DHA - New rackmount pre-amp

[DHA]

Hi all,

I am building a new 2U rack pre-amp for bass and I would grateful of a bit of market research before the design is set in stone.

It will have two separate channels, channel 1 will be a VT1-MK3-Bass but with tone controls, channel 2 will be a VT2-Dual-Custom-Bass but set to 1+2. Switching will be 1 or 2 and by-pass giving two separate channels 1 being low to mid gain and 2 being low to very high gain. It will also have a valve driven FX loop with blend (this is my "Bob the Blender") which will be switchable pre and post the overdrive channels. There will be a tuner output and footswitch mute. All the switching functions will be controlled with a footswitch as well as front panel overrides.

We are talking 5 or 6 valves here.

The plan would be to add my valve compressor design in as well once I am happy with the design. The Guitar version will have a valve Tremolo instead of the compressor.

So, would it be good to know if this is a useful set up and should I have 2 valve FX loops one pre and one post? What have I missed, what's nice to have and what's must have? Would an LED level meter be good?

thanks in advance for your help

Dave

[Kiwi]

Dave how will we set the levels of either channel so that loudness isn't affected when we change channel? Would it be worth putting in a crossover as well?

[DHA]

[quote name='Crazykiwi' post='14187' date='Jun 8 2007, 01:47 PM']Dave how will we set the levels of either channel so that loudness isn't affected when we change channel? Would it be worth putting in a crossover as well?[/quote]

Hi,

Each channel is a separate circuit with it's own boost and output level controls so that the level of each channel can be matched regardless of gain settings. There will be a master output level as well.

Being a simple guitarist I am not up to speed on crossovers, got anymore info?

Dave

[Kiwi]

[quote name='DHA' post='14205' date='Jun 8 2007, 02:13 PM']Hi,

Each channel is a separate circuit with it's own boost and output level controls so that the level of each channel can be matched regardless of gain settings. There will be a master output level as well.

Being a simple guitarist I am not up to speed on crossovers, got anymore info?

Dave[/quote]

Big discussion on it here Dave

[url="http://basschat.co.uk/index.php?showtopic=1197"]http://basschat.co.uk/index.php?showtopic=1197[/url]

Basically its about splitting the output signal up into frequency bands and sending each band to a set of speakers that are better optimised for handling that specific band efficiently.

[guyl]

A DI with a level control/mute and earth lift for me please! On the front if possible.

A decent eq would be handy too.

An LED meter would be useful, but more importantly flashing lights make any piece of rackmount gear look cool IMHO.

[bass_ferret]

+1 for the DI - I dont use it myself but lots do. Less convinced about the x-over, not a lot of people run true bi-amp.

[MoJ]

[quote name='DHA' post='14177' date='Jun 8 2007, 01:32 PM']Hi all,

I am building a new 2U rack pre-amp for bass and I would grateful of a bit of market research before the design is set in stone.

Dave[/quote]

WOOOOOO!!!!!

[quote name='Crazykiwi' post='14187' date='Jun 8 2007, 01:47 PM']Dave how will we set the levels of either channel so that loudness isn't affected when we change channel? Would it be worth putting in a crossover as well?[/quote]

+1 for that!

[quote name='bass_ferret' post='14947' date='Jun 10 2007, 09:47 AM']+1 for the DI - I dont use it myself but lots do. Less convinced about the x-over, not a lot of people run true bi-amp.[/quote]

And +1 for a DI out too.
I would say maybe not a crossover, but how about stereo/dual outputs, to at least allow a crossover to be used, or to bypass the 'high' part of the crossover for a full range and low pass arrangement. It would allow for a very flexible set up whatever though.

I definitley like the idea of each channel having its own output so that levels could be matched.
How about a blend control (not just the fx loop blender) to allow blending of the clean and overdrive channels? Would definitley like that option.

How much roughly would soemthing like this go for Dave?
Thanks
Andy

[MoJ]

[quote name='guyl' post='14912' date='Jun 10 2007, 01:21 AM']....but more importantly flashing lights make any piece of rackmount gear look cool IMHO....[/quote]

You do know Dave puts little 'windows' in the front of his designs so you can see some of the valves, and are backlit with BLUE led's?

Very cool indeed, especially on a darkly lit stage! Guess you can never have enough lighty bits though

Andy

[DHA]

[quote name='MoJ' post='14950' date='Jun 10 2007, 09:56 AM']WOOOOOO!!!!!
+1 for that!
And +1 for a DI out too.
I would say maybe not a crossover, but how about stereo/dual outputs, to at least allow a crossover to be used, or to bypass the 'high' part of the crossover for a full range and low pass arrangement. It would allow for a very flexible set up whatever though.

I definitley like the idea of each channel having its own output so that levels could be matched.
How about a blend control (not just the fx loop blender) to allow blending of the clean and overdrive channels? Would definitley like that option.

