alstocko Posted November 11, 2012 Share Posted November 11, 2012 I was thinking about building my perfect bass head (oh no!) I want to make a amp with a valve preamp stage (several tubes please!) but power stage like a solid stage amp. By this I mean an amp like a Markbass TTE 500, but to my spec (dimensions really, weight would be nice to stay under 8kg like the TTE) Would this be possible, my electronics skills are alright, but I'm getting better rapidly (it helps having a granddad who made tube radios and is an electronics whizz, what doesn't help is that he's almost blind) Help would be greatly appreciated! Quote Link to comment Share on other sites More sharing options...
LukeFRC Posted November 12, 2012 Share Posted November 12, 2012 I'm sure it would be possible - not easy though at all .... and something like the Eden WT500 would almost hit your weight limit... or Genz Benz make a lightweight head with a valve preamp, and do a few other makes.... Quote Link to comment Share on other sites More sharing options...
Mr. Foxen Posted November 12, 2012 Share Posted November 12, 2012 I think there is some fun coupling a valve preamp with a class D power module, because of the sensitivity/impedance requirements. Call Matamp as they were working on that sort of thing, probably going to be easiest to get a valve pre you like and run it into a Peavey IPR or another lightweight head. Quote Link to comment Share on other sites More sharing options...
PlungerModerno Posted November 12, 2012 Share Posted November 12, 2012 If you are willing to read up, amazing things can be achieved by a hobbyist. If you check around for DIY tube preamp designs and theory of their design, and are willing to use a pre built power amp section you may be onto something. The high loads in a power section is, as I understand, far harder to work with and make a safe, reliable amp with. As I understand it good amplifiers that are light tend to be complex - I've read that many competing class D micro heads are using identical power amps, many made by [url="http://www.icepower.bang-olufsen.com/en/technology/power/"]Bang & Olufsen[/url] . The simple ones that a hobbyist would have a chance of doing well would be heavier, Class A/B designs - more like tube power amps. In short I'd look at a pre and power amp setup for simplicity, and safety first etc. as well. Those preamp voltages get high too, but nowhere near poweramp lethality as I understand it. Quote Link to comment Share on other sites More sharing options...
Beer of the Bass Posted November 12, 2012 Share Posted November 12, 2012 (edited) This is something I've also been looking into, but the funds to buy my parts are dependant on stuff shifting in the classifieds, so I may not go ahead with it at the moment. I have built and repaired a few bits of valve kit in the past, and I'm regularly gigging with a guitar amp I made, so building something for bass seems like a logical step for me. There are a few different suppliers of Class D amp modules and SMPS, like the Coldamp stuff used in this build thread; [url="http://basschat.co.uk/topic/20284-compact-power-amp"]http://basschat.co.u...mpact-power-amp[/url]. I was also looking at modules from Hypex. As Mr Foxen alludes to, the voltage swing at the output of a valve preamp is likely to be bigger than the input sensitivity of the amp module and there can also be large, damaging transients at switch-on so you would need to look at reducing the output and limiting transients to avoid damage to the module. This could be as simple as a resistive divider and a couple of diodes (to clamp the transients) on the preamp output, but would take some fiddling to optimise. Also many of the popular valve preamps like the Alembic F2B want to see an impedance of 1M ohm or so, but most amp modules have an input impedance of 10K to 100K ohms, so you would want either a cathode follower on the output of your preamp or some sort of buffer in between. If you're new to building valve amps, it might be wise to build and test your preamp first using an established design and layout, before laying out the cash for the amp modules. In terms of expense, it's unlikely to be a lot cheaper than just buying an amp, but you could end up with something rather classy if it's executed well. Edited November 12, 2012 by Beer of the Bass Quote Link to comment Share on other sites More sharing options...
bremen Posted November 12, 2012 Share Posted November 12, 2012 What Beer said. http://connexelectronic.com www.diyaudio.com I've already got the Connex SMPS and class-D modules and the bits (including ancient Mullard valves) for an Alembic-a-like pre. I will use a resistive divider, clamping diodes and a high input impedance opamp buffer between pre and active crossover, then the power stages. I have a schematic for the Ampeg SVP; it's do-able, and happily drives solid state power amps, but is very complicated compared to the Fender/Alembic and uses a multi-tapped inductor you'd have to wind yourself (unless you could find discrete inductors of the appropriate values). That Bang and Olufsen have a patent on Class D and are the only manufacturers of modules is an urban myth that was repeated on another thread. Quote Link to comment Share on other sites More sharing options...
