I don't usually crank mine up, but I sold one of my pair recently to a guitarist and we cranked them up a bit to test them out. Really nice pushed tone once you get up there. Stupid loud. But really nice.
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Ampeg V4 Club
- Thread starter birdman14
- Start date
I don't usually crank mine up, but I sold one of my pair recently to a guitarist and we cranked them up a bit to test them out. Really nice pushed tone once you get up there. Stupid loud. But really nice.
Yes I have a V4B and two BB2's. Sounds amazing. Best tone I ever got out of a rig. I'm always amazed by the V4B, as I can get so many different tones out of it.
Using it with the BB2's gives me a deep bass sound that is not muddy and does not fart out at all. The horns on the BB2's provide clarity, brightness and definition when needed. Switch on the deep switch on the V4B and you get an even fuller, thicker sound out of the BB2's.
I also own a D800 which sound great through the BB2's as well, but the V4B through the BB2's is on a whole other level tonewise.
This thread hasn't seen any activity in awhile. I wanted to hear the opinions here about a V4B I picked up today.
I picked up a late '70s V4B today and found 1 6L6 and 3 7027 tubes in the power section that are all 'NOS'. The seller was a cool guy and told me he played it for years like that after I emailed him about it.
My question is do I need to retube it with a new set of 6L6's or find a quad of 7027s and maybe try to sell or keep the existing 7027s? I noticed this when I got it home and it sounds great and has no issues, but I am thinking the mismatch may not be good for the amp and maybe I should get it looked at before entering it into rotation.
Any advice is appreciated. Thanks in advance.
I picked up a late '70s V4B today and found 1 6L6 and 3 7027 tubes in the power section that are all 'NOS'. The seller was a cool guy and told me he played it for years like that after I emailed him about it.
My question is do I need to retube it with a new set of 6L6's or find a quad of 7027s and maybe try to sell or keep the existing 7027s? I noticed this when I got it home and it sounds great and has no issues, but I am thinking the mismatch may not be good for the amp and maybe I should get it looked at before entering it into rotation.
Any advice is appreciated. Thanks in advance.
A 7027A is - as used in these amps - basically a beefed up 6L6GC. The 6L6GC by the data sheet is not designed to handle the voltages in the V4, a proper 7027A will. If the amp has been biased properly and is running stable with those tubes it should be okay.
There are new production 7027A being made, new sensor makes the Sovtek and Tung sol versions, JJ makes some too. The plate voltage specs in the JJ datasheets show a lower plate max rating than the older 7027A datasheets. Had a set of the Sovtek in my V4 and they didn’t last long. Haven’t tried the Tung sol yet as I haven’t had to retube since they were released, usually go NOS in mine.
Note the 7027A is the tube you want, not just a 7027.
daveobieone
Providing the "musical foundation" since 1966
I just bought a 70's V4B a couple of weeks ago. It has the 3 prong power and aux outlet. I gather that makes it mid-70's.?. I've been into it a bit, but forgot to check for date codes. Nearly all the coupling caps were bad (leaking), and one of the screen filter caps was shorted. All that stuff is replaced now. I added bypass resistors across the seriesed filter caps. All but the screen supply caps had them, and it was a screen cap that failed.
I loaded some older, used 6L6GC's I had laying around into it. It made a tad over 100 watts into my dummy load at clip. I took it to rehearsal with my 10 piece horn-band, and hoped for the best. The best is what I got!!! Loaded into my Mesa Subway 15, the guys in my band said it was some of the best bass tone they've ever heard. Not super loud (this band plays really loud!), but really sounded great. I'll try some other cabs with it later. It was louder than the B100R I've been using at rehearsal...and really sounded much nicer.
So, now that I know this amp could be a keeper / winner, I loaded a NOS set of Phillips JAN 7581's into it as a test. Wow...Even better tone and dynamics. I don't think I wanna keep running a $500 set of tubes in it, so today I ordered a new set of 7027A Tung Sols. This amp puts about 545 volts on the plates at 120 volts of AC. I'm also a little concerned about doing that to such an expensive set of tubes rated for 500v. So, hopefully the Tung Sol's will be here before next weeks practice.
