| Author | Message | ||
     Brian |
I just had a Hd 150 given to me and was wondering if anyone could tell me about some of the features of these amps. What do the High and Low on the power mean? Is it different power settings or what. I hope to have the amp running soon. It had all the tubes broken out of it. I'm waiting for new tubes to come in so I can check out if it works or not. If anyone has any tips or hints for me let me know. Thanks alot. Great site by the way.I had no idea these amp even exsisted before last week and now I have found your great resourse site. Great work. | ||
| Steve Kennedy |
You can learn a ton by reviewing all the postings from the last year or so. The answers to most of the commonly asked Music Man questions are in there! You can download them for off-line viewing with your browser from this site in the Archives section under History at: http://www.pacair.com/mmamps/Misc__Info/History/Archives/archives.html The High/Low power switch simply cuts the B+ plate voltage to the output tubes in half (from approx. 700Vdc to just under 400Vdc). This results in approximately 1/2 power. Generally, it is MUCH easier on a Music Man amp if you run it ALL the time at Low power and only use the High power setting when Low Power proves to be inadequate for the situation. The amp will run cooler and the tubes will last a LOT longer at Low Power. The audio level difference between the two settings can vary from un-noticeable to "just enough to get over the top" (depending on a variety of factors including speakers and impedance and AC power sourcing). The audio difference your ear will hear between 75 and 150 watts is not all that much and is actually much smaller than the numbers would indicate. Steve (Message edited by admin on December 07, 2003) | ||
| Pat |
I rarely break out of low power mode with my 212-65, unless I want to get really spanky clean at high volumes, and even then, it better be outdoors. | ||
| Al |
I tried running my 212-65 at low power, but I didn't like the effect on tone - sounds better to me at full power. Guess I'll take my chances on the tubes burning out early (life's too short to sacrifice tone). Al | ||
| cedric |
i've got a 212-65 too. and i guess it needs a new bias job. since it always growls and splutters when i play through it. but i like that sounds. it's not crystal clean - it can't be. ain't those musicman amps just great?!  i've been thinking of buying a HD 150 Reverb head too - with a matching MusicMan 4x12 (!! i've NEVER seen or heard of THIS before?) cab. so please.... how does the HD 150 compare to a Fender Super Reverb? - ced - ced | ||
| Marc |
Steve- Undoubtedly, you've addressed this elsewhere, and if so, could you please direct me to the site &/or cut and paste an answer? The push/pull SPEED knob/switch on my HD-150 combo works in tandem w/ the adjacent INTENSITY knob. I leave it pulled out, because the whole tremolo effect is bogus. In doing so, there's an interesting and effective new spectrum of tonal variety available to the player who rotates the PULLED OUT "SPEED" knob (to ear-choice). I keep mine subtle, set for "2", w/ the "INTENSITY" set between 2-3. What do you know or can you say about this? I think it's a real variety plus as the renowned MM Clean Tone goes! Thanks, Marc | ||
| Steve Kennedy |
The HD-150 has the Music Man "Phasor" circuit, which is supposed to be a phase shifter (similar to but not exactly the same as a Tremelo). By pulling the knob, you turn off the sweep and allow the the phase point to be set manually by the knob. It is a little like setting a Wah-Wah at one point and leaving it there rather than working the pedal. This gives you and interesting tone variant you can control that will sound different than standard tone controls because it is phase dependent! Pretty cool! I have covered this elsewhere, but I am not sure just where to point you! | ||
| greg |
i have a MM HD150 reverb as well. although i have had it retubed, i had it done by a hack and don't believe he ever biased the amp. when the amp is running, only two of the tubes glow with the blue haze that tubes seem to have. the hi/lo switch has no effect on it either. is this a result of the amp being out of bias, or is it a problem with the power switch or wiring from the power switch? thanks for your attention. greg | ||
| Langley |
Need more info. Is there a power output difference between the High/Low power settings? Which 2 tubes (positions: 1, 2, 3, 4) show no 'blue haze'? Tubes all hot? Redness on any tube plates (excluding heaters which should be lit)? Are all 4 tubes matched (same brand, same appearance inside and out)? How does the amp sound Hi setting with master on 10, channel on 2~3, tones on 5? (Is it clean sounding or has some kind of distortion?) General condition (rust, odd noises, etc), and known history (usage/service) of amp. Recolections of 'first beer'. | ||
| greg |
Is there a power output difference between the High/Low power settings? not that i can tell, there is no discernable difference in tone or volume. Which 2 tubes (positions: 1, 2, 3, 4) show no 'blue haze'? Tubes all hot? Redness on any tube plates (excluding heaters which should be lit)? Are all 4 tubes matched (same brand, same appearance inside and out)? i'll have to double check, but my recollection is (if you are looking at the back of the amp)the two tubes on the left hand side have the blue halo. all the tubes are hot and show the typical orange glow, no redness on the plates. as far as the tubes being matched, i'm not positive, they are all alike, but i just found out that they are EL34s, so someone has had the amp modified to accommidate these tubes. How does the amp sound Hi setting with master on 10, channel on 2~3, tones on 5? (Is it clean sounding or has some kind of distortion?) i'll have to check these settings out and get back to you on this, i use the amp for bass, so i usually keep the master and channel levels about the same. they max out at about 7 before the amp starts to distort. General condition (rust, odd noises, etc), and known history (usage/service) of amp. Recolections of 'first beer'. the amp, visually, is in good to very good condition. no odd noises or malfunctions otherwise. i used the amp fairly regularly(gigs 3/6 a month,same for rehearsals for about three years, then it sat idle for a while. the blue tube condition has always been the same since i owned it. now that i write this all down, i feel like a bit of a dips#it for not addressing it earlier, but i would like to get the amp back in shape, and this condition seems abnormal(to me). how much would i stand to gain if i had the amp rewired to accomidate KT88s or 6550s? is this a bad idea? thanks again, greg | ||
| Langley |
Well, if the amp sounds fine, I'd leave it alone. I would do one curiosity test: Swap the tubes around and see if the ones that were 'blue' before lose the hue, and the ones without the blue hue are now blue. If the hue/lack of hue moves with the tubes, then something may be up with the tubes. If the hue/lack of hue is chasis socket position dependent then I'd check those positions for B+ or screen issue(s). Scope at output may show up as a non-symmetrical wave. Moding the output section would probably cost close to what the amp' is worth. A good transistorized bass amp will do more for your sound than modding the HD-150. |