4 7591 power tubes...

[Bmxbarspin724]

I have 2 amps that both use a pair of 7591 power tubes with various preamp tubes. I was wondering if there were any amps that have been made that use 4 7591 power tubes. I looked and all I found was some old fisher hi-fi stereos that used them.

I really like the sound of the 7591 tube, as opposed to a 6L6 quad, or an EL84 quad. But the amps that I have found that use 7591's seem to put out at most, like 30 watts, and I really would like to have like 50+ watts.

Is there something inherent about the 7591 tube that disallows it to be used in a quad?

what's up with that?

[Jazz P Bass]

I would not think the tube itself would care how many you use in parallel The circuit itself would.

[Tom Phillips]

There is nothing inherent about the 7591 tube that disallows it to be used in a quad. It is just from an era where the designer would change to another tube type if power output in the 50 watt region was desired.

[Prairie Dawg]

Originally Posted by Tom Phillips

There is nothing inherent about the 7591 tube that disallows it to be used in a quad. It is just from an era where the designer would change to another tube type if power output in the 50 watt region was desired.

Another thing is whether the RCA salesman or the Sylvania salesman stopped by shortly before the particular production run and offered product at sale prices.

[Rhodesplyr]

Originally Posted by Tom Phillips

There is nothing inherent about the 7591 tube that disallows it to be used in a quad. It is just from an era where the designer would change to another tube type if power output in the 50 watt region was desired.

Exactly. I think the target application for the 7591 was integrated Hi-Fi amps where it frequently superseded the EL84/7189 in amps by H.H. Scott, Sherwood, Fisher, etc... It allowed designers to get 30-35W from a pair of fairly small power tubes that required only 800mA of heater current per tube and that were easier to drive than, say, a 6L6 or 5881. Though I've never owned a 7591-based Hi-Fi amp, those who do seem to like them a lot.

Hammond use them in a few of their later designs.

[Jazz P Bass]

I have two pairs of these 7591 tubes in my Fisher 800-B.
I think it is a synergy thing. Fisher- 7591. This amp sounds awesome.

[capnjuan]

Originally Posted by Bmxbarspin724

I was wondering if there were any amps that have been made that use 4 7591 power tubes ... I really like the sound of the 7591 tube ... but the amps that I have found that use 7591's seem to put out at most, like 30 watts ... is there something inherent about the 7591 tube that disallows it to be used in a quad?

Hi; Panaramic / Audio Guild amps from the mid-60s used quads of 7591As (one is missing from its socket):



The power output of tubes is a function of the ability of tube to handle voltage on its plate and current. Link to the Tube Data Sheet for the 7591A:

http://www.tubezone.net/pdf/7591.pdf

The tube was very popular in the mid-60s because of increased power handling / cleaner tone v. 6V6s; Ampeg, Gibson, Guild, Audio Guild ... many others made 7591 amps ... usually 25-30 watts for push/pull twins. I don't know of any other quad 7591 designs. CJ