Marvel Posted December 6, 2008 Share Posted December 6, 2008 Does anyone on here have an unused ART Matchbox or Rolls MB12b Promatch they aren't using at the moment and are willing to loan me for a couple of weeks? I want to try my SS power amp with the Merlin again, but the SS amp has too low an input impedance to work correctly. ART doesn't give enough tech specs on their website, but the Rolls looks like it would be ok. (rca has 100k input z, and my SS amp has balanced inputs which would match up great) I was thinking someone on here had tried one.... Either that or the schematic for a tube linestage with a low enough output z for me to build. I have some 12ax7 and vintage 6dj8s, 12au7s... Should only take a couple of tubes, but I can't scrounge up a schematic. Bruce Quote Link to comment Share on other sites More sharing options...
DrWho Posted December 6, 2008 Share Posted December 6, 2008 I could loan you a small Behringer mixer if you want. I'm not using it right now, but in the past I have used it to address the same issue you're dealing with. Quote Link to comment Share on other sites More sharing options...
Coytee Posted December 7, 2008 Share Posted December 7, 2008 I can if you still need one. I've got the Cleanbox (which is what I presume you refer to?) and have yanked it out of my system just sitting there as a dust ornamentation. I could probably get it boxed and shipped out on Monday. Quote Link to comment Share on other sites More sharing options...
Marvel Posted December 7, 2008 Author Share Posted December 7, 2008 Mike, they don't give the impedance for the line inputs on the Behringer. If it's 10k, it wouldn't help me. The Rolls has 100k, which would work. Richard, I found the schematic for the Rolls... I only need two ICs and a few other parts. I might have most the right parts to wire it up. Let me try that first. I know that ART doesn't list the impedance on their line ins either. Did the Cleanbox work ok? I need the high input impedance, or the bass really rolls off when I plug the Merlin into the SS with a low Z input.. Bruce Quote Link to comment Share on other sites More sharing options...
Coytee Posted December 7, 2008 Share Posted December 7, 2008 Did the Cleanbox work ok? I need the high input impedance, or the bass really rolls off when I plug the Merlin into the SS with a low Z input.. For my needs, simply converting RCA to XLR and then XLR back to RCA it worked fine. I don't know if that's what you need or if you have a different issue. If you come to a roadblock with your gatherings, lemme know and I'll get this out and you can try it. [] Quote Link to comment Share on other sites More sharing options...
michael hurd Posted December 7, 2008 Share Posted December 7, 2008 I know the ART cleanbox in stock form starts to roll off around 30 hz, there is a modification to replace a pair of capacitors to change the corner frequency. Quote Link to comment Share on other sites More sharing options...
Coytee Posted December 7, 2008 Share Posted December 7, 2008 Mike is right... also, for what it's worth, the one I have has had that modification done to it. Quote Link to comment Share on other sites More sharing options...
Marvel Posted December 7, 2008 Author Share Posted December 7, 2008 Thanks Richard... I have LS, so I don't need it that low anyway, right? [] I have all the docs to perform the cap swap in one of those, in case I end up buying one, but I am a little annoyed that they don't list many specs on the unit. I need it mostly for an impedance match... and the Rolls section I need should work great if I can get it built. They list all the values on their schematic, so I'll have a go at it. We'll see how quiet it turns out to be. My SS does have balanced inputs, to the match up should work out. I'll keep you informed. Bruce Quote Link to comment Share on other sites More sharing options...
DrWho Posted December 7, 2008 Share Posted December 7, 2008 Are you just gonna breadboard the circuit, or do you have the means to etch your own board or what? It would probably be way less work (and sound better) to just wire up a transformer to do your impedance matching... Quote Link to comment Share on other sites More sharing options...
mark1101 Posted December 8, 2008 Share Posted December 8, 2008 Bruce, I had a couple of Art Cleanboxes. They do the job of improving the impedance matching but they aren't so clean sounding. They should change the name. I did perform the cap upgrade myself and got it to where it sounded about as good as it could. In the end I got rid of the mismatched equipment so I wouldn't need the Cleanboxes. I'll predict you won't tolerate this box in your system. I would talk to DeanG, he had a Rolls and liked it a lot. Quote Link to comment Share on other sites More sharing options...
Marvel Posted December 8, 2008 Author Share Posted December 8, 2008 Mike, at about $70 a pop for a transformer, I can breadboard the section of the Rolls and try it. I can etch it if it does the trick. Mark, the Cleanbox doesn't interest me as much since they give you no specs at all. Sheeeesh... at least it is a place to start. Bruce Quote Link to comment Share on other sites More sharing options...
DrWho Posted December 8, 2008 Share Posted December 8, 2008 Well you definitely don't need to be spending $70 on the transformer. [] Heck, you could get a pair of Direct Boxes for that kind of money... Quote Link to comment Share on other sites More sharing options...
Marvel Posted December 9, 2008 Author Share Posted December 9, 2008 I was looking at some Jensens... you get what you pay for, you know. Bruce Quote Link to comment Share on other sites More sharing options...
PrestonTom Posted December 9, 2008 Share Posted December 9, 2008 I was looking at some Jensens... you get what you pay for, you know. Bruce Jensens are good transformers and you do get what you pay for. However, there are still deals out there for transformers that are pretty good. Edcor transformers are less than 1/5 the price of Jensens and CineMag are about 1/2 the price. -Tom Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.