA tone section) and SWR stuff extensively - here are some thoughts.

The "fender" passive eq is great, but only once you really understand how it works. There are situations where you think some sort of active mid control would be great...but you don't actually need it. Turning the bass down can work wonders, but is very hard for a bassist to do!

I've never really got on with the SWR (Studio220/SM400) eq. I can make it work, but I always end up with the same settings...and I only seem to use the lowest band as a high pass filter to remove the rumbly ultra low stuff.

My ultimate small gig/recording set up is this:
Alembic preamp into SWR Mr Tone controls, into Radial passive DI, into power amp of SWR Studio 220 (low wattage, Mosfet). Its not loud, but it is a fantastic sounding combination. I just wish it could all be squashed into a small box....

[umph]

[quote name='fatgoogle' post='702620' date='Jan 6 2010, 11:23 AM']I would be for a really nice practice amp, how loud would a 5-10 watt valve bass amp be?

I would prefer a simple preamp myself, maybe gain, bass, mids, treble, master sort of like those fender tv combo's.
Would the ohms be 16,8,4 or similar?[/quote]
5-10 watts is more than enough for home, it might get a little loud if you have touchy neighbours and your cranking it, but it should be fine. It will have 4/8/16 ohm outputs on a selector.

As for the tone stack i'd prefer to keep it valve and a 4 band parametric eq is going to use alot of valves which will result in needing bigger power transformers etc. I'm not a huge fan of the fender tone stack either since you can't really avoid the mid scoop at all and bass and treble centre frequencys are to low and to high.

I'm guessing more flexibility would be more ideal then, i'll look into a few different active circuits with shiftable centre frequencys, so it'll still be bass / treble but you'll be able to choose the centre frequency to boost something like 70 / 100 / 300 hertz for the bass and 700 / 1000 / 1500 for the treble. How does that sound, it'll keep the valve count down and keep it fairly simple still.

you'll still be able to scoop the mids though by boosting the bass and treble or have a big mid boost by cutting them both.

[BassBod]

There are two things the F2B really needs, and would be nice additions to a simple valve preamp. A very good passive DI transformer/circuit and a simple "eq bypass" switch, so you compare the "tone-stack/no stack". Also maybe a low boost and high boost switch (Trace valve preamp?) but with a more gentle effect than most. The high boost on the F2B really is way too aggressive for modern speakers and tweeters - was probably fine with cabs in the 70s.