The old, original RCA and TS 7027A tubes were supposed to be rated at 600 volts, and 35 watts of plate dissipation. That's likely why Ampeg spec'ed them. I haven't been able to find ratings for these reissues. Perhaps someone else here has.?. Hopefully the sound will be as nice as the NOS 7581's in it now. I'll do some measurements and play-testing, and report back after the 7027A's are in.
I apologize if someone has already covered this in a previous post in this thread. I haven't read all they way back to the beginning.
Dave O.
I loaded some older, used 6L6GC's I had laying around into it. It made a tad over 100 watts into my dummy load at clip. I took it to rehearsal with my 10 piece horn-band, and hoped for the best. The best is what I got!!! Loaded into my Mesa Subway 15, the guys in my band said it was some of the best bass tone they've ever heard. Not super loud (this band plays really loud!), but really sounded great. I'll try some other cabs with it later. It was louder than the B100R I've been using at rehearsal...and really sounded much nicer.
So, now that I know this amp could be a keeper / winner, I loaded a NOS set of Phillips JAN 7581's into it as a test. Wow...Even better tone and dynamics. I don't think I wanna keep running a $500 set of tubes in it, so today I ordered a new set of 7027A Tung Sols. This amp puts about 545 volts on the plates at 120 volts of AC. I'm also a little concerned about doing that to such an expensive set of tubes rated for 500v. So, hopefully the Tung Sol's will be here before next weeks practice.
The old, original RCA and TS 7027A tubes were supposed to be rated at 600 volts, and 35 watts of plate dissipation. That's likely why Ampeg spec'ed them. I haven't been able to find ratings for these reissues. Perhaps someone else here has.?. Hopefully the sound will be as nice as the NOS 7581's in it now. I'll do some measurements and play-testing, and report back after the 7027A's are in.
I apologize if someone has already covered this in a previous post in this thread. I haven't read all they way back to the beginning.
Dave O.
If I’m remembering correctly somewhere in this or another thread it was estimated that the three prong cord/outlet change was around 71-72 so the amp could be 72-75ish if it’s the older style graphics, 75-79 if the second style.
I haven’t seen a data sheet for the Tung sol reissues but its new sensor and they usually just reproduce the old sheets with their logo added anyways. I haven’t seen a data sheet for the Sovtek 7027A, only the 7027, but I have seen both versions of the tube out there. Their 7027 datasheet says 550 I think? They have 7581 and 7581A available in the Tung sol reissue line and I think as I mentioned above they just reused the old datasheets. Beans-on-Toast has been running the 7581A reissues in his V4 with success so I’d hope that the 7027A would be solid.
I haven’t seen a data sheet for the Tung sol reissues but its new sensor and they usually just reproduce the old sheets with their logo added anyways. I haven’t seen a data sheet for the Sovtek 7027A, only the 7027, but I have seen both versions of the tube out there. Their 7027 datasheet says 550 I think? They have 7581 and 7581A available in the Tung sol reissue line and I think as I mentioned above they just reused the old datasheets. Beans-on-Toast has been running the 7581A reissues in his V4 with success so I’d hope that the 7027A would be solid.
Let us know what you think of the Tung-Sol 7027A's.
I find that in this amp, if you set the power tube bias for a bit less hot than the typical 70% maximum plate dissipation, the amp still sounds very good and tube life is extended.
daveobieone
Providing the "musical foundation" since 1966
I sure wish this V4B had cathode resistors so I could easily check how hot the tubes are running. Since it doesn't have a bias adjust pot, I didn't bother to install any when I was inside last time.
I use a somewhat unusual method for random checking of how hot the power amp tubes are running (this also works for solid state BTW). My variac has both a volt meter, and a wattmeter. Feeding the amp into my 1kw dummy load, I slowly bring up the level till the wattmeter starts to increase above its idle value. That tells me the amp is going from Class A, into AB1 (or whatever). From that, I can get a relative idea of how hot the tubes are running. I also use a IR thermometer to check the temp of the plates, and see if they match pretty closely.