How much roughly would soemthing like this go for Dave?
Thanks
Andy[/quote]

Hi Andy,

I think just a splitter and extra op-amp should give a line-level DI. Does anyone know what the impedance and level of a DI out is?

Blending one channel with the other is interesting

LED VU meter is in. Looking at crossovers. Stereo output could be an option and might even cover the DI issue as well.

Cost would depend a bit on what we end up with and it may even be two or three models. But aiming to keep it around £500-£600. I know it's a lot but this will take about 2 weeks to make and have well over £250 in parts.

Dave

[MoJ]

[quote name='DHA' post='14969' date='Jun 10 2007, 10:33 AM']Hi Andy,

I think just a splitter and extra op-amp should give a line-level DI. Does anyone know what the impedance and level of a DI out is?

Blending one channel with the other is interesting

LED VU meter is in. Looking at crossovers. Stereo output could be an option and might even cover the DI issue as well.

Cost would depend a bit on what we end up with and it may even be two or three models. But aiming to keep it around £500-£600. I know it's a lot but this will take about 2 weeks to make and have well over £250 in parts.

Dave[/quote]

Well, its not [i]that[/i] much when you consider that the only two Ampeg preamps being made at the moment are coming in at around that price. Add in to the equation that you're giving both channels tone controls (independant of each other I assume?) which Ive only seen on say the Ampeg BSP, and you maybe adding a compressor in there too, plus a footswitch to control all this (which I dont think are included wiht the Ampeg's but could be wrong) and its about right.
Would taking out the silicon and germanium diodes and associated controls, and the colour controls do much to the price? I know I for one don't use those on my VT2, but cant speak for anyone else.

Out of interest, where are you considering putting the compressor in the chain?

As for the DI impedance, just looking in my trusty TE manual, which just so so happens to be near my PC, the spec at he back states the impedance as 600 ohms or greater. Wouldnt know if thats standard though. Not sure if DI out is overly essential, but if you did fit it Id make it post EQ if there is the option.

Thanks
Andy

[Stewart]

Hi Dave,

[quote name='DHA' post='14969' date='Jun 10 2007, 10:33 AM']...
I think just a splitter and extra op-amp should give a line-level DI. Does anyone know what the impedance and level of a DI out is?[/quote]

It should be capable of feeding 600 ohm at 0dB.
There's a nice transformerless circuit here (figure 3):

[url="http://sound.westhost.com/project87.htm"]http://sound.westhost.com/project87.htm[/url]

Cheers,
Stewart

[DHA]

[quote name='Stewart' post='14977' date='Jun 10 2007, 11:02 AM']Hi Dave,
It should be capable of feeding 600 ohm at 0dB.
There's a nice transformerless circuit here (figure 3):

[url="http://sound.westhost.com/project87.htm"]http://sound.westhost.com/project87.htm[/url]

Cheers,
Stewart[/quote]

Very useful, thanks Stewart.

That's the balanced DI out sorted then!

Dave

[DHA]

[quote name='MoJ' post='14973' date='Jun 10 2007, 10:47 AM']Well, its not [i]that[/i] much when you consider that the only two Ampeg preamps being made at the moment are coming in at around that price. Add in to the equation that you're giving both channels tone controls (independant of each other I assume?) which Ive only seen on say the Ampeg BSP, and you maybe adding a compressor in there too, plus a footswitch to control all this (which I dont think are included wiht the Ampeg's but could be wrong) and its about right.
Would taking out the silicon and germanium diodes and associated controls, and the colour controls do much to the price? I know I for one don't use those on my VT2, but cant speak for anyone else.

Out of interest, where are you considering putting the compressor in the chain?

As for the DI impedance, just looking in my trusty TE manual, which just so so happens to be near my PC, the spec at he back states the impedance as 600 ohms or greater. Wouldnt know if thats standard though. Not sure if DI out is overly essential, but if you did fit it Id make it post EQ if there is the option.

Thanks
Andy[/quote]

Hi Andy,

There will be a separate passive EQ on each channel. I may consider a different version with active EQ but I want to do this one first so that the signal path is pure and without solid state.

I was going to leave the clipping and colour controls on each channel as they are not big cost drivers.

Dave

[MoJ]

[quote name='DHA' post='15008' date='Jun 10 2007, 12:23 PM']Hi Andy,

There will be a separate passive EQ on each channel. I may consider a different version with active EQ but I want to do this one first so that the signal path is pure and without solid state.

I was going to leave the clipping and colour controls on each channel as they are not big cost drivers.

Dave[/quote]

No, passive is fine Dave.
Seperate EQ per channel would be awesome. Would allow to have two separate clean channels with different tones, or to re-EQ overdrive.

Dave, I think this is some of the greatest news Ive heard, this new rackmount. Now that Im considering seperates, Im easliy tempted by the current VT2RM, but to have all these features would be great.

Personally, I think the most essential thing is independant channel EQ, and maybe the fx loop and compressor, but those 2 I could easily live without.

Cant wait to hear if this goes into action Dave!

