I am starting my research for my ODS Clone!

[keithrick]

Hi Guys,

I have just finished my Express Clone that turned out great! Now I am starting to plan my ODS build and have a quick question.

I have looked at every schematic and layout and am now basically overwhelmed. SOOOO....

Is the "Hybrid A Rev A" the schematic to use? 1977 Achitechture with 1997 values?

I am looking to build a 50watt 6L6 based amp. I was also considering using a SF bassman as a donor amp. Any thoughts or opinions would be greatly appreciated!

[mlp-mx6]

That schem is a great place to start.

When you make your layout, try to leave some extra turrets/eyelets in the OD entrance area, so you can play around there. Seems to be THE critical area of the amp for finding the right tone. I would also recommend that you NOT put the "snubber caps" (from plate to grid on the 2 OD triodes) on the socket pins - this is another heavy custom-tuning area. Will you plan to incorporate an effects loop? (esp. since you'll have an extra preamp tube to play with...)

I have some layouts I'd be happy to share if you do turret boards.

[keithrick]

mlp-mx6,

I am definately going to be using a turret board! I used one (From Dana) with the Express I just completed and it made it easy!

If you have some layouts I would love to have a look at them!

When finalized, I am also going to upload the BOM (for the Hybrid A REV A schem) on this board with Mousers latest part numbers, several changed, this way people can upload the BOM and save ALOT of time on Mousers website!

[Bob-I]

mlp-mx6,

I am definately going to be using a turret board! I used one (From Dana) with the Express I just completed and it made it easy!

Turret boards are the way to go for sure.

If you have some layouts I would love to have a look at them!

This one from Normster is excellent

https://tubeamparchive.com/files/dclone_layout_310.jpg

Once you get the amp working using known good values there are many small tweaks that really help. Start with the right components, metal film plate resistors, Vishay Dales seem to be the best, Orange drop or xicon caps for the uF range caps, ceramic disk for the pF range.

Good luck.

[mlp-mx6]

OK, here are two preamp layouts. One includes the filter caps, one does not. They are available for tweakage, of course. The other is 3 different (nearly identical) layouts for the effects loop (Dumbleator) and the phase inverter.

Any critiques welcome.

[Normster]

When I posted the Bassman layout, I had no idea it was going to be used so much. But since it is, here's an updated version that more closely reflects what I ended up with. Note that I don't use any relays, but it's easy enough to substitute the DPDT switches with relays. Hopefully this will get you into the ballpark a little quicker. If you see any errors, let me know and I'll correct them.

[img846]http://bad-domain/Pics/Bassman_Dclone_LayoutV2.JPG[/img]

Edit: Correction made to layout 5/14/2006. Master and OD input leads were reversed. Thanks, Ampdoc!

[keithrick]

When I posted the Bassman layout, I had no idea it was going to be used so much.

Yeah sure! With those killer clips you posted a while ago! I am sure alot more people are using the layout as a launchpad then are letting on!

Thanks for the updated layout! I and many others really appreciate the help. I am going to see how close I come to your layout. I have started with the Hybrid Rev A and have been pouring over every post on this board between you, Gil, Dogears, Bob-I ect. and have been taking notes on the Hybrid A schematic. I can wait to order some parts! However, I still have alot of homework to do. I am still fuzzy on the OD entrance

Anyway thanks again Normster and thanks to everyone on the board who has posted and shared there knowledge!

[Bob-I]

I am still fuzzy on the OD entrance

Yes, that's a tricky part.

I settled on a 100K into a 100K trim pot, then into a 68K grid stopper. I set the trim pot so that I have a total series resistance of 235K.

There's a thread on other options in the files section.

[glasman]

When I posted the Bassman layout, I had no idea it was going to be used so much. But since it is, here's an updated version that more closely reflects what I ended up with. Note that I don't use any relays, but it's easy enough to substitute the DPDT switches with relays. Hopefully this will get you into the ballpark a little quicker. If you see any errors, let me know and I'll correct them.
[img846]http://bad-domain/Pics/Bassman%20Dclone%20Layout.JPG[/img]

Hmmm, that looks mighty familar including the after thought .01uf reverb coupler eyelet !

[caglej]

I settled on a 100K into a 100K trim pot, then into a 68K grid stopper. I set the trim pot so that I have a total series resistance of 235K.

+1 on that....

[Normster]

Hmmm, that looks mighty familar including the after thought .01uf reverb coupler eyelet !

Yup. There's a reason for about 300 of those hits on your site. Shucks, I even used a 3" board planning to copy your relays...just never got around to it. BTW, I always thought the reverb coupler was kinda elegant. Saves space! lol

[keithrick]

Hello all, Thanks again for all the info. I now have a basic understanding of the the layout but still have some confusion with the reverb circuit.

Can anyone direct me to a link with a quick theory on how a reverb circuit works?

Also, Normster are you using the stock Bassman power supply or Hybrid A?

Because....: I have decided to build this amp from scratch (no donor amp). However, I am still considering using the Bassman transformers. Is there a transformer combo that people favor on this board? Personally I like the Marshall style that Moose sells for the Express that are vertical mounting, but it looks like the B+ voltages are a little low. Any suggestions?

Glasman: nice clips.

[Normster]

Also, Normster are you using the stock Bassman power supply or Hybrid A?

Because....: I have decided to build this amp from scratch (no donor amp). However, I am still considering using the Bassman transformers.

The first Bassman I converted used the stock PS. The second used the Hybrid-A values. Both worked OK, but the stock SFBM values were a little flabby on the bottom end. (Loren, the owner of the first amp, has since converted to Hybrid-A PS values and likes the amp better that way.)

As for transformers, I've used Bassman trannys for 3 amps so far and each sounds completely different. I have a 100 watt HRM build in progress that uses Marshall PT and Fender OPT but haven't completed it yet. I'm pretty sure Gary, Bob, and Funk have tried out all the iron between them. Hopefully they'll drop in and enlighten us.

[mlp-mx6]

Just for clarity - my layout does not include reverb, instead it has the built-in effects loop (Dumbleator). I guess my "wedding gig" background influenced me here - I've played on too many wobbly platform stages where the "reverb thunder" forced me to turn the reverb off. I have the preamp on one board and the effects loop and phase inverter on another. I did not include the relay board because your relay choice forces that to be specific to your relays. For mine I bridge-rectified the unused 5V taps from the power xfmr to power 5-6V relays - the relay choice suggested by glasman. Worked great.

[glasman]

Hello all, Thanks again for all the info. I now have a basic understanding of the the layout but still have some confusion with the reverb circuit.

Can anyone direct me to a link with a quick theory on how a reverb circuit works?

Sure try this link. http://www.accutronicsreverb.com/

Also, Normster are you using the stock Bassman power supply or Hybrid A?

Because....: I have decided to build this amp from scratch (no donor amp). However, I am still considering using the Bassman transformers. Is there a transformer combo that people favor on this board? Personally I like the Marshall style that Moose sells for the Express that are vertical mounting, but it looks like the B+ voltages are a little low. Any suggestions?

Glasman: nice clips.

Thanks, but the better ones on my site are from Dogears and Harry McGraw

As far as transformers, up until recently I have been using replacement 50 watt marshall transformers. These work well with both 6L6 and EL34's. The amp that I built for Dogears uses this setup with a replacement choke for a Fender Twin. The reverb transformer is a fender replacement part. I source either from CE distribution or New Sensor.

Gary