Beer of the Bass Posted November 12, 2012 Share Posted November 12, 2012 The Connex modules look very well priced compared to the other suppliers. I'll be interested to see how you get on with them. Quote Link to comment Share on other sites More sharing options...
PlungerModerno Posted November 12, 2012 Share Posted November 12, 2012 (edited) [quote name='bremen' timestamp='1352720481' post='1866418'] What Beer said. [url="http://connexelectronic.com"]http://connexelectronic.com[/url] www.diyaudio.com I've already got the Connex SMPS and class-D modules and the bits (including ancient Mullard valves) for an Alembic-a-like pre. I will use a resistive divider, clamping diodes and a high input impedance opamp buffer between pre and active crossover, then the power stages. I have a schematic for the Ampeg SVP; it's do-able, and happily drives solid state power amps, but is very complicated compared to the Fender/Alembic and uses a multi-tapped inductor you'd have to wind yourself (unless you could find discrete inductors of the appropriate values). That Bang and Olufsen have a patent on Class D and are the only manufacturers of modules is an urban myth that was repeated on another thread. [/quote] FWIW I was unaware there was a suggestion that Bang and Olufsen had a patent on Class D - I just thought they had a tested and economic line that other manufacturers were using in their micro lines for convenience. I've never heard rumours of a monopoly on the technology. They probably have patents on some of their specific discoveries and the like but Class D is used by Power amp makers quite widely so a monopoly seems fanciful! I think the whole process presents a daunting task to a hobbyist starting from scratch. I think I've seen a schematic (or part of one) for an Ampeg preamp . . . it's not a straightforward design at all to me, effectively a lay person/ novice hobbyist. EDIT: By the above I mean to suggest simpler designs may prove more within the reach of a hobbyist to get working - without the need for trial and error and/or lots of troubleshooting. Edited November 12, 2012 by PlungerModerno Quote Link to comment Share on other sites More sharing options...
bremen Posted November 12, 2012 Share Posted November 12, 2012 [quote name='PlungerModerno' timestamp='1352744849' post='1866927'] FWIW I was unaware there was a suggestion that Bang and Olufsen had a patent on Class D - I just thought they had a tested and economic line that other manufacturers were using in their micro lines for convenience. I've never heard rumours of a monopoly on the technology. They probably have patents on some of their specific discoveries and the like but Class D is used by Power amp makers quite widely so a monopoly seems fanciful! I think the whole process presents a daunting task to a hobbyist starting from scratch. I think I've seen a schematic (or part of one) for an Ampeg preamp . . . it's not a straightforward design at all to me, effectively a lay person/ novice hobbyist. [/quote] I wasn't suggesting it was you who spread the rumour Quite possibly someone heard that they were selling OEM modules and concluded that they were patented. No matter. The SVP schematic is particularly hard to follow as it shows all the valves on a separate board...I've redrawn it to try and understand it and it's still pretty complex. Quote Link to comment Share on other sites More sharing options...
PlungerModerno Posted November 12, 2012 Share Posted November 12, 2012 [quote name='bremen' timestamp='1352745194' post='1866931'] I wasn't suggesting it was you who spread the rumour Quite possibly someone heard that they were selling OEM modules and concluded that they were patented. No matter. The SVP schematic is particularly hard to follow as it shows all the valves on a separate board...I've redrawn it to try and understand it and it's still pretty complex. [/quote] Cool cool. A lot of the specifics are well outside my level of experience, but I may change that in the near future. Quote Link to comment Share on other sites More sharing options...
3below Posted November 12, 2012 Share Posted November 12, 2012 Cost effectiveness may be a big issue. In my valve amp building moments I have found it cheaper to buy s/h kit e.g. Peavey 120 W combos and use the big iron - transformers, chassis etc from these. Also get RCA / GE valves thrown in. For your project the lightweight Class D power amo combined with own pre amp might be the way to go (as mentioned before). You could build own chassis /cabinet to house? Quote Link to comment Share on other sites More sharing options...
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