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svt vr 4 ohm into 8 ohm cabs, ampeg say don´t do it

S

solitario

Oct 13, 2011
170
2
Spain
#1
svt vr 4 ohm into 8 ohm cabs, ampeg told me not todo it but if have seen many players vith vr and svt classic with ampeg 410 he cab that are 8 ohm.

I asked some tech and they told me that if the cab in 8 ohm and the amp 4 ohm there should be no problem.

are all those players with ampeg valve heads and 410 he wrong?

thank you
 
#2
solitario said:
svt vr 4 ohm into 8 ohm cabs, ampeg told me not todo it but if have seen many players vith vr and svt classic with ampeg 410 he cab that are 8 ohm.

I asked some tech and they told me that if the cab in 8 ohm and the amp 4 ohm there should be no problem.

are all those players with ampeg valve heads and 410 he wrong?

thank you
Click to expand...
If you run an SVT into an 8 ohm cabinet using the 4 ohm tap you are stressing the output tubes because there is not enough current to pull the voltages down and the output transformer insulation might start failing, causing the dreaded shorted turn and an untimely death.
You can get away with it, but for how long? it sucks the power and it's a huge risk, don't do it.:bassist:
PS did the engineer you asked get the tube amp concept or did he just give you a semiconductor based answer.
If the latter he is right. Quite a lot of young engineers have no experience with tube technology.
 
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#5
solitario said:
I told him it vas a svt vr... he is supoused to know svt vr are all tube amps... I hope...
Click to expand...
He gave you a semiconductor answer so he didn't seem to understand the concept of output transformer load matching in tube amps.
Of course you could just check your cab and see if it is actually 4 X 8 ohm drivers in series parallel to arrive at 8 ohms total.
which would add up to 2 ohms if you rewired the cab all drivers In parallel.
You have an impedance tap on your VR for 2 Ohms so match it.:bassist:
 
#8
derridiandrift said:
Pretty sure the drivers in the 410HE are the same 32 ohm drivers from the 810E.
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If they are, it's not going to be possible.
do they still use 32 ohm drivers these days, I know my old CTS driver'd 8 X 10 was, seems odd because it must cost them in Ampeg only application terms. quantity ordered cost considerations.
That's why I said if they are 8 ohms.:bassist:
 
#13
In the ignorance is bliss column, I used my V-9 SVT (1976 Magnavox era) through 8 ohm cabs many times, although for relatively low volume sits... Back then I was told you could go "up or down" basically one level - meaning using an 8 ohm amp into 4 ohms, and/or a 4 ohm amp into 8 ohms (with tube heads anyway)... But matching is the best option.
 
#14
Bassmec said:
If you run an SVT into an 8 ohm cabinet using the 4 ohm tap you are stressing the output tubes because there is not enough current to pull the voltages down and the output transformer insulation might start failing, causing the dreaded shorted turn and an untimely death.
You can get away with it, but for how long? it sucks the power and it's a huge risk, don't do it.:bassist:
PS did the engineer you asked get the tube amp concept or did he just give you a semiconductor based answer.
If the latter he is right. Quite a lot of young engineers have no experience with tube technology.
Click to expand...
I just had this same problem on a mesa bass prodigy. (Amps and cabs section -blew a kt88....) the manual called for a 4 ohm tap to a 8 ohm cab (this amp has a half power switch which drops it to two kt88s as output) and i blew a kt88 and a fuse with this setup. Now everyone was giving me crap about blowing a kt88 but i was following procedure via prodigy manual- setup. But i can almost see the relation on your comment on stressing the output tubes- weather or not if its a svt, mesa, whatever. Even if it calls for it on half power. Anyway, got the problem fixed and only now running full power (no more half power playing) and for now havent tried my 8 ohm 212 again (cab used when the tube blew up) but i do have an 8 ohm tap from the amp to the 2x12 cab. No issues at all on half power or full power on my svt 6x10. But just wondering what u think of my situation cause everyone on my kt88 thread, was just beating around the bush and i dont think hardly no one that stuck their nose in my thread even knew what they were talking about. Hit me up with a reply. Sorry such a long type. D
 
#17
west al said:
One reason I went with the Fender Super Bassman. It has a 8, 4, and 2 ohm selector for impedances. I myself wouldn't mix the impedances if the Amped says no, or doesn't advise it.
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Thats the bad thing about what happend. It actually sais to put a 8ohm cab to a 4ohm load.....but ill be danged if thats not the third or fourth time ive heard someone mention owning a fender bassman. I might just have to bite the bullet and sell my mesa and get one. Does the bassman get dirty though? Not too dirty, just a little grind whenever i start banging the crap out of those bass strings.
 
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#19
D Rock 247 said:
Thats the bad thing about what happend. It actually sais to put a 8ohm cab to a 4ohm load.....but ill be danged if thats not the third or fourth time ive heard someone mention owning a fender bassman. I might just have to bite the bullet and sell my mesa and get one. Does the bassman get dirty though? Not too dirty, just a little grind whenever i start banging the crap out of those bass strings.
Click to expand...

Use the Overdrive Channel on it. I'm liking the Vintage Channel too much.
 

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