New Build- Modded ODS Type #0124 Using Sub-Miniature Dual Triodes & Miniature Output Valves/Tubes

Overdrive Special, Steel String Singer, Dumbleland, Odyssey, Winterland, etc. -
Members Only

Moderators: pompeiisneaks, Colossal

Post Reply
User avatar
GuitarBloke
Posts: 6
Joined: Wed May 28, 2014 8:46 pm
Location: Antrim UK

New Build- Modded ODS Type #0124 Using Sub-Miniature Dual Triodes & Miniature Output Valves/Tubes

Post by GuitarBloke »

I've been lurking around The Amp Garage for a few years since I bumped into Mark Jensen Fowler on another amp building forum somewhere and he gave me a steer in this direction. Thanks Mark. Anyway after building a few Tweed and Blackface Fenders I thought I would try something a bit more complex. In the meantime I stumbled across subminiature dual triodes which I don't think were widely available when Mr Fender or Mr Dumble were developing circuits and which were the last gasp of Valve/Tube R&D as I understand it. So I wondered if they could be used to substitute the usual 12A*7 suspects. And having taken that step and lowered B+ voltages, why not use 6AQ5s in the output section? And since small is the new big in the amp world and I'm not getting any younger and still have to carry my own gear, I though I would give it a go. Here's a link to a demo video on YouTube. I can post more information if there are any questions, but I don't want this first post to be too long. And I know for the purists there are many things in this Amp that are different, so apologies in advance if I offend anyone's tender sensibilities. This is not the prettiest or neatest build I have ever seen, or even built, I had to make some compromises to fit everything in and I'm not a designer or engineer. I hope there is something here of interest and I will be happy to supply more info on request.

https://youtu.be/3SUIrtNvlTM

Thanks for reading this far.

Edited 22 July 2017 Video with improved sound quality
Last edited by GuitarBloke on Sat Jul 22, 2017 5:23 pm, edited 1 time in total.
John
User avatar
xtian
Posts: 6990
Joined: Mon Apr 19, 2010 8:15 pm
Location: NorCal
Contact:

Re: New Build- Modded ODS Type #0124 Using Sub-Miniature Dual Triodes & Miniature Output Valves/Tubes

Post by xtian »

Hello, John, and welcome!

Nice looking build and good playing. I can't say whether the amp sounds good, because the recording distorts badly. Interested to see your modified schematic.

Cheers.
I build and repair tube amps. http://amps.monkeymatic.com
10thTx
Posts: 1863
Joined: Sat Dec 30, 2006 1:13 am

Re: New Build- Modded ODS Type #0124 Using Sub-Miniature Dual Triodes & Miniature Output Valves/Tubes

Post by 10thTx »

I love innovative designs. THANKS for sharing your work! Build looks great. I'd also be interested in seeing a schematic if you have one to share.

With respect, 10thtx
User avatar
GuitarBloke
Posts: 6
Joined: Wed May 28, 2014 8:46 pm
Location: Antrim UK

Re: New Build- Modded ODS Type #0124 Using Sub-Miniature Dual Triodes & Miniature Output Valves/Tubes

Post by GuitarBloke »

xtian, 10thTx,
Thanks for the kind words of welcome. Sorry about the sound quality, I didn't realise it was so bad, yes the iPhone microphone I was using seems to have been clipping throughout.

I don't have a modified schematic, but for the preamp and most of the other circuitry I followed very closely the #0124 layout by Martin Manning and Tony Albany which I found on this forum, and the D'Lite ODS schematic Rev 1.2 dated 18/04/2007 which I also found here.

Points of departure are
Power supply.
I am using the 190v tap of 0-190-275 Toroidal PT from a vendor in the UK called Ampmaker. The 190V bridge rectifies to ~ 280V at B+1
Filtered by 5 x 40uf filter caps
220R 25W resistor instead of a choke
Dropping resistors of 4.7k, 2.2k 2.2k between the remaining stages
For the 3 preamp dual triode filaments I built a DC supply using a bridge rectifier and 4x 2200uf radial caps. Fed by the PT filament winding. The voltage was a little high so I put in a 0R5 dropping resistor and preamp valve voltage is sitting at about 6.5V
The ground side of the filament supply bridge rectifier goes to the cathodes of the power valves/tubes and there therefore is no need for the centre tap of the filament winding to be grounded
The power valves filaments are fed directly by the 6.3V ac filament winding

Auxiliary power supply
This is a 3VA 12-0-12 transformer full wave rectified to ~17V (I meant to buy a 6-0-6 and bridge rectify)
This feeds a 5V regulator for the relays and a 9V regulator for the reverb circuit

Valves/Tubes
The output valves/tubes are cathode biased mainly for simplicity and because the PT I chose has no bias tap
They are biased in pairs with 2x150R 5 watt resistors with 25uf bypass cap
When running with 2 pairs of valves the second resistor is switched in in parallel to cut the cathode resistor value to 75R

The output valves are 2x6AQ5/6005s which are lower voltage lower output analogues of the 6V6. They have a 7 pin base. And a pair of Russian 6P1PEVs which seem to be roughly equivalent and which have a standard Noval 9 pin base. They look like a well fed 12AX7.

