Tube Amps / Music Electronics
For current discussions, please visit Music Electronics Forum. New: view Recent Searches.
New: visit Schematic Hell!
The sunn still shines online!

Listen to great tunes streaming live right now!

ampage archive

Vintage threads from the first ten years

Search for:  Mode:  

Vox Pacemaker high volume harsh

6/4/2005 2:52 PM
Vox Pacemaker high volume harsh
hi all!  
I finished my pacemaker copy, it sounds good, but not at high volume. the tone is hidden behind trebly harshy sound. It come earlier depending on treble control pot. I put of the 47pF volume pot cap and it is much better (the harsh come later)please help!
6/4/2005 4:32 PM
It sounds like you may have a parasitic oscillation creeping in at overdrive levels. Does the harshness sound raspy and unrelated to the fundamental note?  
Book Of The Day The Ultimate Tone, Volume III by Kevin O'Connor
Have you ever wondered if there is a better way to build a Bassman, Champ, Plexi, an 800, AC-30, Bulldog or Portaflex? Or you wanted to build an SVT with off-the-shelf parts? How about a master-volume amp that doesn’t change tone with the master setting? Everything you need to know is right here, including: proper grounding techniques, wiring methods, and mechanical considerations. Eighteen chapters cover the “iconic” amps everyone knows and loves, with schematics and layouts for each, along with the technical history of the product. Eyelet-board and chassis-mounted tube socket construction is used throughout, for easy servicing and modding. TUT3 is very accessible even if you cannot fully read a schematic and is a "must have" if you are going to build an amp for your self.

Note: The Ampage Archive is an Amazon Associate site. A small commission is paid to the site owner on any qualified purchase made after clicking an associate link such as the one above.
6/5/2005 4:26 AM
Thanks,you are right! It probably causes,that the OT wires are close to input tube.. i will replace them and we will see..
6/5/2005 8:59 AM
If your going to relocate those leads anyway you may want to twist them together for as much length as you can. This is suppose to help. There was a thread here about it not very long ago.
6/5/2005 9:56 AM
Now it is quite ok, it still has little bit of hiss,but the sound is better. But I am not satisfied with the tone. It is to bright.. I expected fat tone, the trebles are crystal bright, what to do with it? I try to put the input signal behind the equalizer section directly to the volume pot,and it isn´t equalization problem.I have Gibson Les Paul studio and play throw 2x12 Celestion clasic lead box 160W. The OT is made to have hifi parametres,but is smaler (Ei 64x32). I hope, it will sound better with small speaker, i am going to buy Celestion Tube10 (30W), but i am not sure. Maybe the solution is to change some capacitor..? Tom
6/5/2005 7:29 PM
I would tune the amp to work with whatever speakers I wanted to use. Since this amp doesn't use a negative feedback loop you could install one for the top end only. You could even put it on a pot and use it like a "presence" control. By using NFB on the top end only you will still get all the midrange harmonics of no feedback loop and you'll get the brittleness under control.  
6/6/2005 8:24 AM
Ray Ivers

Try running the output tubes in "triode" mode, with 1K 3W or 5W screen resistors connected from each screen to each plate. If you have the resistors, it will take you ten minutes to do.  
Can you get Eminence speakers where you are?  
   Page 1 of 2 Next> Last Page>>