ECC807, substitute !

[vinrads]

Has anyone tried a n ECC83 in place of the ECC807 , the only difference as far as I can see is the gain , which is not rely a problem ! have you seen the price of the ECC807's any thought's welcome. Mick.

[jjl]

The ECC807 has a different pin-out to the ECC83 so that would be a problem. I've only ever seen the ECC807 used in various models of Rogers Cadet amplifiers, is that your desired application?
Apparently the ECC807 is equivalent to the 13D7, also by Brimar. I don't think I've ever seen a 13D7.

John

[vinrads]

Hi John pin out is not a problem , it's for a new build , a Brimar cct using EL506'S like you I have never seen a 13d7 in fact I don't think I have seen an ECC807 in the flesh ,cheers Mick.

[yestertech]

Is that the 20W power amp circuit at the back of the Brimar book ? I'd be interested to see how it goes as I lost count of the number of times I was going to build that amp!

I'm of the opinion that there is no 'magic' to ECC807s. Maybe they're slightly quieter than the '83 - (never done an A/B comparison ) It has to be admitted that The Cadet III's noise levels on the disc input are rather good for a valve amp.
I had the similar Rogers HG88 on which I decided to as an exercise to rewire the bases to take ECC83s. Before I did this, I measured the gain from a line input through to the power amp output ( resistive load )
When re-measured after the 'transplant' the gain was within 1 db. Although the 807 may have higher Mu, it seems in practice it makes very little difference, especially when used within a feedback loop where the feedback elements mostly set the gain.
New production cheapish ECC83 vs. V. expensive NOS ECC807 ? not worth it.


Andy

[usradcoll1]

Originally Posted by yestertech

Is that the 20W power amp circuit at the back of the Brimar book ? I'd be interested to see how it goes as I lost count of the number of times I was going to build that amp!

I'm of the opinion that there is no 'magic' to ECC807s. Maybe they're slightly quieter than the '83 - (never done an A/B comparison ) It has to be admitted that The Cadet III's noise levels on the disc input are rather good for a valve amp.
I had the similar Rogers HG88 on which I decided to as an exercise to rewire the bases to take ECC83s. Before I did this, I measured the gain from a line input through to the power amp output ( resistive load )
When re-measured after the 'transplant' the gain was within 1 db. Although the 807 may have higher Mu, it seems in practice it makes very little difference, especially when used within a feedback loop where the feedback elements mostly set the gain.
New production cheapish ECC83 vs. V. expensive NOS ECC807 ? not worth it.


Andy

I never heard of a valve (tube) having a mu over 100!
At the price, it really must be special, or just an audio fools dream.
I'll stick with a ECC83. I'm going to rewire to sockets for a ECC88.

Dave, USradcoll1.

[Robert Gribnau]

The 811 (transmitting power triode) has a mu of 160.

If you connect the control grid and the screengrid of a GU50 (ГУ-50) together, you get a triode with a mu of 285.

Because of the high mu, combined with driving the triode with grid-current, their behaviour looks a bit like a pentode.

[Radio Wrangler]

The ECC807 has 50% more mu, and double the Gm of the ECC83

Whether this is significant depends on what you want to do with it.

David

[vinrads]

Hi David, this is the amplifier I am thinking of building .Like Andy (yestertech) I have wanted to build this amp for years. Unless someone has a circuit using EL506's .Mick.

[Radio Wrangler]

It's a valve manufacturer circuit, so it's probably showing off the advantages of their wonderbottles compared to more common types.

By the way, the circuit contains nasty bits that will create pops and bangs when the selector switch is moved.

180mV/13mV = 23dB of feedback how kind of them to give that figure.

The phase splitter sees 150k//330k as the anode load, with 2.4mA/V that's trying for a gain of 247, but Mu is only 150, so gain is going to be anode slope-limited. Drop an ECC83 in and the circuit is trying for a gain of 123, but the mu is only 100.

You're going to lose 4 or 5db of loop gain.

As suspected, that circuit's been optimised to make the most of the differences of those valves. ECC807s will be rare and pricy because most will have been mopped up for vitally important tube-rolling supplies.

The Gardners transformer may also stop you finding out what the real thing is like. If you make any changes, you wind up finding out about something else.

The problem with valve amplifiers is that the circuits are highly simplified and so the results depend very strongly on the devices use.

Circuit-wise, there's nothing special in it apart from the parts that would be very difficult and expensive to get.

David

[Herald1360]

The power amp uses an ECC83 anyway as phase splitter. Surprised to see EF86 there instead of 6BR7. Or indeed ECC83 rather than 12AX7.

The preamp uses ECC807s.

Use someone else's preamp circuit that doesn't?

[GrimJosef]

Originally Posted by Radio Wrangler

... ECC807s will be rare and pricy because most will have been mopped up for vitally important tube-rolling supplies ...

Sometimes true (although not nearly as often as we might hear). But not this time. Their unusual pin-out makes them near-to-useless for tube-rolling.

They're pricy because they are rare. There are quite a few Rogers amps out there which were built for them, and relatively few of the valves were made. It's the purest of supply/demand situations .

Cheers,

GJ

[Radio Wrangler]

Some people have been dedicated enough to rewire things ... Slow rolling? and I've come across home-made plug/socket adaptors.

Hadn't spotted it was an ECC83 in the power amp. Odd for Brimar, fraternising with the enemy.

David

[Diabolical Artificer]

"The power amp uses an ECC83 anyway as phase splitter." Big no, no, the ECC83 is ill suited for this task as they are for cathode followers where you see them used in quite a few pre-amp designs, a ECC82 is far better in these applications.

"The preamp uses ECC807s....Use someone else's preamp circuit that doesn't?" I'd go further, sell the EL509's and buy new EL34's, unless you have a good supply of 509's. at some point the OP valves will need replacing, best to build an amp with readily available current production valves.

This amp and the Mullard amps were designed to sell valves and show off the latest valve types, if anyone's trying to sell me something I'd treat it with caution and look on the design with suspicion.

Andy.

[Electronpusher0]

Originally Posted by Diabolical Artificer

This amp and the Mullard amps were designed to sell valves and show off the latest valve types, if anyone's trying to sell me something I'd treat it with caution and look on the design with suspicion.

Andy.

True, but the Mullard designs have stood the test of time and the valves used in their designs are readily available, or is that because the designs were so popular?


Peter

[vinrads]

Thank's Andy (post 13) the output valves are in fact EL506'S New Brimar Mick.

[barretter]

The ECC807 (1964) and EL506 (1966) were both pretty late valves. Whereas the ECC807 has virtually disappeared you can still buy EL506s on eBay from a chap in Taiwan (!) who still has 79 available at £19 each.
If you can find some of the double triodes Brimar also designed an EL506 power amp with an ECC807 as the input valve.
They were also used by Selmer in guitar amplifiers.

[vinrads]

Hi Thank's for the cct's the all purpose 30 looks interesting with the fixed bias , cheers Mick.