Page 1 of 2 12 LastLast
Results 1 to 15 of 20

Thread: An "Omage" to Harvey Gerst - D130 Question

  1. #1
    Junior Member
    Join Date
    Feb 2007
    Location
    New York, Ny
    Posts
    23

    An "Omage" to Harvey Gerst - D130 Question

    It certainly is an honor to have my first query answered by the big man himself, Wow! Thanks Harv.
    I have another question: I want to use a d130 to replace the two 12 Jensens in my 1965 silvertone 1484 piggy back amp. (It has two 6L6's in a push pull circuit, but I don't know how many ohms the amp is looking for) I don't know if I should use a 16 ohm or a 8 ohm speaker. The problem is that the amp is too loud for my requirements so i was thinking of using a 16 OHM speaker to soak up some of the power. I read some other missives about the cab size and sound deadening material which I will also incorporate but I still need to get the amp up to "3" or "4 " to get the full amp character.

  2. #2
    Junior Member
    Join Date
    Feb 2007
    Location
    New York, Ny
    Posts
    23
    i wonder why my original thread was moved

  3. #3
    Senior Member
    Join Date
    Feb 2004
    Location
    Central Coast California
    Posts
    9,018

    Hi Jack.

    It was in the wrong forum.

    Originally, you posted it (twice) in the "Music" forum in "Lansing Related Forums." The content of your thread really is about a Lansing product, D130, and some do-it-yourself modifications, so it was moved here. In moving it, the double posting was eliminated, too.

    So it was a little bit of housekeeping, nothing more.

    Just to be very clear, I PMed a moderator and suggested he look at the posts and move them to an appropriate place. I don't know if anyone else mentioned, too. Whatever the case, the intent was just to get the thread into the right forum.

    Hope this helps.

  4. #4
    Senior Member
    Join Date
    Mar 2004
    Location
    Sanger, Texas
    Posts
    559
    Quote Originally Posted by jackrhein View Post
    It certainly is an honor to have my first query answered by the big man himself, Wow! Thanks Harv.
    I have another question: I want to use a d130 to replace the two 12 Jensens in my 1965 silvertone 1484 piggy back amp. (It has two 6L6's in a push pull circuit, but I don't know how many ohms the amp is looking for) I don't know if I should use a 16 ohm or a 8 ohm speaker. The problem is that the amp is too loud for my requirements so i was thinking of using a 16 OHM speaker to soak up some of the power. I read some other missives about the cab size and sound deadening material which I will also incorporate but I still need to get the amp up to "3" or "4 " to get the full amp character.
    First, we hafta figure out what the load is now, so get a multi meter and measure the DC resistance of the speakers. Then, we can work from there.

  5. #5
    Senior Member duaneage's Avatar
    Join Date
    Jan 2005
    Location
    The First State
    Posts
    1,584
    IIRC tube amps don't like higher impedance loads. If it is too loud could you just adjust the gain down a bit or does this amp go to 11?

  6. #6
    Junior Member
    Join Date
    Feb 2007
    Location
    New York, Ny
    Posts
    23

    Ohm rating

    It had 2 jensen 8 ohm speakers wired in parallel which it would have made the amp originally looking for a 4 ohm load. Do think a 16 ohm load would change change the tone or fry the output transfromer?.

  7. #7
    RIP 2011 Zilch's Avatar
    Join Date
    Jun 2004
    Location
    Berkeley, CA
    Posts
    10,036
    Well, we've got one post that tube amps don't mind higher impedance loads, and one that says they don't mind them.

    [Somebody gotta get definitive soon.... ]

  8. #8
    Senior Member jcrobso's Avatar
    Join Date
    Oct 2008
    Location
    Chicago
    Posts
    1,103

    The D130 might play louder than the Jensens

    Quote Originally Posted by jackrhein View Post
    It certainly is an honor to have my first query answered by the big man himself, Wow! Thanks Harv.
    I have another question: I want to use a d130 to replace the two 12 Jensens in my 1965 silvertone 1484 piggy back amp. (It has two 6L6's in a push pull circuit, but I don't know how many ohms the amp is looking for) I don't know if I should use a 16 ohm or a 8 ohm speaker. The problem is that the amp is too loud for my requirements so i was thinking of using a 16 OHM speaker to soak up some of the power. I read some other missives about the cab size and sound deadening material which I will also incorporate but I still need to get the amp up to "3" or "4 " to get the full amp character.
    Most guitar speakers have a sensitivity rating of 92~95db. Lets say the Jensen's are 94db for one speaker, two speakers will give 97 db. The sensitivity for a D130 is 101db, so the amp will play louder with the D130.

    I suggest that you get a 100W 8 Ohm L-pad connect this between the amp and the speakers. The amp will see 8 Ohms and you can turn down the speakers to a lower level. If you want to use a D130 to get better over all sound GO FOR IT!!! John

  9. #9
    Senior Member 4343's Avatar
    Join Date
    Jan 2006
    Location
    SJ, CA
    Posts
    515

    Cool

    Quote Originally Posted by Zilch View Post
    Well, we've got one post that tube amps don't mind higher impedance loads, and one that says they don't mind them.

    [Somebody gotta get definitive soon.... ]
    Maybe not definitive, but "hear" goes...

