• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

parallel se 6bq5 amp schematic

D

Don P

Active Member
Hi all i need a schematic for a parallel se 6bq5 amp.

Why you say. i have a Magnavox 9302 pp amp and i love it.

But after having a Heathkit 6bq5 set amp it just dose not have that ?????.

the heathkit amp had a sound like no other amp i have had, it just need a little more power to drive my speakers the 9302 ha more than enough power to drive my speakers but it is a/b not A class. it is not clean SE class A sound that i have come to love.

i sold the heathkit amp an now wanting to rebuild my 9302 to a parallel se 6bq5 amp

now my Magnavox 9302 has developed a hisss in the right channel so it time to do it lol. total rebuild op trans and all.

Thanks Don
 
Register to hide this ad
You'll need new output transformers and a new driver arrangement and you'll need to remove the phase splitter. You could sell the maggy as is and buy all new stuff.
 
Last edited:
HI battradio, kyle.
thanks for the response. but going to a 2a3 is a big pain new tubes new sockets redo power supply new chassis (different) socket hole size etc BIG EXPENSE.

by using what i have i can get 6 or 7 watts out (Class A SE) and just rewire most of what i have just add new output transformers. i was going to up grade them any way.

i found some good 6bq5 se schematic i will use it, and add a second tube. i just need to know on what op transformer 2.5k 4k 5k 6k 7k 8k 9k etc.



Thanks Don

.
 
Last edited:
battradio thanks


edcor web site has been down on and off for 3 day i know of. thanks again.

Don
 
Last edited:
6DZ7 did not think of that. Huuuuummmm. guess i will just rebuild it to get rid of the hum and put new Edcor transformers and go Ultra-Linear.

Thanks Don
 
The power trans former is fine all you would need to do is use a choke input to the power supply and add a second choke . It would be cheaper to just go ultra linear though and add a second choke to really smooth out the power supply .
 
i miss spoke i do not have a hum in this amp sorry. it is a hiss in the right channel only and it has started to get worse. i replaces all caps when i got this amp and replaces 1 or 2 resistors that were out of spec. so i am going to disassemble it and get some silver plate 20 ga wire and rebuild it like should have to begin with all caps are hi quality in power supply and i got pio cap too.

what do you all think of meta film resistors? that seems to be what the high end tube amp makers are using now.

Don
 
That is mostly all i ever use is metal film resistors ,The 470 K resistors in that amp are almost always out of spec .
 
I use metal film or oxide resistors in everything as well. Low noise, flameproof, values don't drift over time.

A hiss in one channel only? Sounds more like a bad tube, or HF oscillation. Have you swapped tubes from one channel to the other to see if it follows the tubes? If it stays in the one channel, it would be worthwhile to put it on a scope to look for HF noise.
 
nashvillebill i thought so too. i switched all 3 tubes from left to right and right to left no difference. could be a old carbon resistors starting to let go. 50+ years old.

i guess i could stick it on the scope and see where it starts in the signal chain.

Thanks Don
 
Don P said:
nashvillebill i thought so too. i switched all 3 tubes from left to right and right to left no difference. could be a old carbon resistors starting to let go. 50+ years old.

i guess i could stick it on the scope and see where it starts in the signal chain.

Thanks Don
Click to expand...

A plate resistor starting to sizzle, maybe, or leaky coupling cap. Usually I don't advocate trying to "shotgun" a problem by just replacing random parts, but in the case of this old stuff with carbon resistors and old coupling caps, I've found it's just quicker to go ahead and replace them. A couple or three hours and all the old carbon resistors and coupling caps could be out and new ones in their place.

I had one old guitar amp that would suddenly "thunder" randomly. It took maybe an hour to replace all the carbon resistors (I had already replaced all the caps). Problem solved, amp no longer had random bursts of "thunder". It was faster to just bite the bullet and refresh all the old stuff than to try to find which resistor was causing the problem.

My opinion...there is absolutely no "mojo" in old noisy caps or resistors.
 
6DZ7 go back and reread my post. i did not ask any one to diagnose the hiss in this amp!

you read that in for yourself.

i ask for a schematic.
Post #1 "Hi all i need a schematic for a parallel se 6bq5 amp."
Post #4 "i just need to know on what op transformer 2.5k 4k 5k 6k 7k 8k 9k etc."
Post #10 "what do you all think of meta film resistors?"

where did i ask for help with a hiss?


So get your facts strait before you bust my chops.

so what do i think you don't want to know
 
6DZ7 nashvillebill mentioned scope in post #12 first, i just responded in post #13. again get your facts right.


i looked i don't see you having title post police. so
 
Last edited:
Whoa fellers, no need to get all riled up.

OP, your first post is indeed a little confusing. You say you love the 9302 amp...but then you want to completely change it to something different? That truly is a "what the ??" contradiction.

Especially since you said it hasn't been recapped or refreshed. Judging the performance of an amp which contains 50 year old caps and resistors isn't really a fair test of the amp.

So IMHO if you love it--per your first part of your first post--at least give it a chance to prove itself, by recapping it and replacing resistors as necessary, before you gut it and start from scratch. A hiss that has gotten worse usually isn't the fault of a poor amp design. If one channel doesn't hiss, the other channel shouldn't hiss either. That's why I mentioned the scope.

My advice, FWIW, get the amp working properly as designed and listen to it. If it still doesn't float your boat, THEN go in another direction.
 
You must log in or register to reply here.
Back
Top Bottom