Beginner looking for vintage mono valve amp recommendations

[repeatclicks]

I also posted this in the Mono thread, but not really getting the response I hoped for.

I have a 1950s Lenco F50-8 with a two pin mono headshell.

I just want a simple mono valve amp, and I would like to run two speakers through it. I plan on using Ronette flip cartridges with it, and possibly a mono lp cartridge (yes, I know they are  rare, but I know someone who has some and will sell me one). My wife and I live in a small flat, so I don't need something powerful, I am assuming 15-20 watts would suffice... and ideally I would like it to be integrated, but if someone can recommend a good solid preamp/amp setup, I'm open to anything.  
 

There are so many variables in valve technology, that I don't know where to start. I was looking at some Heathkits on ebay and those seem to interest me, but I am not sure... I already have a 300 Watt AC converter that steps down to 120V if necessary, since my guitar amp is American ( I am originally from Detroit).

Any help is greatly appreciated!

-Adam

[GP49]

There were many amplifiers in the market that could meet your desires, and what you wind up with is going to depend on what is available in the used market anyway.  For a 15-watt amplifier, I'd look for something with a pair (push-pull) of 6BQ5/EL84 output tubes.  Once you go up to 20 watts, that's too much for the EL84, so a pair of 6L6 or their near-equivalents 5881 and 1614, good for 25 watts or so.  Above that, you'll find the 6CA7/EL34 for up to 50 watts or so; and the 6550/KT88 in the 60 watt range. 

[repeatclicks]

Can I run two speakers off a mono amp, or should I be looking to get a stereo amp instead if I want to run two speakers? Stupid question, I'm sure, but I am totally new to this. I am assuming if I wanted to run mono with two speakers, I would need to run a matching pair of monoblocks...

[rfgumby]

Can I run two speakers off a mono amp, or should I be looking to get a stereo amp instead if I want to run two speakers? Stupid question, I'm sure, but I am totally new to this. I am assuming if I wanted to run mono with two speakers, I would need to run a matching pair of monoblocks...

It depends on the speakers and the amp.  What's the speaker impedance for the two you want to run at the same time?

[repeatclicks]

It depends on the speakers and the amp.  What's the speaker impedance for the two you want to run at the same time?

Thats the thing, I don't have a chosen set of speakers yet, although a friend of mine wants to sell me a vintage pair of 13x8 EMI's from the early 50s although I don't know their impedance. I suppose I should choose an amp first...

[GP49]

Can I run two speakers off a mono amp, or should I be looking to get a stereo amp instead if I want to run two speakers? Stupid question, I'm sure, but I am totally new to this. I am assuming if I wanted to run mono with two speakers, I would need to run a matching pair of monoblocks...

Yes, in most cases you can run two loudspeakers on one amplifier.  For ideal impedance matching and power transfer: connect the two loudspeakers together to the amplifier and use the connection for HALF the specified loudspeaker's impedance.  For example, two 8Ω loudspeakers would be connected in PARALLEL: the two speakers together to the ground and 4Ω connections on the amplifier.  If the amp has no 4Ω tap but does have 16Ω, you can connect two 8Ω loudspeakers in SERIES (daisy-chain) to the ground and 16Ω connections.  Keep in mind, though: the specified loudspeaker impedance is nominal only, as the impedance varies at different frequencies; usually it's the lowest it goes, within the audio band.  On tube amplifiers, a mismatch on the order of 2:1 is generally not a big issue (on transistor amps you can risk damage if running into too low an impedance).

[repeatclicks]

Sounds good.

Thanks for your help!

-Adam

[repeatclicks]

Ive been doing a little bit of digging around, and came across the Grommes Little Jewel amplifiers. From what I can tell, these were DIY amps like heathkits and were about 10W total. I think that I will try to hunt down one to get myself going. They seem to fetch about $100 - $250 each depending on condition. I really want something no-frills, and these seem just the ticket.


I'm not after a fancy pair of monoblocks with the most expensive gear available, and I probably never will be. I have a 1949 Ford to buy someday ya know!  


