Hey guys - posted this thread a little while ago on TGP - http://www.thegearpage.net/board/showth ... p?t=791859
I'm thinking I may want to try my hand at replacing the coupling caps in my amp, but want some Hiwatt expert thoughts first.
Before reading the thread - here's a little history on my amp. Bought it from Jarret a couple of years ago - JC103 on here I think.
The amp has always functioned, but in my opinion it has just sounded ok. Notes don't seem to bloom and it lacks sustain....been this
way since day one. I knew going into it that it would need the filter caps replaced, so I bought the VHR kit and did it myself. This really
did not change the tone at all imo, but it needed to be done since the old ones were bulging. Pics after cap job - http://www.spinningaroundthesun.com/ima ... 04/Hiwatt/ Since then, I've had a couple of techs look at it
and asked that they check all values for drift, etc, but I don't think they really did it thoroughly enough. I also had Bruce at Mission Amps
install a bias mod ciruit so I could use some new prod power tubes - he did a great job....this mod did not change the tone of the amp either imo.
So, the problem I'm trying to resolve is mainly that the amp seems to not have much volume until the master is around 3/4 of the way up and
it lacks sustain and sounds a little dull.....I also have a Reeves Custom 50 head (realize it's not the same circuit) - this amp has
plenty of clean sustain, bloom, and sounds wonderful. I've tried a variety of good NOS tubes in the Hiwatt (always run NOS in the preamp) and they sound
better than new preamp tubes, but still it doesn't sound like it should imo. I don't want to devalue it or "mod" it to that effect, but I'd like
to get more use out of it - I'm a player not a collector : ) Do you guys agree with TGP thread? Any other ideas? I'm not an amp tech, but I do feel ok
with checking the filter cap voltage and soldering - I did the cap job as I mentioned and 2 techs checked my work and said it looked fine. So if possible,
it would be nice avoiding paying a tech.....I just need some expert advice on how to get this amp singing.....so, if you tell me what to replace and maybe where it is and if I can maybe buy at VHR, that would great!
Advice on 74 Hiwatt DR504......
Moderator: Mods
Re: Advice on 74 Hiwatt DR504......
Hmmm. The coupling caps in there now are Phillips "mustard" caps, which are in general highly sought after! I seriously doubt that replacing the coupling capacitors will fix your complaint.
The older Hiwatts are generally "clean machines," and don't really sing on their own unless really cranked (vol 10, master 7..10). This tends to be a bit loud!
You might try adding a bypass cap across the V2 cathode resistor (the 1k resistor next to the large 10k resistor in the bottom right of your IMG_2152.jpg picture). You can try anything from .047 to 1uF in this position, but use a good quality film cap.
--mark
The older Hiwatts are generally "clean machines," and don't really sing on their own unless really cranked (vol 10, master 7..10). This tends to be a bit loud!
You might try adding a bypass cap across the V2 cathode resistor (the 1k resistor next to the large 10k resistor in the bottom right of your IMG_2152.jpg picture). You can try anything from .047 to 1uF in this position, but use a good quality film cap.
--mark
Re: Advice on 74 Hiwatt DR504......
Thx a million Mark....appreciate your thoughts. Yeah, I realize they are clean machines and maybe "sing" was the best word to use - I do use these amps as a clean slate for great pedals ala Gilmour, but the base tone is important obviously. The Reeves is a clean machine too, but at low volume when you bend and hold a note for instance, it will hang onto it for quite a while and my Hiwatt feels and sounds quite a bit weaker when you do this like something is choking it....that's a better way of explaining it I think. I'll be happy to try your suggestion - would you mind drawing a red line on the pic where exactly it should go and email to me just to be sure I put it in the right spot - you recommend the mustard caps on the VHR site I suppose? Also, what does this do technically? Sorry, just trying to learn more. I really appreciate your help.
Hmmm. The coupling caps in there now are Phillips "mustard" caps, which are in general highly sought after! I seriously doubt that replacing the coupling capacitors will fix your complaint.
The older Hiwatts are generally "clean machines," and don't really sing on their own unless really cranked (vol 10, master 7..10). This tends to be a bit loud!
You might try adding a bypass cap across the V2 cathode resistor (the 1k resistor next to the large 10k resistor in the bottom right of your IMG_2152.jpg picture). You can try anything from .047 to 1uF in this position, but use a good quality film cap.
--mark