Thanks
Andy

[Dood]

I know there's a minority of stereo users out there, but if there was always one thing that made my choice of preamp even harder, was trying to find one with a stereo FX loop with a DI out (post loop) for each channel. The Warwick Quadruplet has one, as does the EBS classic, I think. but none others come to mind at the moment.

I suspect not many people will want it or need it to warrant the cost addition.. but it'd be nice! (I have actually half decided to start building a preamp myself, including all the things I like - I have the rack case and most of the components too - but I'm lazy.. and it has always just been 'half' a thought! lol lol)

[DHA]

[quote name='dood' post='15027' date='Jun 10 2007, 01:06 PM']I know there's a minority of stereo users out there, but if there was always one thing that made my choice of preamp even harder, was trying to find one with a stereo FX loop with a DI out (post loop) for each channel. The Warwick Quadruplet has one, as does the EBS classic, I think. but none others come to mind at the moment.

I suspect not many people will want it or need it to warrant the cost addition.. but it'd be nice! (I have actually half decided to start building a preamp myself, including all the things I like - I have the rack case and most of the components too - but I'm lazy.. and it has always just been 'half' a thought! lol lol)[/quote]

Hi,

As all my stuff is handbuilt it's really not a problem to pick and mix the bits people want, so if there is a request for a stereo FX loop and stereo DI then you got it. I use a stereo FX return and stereo output stage on my own amp. Once you have tried stereo chorus and stereo echo there is no going back.

Dave

[Dood]

I was reading (i think on this forum) a post a while back where someone asked "why don't manufacturers build custom amps in the same way that luthiers do with Guitars?"

I'll skip the answer, but I just wanted to say that I think you have hit upon an excellent idea, making 'modular' units that can be built to spec. I have a bit of a review to write with respoect to how my rig has changed totally in the last few days and the ability to custom build opens a few doors. Interestingly, There are so many people building basses and cabinets, Amps and "the bits in between" appear not to be 'fussed with' as much. I think this is something I want to investigate further as I have zero woodwork skills but have an unhealthy interest in electronics!

[Kiwi]

[quote name='DHA' post='15033' date='Jun 10 2007, 01:18 PM']Once you have tried stereo chorus and stereo echo there is no going back.[/quote]

I think you're preaching to some of the converted on that one, Dave. I usually get an engineer telling me that the lower frequencies are going to sound muddy if the bass is in stereo and there's no way the average desk-monkey would ever take three DI from a bass amp (stereo highs and mono lows).

Easiest way is to compete with the PA like Dood's system

[Dood]

oh, I'd love to hear that compressor too!

[MoJ]

[quote name='DHA' post='15033' date='Jun 10 2007, 01:18 PM']Hi,

As all my stuff is handbuilt it's really not a problem to pick and mix the bits people want, so if there is a request for a stereo FX loop and stereo DI then you got it. I use a stereo FX return and stereo output stage on my own amp. Once you have tried stereo chorus and stereo echo there is no going back.

Dave[/quote]

Dave,
I know you mentioned earlyier that you may possibley do a couple of units, but would it be worth doing a 'core' unit of say just the 2 independant channels, and then a list of optional extras that could be added like the compressor or blender? Obviously you couldnt have too many options as it would get silly and you only have so many hours in the day you can dedicate to your work.

Not sure if that helps or is possible?
Andy

[MoJ]

Dammit! Dood got there 1st!
Still, looks like its an idea that could catch on..
Andy

[Dood]

[quote name='Crazykiwi' post='15041' date='Jun 10 2007, 01:37 PM']I think you're preaching to some of the converted on that one, Dave. I usually get an engineer telling me that the lower frequencies are going to sound muddy if the bass is in stereo and there's no way the average desk-monkey would ever take three DI from a bass amp (stereo highs and mono lows).[/quote]


lol lol!! welcome to my world too!! I have been using a stereo DI box. I befriend the PA guy (always a good move) and tell him I'll be supplying him with a stereo signal. The looks I get back speak a thousand words!

(actually - with all this talk of stereo, I'm afraid to say that, temporarily at least I will be going 'mono' in my back line - the FOH will still get stereo where possible)

[Kiwi]

Well, to give the desk-monkeys some credit, the bass does sound a little cleaner on the whole but lacks the enveloping, immersional experience when I break out the fretless and stereo chorus.

[Dood]

[quote name='Crazykiwi' post='15050' date='Jun 10 2007, 01:49 PM']Well, to give the desk-monkeys some credit, the bass does sound a little cleaner on the whole but lacks the enveloping, immersional experience when I break out the fretless and stereo chorus.[/quote]


Yeh, that Pentabuzz did ooze a certain 3D aural pleasure in stereo!!

[Kiwi]

[quote name='dood' post='15052' date='Jun 10 2007, 01:54 PM']Yeh, that Pentabuzz did ooze a certain 3D aural pleasure in stereo!![/quote]

And it sounds better through my GK amps mate Loads of sparkle! I'll bring both of them to the next bash.