mulveling Posted January 21, 2009 Report Share Posted January 21, 2009 I've got an old Headamp Gilmore Reference (single-ended) on the way. I believe this unit was later modified to a gain of 1, which should be a good preamp gain. But, it doesn't have pre outs, just a 2nd headphone out. In these older Headamps, is there any circuitry difference between the pre out and headphone out, or does it merely boil down to the physical differences in connectors? Any other reason why I shouldn't try this as a preamp with a Y cable/adaptor? The V2 I recently picked up is a real performance killer, as both preamp and headphone amp, for the $200 I paid. Super-nice match to the L3000 w/ Duet, and to the HD650 or L3000 with vinyl Quote Link to comment Share on other sites More sharing options...
Pars Posted January 21, 2009 Report Share Posted January 21, 2009 The Headamp V2 board I have just has a spot for a series resistor per channel (10 ohms) for the pre out spot on it. Otherwise, no difference. I would doubt that resistor is critical either. If yours is built on a V2 board, there should be a spot on the back left edge of the board for this. Quote Link to comment Share on other sites More sharing options...
mulveling Posted January 21, 2009 Author Report Share Posted January 21, 2009 The Headamp V2 board I have just has a spot for a series resistor per channel (10 ohms) for the pre out spot on it. Otherwise, no difference. I would doubt that resistor is critical either. If yours is built on a V2 board, there should be a spot on the back left edge of the board for this. Cool, thanks for the info. It would be easy enough, even for me, to hack a lil RCA->RCA box that has a 10ohm resistor in series, if in fact that is necessary. What I wonder is whether 10ohms was chosen to work well over common load impedances, and whether there might be a more optimal value choice if you know your power amp's specific value. Is there any conventional wisdom on a best ratio of input impedance/output impedance for a preamp out? I don't have any clue when it comes to impedance matching bewteen pre/power, other than that the ratio should be high. Quote Link to comment Share on other sites More sharing options...
justin Posted January 21, 2009 Report Share Posted January 21, 2009 i would use larger than 10 ohms, something like 50 or 100 Quote Link to comment Share on other sites More sharing options...
grawk Posted January 21, 2009 Report Share Posted January 21, 2009 yah, but what do you know, this is about a gilmore amp Quote Link to comment Share on other sites More sharing options...
mulveling Posted January 21, 2009 Author Report Share Posted January 21, 2009 Well, it's hard to argue with Justin on this Many thanks, I'll try 100ohms first since it turns out my amps are on the rather high side for input impedance (200K McIntosh and 500K Eico). Quote Link to comment Share on other sites More sharing options...
Pars Posted January 21, 2009 Report Share Posted January 21, 2009 i would use larger than 10 ohms, something like 50 or 100 Just out of curiosity, what is the purpose of these resistors? Impedance? Quote Link to comment Share on other sites More sharing options...
HeadphoneAddict Posted January 22, 2009 Report Share Posted January 22, 2009 I've got an old Headamp Gilmore Reference (single-ended) on the way. I believe this unit was later modified to a gain of 1, which should be a good preamp gain. But, it doesn't have pre outs, just a 2nd headphone out. In these older Headamps, is there any circuitry difference between the pre out and headphone out, or does it merely boil down to the physical differences in connectors? Any other reason why I shouldn't try this as a preamp with a Y cable/adaptor? The V2 I recently picked up is a real performance killer, as both preamp and headphone amp, for the $200 I paid. Super-nice match to the L3000 w/ Duet, and to the HD650 or L3000 with vinyl Personally, I would just use it as a headphone amp. I'm not sure what the advantage is to use it as a large and expensive volume control when there are not multiple inputs and RCA or XLR out? While it was on loan to me for the past month I liked it best with Denon D2000 (woodied re-cabled) and Edition 9, but wanted a little more warmth with RS-1 and more power with HD600. It's a very nice amp. Quote Link to comment Share on other sites More sharing options...
mulveling Posted January 22, 2009 Author Report Share Posted January 22, 2009 Personally, I would just use it as a headphone amp. I'm not sure what the advantage is to use it as a large and expensive volume control when there are not multiple inputs and RCA or XLR out? While it was on loan to me for the past month I liked it best with Denon D2000 (woodied re-cabled) and Edition 9, but wanted a little more warmth with RS-1 and more power with HD600. It's a very nice amp. I would be fine using it as just a headphone amp, but curious how it compares to the Zana Deux as a preamp. If it's better than other large, expensive volume controls, then it would be worthwhile to get an input switchbox The Zana is going to be hard to beat, but I wonder at this level whether most sonic differences might just stem from differences in output impedance. The Zana lists an output impedance of 16 ohms, not 100% sure if that applies to the preamp out. The Gilmores I've heard are certainly not warm, but not the least bit cold either. I think it would take an amp with a very peculiar coloration to make me love the RS1 long term - haven't determined what that specific coloration is yet That particular Gilmore Ref has been modded to a gain of 1, which could definitely limit the upper-end of the volume with high impedance headphones and low-output sources. Not an issue with lack of power, so much as getting the input signal high enough. I'm wondering if it will be an issue for me with my TT and HD650, but at least I have the L3000 and Qualia on hand Quote Link to comment Share on other sites More sharing options...
n_maher Posted January 22, 2009 Report Share Posted January 22, 2009 That particular Gilmore Ref has been modded to a gain of 1, which could definitely limit the upper-end of the volume with high impedance headphones and low-output sources. Not an issue with lack of power, so much as getting the input signal high enough. I'm wondering if it will be an issue for me with my TT and HD650, but at least I have the L3000 and Qualia on hand Remember that it isn't just about impedance, leaving sensitivity out of the equation is unwise. Quote Link to comment Share on other sites More sharing options...
justin Posted January 22, 2009 Report Share Posted January 22, 2009 Just out of curiosity, what is the purpose of these resistors? Impedance? I think they're just a good idea for isolating the headphone amp from any amps/receivers that are left permanently connected to the pre-out. Some of them will short their inputs when another input is selected or the power is turned off. Quote Link to comment Share on other sites More sharing options...
Pars Posted January 22, 2009 Report Share Posted January 22, 2009 I think they're just a good idea for isolating the headphone amp from any amps/receivers that are left permanently connected to the pre-out. Some of them will short their inputs when another input is selected or the power is turned off. Ahhh, I see. Yes, 100 ohms would be a good idea then, much like the series resistors used in many CDPs ahead of the muting relays. Quote Link to comment Share on other sites More sharing options...
mulveling Posted January 23, 2009 Author Report Share Posted January 23, 2009 I think they're just a good idea for isolating the headphone amp from any amps/receivers that are left permanently connected to the pre-out. Some of them will short their inputs when another input is selected or the power is turned off. Ok, I kind of get that - thanks for the explanation! So would I be correct to assume that my amps that have their inputs hooked up to a high-impedance pot (schematics are in the manuals), would not have this issue? Quote Link to comment Share on other sites More sharing options...
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