These two valve types appear to be similar and seem able to operate side by side at least so far. They both need about 500ma filament current

The preamp valves are sub-miniature dual triodes. V1 is a 6N17 which is a Russian hi mu valve. It needs about 400ma filament current and has a gain factor of about 85. These valves have a Russian military mark. Gain is similar to a 12AX7

V2 and V3 are 6112 which are the Western equivalent. They consume about 300ma current and have a gain factor of about 70. Gain is similar to a 5751. The ones that I am using have a JAN designation and I think they were probably NATO inventory

Both types have flying leads and are hard wired into the circuit, so the opportunities for tube rolling are limited unless you enjoy inhaling solder fumes

Datasheets available if you google the designations. If you can't find them let me know and I will post a link

The reverb circuit is basically a digital reverb pedal hard wired into the amp with a DPDT switch which allows it to be hard bypassed. The engine for the reverb is an Accutronics BTDR-2 Reverb module built into a PCB supplied by Fuzzdog Pedal parts in the UK. I have used this in multiple pedal and amp builds and I think the sound is pretty good as long as you don't turn it up full when it gets a bit chorusy. And in this very compact build preferable to at least one additional dual triode needing more current, more circuitry and an additional transformer, chassis real estate and a reverb tank.

The reverb breaks into the pre-amp circuit after the master volume i.e. the master volume wiper goes to one common terminal of the reverb DPDT switch and the other common to the phase inverter input allowing the digital reverb to switched in or out of the signal chain. It could be footswitchable with another relay, but I tend leave reverb on all the time, a bit more when playing at home, and a bit less when playing out, in general.

Fuzzdog circuit information is available if you google Fuzzdog Pedalparts. If you can't find what you need let me know and I will post a link

The footswitch is a generic 2 button unit to which I added LEDs and a 5 pin XLR connector

Relays are generic 5V modules that I found on eBay.

Things I didn't put in are
FET input
Phase inverter trimmer
Fixed bias
Effects loop
Rotary OT selector
Half power switch
Choke

Again, thanks for your interest and the feedback. Let me know if there is anything else you would like to know.
John
User avatar
M Fowler
Posts: 14017
Joined: Wed Jan 16, 2008 2:19 am
Location: Walcott ND

Re: New Build- Modded ODS Type #0124 Using Sub-Miniature Dual Triodes & Miniature Output Valves/Tubes

Post by M Fowler »

John,

Very interesting as well as fun to see other tubes utilized in the 124 circuit. Very good looking amp and sound is still good, I have a hard time with video's anyway because people are unable to crank the amps up for a real feel test.

Great to see you on Amp Garage.

Mark
User avatar
norburybrook
Posts: 3290
Joined: Mon Jan 06, 2014 12:47 am
Location: London
Contact:

Re: New Build- Modded ODS Type #0124 Using Sub-Miniature Dual Triodes & Miniature Output Valves/Tubes

Post by norburybrook »

John, really interesting stuff thanks for sharing. Nice to see another UK based person too. My first ever amp build was one of Ampmakers 5w SE amps, Barry is a great resource for new builders in the UK. I still buy the odd part from him now and again if I've forgotten something on a Mouser order.

I'm going to try your reverb idea in an amp :D



Marcus
User avatar
GuitarBloke
Posts: 6
Joined: Wed May 28, 2014 8:46 pm
Location: Antrim UK

Re: New Build- Modded ODS Type #0124 Using Sub-Miniature Dual Triodes & Miniature Output Valves/Tubes

Post by GuitarBloke »

Hi Mark,

Thanks for the kind words. It's been a while right? I filed the various schematics that you emailed me back in 2010 and had a look at them every now and then, and finally decided to try the Dumble ODS build with the sub-miniature twist that I picked up along the way.

Yes the sound is difficult to capture, especially since I am recording at home and not really able to crank the volume. This amp is loud and so far I haven't got beyond about 0.5 out of 11. What I have got is a decent clean sound, a boosted sound with some hair on it and a usable overdrive sound. I'm still messing with the OD trim pot which with unusual foresight I left accessible without having to dismantle the amp, and the 2 Overdrive controls. I haven't found the creamy Larry Carlton type sound or the ''note flipping' yet. With these different valves and voltages I may have compromised the gain structure and harmonics of the original circuit and they may not even be in there, and that's ok, I'll keep looking.

Anyway thanks for pointing me in this direction. I'm very grateful for the information here and the layouts and schematics that have been researched and presented with a forensic level of detail that is extraordinary. And then made available for enthusiasts like me to mess with. I wouldn't have dreamed of attempting this build without those layouts.
Sincerely,
John
Last edited by GuitarBloke on Sun Jul 23, 2017 11:06 am, edited 1 time in total.
John
User avatar
GuitarBloke
Posts: 6
Joined: Wed May 28, 2014 8:46 pm
Location: Antrim UK

Re: New Build- Modded ODS Type #0124 Using Sub-Miniature Dual Triodes & Miniature Output Valves/Tubes

Post by GuitarBloke »

Hi Marcus,

Good to hear from you and thanks for the feedback. I agree, it's great to have Ampmaker as a UK based source. I've been buying stuff, mainly transformers from Barry for a while. I have used his 0-190-275 PT in several builds both toroidal and lay down version. It's so compact and perfect for bridge rectified power supplies for a pair valves in push pull up to about 20 Watts. He also has a small output transformer that works perfectly as a reverb driver if you decide to go that route.

If you haven't looked already, the reverb Circuit that I have used successfully is here.

http://shop.pedalparts.co.uk/The_Verb_- ... 30526.aspx

You can buy the PCB only, or a kit. In any case you will also need to buy the accutronics/Belton brick and if you buy the PCB only you will need to buy the components to populate the PCB including a 5V regulator and a TL074 opamp or similar. You will need a regulated 9-15V dc supply to run it. The Reverb module/Brick itself needs a 5V regulator which sits in the PCB

I hope this is helpful, regards,
John
Post Reply