    Rules of thumb:

    SS Amps don't like Shorts, Tubes/Valves don't mind so much.
    Tube/Valve Amps don't like Opens, Solid State don't mind at all in most cases.

    Me, I wear shorts in the open, most of the year...

    There are several commercial products designed to lower the level to the speakers, "Power Soak" by Tom Sholtz for instance.
    Mike Scott in SJ, CA
    Drive 'em to the Xmax!

  10. #10
    Senior Member Hamilton's Avatar
    Join Date
    Aug 2005
    Location
    Huntington Beach, CA
    Posts
    229
    Tube amps don't care for a load mismatch, but will tolerate them....to a point.

    With a low impedance load the tubes will be forced to put out more current as the volume goes up since the load is closer to a short : thus tube life will be shortened.

    In high impedance loads, and as the volume goes up, there is the danger of flyback, which are high voltage spikes that can arc through the output transformer insulation, across tube sockets or inside the tubes themselves. Once an arc has occured...it will probably happen again...and again.

    If it's impossible to have the correct match, a lower load might be the safer bet. Leo went that way with the external speaker jack on his Fender amps.
    There are two theories to arguing with women, but...neither has worked.

  11. #11
    Senior Member
    Join Date
    Feb 2007
    Location
    Christchurch, NZ
    Posts
    1,469
    Quote Originally Posted by Zilch View Post
    Well, we've got one post that tube amps don't mind higher impedance loads, and one that says they don't mind them.

    [Somebody gotta get definitive soon.... ]
    I will give you a definative answer. It depends very much on the clever guy that designed the output transformer. Having the correct impedence load on the output transformer will result in a better power transfer. If you use a mismatched load the power transfer won't be as good. It generaly wont harm most amplifiers and it could result in a different sound that is to your liking.

  12. #12
    Senior Member duaneage's Avatar
    Join Date
    Jan 2005
    Location
    The First State
    Posts
    1,584
    Since speakers are not a flat resistive load across the deck the best thing to do is sweep the speaker system and plot the impedance to see what the max and minimum impedance is. The WT2 (Woofer Tester 2) can plot this in about 60 seconds and also give phase relationships as well.

    From this you can compare two systems and see what the difference is. Makes more sense than guessing, or asking everyone what they "think" will happen. If you post the curves from these tests the group of experience here can make recommendations, including modifications.

    Too many times posters ask for someone to measure a cab or a duct tube and then merely duplicate. The right approach is to measure and adjust until it's right. I've never had a system match simulated designs exactly, there are too many variables.
    Why buy used when you can build your own?

  13. #13
    Senior Member Beowulf57's Avatar
    Join Date
    May 2008
    Location
    Ontario, Canada
    Posts
    367
    I've been driving a D130 & a D131 (ostensibly 16 ohms, but measure 6.3 ohms DCR) both with and without networks using 30 watt P-P tube amps for over 40 years. My Peerless OT's are set to the 16 ohm taps and I have never had any problems. Tube amplifiers are voltage amplifiers and as was noted, when you drop the load impedance below nominal, more current is demanded of the output stage and the OT. Unless you drive the amp hard, it is unilkely to cause any problem. Some people like to use a low impedance OT tap as this means less wire is in the OT secondary..."purer" sound? Hmm, not likely to be audible IMO. Note that if you have NFB (almost all tube amps of that era do) taken from the OT secondary circuit in your amp design, changing the load impedance will change the amount of loop feedback (in my amps this is fully adjustable, so no issue). This will certainly alter the sound and even possibly the stability of the amp

    As someone also noted, the D130 is a very high sensitivity speaker (mine are rated at 103dB/W/M) and thus you are likely to get an increase in output level. I believe the Silvertone 1484 is a 100 watt unit? Way more than you should ever need...in fact you could overdrive the D130. Rather than adding an attenuator at the output (which will soak up alot of power unnecessarily), you could consider adding 10 dB inline RCA attenuators to your source inputs to the amp and reduce the level more efficiently. Running the D130 from a lower impedance output tap is not that likely to effectively lower the output level. You could also check the OT's on your amp...perhaps there are different impedance taps, but again this is not an effective method of reducing output level.

  14. #14
    Senior Member Beowulf57's Avatar
    Join Date
    May 2008
    Location
    Ontario, Canada
    Posts
    367

    Silvertone 1484 Schematic

    Okay...I found a schematic for the 1484. It certainly doesn't produce 100 watts (so no problem there) with only 2 6L6GC's and there is no overall loop feedback from the secondary. As well there is only one output tap on the transformer...I'd go with he 8 ohm D130 and input level attenuators.
    Attached Images Attached Images

  15. #15
    Senior Member duaneage's Avatar
    Join Date
    Jan 2005
    Location
    The First State
    Posts
    1,584
    I think the 100 watt assumption came from power consumption ratings at the wall, more like 35 watts audio output. Still enough for decent volume from a pair of 12's
    Why buy used when you can build your own?

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Serial Number registry?
    By glen in forum Lansing Product General Information
    Replies: 664
    Last Post: 03-08-2019, 12:15 PM
  2. Harvey Gerst/ D130
    By 57BELAIRE in forum Lansing Product General Information
    Replies: 8
    Last Post: 06-01-2005, 11:35 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •