Valve tremolo circuit - UK Vintage Radio Repair and Restoration Discussion Forum

MrElectronicman · 26th Feb 2011, 11:51 pm

Does any one remember a circuit for a valve tremolo, that may have been published in Practical Wireless, or some of the other magazines.
I remember building one when I was in secondary school, and the design may have come out of one of the Practical Mags, it would have been in the mid to late 1950's.

I have various designs using both triodes and pentodes but I cannot remember much about the one I built, it was a long time ago, and I would like to try to build it again.

Thanks for any insight.

Mike Phelan · 27th Feb 2011, 10:56 am

If no luck with finding the circuit referred to, most of these used in electronic organs used a Wien Bridge as an LF oscillator, typically using a double triode.

Hammond used a set of LC sections scanned using a motor.

Note that tremolo is not the same thing as vibrato. Tremolo is an amplitude variation, vibrato is a frequency variation.

terrybull · 27th Feb 2011, 10:57 am

I have a copy of Babani Press No12 (HiFi, PA & Discotheque Amp Designs) which has designs for a 2 valve tremelo unit 1 x ECC82 & 1 x ECL86 and also a combined tremelo and vibrato unit using just 1 ECC83. Any use?

MrElectronicman · 28th Feb 2011, 12:14 am

Thanks for the feedback.

The unit I had built those many year ago was only a tremolo, not a vibrato. As I recall there were two valves one of which was a pentode, and I think it may have been an EF80, I know this is an RF valve, but EF80's were everywhere, and thus cheap.

Anyway, I am going to go with one I have found that uses an ECC83 as a phase shift oscillator, and an ECC82 as a cathode follower, and see out it works out. It helps that I have a number of ECC8_'s and the 12A_7 equivalents to play with.

DangerMan · 28th Feb 2011, 1:21 am

I wonder if this was part of the circuit used in the "PW Guitar Amplifier"? That certainly used an EF80 oscillator valve, as a phase shift oscillator I think.. The main amplifier used two 807's, and I think it dated from about 1965, plus or minus a bit.

If so, I have a very tatty PW "blueprint" somewhere. I will try and find it if that's the one, and happily scan it... it's a big sheet and in many shreds but the circuit should be recoverble at least.
Pete

Diabolical Artificer · 28th Feb 2011, 11:05 am

The Wem dominator had a tremolo effect on it using an ECC83 I think.Quite a simple circuits as I recall,Andy

MrElectronicman · 1st Mar 2011, 12:14 am

Hi DangerMan,

I would like to the see the cct. Might bring back some memories.

DangerMan · 1st Mar 2011, 9:25 am

Hi MrElectronicman,
I've scanned the circuit diagram of the preamplifier and also, for what it's worth, the main amp. Now I just hope I've attached them successfully!

Pete

MrElectronicman · 1st Mar 2011, 9:12 pm

Hi DangerMan,

Thanks for the diagrams, they came through just fine.

I now have to find a good EF80, I had one in my box but when I looked at it closely the tip must have broken and the vacuum has gone.

The pre-amp looks very much like I one I am looking for, but in the mean time I have made a lash-up, and I mean a lash-up, using the ECC83.

When I left the UK many years ago now, I threw out most of my Practical Wireless and Practical Television magazines, and only kept a few. Unfortunately years later we had a flood in the basement and that put paid to the rest.

Danny · 3rd Mar 2011, 11:30 pm

Wow this looks interesting iI would like to see Tterry Bbull,'s diagrams and am interested in getting a copy of his book. Danny.

peter_sol · 4th Mar 2011, 11:18 am

I am sure any small signal pentode would do or even triode.

Alistair D · 4th Mar 2011, 11:31 am

Quote:

Originally Posted by Danny

Wow this looks interesting i would like to see terrybull,s diagrams and am interested in getting a copy of his book. Danny

Me too.

Al

radioman · 4th Mar 2011, 11:46 am

You may be interested in also having a look at the tremelo circuit of the Heathkit PA-1 amplifier.
I posted the manual for it here : https://www.vintage-radio.net/forum/...2&postcount=13
It uses half an ECC83 as a phase-shift oscillator to modulate the screen grid of an EF86.

Andy

terrybull · 4th Mar 2011, 7:48 pm

Here is a pdf of the tremolo circuits I previously referred to. A couple expressed interest. I apologise for the poor quality

but my scanner is not here at present so they were done quickly on a phone camera. You can just about make out the detail. If anyone wants a better scan send me a PM and I'll sort it out.

MrElectronicman · 4th Mar 2011, 9:25 pm

Looks as if I have started something here. I now have a circuit working using an ECC83 and ECC82, and I am now going to try using an EF80.

I found these diagrams at following website, they look much like the ones in terrybull's pdf.

http://www.triodeel.com/studio.htm

There are some interesting circuits that use a phase shift oscillator to directly modulate the drive current of a couple of EL84's in push-pull. A bit of overkill if you ask me.

I like the idea of using a ring modulator for the vibrato, so I might try to incorporate this option as well.

terrybull · 4th Mar 2011, 9:36 pm

You are right MrElectronicman. The link you posted look precisely like scans from the Babani book and my pdf

Valvepower · 9th Mar 2011, 10:31 pm

Hi There,

I’ve attached a picture of a Tremolo project in the Feb 1961 copy of Practical wireless; it may be the one you’re after?

If it’s the one I can do a better scan/copy for you.

I also remember Practical Wireless doing a complete valve guitar amplifier project in 1964. This used 807’s and the Radiospares De-Luxe output transformer.

Regards
Terry.

Alistair D · 9th Mar 2011, 10:53 pm

Hi Valvepower.

A very elegant implementation there, using the variable slope characteristics of the EF80. To my mind it should sound very good.

Al

Atomic Boogaloo · 10th Mar 2011, 4:15 am

Hi .. mm very interesting - F J Camm's usual ingenuity, but its got to be mentioned the EF80 ISN'T strictly a Vari-Mu type - so by all means build the circuit, but then perhaps try popping in an EF85 or EF183 for smoother operation ?

BTW, Tremolo Pedantry:- SOME people used the term to mean pitch bend (eg a 'Tremolo arm') though it IS actually 'Vibrato' (says Wikipedia and the dictionary)

The only serious attempts at THIS (using, phase-rotation) are the aforementioned Hammond scanner - (wonderful ol' thing with a spinning 'distributor arm') and Magnatone guitar amps http://www.vibroworld.com/magnatone/ (DO read the diagrams - great stuff!) - who I suspect had shares in a Valve company, due to the mega preamp arrangement - Vox and fender used something far simpler, and concentrated on raw power !

Just my .02 worth - F J Camm Lives !
Pete G

MrElectronicman · 10th Mar 2011, 11:05 pm

Hi Valvepower,

That's the circuit I was looking for, I see It was in PW in 1961, so it's about the right date give or take a couple of years.

Can you do a better scan? or shall I PM you?

26th Feb 2011, 11:51 pm	#1
MrElectronicman Heptode Join Date: Feb 2011 Location: Washington DC, USA Posts: 619	Valve tremolo circuit Does any one remember a circuit for a valve tremolo, that may have been published in Practical Wireless, or some of the other magazines. I remember building one when I was in secondary school, and the design may have come out of one of the Practical Mags, it would have been in the mid to late 1950's. I have various designs using both triodes and pentodes but I cannot remember much about the one I built, it was a long time ago, and I would like to try to build it again. Thanks for any insight.

27th Feb 2011, 10:56 am	#2
Mike Phelan Dekatron Join Date: Nov 2003 Location: Near Leeds, West Yorkshire, UK Posts: 4,609	Re: Valve tremolo circuit If no luck with finding the circuit referred to, most of these used in electronic organs used a Wien Bridge as an LF oscillator, typically using a double triode. Hammond used a set of LC sections scanned using a motor. Note that tremolo is not the same thing as vibrato. Tremolo is an amplitude variation, vibrato is a frequency variation. __________________ Mike.

27th Feb 2011, 10:57 am	#3
terrybull Octode Join Date: Jan 2011 Location: Southwell, Nottinghamshire, UK. Posts: 1,784	Re: Valve tremolo circuit I have a copy of Babani Press No12 (HiFi, PA & Discotheque Amp Designs) which has designs for a 2 valve tremelo unit 1 x ECC82 & 1 x ECL86 and also a combined tremelo and vibrato unit using just 1 ECC83. Any use?

28th Feb 2011, 12:14 am	#4
MrElectronicman Heptode Join Date: Feb 2011 Location: Washington DC, USA Posts: 619	Re: Valve tremolo circuit Thanks for the feedback. The unit I had built those many year ago was only a tremolo, not a vibrato. As I recall there were two valves one of which was a pentode, and I think it may have been an EF80, I know this is an RF valve, but EF80's were everywhere, and thus cheap. Anyway, I am going to go with one I have found that uses an ECC83 as a phase shift oscillator, and an ECC82 as a cathode follower, and see out it works out. It helps that I have a number of ECC8_'s and the 12A_7 equivalents to play with.

28th Feb 2011, 1:21 am	#5
DangerMan Heptode Join Date: Jul 2009 Location: Stoke-on-Trent, Staffordshire, UK. Posts: 719	Re: Valve tremolo circuit I wonder if this was part of the circuit used in the "PW Guitar Amplifier"? That certainly used an EF80 oscillator valve, as a phase shift oscillator I think.. The main amplifier used two 807's, and I think it dated from about 1965, plus or minus a bit. If so, I have a very tatty PW "blueprint" somewhere. I will try and find it if that's the one, and happily scan it... it's a big sheet and in many shreds but the circuit should be recoverble at least. Pete

28th Feb 2011, 11:05 am	#6
Diabolical Artificer Dekatron Join Date: Jul 2009 Location: Sleaford, Lincs. UK. Posts: 7,667	Re: Valve tremolo circuit The Wem dominator had a tremolo effect on it using an ECC83 I think.Quite a simple circuits as I recall,Andy __________________ Curiosity hasn't killed this cat...so far.

1st Mar 2011, 12:14 am	#7
MrElectronicman Heptode Join Date: Feb 2011 Location: Washington DC, USA Posts: 619	Re: Valve tremolo circuit Hi DangerMan, I would like to the see the cct. Might bring back some memories.

1st Mar 2011, 9:12 pm	#9
MrElectronicman Heptode Join Date: Feb 2011 Location: Washington DC, USA Posts: 619	Re: Valve tremolo circuit Hi DangerMan, Thanks for the diagrams, they came through just fine. I now have to find a good EF80, I had one in my box but when I looked at it closely the tip must have broken and the vacuum has gone. The pre-amp looks very much like I one I am looking for, but in the mean time I have made a lash-up, and I mean a lash-up, using the ECC83. When I left the UK many years ago now, I threw out most of my Practical Wireless and Practical Television magazines, and only kept a few. Unfortunately years later we had a flood in the basement and that put paid to the rest.

3rd Mar 2011, 11:30 pm	#10
Danny Heptode Join Date: Jul 2003 Location: North Walsham, Norfolk, UK. Posts: 516	Re: Valve tremolo circuit Wow this looks interesting iI would like to see Tterry Bbull,'s diagrams and am interested in getting a copy of his book. Danny.

4th Mar 2011, 11:18 am	#11
peter_sol Octode Join Date: Aug 2003 Location: Welwyn Garden City, Herts. UK. Posts: 1,906	Re: Valve tremolo circuit I am sure any small signal pentode would do or even triode.

4th Mar 2011, 11:46 am	#13
radioman Heptode Join Date: Apr 2003 Location: Ayr, Ayrshire, UK. Posts: 631	Re: Valve tremolo circuit You may be interested in also having a look at the tremelo circuit of the Heathkit PA-1 amplifier. I posted the manual for it here : https://www.vintage-radio.net/forum/...2&postcount=13 It uses half an ECC83 as a phase-shift oscillator to modulate the screen grid of an EF86. Andy __________________ G-QRP #12697

4th Mar 2011, 9:25 pm	#15
MrElectronicman Heptode Join Date: Feb 2011 Location: Washington DC, USA Posts: 619	Re: Valve tremolo circuit Looks as if I have started something here. I now have a circuit working using an ECC83 and ECC82, and I am now going to try using an EF80. I found these diagrams at following website, they look much like the ones in terrybull's pdf. http://www.triodeel.com/studio.htm There are some interesting circuits that use a phase shift oscillator to directly modulate the drive current of a couple of EL84's in push-pull. A bit of overkill if you ask me. I like the idea of using a ring modulator for the vibrato, so I might try to incorporate this option as well.

4th Mar 2011, 9:36 pm	#16
terrybull Octode Join Date: Jan 2011 Location: Southwell, Nottinghamshire, UK. Posts: 1,784	Re: Valve tremolo circuit You are right MrElectronicman. The link you posted look precisely like scans from the Babani book and my pdf

9th Mar 2011, 10:31 pm	#17
Valvepower Octode Join Date: Aug 2008 Location: Rayleigh near Southend-On-Sea, Essex, UK. Posts: 1,883	Re: Valve tremolo circuit Hi There, I’ve attached a picture of a Tremolo project in the Feb 1961 copy of Practical wireless; it may be the one you’re after? If it’s the one I can do a better scan/copy for you. I also remember Practical Wireless doing a complete valve guitar amplifier project in 1964. This used 807’s and the Radiospares De-Luxe output transformer. Regards Terry. Attached Thumbnails

9th Mar 2011, 10:53 pm	#18
Alistair D Nonode Join Date: Jan 2010 Location: Edinburgh, UK. Posts: 2,008	Re: Valve tremolo circuit Hi Valvepower. A very elegant implementation there, using the variable slope characteristics of the EF80. To my mind it should sound very good. Al __________________ I won't tell you how I discovered that.

10th Mar 2011, 4:15 am	#19
Atomic Boogaloo Retired Dormant Member Join Date: Mar 2011 Location: North London Posts: 5	Re: Valve tremolo circuit Hi .. mm very interesting - F J Camm's usual ingenuity, but its got to be mentioned the EF80 ISN'T strictly a Vari-Mu type - so by all means build the circuit, but then perhaps try popping in an EF85 or EF183 for smoother operation ? BTW, Tremolo Pedantry:- SOME people used the term to mean pitch bend (eg a 'Tremolo arm') though it IS actually 'Vibrato' (says Wikipedia and the dictionary) The only serious attempts at THIS (using, phase-rotation) are the aforementioned Hammond scanner - (wonderful ol' thing with a spinning 'distributor arm') and Magnatone guitar amps http://www.vibroworld.com/magnatone/ (DO read the diagrams - great stuff!) - who I suspect had shares in a Valve company, due to the mega preamp arrangement - Vox and fender used something far simpler, and concentrated on raw power ! Just my .02 worth - F J Camm Lives ! Pete G

10th Mar 2011, 11:05 pm	#20
MrElectronicman Heptode Join Date: Feb 2011 Location: Washington DC, USA Posts: 619	Re: Valve tremolo circuit Hi Valvepower, That's the circuit I was looking for, I see It was in PW in 1961, so it's about the right date give or take a couple of years. Can you do a better scan? or shall I PM you?