With the first set of rather well-used 6L6GC's, the V4B came out of Class A very early...like under 1 watt. So, I knew those tubes were running pretty cold. They were about 5000 on my Hickok tester. When I installed the NOS 7581A JAN/Phillips, the thing stayed in Class A till it got up to over 10 watts. So, those tubes are running fairly hot by comparison. Those test at 5800 to 6300. The ones I installed all were about 5800.
The 7581A tubes are all running about 380 degrees F., and all within about 10 degrees of each other.
BTW, with the 7581A's in there, the amp doesn't hit 3% distortion (clipping) till 115 watts at 120 VAC. So, you DO NOT need to run 6550's in a V4B to get it up to 115 watts.
I don't have a plug-in bias checker thingy (with the tube base and socket). I guess I may buy one. Does anyone have suggestions for which ones work best? There's not a lot of clearance to the cabinet bottom with tall-bottle tubes in it...so it would need to be a pretty low-profile thing to avoid removing the chassis.
Dave O.
I use a somewhat unusual method for random checking of how hot the power amp tubes are running (this also works for solid state BTW). My variac has both a volt meter, and a wattmeter. Feeding the amp into my 1kw dummy load, I slowly bring up the level till the wattmeter starts to increase above its idle value. That tells me the amp is going from Class A, into AB1 (or whatever). From that, I can get a relative idea of how hot the tubes are running. I also use a IR thermometer to check the temp of the plates, and see if they match pretty closely.
With the first set of rather well-used 6L6GC's, the V4B came out of Class A very early...like under 1 watt. So, I knew those tubes were running pretty cold. They were about 5000 on my Hickok tester. When I installed the NOS 7581A JAN/Phillips, the thing stayed in Class A till it got up to over 10 watts. So, those tubes are running fairly hot by comparison. Those test at 5800 to 6300. The ones I installed all were about 5800.
The 7581A tubes are all running about 380 degrees F., and all within about 10 degrees of each other.
BTW, with the 7581A's in there, the amp doesn't hit 3% distortion (clipping) till 115 watts at 120 VAC. So, you DO NOT need to run 6550's in a V4B to get it up to 115 watts.
I don't have a plug-in bias checker thingy (with the tube base and socket). I guess I may buy one. Does anyone have suggestions for which ones work best? There's not a lot of clearance to the cabinet bottom with tall-bottle tubes in it...so it would need to be a pretty low-profile thing to avoid removing the chassis.
Dave O.
You can install 1 ohm cathode resistors easily enough or use a plug in bias probe. I have a few of the little eurotubes units, one that just connects to a meter and one of the fancier ones that reads plate voltage and current directly. Comes in handy.
I installed a simple bias pot on mine, just a little 22k pot and 68k series resistor in place of the 75k resistor. Works well enough. I think at the stock 75k value it ran fairly cool but the amp sounded great with the set of sylvannia 7027A I had in there.
daveobieone
Providing the "musical foundation" since 1966
Quick question about the cathode resistors...
I'd probably use 1 ohm, 1%, metal film. Typically in smaller HiFi amps I would use a 1 watt. Is that too small? Should I go to 2 watt, or 5 watt?
Just wondering what the general preference would be for a V4B?
Thanks for the guidance!
Dave O.
I'd probably use 1 ohm, 1%, metal film. Typically in smaller HiFi amps I would use a 1 watt. Is that too small? Should I go to 2 watt, or 5 watt?
Just wondering what the general preference would be for a V4B?
Thanks for the guidance!
Dave O.
I just picked up a 77 V-4 a couple of weeks ago, I'm looking for the head logo, anyone have a extra one? I'm also into resin casting one if I could get someone to loan me one for about a week.
1 watt should be more than fine. You're talking about reading mV across a 1 ohm resistor. P=V*I, so assuming you're looking at measuring in the 20-30mV range for biasing, lets say 0.04 V which means 0.04 A (the point of using a 1 ohm resistor) so you have 0.0016 W. You'd have total overkill with a 1 watt.
I might have an old beat up one from my SVT sitting around. I think fliptops was selling them at one point but don't know if they still stock them.
I have the logo, but the finish isn’t great, but should be good enough for casting. Happy to exchange it for a few return castings. PM me if you want to go for it.