What does everyone else think about this idea? As a starting point, can anyone recommend integrated amps similar to the Little Jewel that could help me along?

[rfgumby]

Hi Adam-

  Those Grommes amps would probably be a fine start, as long as you don't expect too much from 10 watt amps.  But you might be surprised.

Does Genes description of series and parallel speaker hook up make sense to you?  That's where we were going, but sometimes these explanations requires smaller steps to get to the destination.

[repeatclicks]

Yes Genes description made perfect sense. I looked up a diagram showing the difference between the two as a visual aid.

I was also considering a Heathkit AA 181, which would give me 25W, so a bit more power... has anyone used it before? I know people go crazy for the higher end Heathkits.

[GP49]

Heathkit AA-181 is a 25-watt amplifier with very good potential.  Its power transformer is of more-than-adequate capacity and its output transformer is very fine.  Being designed as a kit to be put together by the owner, it has lots of room in the chassis and making parts upgrades should be easy. 

My concern is with the output tubes.  The 7591 output tube is no longer in production.  It originated and was made only in the USA,  designed to fit into a small space, for amplifiers in the 25-30 watt range.  This compact envelope made possible smaller chassis but also meant the tube ran HOT; and in many applications where the output tubes were close together and in a confined space, that meant they didn't last very long.  A lot of equipment was designed around the 7591, including very popular tuner/amplifiers and integrated amplifiers from the major US makers Fisher and Scott.

New old stock 7591 tubes go for around $79-80 each.  It is said that the Japanese bought up large quantities of the 7591 tube, as they covet Fisher, Scott and Eico equipment, and the McIntosh MC225 and MA230, all of which use the 7591; this left few in the USA and ran their prices up.

The Russian "7591" I have tried in my Fisher 500B receiver is actually a 6L6 type with the 7591 pinout.  It's not capable of the same plate current as a true 7591.  The JJ 7591 is said to be a better performer, almost a true 7591 in performance but not quite as small as a true American 7591; however, they have reliability issues.

The 7868 and 6GM5 are the same internally as the original, American 7591, but use nine-pin sockets of two different sizes instead of the octal base of the 7591.  However in my experience they are even harder to find than the 7591 and you'd have to change sockets to use them.

I still have sufficient original 7591 for my current needs; but when I restore my dad's Eico ST-40, however, I'll need to think about what I put in there. The ST-40 has a lot of potential, as it runs Class A well up into its power range. I may just bite the bullet and buy a set of four new old stock American 7591s for it.

[pfowler]

Jumping in here...

One thing you may run into with any vintage amp (tube or solid state) is they are many years old and quite often have not been maintained properly. Also, anything designed and built in the 50's, 60's and 70's will need some attention just to work as designed today. I certainly do... 

It's a tradeoff - you can buy a tatty unit in need of repairs for very little money, or you can spend more cash to get an amp that has already been restored. Spend even more cash and you can get a unit that's much better than new, but I don't think you want to go that direction.

My advice? Find a tube repair tech or an audio club close by and have anything you buy checked out by someone who's familiar with tube amps in general. There are several interesting ways an old tube amp can fail, some of which involve smoke and melty bits...

Good luck in your search!

Pete

[ken13]

Hi Adam,

 This may be worth a visit,
 www.audiojumble.co.uk
 Not untill October so you have a bit of time to sort out what you need / want.
 Good luck.

[repeatclicks]

Hi Adam,

 This may be worth a visit,
 www.audiojumble.co.uk
 Not untill October so you have a bit of time to sort out what you need / want.
 Good luck.

This is perfect! I am in no rush to set up my gear just yet, so yes, I will have loads of time to prepare. Now I just need to find some good UK based manufacturers of smaller integrated amps like the Heathkit and Grommes...

[richardz]

The Grommes look really interesting, I've not heard of them before - and haven't seen any reference to them in the UK.

However Heathkit were sold in the UK and do turn up.